Basalt

(1905). THE ROCKS OF TRISTAN D'ACUNHA, BROUGHT BACK BY H.M.S. ODIN, 1904, WITH THEIR BEARING ON THE QUESTION OF THE PERMANENCE OF OCEAN BASINS. Transactions of the South African Philosophical Society: Vol. 16, No. 1, pp. 9-51.

@article{doi1010802156038219059526044,
    author = "Schwarz, E. H. L.",
    title = "THE ROCKS OF TRISTAN D'ACUNHA, BROUGHT BACK BY H.M.S. ODIN, 1904, WITH THEIR BEARING ON THE QUESTION OF THE PERMANENCE OF OCEAN BASINS",
    year = "1905",
    journal = "Transactions of the South African Philosophical Society",
    abstract = "(1905). THE ROCKS OF TRISTAN D'ACUNHA, BROUGHT BACK BY H.M.S. ODIN, 1904, WITH THEIR BEARING ON THE QUESTION OF THE PERMANENCE OF OCEAN BASINS. Transactions of the South African Philosophical Society: Vol. 16, No. 1, pp. 9-51.",
    url = "https://doi.org/10.1080/21560382.1905.9526044",
    doi = "10.1080/21560382.1905.9526044",
    openalex = "W1971527655"
}

This classic paper presents Fenner9s views of magmatic differentiation against those of N.L. Bowen (1928). Fenner presents the original case for iron-enrichment trends in residual basaltic liquids, contrasted with an iron depletion trend leading to rhyolite. He discusses the general crystallization process of basaltic lavas, mentions Clarence King9s (1878) identification of olivine settling in Hawaii, and considers the results of the crystallization of augite and olivine from a picrite-basalt of East Maui.

@article{doi102475ajss518105225,
    author = "Fenner, C. N.",
    title = "The crystallization of basalts",
    year = "1929",
    journal = "American Journal of Science",
    abstract = "This classic paper presents Fenner9s views of magmatic differentiation against those of N.L. Bowen (1928). Fenner presents the original case for iron-enrichment trends in residual basaltic liquids, contrasted with an iron depletion trend leading to rhyolite. He discusses the general crystallization process of basaltic lavas, mentions Clarence King9s (1878) identification of olivine settling in Hawaii, and considers the results of the crystallization of augite and olivine from a picrite-basalt of East Maui.",
    url = "https://doi.org/10.2475/ajs.s5-18.105.225",
    doi = "10.2475/ajs.s5-18.105.225",
    openalex = "W2312581690"
}

The Physiographic Diagram: Atlantic Ocean, Sheet 1, which portrays the North Atlantic between 17° and 50° North Latitude, is the first of a projected series of diagrams. The diagram is based on continuous echo-sounding traverses made by research vessels. The relief shown on the profiles was sketched in perspective using the technique introduced by Lobeck. Between sounding profiles the relief is speculative, based on extrapolation of trends noted in the profiles.

@incollection{doi101130spe65p1,
    author = "Heezen, Bruce C. and Tharp, Marie and Ewing, Maurice",
    title = "The Floors of the Oceans",
    year = "1959",
    booktitle = "Geological Society of America Special Papers",
    abstract = "The Physiographic Diagram: Atlantic Ocean, Sheet 1, which portrays the North Atlantic between 17° and 50° North Latitude, is the first of a projected series of diagrams. The diagram is based on continuous echo-sounding traverses made by research vessels. The relief shown on the profiles was sketched in perspective using the technique introduced by Lobeck. Between sounding profiles the relief is speculative, based on extrapolation of trends noted in the profiles.",
    url = "https://doi.org/10.1130/spe65-p1",
    doi = "10.1130/spe65-p1",
    openalex = "W2401423790"
}

Aphyric basalts of central Honsyū and the Izu Islands, Japan, are classified into three types: tholeiite with low Al2O3 and alkalis, alkali basalt with variable Al2O3 and higher alkalis, and high-alumina basalt with higher Al2O3 and intermediate alkalis. The tholeliite invariably yields normative quartz whereas the high-alumina basalt may yield a little normative quartz or normative olivine. The alkali basalt is undersaturated with SiO2. Mineralogically, the high-alumina basalt is intermediate between the tholeiite and alkali basalt. Thus the high-alumina basalt is transitional between the other two basalt types. The high-alumina basalt occurs in a zone extending between the tholeliite provinces and alkali province of the Japanese islands. There is a complete gradation from the tholeiite provinces, passing through the high-alumina basalt zone, to the alkali province. The high-alumina basalt is not a derivative of the tholeiite magma or of the alkali olivine basalt magma, but represents a primary magma. It is suggested that the high-alumina basalt magma is produced by partial melting of the mantle peridotite at depths intermediate between those of the tholeiite and alkali olivine basalt magma production, say at about 200 km. The high-alumina basalt is common in other orogenic belts of the world, but is absent, from the oceanic regions. It is rarely present in non-orogenic continental regions such as Manchuria and Skaergaard, Greenland. The fractionation trend of the high-alumina basalt magma is generally similar to that of the tholeiite magma, although higher concentration of alkalis in the middle stage may take place. From distribution of granitic xenoliths in volcanic rocks it is concluded that the limit of the sialic crust or ‘andesite line’ passes a little to the south-east of the Pacific coast of Honsyū and not along the east of the Izu Islands as previously considered.

@article{doi101093petrology12121,
    author = "Kuno, Hisashi",
    title = "High-alumina Basalt",
    year = "1960",
    journal = "Journal of Petrology",
    abstract = "Aphyric basalts of central Honsyū and the Izu Islands, Japan, are classified into three types: tholeiite with low Al2O3 and alkalis, alkali basalt with variable Al2O3 and higher alkalis, and high-alumina basalt with higher Al2O3 and intermediate alkalis. The tholeliite invariably yields normative quartz whereas the high-alumina basalt may yield a little normative quartz or normative olivine. The alkali basalt is undersaturated with SiO2. Mineralogically, the high-alumina basalt is intermediate between the tholeiite and alkali basalt. Thus the high-alumina basalt is transitional between the other two basalt types. The high-alumina basalt occurs in a zone extending between the tholeliite provinces and alkali province of the Japanese islands. There is a complete gradation from the tholeiite provinces, passing through the high-alumina basalt zone, to the alkali province. The high-alumina basalt is not a derivative of the tholeiite magma or of the alkali olivine basalt magma, but represents a primary magma. It is suggested that the high-alumina basalt magma is produced by partial melting of the mantle peridotite at depths intermediate between those of the tholeiite and alkali olivine basalt magma production, say at about 200 km. The high-alumina basalt is common in other orogenic belts of the world, but is absent, from the oceanic regions. It is rarely present in non-orogenic continental regions such as Manchuria and Skaergaard, Greenland. The fractionation trend of the high-alumina basalt magma is generally similar to that of the tholeiite magma, although higher concentration of alkalis in the middle stage may take place. From distribution of granitic xenoliths in volcanic rocks it is concluded that the limit of the sialic crust or ‘andesite line’ passes a little to the south-east of the Pacific coast of Honsyū and not along the east of the Izu Islands as previously considered.",
    url = "https://doi.org/10.1093/petrology/1.2.121",
    doi = "10.1093/petrology/1.2.121",
    openalex = "W2321981993"
}

Natural basalts and eclogites were investigated experimentally at a series of temperatures in the pressure range 1 atm to 40 kb and with water pressures 1 to 10 kb. Some runs were also made on related synthetic systems at 10 and 33 kb. The two principal magma types recognized by field investigators—tholeiite and alkali basalt types-appear to be separated by equilibrium thermal divides at 1 atm. The principal divides were found by experiment at elevated pressures to give way to a new set of equilibrium thermal divides resulting from a new mineralogy. The change of the equilibrium thermal divides with pressure leads to the derivation of the two principal magma trends from the same bulk composition. The melting behavior of basalts and eclogites indicates that both are the partial melting products of a more primitive rock (e.g. garnet peridotite). In the region of magma generation (below 60 km) the parental material, presumed to be garnet peridotite, yields an eclogitic magma and its fractionation depends on the garnet and omphacite of the eclogite, not on plagioclase and clinopyroxene of a basaltic magma. Increase of the garnet constituents in the magma at high pressure by effective removal of omphacite or shift of the garnet-omphacite boundary ‘surface’ will give rise to a tholeiite-type magma at low pressure. Similarly, increase of the omphacite constituents in the magma at high pressure by physical or physicochemical means will give rise to an alkali basalt-type magma at low pressure. In general, alkali basalt-type magmas are to be expected to be generated at greater depths than tholeiite-type magmas from the same primary source rock. Establishment of the two major basalt series takes place in the region of generation; additional minor diversification of each series may come about after emplacement in or on the crust by crystal settling, oxidation or reduction, gas fluxing, contamination, and other processes. The derivative magmas are greatly restricted by the course of liquid thermal descent imposed at generation. Pressure-temperature limits established experimentally suggest that the basalt-eclogite transformation may be responsible for the Mohoroviĉić discontinuity under the continents, but not under the oceans. The field of stability of basalt is drastically reduced in the presence of water, and amphibolite is produced. The melting of amphibolite takes place over a much greater range of temperature than basalt. At 10 kb water pressure the beginning of melting of amphibolite closely approaches that of granite. Partial melting of amphibolite may yield anorthositic liquids having a relatively low anorthite content at exceptionally low temperatures. Eclogite itself is not stable in the presence of water and gives place to amphibolite or pyroxene hornblendite. Magmas which crystallize to basalt, gabbro, or eclogite must have had a low water-content at the time of crystallization. Fifteen rock and twenty-three mineral analyses as well as numerous partial chemical analyses of experimental products were made by J. H. Scoon in the course of the investigation. These chemical analyses bear on many mineralogical and petrological problems.

@article{doi101093petrology33342,
    author = "Yoder, H. S. and Tilley, C. E.",
    title = "Origin of Basalt Magmas: An Experimental Study of Natural and Synthetic Rock Systems",
    year = "1962",
    journal = "Journal of Petrology",
    abstract = "Natural basalts and eclogites were investigated experimentally at a series of temperatures in the pressure range 1 atm to 40 kb and with water pressures 1 to 10 kb. Some runs were also made on related synthetic systems at 10 and 33 kb. The two principal magma types recognized by field investigators—tholeiite and alkali basalt types-appear to be separated by equilibrium thermal divides at 1 atm. The principal divides were found by experiment at elevated pressures to give way to a new set of equilibrium thermal divides resulting from a new mineralogy. The change of the equilibrium thermal divides with pressure leads to the derivation of the two principal magma trends from the same bulk composition. The melting behavior of basalts and eclogites indicates that both are the partial melting products of a more primitive rock (e.g. garnet peridotite). In the region of magma generation (below 60 km) the parental material, presumed to be garnet peridotite, yields an eclogitic magma and its fractionation depends on the garnet and omphacite of the eclogite, not on plagioclase and clinopyroxene of a basaltic magma. Increase of the garnet constituents in the magma at high pressure by effective removal of omphacite or shift of the garnet-omphacite boundary ‘surface’ will give rise to a tholeiite-type magma at low pressure. Similarly, increase of the omphacite constituents in the magma at high pressure by physical or physicochemical means will give rise to an alkali basalt-type magma at low pressure. In general, alkali basalt-type magmas are to be expected to be generated at greater depths than tholeiite-type magmas from the same primary source rock. Establishment of the two major basalt series takes place in the region of generation; additional minor diversification of each series may come about after emplacement in or on the crust by crystal settling, oxidation or reduction, gas fluxing, contamination, and other processes. The derivative magmas are greatly restricted by the course of liquid thermal descent imposed at generation. Pressure-temperature limits established experimentally suggest that the basalt-eclogite transformation may be responsible for the Mohoroviĉić discontinuity under the continents, but not under the oceans. The field of stability of basalt is drastically reduced in the presence of water, and amphibolite is produced. The melting of amphibolite takes place over a much greater range of temperature than basalt. At 10 kb water pressure the beginning of melting of amphibolite closely approaches that of granite. Partial melting of amphibolite may yield anorthositic liquids having a relatively low anorthite content at exceptionally low temperatures. Eclogite itself is not stable in the presence of water and gives place to amphibolite or pyroxene hornblendite. Magmas which crystallize to basalt, gabbro, or eclogite must have had a low water-content at the time of crystallization. Fifteen rock and twenty-three mineral analyses as well as numerous partial chemical analyses of experimental products were made by J. H. Scoon in the course of the investigation. These chemical analyses bear on many mineralogical and petrological problems.",
    url = "https://doi.org/10.1093/petrology/3.3.342",
    doi = "10.1093/petrology/3.3.342",
    openalex = "W2333414322"
}

Journal Article Basalts from the Northern Part of the Rift Zone of the Mid-Atlantic Ridge Get access I. D. MUIR, I. D. MUIR Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar C. E. TILLEY, C. E. TILLEY Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar J. H. SCOON J. H. SCOON Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar Journal of Petrology, Volume 5, Issue 3, 1964, Pages 409–434, https://doi.org/10.1093/petrology/5.3.409 Published: 01 January 1964

@article{doi101093petrology53409,
    author = "Muir, I. D. and Tilley, C. E. and Scoon, J. H.",
    title = "Basalts from the Northern Part of the Rift Zone of the Mid-Atlantic Ridge",
    year = "1964",
    journal = "Journal of Petrology",
    abstract = "Journal Article Basalts from the Northern Part of the Rift Zone of the Mid-Atlantic Ridge Get access I. D. MUIR, I. D. MUIR Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar C. E. TILLEY, C. E. TILLEY Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar J. H. SCOON J. H. SCOON Department of Mineralogy and Petrology, University of CambridgeEngland Search for other works by this author on: Oxford Academic Google Scholar Journal of Petrology, Volume 5, Issue 3, 1964, Pages 409–434, https://doi.org/10.1093/petrology/5.3.409 Published: 01 January 1964",
    url = "https://doi.org/10.1093/petrology/5.3.409",
    doi = "10.1093/petrology/5.3.409",
    openalex = "W2324244126"
}

The average concentrations of potassium, rubidium, strontium, thorium, and uranium in oceanic tholeiitic basalt are (in parts per million) K, 1400; Rb, 1.2; Sr, 120; Th, 0.2; and U, 0.1. The ratio Sr(87) to Sr(86) is about 0.702, that of K to U is 1.4 x 10(4), and of Th to U is 1.8. These amounts of K, Th, U, and radiogenic Sr(87) are less than in other common igneous rocks. The ratios of Th to U and Sr(87) to Sr(86) suggest that the source region of the oceanic tholeiites was differentiated from the original mantle material some time in the geologic past.

@article{doi101126science1503698886,
    author = "Tatsumoto, M. and Hedge, C. E. and Engel, A. E. J.",
    title = "Potassium, Rubidium, Strontium, Thorium, Uranium, and the Ratio of Strontium-87 to Strontium-86 in Oceanic Tholeiitic Basalt",
    year = "1965",
    journal = "Science",
    abstract = "The average concentrations of potassium, rubidium, strontium, thorium, and uranium in oceanic tholeiitic basalt are (in parts per million) K, 1400; Rb, 1.2; Sr, 120; Th, 0.2; and U, 0.1. The ratio Sr(87) to Sr(86) is about 0.702, that of K to U is 1.4 x 10(4), and of Th to U is 1.8. These amounts of K, Th, U, and radiogenic Sr(87) are less than in other common igneous rocks. The ratios of Th to U and Sr(87) to Sr(86) suggest that the source region of the oceanic tholeiites was differentiated from the original mantle material some time in the geologic past.",
    url = "https://doi.org/10.1126/science.150.3698.886",
    doi = "10.1126/science.150.3698.886",
    openalex = "W1971822376"
}

Summary Basalts dredged from the floor of the deep ocean show general tholeiitic affinities. Some samples are rich in aluminium and of very similar composition to the Warner high-alumina basalt from California. Both olivine tholeiite and high-alumina basalt have been found in the form of glass in dredgings from the Mid-Atlantic Ridge, indicating that liquid magmas of both compositions have been erupted on to the sea bed in this area. In explanation of this association a tentative hypothesis of fractional melting of hydrated upper mantle material is proposed. It is suggested that under the mid-ocean ridges the ‘basaltic fraction’ of the mantle is locally in the form of an amphibole. Fractional incongruent melting of this amphibole appears to be a possible explanation of the range of composition encountered in dredged glass samples.

@article{doi101180minmag196503426832,
    author = "Nicholls, G. D.",
    title = "Basalts from the deep ocean floor",
    year = "1965",
    journal = "Mineralogical Magazine and Journal of the Mineralogical Society",
    abstract = "Summary Basalts dredged from the floor of the deep ocean show general tholeiitic affinities. Some samples are rich in aluminium and of very similar composition to the Warner high-alumina basalt from California. Both olivine tholeiite and high-alumina basalt have been found in the form of glass in dredgings from the Mid-Atlantic Ridge, indicating that liquid magmas of both compositions have been erupted on to the sea bed in this area. In explanation of this association a tentative hypothesis of fractional melting of hydrated upper mantle material is proposed. It is suggested that under the mid-ocean ridges the ‘basaltic fraction’ of the mantle is locally in the form of an amphibole. Fractional incongruent melting of this amphibole appears to be a possible explanation of the range of composition encountered in dredged glass samples.",
    url = "https://doi.org/10.1180/minmag.1965.034.268.32",
    doi = "10.1180/minmag.1965.034.268.32",
    openalex = "W2075166895",
    references = "doi1010160025322764900192, doi1010160025322764900428, doi101017s0080456800038424, doi101029jz067i003p01109, doi101086625580, doi101093petrology12121, doi101093petrology33342, doi101144gsljgs1950106010404, doi1023071794727, openalexw2271364307"
}

Summary Basalts dredged from the floor of the deep ocean show general tholeiitic affinities. Some samples are rich in aluminium and of very similar composition to the Warner high-alumina basalt from California. Both olivine tholeiite and high-alumina basalt have been found in the form of glass in dredgings from the Mid-Atlantic Ridge, indicating that liquid magmas of both compositions have been erupted on to the sea bed in this area. In explanation of this association a tentative hypothesis of fractional melting of hydrated upper mantle material is proposed. It is suggested that under the mid-ocean ridges the ‘basaltic fraction’ of the mantle is locally in the form of an amphibole. Fractional incongruent melting of this amphibole appears to be a possible explanation of the range of composition encountered in dredged glass samples.

@article{nicholls1965basalts,
    author = "Nicholls, G. D.",
    title = "Basalts from the deep ocean floor",
    year = "1965",
    journal = "Mineralogical Magazine and Journal of the Mineralogical Society",
    abstract = "Summary Basalts dredged from the floor of the deep ocean show general tholeiitic affinities. Some samples are rich in aluminium and of very similar composition to the Warner high-alumina basalt from California. Both olivine tholeiite and high-alumina basalt have been found in the form of glass in dredgings from the Mid-Atlantic Ridge, indicating that liquid magmas of both compositions have been erupted on to the sea bed in this area. In explanation of this association a tentative hypothesis of fractional melting of hydrated upper mantle material is proposed. It is suggested that under the mid-ocean ridges the ‘basaltic fraction’ of the mantle is locally in the form of an amphibole. Fractional incongruent melting of this amphibole appears to be a possible explanation of the range of composition encountered in dredged glass samples.",
    url = "https://doi.org/10.1180/minmag.1965.034.268.32",
    doi = "10.1180/minmag.1965.034.268.32",
    number = "268",
    openalex = "W2075166895",
    pages = "373-388",
    volume = "34",
    references = "doi1010160025322764900192, doi1010160025322764900428, doi101017s0080456800038424, doi101029jz067i003p01109, doi101086625580, doi101093petrology12121, doi101093petrology33342, doi101144gsljgs1950106010404, doi1023071794727, openalexw2271364307"
}

Abstract Rocks collected in the vicinity of a transcurrent fault cutting the crest of the Ridge have been affected by brecciation and, in some cases, metamorphism and hydrothermal action. These processes have led to the formation of spilites from crystalline basalts, and ultramafic rocks from basalt glasses Further hydrothermal action has taken the form of replacement of some ultramafic rocks by quartz, ending in a nearly pure quartzite. The mineralogy is characteristic of greenschist facies meta-morphism. Fresh basalts were collected from a nearby hill, which seems to be a recent volcano post-dating the faulting and metamorphism. The magnetic survey reveals a marked parallelism between the anomalies and the trend of the ridge, regardless of bathymetry. Computations confirm that uniform magnetization of the material represented by the bathymetry can in no way simulate the observed anomalies. Application of the vector fitting technique suggests that the remanent magnetization of this material is often reversed and from this a very crude and simple model is developed to account for the observed anomalies. The model is consistent with an ocean floor spreading hypothesis and periodic reversals in the earth's magnetic field. If substantiated it would have important implications in deducing the history of the ocean basins. Above all it provides a plausible explanation to account for the magnetic gradients and amplitudes observed over ridges without implying improbable magnetic contrasts, structures, or changes in petrology.

@article{doi101098rsta19660007,
    author = "Cann, J. R. and Vine, F. J.",
    title = "A discussion concerning the floor of the northwest Indian Ocean - An area on the crest of the Carlsberg Ridge: petrology and magnetic survey",
    year = "1966",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract Rocks collected in the vicinity of a transcurrent fault cutting the crest of the Ridge have been affected by brecciation and, in some cases, metamorphism and hydrothermal action. These processes have led to the formation of spilites from crystalline basalts, and ultramafic rocks from basalt glasses Further hydrothermal action has taken the form of replacement of some ultramafic rocks by quartz, ending in a nearly pure quartzite. The mineralogy is characteristic of greenschist facies meta-morphism. Fresh basalts were collected from a nearby hill, which seems to be a recent volcano post-dating the faulting and metamorphism. The magnetic survey reveals a marked parallelism between the anomalies and the trend of the ridge, regardless of bathymetry. Computations confirm that uniform magnetization of the material represented by the bathymetry can in no way simulate the observed anomalies. Application of the vector fitting technique suggests that the remanent magnetization of this material is often reversed and from this a very crude and simple model is developed to account for the observed anomalies. The model is consistent with an ocean floor spreading hypothesis and periodic reversals in the earth's magnetic field. If substantiated it would have important implications in deducing the history of the ocean basins. Above all it provides a plausible explanation to account for the magnetic gradients and amplitudes observed over ridges without implying improbable magnetic contrasts, structures, or changes in petrology.",
    url = "https://doi.org/10.1098/rsta.1966.0007",
    doi = "10.1098/rsta.1966.0007",
    openalex = "W2009447547"
}

Rare-earth elements have been determined by neutron activation analysis in 20 basalts from the Hawaiian Islands. The abundance patterns of these elements form groups coinciding closely with groupings based on other evidence, and a fractional crystallization mechanism for change in rare earth abundance is implied.

@article{doi101126science1533738867,
    author = "Schilling, Jean‐Guy and Winchester, John W.",
    title = "Rare Earths in Hawaiian Basalts",
    year = "1966",
    journal = "Science",
    abstract = "Rare-earth elements have been determined by neutron activation analysis in 20 basalts from the Hawaiian Islands. The abundance patterns of these elements form groups coinciding closely with groupings based on other evidence, and a fractional crystallization mechanism for change in rare earth abundance is implied.",
    url = "https://doi.org/10.1126/science.153.3738.867",
    doi = "10.1126/science.153.3738.867",
    openalex = "W1984730721"
}

It is suggested that the entire history of the ocean basins, in terms of oceanfloor spreading,is contained frozen in the oceanic crust. Variations in the intensity and polarity of Earth's magnetic field are considered to be recorded in the remanent magnetism of the igneous rocks as they solidified and cooled through the Curie temperature at the crest of an oceanic ridge, and subsequently spread away from it at a steady rate. The hypothesis is supported by the extreme linearity and continuity of oceanic magnetic anomalies and their symmetry about the axes of ridges. If the proposed reversal time scale for the last 4 million years is combined with the model, computed anomaly profiles show remarkably good agreement with those observed, and one can deduce rates of spreading for all active parts of the midoceanic ridge system for which magnetic profilesor surveys are available. The rates obtained are in exact agreement with those needed to account for continental drift. An exceptionally high rate of spreading (approximately 4.5 cm/year) in the South Pacific enables one to deduce by extrapolation considerable details of the reversal time scale back to 11.5 million years ago. Again, this scale can be applied to other parts of the ridge system. Thus one isled to the suggestion that the crest of the East Pacific Rise in the northeast Pacific has been overridden and modified by the westward drift of North America, with the production of the anomalous width and unique features of the American cordillera in the western United States. The oceanicmagnetic anomalies also indicate that there was a change in derection of crustal spreading in this region during Pliocene time from eastwest to southeast-northwest. A profile from the crest to the boundary of the East Pacific Rise, and the difference between axial-zone and flank anomalies over ridges, suggest increase in the frequency of reversal of Earth's magnetic field, together, possibly, with decrease in its intensity, approximately 25 million years ago. Within the framework of ocean-floor spreading, it is suggested that magnetic anomaliesmay indicate the nature of oceanic fracture zones and distinguish the parts of the ridge system that are actively spreading. Thus data derived during the past year lend remarkable support to thehypothesis that magnetic anomalies may reveal the history of the ocean basins.

@article{doi101126science15437551405,
    author = "Vine, F. J.",
    title = "Spreading of the Ocean Floor: New Evidence",
    year = "1966",
    journal = "Science",
    abstract = "It is suggested that the entire history of the ocean basins, in terms of oceanfloor spreading,is contained frozen in the oceanic crust. Variations in the intensity and polarity of Earth's magnetic field are considered to be recorded in the remanent magnetism of the igneous rocks as they solidified and cooled through the Curie temperature at the crest of an oceanic ridge, and subsequently spread away from it at a steady rate. The hypothesis is supported by the extreme linearity and continuity of oceanic magnetic anomalies and their symmetry about the axes of ridges. If the proposed reversal time scale for the last 4 million years is combined with the model, computed anomaly profiles show remarkably good agreement with those observed, and one can deduce rates of spreading for all active parts of the midoceanic ridge system for which magnetic profilesor surveys are available. The rates obtained are in exact agreement with those needed to account for continental drift. An exceptionally high rate of spreading (approximately 4.5 cm/year) in the South Pacific enables one to deduce by extrapolation considerable details of the reversal time scale back to 11.5 million years ago. Again, this scale can be applied to other parts of the ridge system. Thus one isled to the suggestion that the crest of the East Pacific Rise in the northeast Pacific has been overridden and modified by the westward drift of North America, with the production of the anomalous width and unique features of the American cordillera in the western United States. The oceanicmagnetic anomalies also indicate that there was a change in derection of crustal spreading in this region during Pliocene time from eastwest to southeast-northwest. A profile from the crest to the boundary of the East Pacific Rise, and the difference between axial-zone and flank anomalies over ridges, suggest increase in the frequency of reversal of Earth's magnetic field, together, possibly, with decrease in its intensity, approximately 25 million years ago. Within the framework of ocean-floor spreading, it is suggested that magnetic anomaliesmay indicate the nature of oceanic fracture zones and distinguish the parts of the ridge system that are actively spreading. Thus data derived during the past year lend remarkable support to thehypothesis that magnetic anomalies may reveal the history of the ocean basins.",
    url = "https://doi.org/10.1126/science.154.3755.1405",
    doi = "10.1126/science.154.3755.1405",
    openalex = "W2014144720",
    references = "doi1010160011747166910783, doi101038199947a0, doi101038201591a0, doi101038207343a0, doi101038207907a0, doi101098rsta19650020, doi101126science14436261537, doi101126science1543747349, doi101126science15437531164, doi101144transglas183559"
}

This paper summarizes the results of the three previous papers in this series, which have shown the presence of a pattern of magnetic anomalies, bilaterally symmetric about the crest of the ridge in the Pacific, Atlantic, and Indian oceans. By assuming that the pattern is caused by a sequence of normally and reversely magnetized blocks that have been produced by sea floor spreading at the axes of the ridges, it is shown that the sequences of blocks correspond to the same geomagnetic time scale. An attempt is made to determine the absolute ages of this time scale using palcomagnetic and paleontological data. The pattern of opening of the oceans is discussed and the implications on continental drift are considered. This pattern is in good agreement with continental drift, in particular with the history of the break up of Gondwanaland.

@article{doi101029jb073i006p02119,
    author = "Heirtzler, J. R. and Dickson, G. O. and Herron, E. M. and Pitman, Walter C. and Pichon, Xavier Le",
    title = "Marine magnetic anomalies, geomagnetic field reversals, and motions of the ocean floor and continents",
    year = "1968",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "This paper summarizes the results of the three previous papers in this series, which have shown the presence of a pattern of magnetic anomalies, bilaterally symmetric about the crest of the ridge in the Pacific, Atlantic, and Indian oceans. By assuming that the pattern is caused by a sequence of normally and reversely magnetized blocks that have been produced by sea floor spreading at the axes of the ridges, it is shown that the sequences of blocks correspond to the same geomagnetic time scale. An attempt is made to determine the absolute ages of this time scale using palcomagnetic and paleontological data. The pattern of opening of the oceans is discussed and the implications on continental drift are considered. This pattern is in good agreement with continental drift, in particular with the history of the break up of Gondwanaland.",
    url = "https://doi.org/10.1029/jb073i006p02119",
    doi = "10.1029/jb073i006p02119",
    openalex = "W2027477351",
    references = "doi101029jb073i006p01959, doi101029jb073i012p03661, doi101029jz072i008p02131, doi101038190854a0, doi101038199947a0, doi101038207343a0, doi101126science15437531164, doi101126science15437551405, doi101130petrologic1962599, openalexw2978227140, sykes1967mechanism"
}

@article{doi101038220683a0,
    author = "O’Hara, M. J.",
    title = "Are Ocean Floor Basalts Primary Magma?",
    year = "1968",
    journal = "Nature",
    url = "https://doi.org/10.1038/220683a0",
    doi = "10.1038/220683a0",
    openalex = "W1997913310",
    references = "doi101180minmag196503426832, nicholls1965basalts"
}

@misc{noble1968deepocean1,
    author = "Noble, C. S. and Naughton, J. J",
    title = "Deep-ocean basalts",
    year = "1968",
    howpublished = "Inert gas and uncertainties in age dating: Science, v. 162, p. 265-267",
    note = "talkorigins\_source = {true}; raw\_reference = {Noble, C. S., and Naughton, J. J., 1968, Deep-ocean basalts: Inert gas and uncertainties in age dating: Science, v. 162, p. 265-267.}"
}

@article{doi1010160012821x70900373,
    author = "Hart, Roger",
    title = "Chemical exchange between sea water and deep ocean basalts",
    year = "1970",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(70)90037-3",
    doi = "10.1016/0012-821x(70)90037-3",
    openalex = "W2017697430",
    references = "doi1010160040195169900390, doi101029jb073i006p02119, doi101029jb073i018p05925, doi101029jz068i003p00937, doi101038190854a0, doi101038199947a0, doi101093petrology33342, doi101093petrology5182, doi10113000167606196576719ccooba20co2, doi101130petrologic1962599"
}

A scheme of deep mantle convection is proposed in which narrow plumes of deep material rise and then spread out radially in the asthenosphere. These vertical plumes spreading outward in the asthenosphere produce stresses on the bottoms of the lithospheric plates, causing them to move and thus providing the driving mechanism for continental drift. One such plume is beneath Iceland, and the outpouring of unusual lava at this spot produced the submarine ridge between Greenland and Great Britain as the Atlantic opened up. It is concluded that all the aseismic ridges, for example, the Walvis Ridge, the Ninetyeast Ridge, the...

@incollection{doi101130mem132p7,
    author = "Morgan, W. Jason",
    title = "Plate Motions and Deep Mantle Convection",
    year = "1972",
    booktitle = "Memoir - Geological Society of America",
    abstract = "A scheme of deep mantle convection is proposed in which narrow plumes of deep material rise and then spread out radially in the asthenosphere. These vertical plumes spreading outward in the asthenosphere produce stresses on the bottoms of the lithospheric plates, causing them to move and thus providing the driving mechanism for continental drift. One such plume is beneath Iceland, and the outpouring of unusual lava at this spot produced the submarine ridge between Greenland and Great Britain as the Atlantic opened up. It is concluded that all the aseismic ridges, for example, the Walvis Ridge, the Ninetyeast Ridge, the...",
    url = "https://doi.org/10.1130/mem132-p7",
    doi = "10.1130/mem132-p7",
    openalex = "W2267527292"
}

The rare earth content of alkali-rich, silica-undersaturated basalts erupted onto oceanic and continental plates is consistent with their derivation by slight amounts of partial melting of hydrous garnet peridotite at the top of the asthenosphere, within the low-velocity, low-Q zone of the mantle. The rare earths are fractionated during partial melting by retention of heavy rare earths relative to light rare earths in garnet and clinopyroxene in the mantle residue. We conclude from a melting model that the amount of melting of hydrous peridotite at the top of the asthenosphere and its clinopyroxene-garnet ratio increase with decreasing thickness of the overlying dry lithospheric plate. Thus, potassic basalts derived by 0.5% melting of peridotite with a clinopyroxene-garnet ratio of 0.3 come from deeper than nephelinites (1% melting, ratio of 1), and alkali basalts (2% melting, ratio of 5). Convection within the partly molten asthenosphere establishes an adiabatic geothermal gradient and localizes renewable magma sources into updwelling plumes, or hot spots, that remain relatively stationary with respect to the overlying lithospheric plates. Unlike the source regions of midoceanic ridge tholeiite basalts, the peridotite source regions of the alkali-rich basalts do not appear to have been previously depleted in large cations (Ba, Rb, light rare earths) and generally have more radiogenic Sr and Pb. If the peridotite source regions of the alkali-rich basalts have chondritic proportions of the rare earths, the partial melting model indicates two to five times chondritic abundance of the rare earths in the peridotite.

@article{doi101086627919,
    author = "Kay, Robert W. and Gast, P. W.",
    title = "The Rare Earth Content and Origin of Alkali-Rich Basalts",
    year = "1973",
    journal = "The Journal of Geology",
    abstract = "The rare earth content of alkali-rich, silica-undersaturated basalts erupted onto oceanic and continental plates is consistent with their derivation by slight amounts of partial melting of hydrous garnet peridotite at the top of the asthenosphere, within the low-velocity, low-Q zone of the mantle. The rare earths are fractionated during partial melting by retention of heavy rare earths relative to light rare earths in garnet and clinopyroxene in the mantle residue. We conclude from a melting model that the amount of melting of hydrous peridotite at the top of the asthenosphere and its clinopyroxene-garnet ratio increase with decreasing thickness of the overlying dry lithospheric plate. Thus, potassic basalts derived by 0.5\% melting of peridotite with a clinopyroxene-garnet ratio of 0.3 come from deeper than nephelinites (1\% melting, ratio of 1), and alkali basalts (2\% melting, ratio of 5). Convection within the partly molten asthenosphere establishes an adiabatic geothermal gradient and localizes renewable magma sources into updwelling plumes, or hot spots, that remain relatively stationary with respect to the overlying lithospheric plates. Unlike the source regions of midoceanic ridge tholeiite basalts, the peridotite source regions of the alkali-rich basalts do not appear to have been previously depleted in large cations (Ba, Rb, light rare earths) and generally have more radiogenic Sr and Pb. If the peridotite source regions of the alkali-rich basalts have chondritic proportions of the rare earths, the partial melting model indicates two to five times chondritic abundance of the rare earths in the peridotite.",
    url = "https://doi.org/10.1086/627919",
    doi = "10.1086/627919",
    openalex = "W2082257231"
}

Basalts cored on legs 2 and 3 of the Deep-Sea Drilling Project (DSDP) range in sea floor spreading age from 18 to 67×106 yr. Although many of the basalts are highly altered, fresh glass is usually present. Except for site 2–10 the fresh glasses are petrographically and geochemically similar to mid-Atlantic ridge (MAR) axial basalts. There are no systematic compositional differences as a function of distance from the MAR axis. Two sites contain basalts with olivine (Fo90) phenocrysts, high Mg/Mg + ΣFe, high Ni and Cr abundances, and very low large ion lithophile (LIL) element abundances. These basalts are the best candidates for primary magma recovered from the sea floor; fractional crystallization of such basalt may yield the more evolved basalts typical of the MAR. More fractionated basalts with clinopyroxene phenocrysts occur at twp other sites, but they retain low LIL element abundances. Site 2-10 contains titaniferous augite and is relatively enriched in LIL elements. It is unlikely that this basalt was derived by fractional crystallization from LIL element depleted tholeiites; instead, the site 2-10 basalt requires a different mantle source. These results imply that the upper Atlantic Ocean basement is dominantly LIL element depleted tholeiite.

@article{doi101029jb079i035p05507,
    author = "Frey, Frederick A. and Bryan, W. B. and Thompson, Geoffrey",
    title = "Atlantic ocean floor: Geochemistry and petrology of basalts from legs 2 and 3 of the Deep-Sea Drilling Project",
    year = "1974",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Basalts cored on legs 2 and 3 of the Deep-Sea Drilling Project (DSDP) range in sea floor spreading age from 18 to 67×106 yr. Although many of the basalts are highly altered, fresh glass is usually present. Except for site 2–10 the fresh glasses are petrographically and geochemically similar to mid-Atlantic ridge (MAR) axial basalts. There are no systematic compositional differences as a function of distance from the MAR axis. Two sites contain basalts with olivine (Fo90) phenocrysts, high Mg/Mg + ΣFe, high Ni and Cr abundances, and very low large ion lithophile (LIL) element abundances. These basalts are the best candidates for primary magma recovered from the sea floor; fractional crystallization of such basalt may yield the more evolved basalts typical of the MAR. More fractionated basalts with clinopyroxene phenocrysts occur at twp other sites, but they retain low LIL element abundances. Site 2-10 contains titaniferous augite and is relatively enriched in LIL elements. It is unlikely that this basalt was derived by fractional crystallization from LIL element depleted tholeiites; instead, the site 2-10 basalt requires a different mantle source. These results imply that the upper Atlantic Ocean basement is dominantly LIL element depleted tholeiite.",
    url = "https://doi.org/10.1029/jb079i035p05507",
    doi = "10.1029/jb079i035p05507",
    openalex = "W2143836610",
    references = "doi101007bf00371276, doi101007bf00372052, doi1010160012821x70900580, doi1010160012825268901475, doi1010160016703768901087, doi1010160016703770901109, doi101016s0012821x6880010x, doi101038242565a0, doi101093petrology33342, doi101139e67004"
}

A suite of 35 fresh basalt glasses collected in >1000-m water depth from 16 localities on or near the Juan de Fuca Ridge and 17 localities elsewhere in the Atlantic and Pacific basins were examined petrographically and with the microprobe. Most are ridge-type tholeiites, but they span the entire range from quartz to nepheline normative varieties. Every sample contains magmatic sulfide. These are globules which occur in clear glass and are composed of finely intergrown pyrrhotite, Cu-Fe sulfide, and frequently pentlandite. Magnetite can be observed in some of the more coarsely intergrown globules. Bulk sulfide compositions generally include >10% Cu + Ni. Petrographie and chemical data suggest that some basalts erupted in a sulfide-saturated state, and the remainder were nearly saturated prior to their being quenched. Glass inclusions in phenocrysts either have compositions similar to matrix glass or are relatively depleted in elements entering host phenocrysts. In either case, their S concentrations are generally similar to or greater than S concentrations of matrix glasses. This and the usually pristine character of fresh basalts with respect to other volatile and trace elements suggest that S in glasses is predominantly juvenile. Concentrations of S dissolved in glass range from 1000 to 1800 ppm and exhibit a nearly perfect linear covariance with Fe concentrations. Because all the glasses contain sulfides this relationship implies that the Fe concentration in the melt controls gas composition with respect to oxygen and sulfur species. However, the moderate range in Fe concentration of the submarine basalts of this study corresponds to a range in ƒs2 and ƒo2 of only about half an order of magnitude each. That is, they all existed under essentially similar ƒs2 and ƒo2 at equivalent temperatures. Fractional crystallization of olivine should cause sulfide liquids to exsolve from the magma, whereas plagioclase fractionation should drive the liquid further from sulfide saturation. However, in more typical fractionation models involving plagioclase and olivine separation in a ratio of ∼10:3, liquid compositions are driven approximately parallel to a sulfide saturation plane if constant temperature is assumed. Thus fractional crystallization need not involve separation of large quantities of sulfide. Many of the most juvenile unfractionated submarine basaltic magmas are probably sulfide saturated and contain ∼900 ppm S.

@article{doi101029jb081i023p04269,
    author = "Mathez, E. A.",
    title = "Sulfur solubility and magmatic sulfides in submarine basalt glass",
    year = "1976",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "A suite of 35 fresh basalt glasses collected in >1000-m water depth from 16 localities on or near the Juan de Fuca Ridge and 17 localities elsewhere in the Atlantic and Pacific basins were examined petrographically and with the microprobe. Most are ridge-type tholeiites, but they span the entire range from quartz to nepheline normative varieties. Every sample contains magmatic sulfide. These are globules which occur in clear glass and are composed of finely intergrown pyrrhotite, Cu-Fe sulfide, and frequently pentlandite. Magnetite can be observed in some of the more coarsely intergrown globules. Bulk sulfide compositions generally include >10\% Cu + Ni. Petrographie and chemical data suggest that some basalts erupted in a sulfide-saturated state, and the remainder were nearly saturated prior to their being quenched. Glass inclusions in phenocrysts either have compositions similar to matrix glass or are relatively depleted in elements entering host phenocrysts. In either case, their S concentrations are generally similar to or greater than S concentrations of matrix glasses. This and the usually pristine character of fresh basalts with respect to other volatile and trace elements suggest that S in glasses is predominantly juvenile. Concentrations of S dissolved in glass range from 1000 to 1800 ppm and exhibit a nearly perfect linear covariance with Fe concentrations. Because all the glasses contain sulfides this relationship implies that the Fe concentration in the melt controls gas composition with respect to oxygen and sulfur species. However, the moderate range in Fe concentration of the submarine basalts of this study corresponds to a range in ƒs2 and ƒo2 of only about half an order of magnitude each. That is, they all existed under essentially similar ƒs2 and ƒo2 at equivalent temperatures. Fractional crystallization of olivine should cause sulfide liquids to exsolve from the magma, whereas plagioclase fractionation should drive the liquid further from sulfide saturation. However, in more typical fractionation models involving plagioclase and olivine separation in a ratio of ∼10:3, liquid compositions are driven approximately parallel to a sulfide saturation plane if constant temperature is assumed. Thus fractional crystallization need not involve separation of large quantities of sulfide. Many of the most juvenile unfractionated submarine basaltic magmas are probably sulfide saturated and contain ∼900 ppm S.",
    url = "https://doi.org/10.1029/jb081i023p04269",
    doi = "10.1029/jb081i023p04269",
    openalex = "W2097756509",
    references = "doi1010160012821x70900373"
}

@article{doi1010160012821x7990013x,
    author = "Sun, Shen‐Su and Nesbitt, R.W. and Sharaskin, A.Ya.",
    title = "Geochemical characteristics of mid-ocean ridge basalts",
    year = "1979",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/0012-821x(79)90013-x",
    doi = "10.1016/0012-821x(79)90013-x",
    openalex = "W2009446672",
    references = "doi101007bf00372052, doi1010160012821x73901295, doi1010160012821x76902193, doi1010160012821x78900535, doi1010160016703768901087, doi1010160016703769901264, doi1010160016703770900098, doi1010160025322764900192, doi101029jb079i035p05507, doi101038242565a0, doi101126science20043451003, openalexw1597830049"
}

Abstract Lead isotopic compositions of young volcanic rocks from different tectonic environments have distinctive characteristics. Their differences are evaluated within the framework of global tectonics and mantle differentiation. Ocean island leads are in general more radiogenic than mid-ocean ridge basalt (m.o.r.b.) leads. They form linear trends on lead isotopic ratio plots. Many of the trends extend toward the field of m.o.r.b. On plots of 207P b /204Pb against 206Pb /204Pb, their slopes are generally close to 0.1. Island arc leads in general are confined between sediment and m.o.r.b. type leads with slopes of ca. 0.30 on a plot of 207P b /204Pb against 206Pb /204Pb. Pb, Sr and Nd isotopic data of Hawaiian volcanics are closely examined. Data from each island support a two-component mixing model. However, there is a lack of full range correlation between islands, indicating heterogeneity in the end members. This mixing model could also be extended to explain data from the Iceland-Reykjanes ridge, and from 45° N on the Atlantic Ridge. The observed chemical and isotopic heterogeneity in young volcanic rocks is considered to be a result of long-term as well as short-term mantle differentiation and mixing. Lead isotopic data from ocean islands are interpreted in terms of mantle evolution models that involve long-term (more than 2 Ga) mantle chemical and isotopic heterogeneity. Incompatible element enriched ‘plume’-type m.o.r.b. have Th/U ratios ca. 3.0 too low and Rb/Sr ratios ca. 0.04 too high to generate the observed 208Pb and 87Sr respectively for long periods of time. Elemental fractionation in the mantle must have occurred very recently. This conclusion also applies to mantle sources for ocean island alkali basalts and nephelinites. Depletion of incompatible elements in m.o.r.b. sources is most probably due to continuous extraction of silicate melt and/or fluid phase from the low-velocity zone throughout geological time. Data on Pb isotopes, Sr isotopes and trace elements on volcanic rocks from island arcs are evaluated in terms of mixing models involving three components derived from (1) sub-arc mantle wedge, (2) dehydration or partial melting of subducted ocean crust, and (3) continental crust contamination. In contrast to the relation between 87Sr/86Sr and 143Nd /144Nd ratios of ocean volcanics, there is a general lack of correlation between Pb and Sr isotopic ratios except that samples with very radiogenic Pb (206Pb /204Pb > 19.5) have low 87Sr/87Sr ratios (0.7028- 0.7035). These samples also have inferred source Th/U ratios (3.0-3.5) not high enough to support long-term growth of 208Pb. Data suggest that their mantle sources have long-term integrated depletion in Rb, Th, U and light r.e.e. High 238U /204Pb (y a)values required by the Pb isotopic data are most probably due to depletion of Pb by separation of a sulphide phase. Relations between Pb, Sr and Nd isotopic ratios of young volcanic rocks could be explained by simultaneous upward migration of silicate and/or fluid phase and downward migration of a sulphide phase in a differentiating mantle.ration of a sulphide phase in a differentiating mantle.

@article{doi101098rsta19800224,
    author = "Sun, Shen‐Su",
    title = "Lead isotopic study of young volcanic rocks from mid-ocean ridges, ocean islands and island arcs",
    year = "1980",
    journal = "Philosophical Transactions of the Royal Society of London Series A Mathematical and Physical Sciences",
    abstract = "Abstract Lead isotopic compositions of young volcanic rocks from different tectonic environments have distinctive characteristics. Their differences are evaluated within the framework of global tectonics and mantle differentiation. Ocean island leads are in general more radiogenic than mid-ocean ridge basalt (m.o.r.b.) leads. They form linear trends on lead isotopic ratio plots. Many of the trends extend toward the field of m.o.r.b. On plots of 207P b /204Pb against 206Pb /204Pb, their slopes are generally close to 0.1. Island arc leads in general are confined between sediment and m.o.r.b. type leads with slopes of ca. 0.30 on a plot of 207P b /204Pb against 206Pb /204Pb. Pb, Sr and Nd isotopic data of Hawaiian volcanics are closely examined. Data from each island support a two-component mixing model. However, there is a lack of full range correlation between islands, indicating heterogeneity in the end members. This mixing model could also be extended to explain data from the Iceland-Reykjanes ridge, and from 45° N on the Atlantic Ridge. The observed chemical and isotopic heterogeneity in young volcanic rocks is considered to be a result of long-term as well as short-term mantle differentiation and mixing. Lead isotopic data from ocean islands are interpreted in terms of mantle evolution models that involve long-term (more than 2 Ga) mantle chemical and isotopic heterogeneity. Incompatible element enriched ‘plume’-type m.o.r.b. have Th/U ratios ca. 3.0 too low and Rb/Sr ratios ca. 0.04 too high to generate the observed 208Pb and 87Sr respectively for long periods of time. Elemental fractionation in the mantle must have occurred very recently. This conclusion also applies to mantle sources for ocean island alkali basalts and nephelinites. Depletion of incompatible elements in m.o.r.b. sources is most probably due to continuous extraction of silicate melt and/or fluid phase from the low-velocity zone throughout geological time. Data on Pb isotopes, Sr isotopes and trace elements on volcanic rocks from island arcs are evaluated in terms of mixing models involving three components derived from (1) sub-arc mantle wedge, (2) dehydration or partial melting of subducted ocean crust, and (3) continental crust contamination. In contrast to the relation between 87Sr/86Sr and 143Nd /144Nd ratios of ocean volcanics, there is a general lack of correlation between Pb and Sr isotopic ratios except that samples with very radiogenic Pb (206Pb /204Pb \> 19.5) have low 87Sr/87Sr ratios (0.7028- 0.7035). These samples also have inferred source Th/U ratios (3.0-3.5) not high enough to support long-term growth of 208Pb. Data suggest that their mantle sources have long-term integrated depletion in Rb, Th, U and light r.e.e. High 238U /204Pb (y a)values required by the Pb isotopic data are most probably due to depletion of Pb by separation of a sulphide phase. Relations between Pb, Sr and Nd isotopic ratios of young volcanic rocks could be explained by simultaneous upward migration of silicate and/or fluid phase and downward migration of a sulphide phase in a differentiating mantle.ration of a sulphide phase in a differentiating mantle.",
    url = "https://doi.org/10.1098/rsta.1980.0224",
    doi = "10.1098/rsta.1980.0224",
    openalex = "W2039100744"
}

Isotopic analyses of 75 samples from the Samail ophiolite indicate that pervasive subsolidus hydrothermal exchange with seawater occurred throughout the upper 75% of this 8‐km‐thick oceanic crustal section; locally, the H 2 O even penetrated down into the tectonized peridotite. Pillow lavas (δ 18 O = 10.7 to 12.7) and sheeted dikes (4.9 to 11.3) are typically enriched in 18 O, and the gabbros (3.7 to 5.9) are depleted in 18 O. In the latter rocks, water/rock ≤ 0.3, and δ 18 O cpx ≈ 2.9 + 0.44 δ 18 O feld, indicating pronounced isotopic disequilibrium. The mineral δ 18 O values approximately follow an exchange (mixing) trajectory which requires that plagioclase must exchange with H 2 O about 3 to 5 times faster than clinopyroxene. The minimum δ 18 O feld value (3.6) occurs about 2.5 km below the diabase‐gabbro contact. Although the gabbro plagioclase appears to be generally petrographically unaltered, its oxygen has been thoroughly exchanged; the absence of hydrous alteration minerals, except for minor talc and/or amphibole, suggests that this exchange occurred at T > 400°–500°C. Plagioclase δ 18 O values increase up section from their minimum values, becoming coincident with primary magmatic values near the gabbro‐sheeted diabase contact and reaching 11.8 in the diabase dikes. These 18 O enrichments in greenschist facies diabases are in part due to exchange with strongly 18 O‐shifted fluids, in addition to retrograde exchange at much lower temperatures. The δ 18 O data and the geometry of the mid‐ocean ridge (MOR) magma chamber require that two decoupled hydrothermal systems must be present during much of the early spreading history of the oceanic crust (approximately the first 10 6 years); one system is centered over the ridge axis and probably involves several convective cells that circulate downward to the roof of the magma chamber, while the other system operates underneath the wings of the chamber, in the layered gabbros. Upward discharge of 18 O‐shifted water into the altered dikes from the lower system, just beyond the distal edge of the magma chamber, combined with the effects of continued low‐ T hydrothermal activity, produces the 18 O enrichments in the dike complex. Integrating δ 18 O as a function of depth for the entire ophiolite establishes (within geologic and analytical error) that the average δ 18 O (5.7 ± 0.2) of the oceanic crust did not change as a result of all these hydrothermal interactions with seawater. Therefore the net change in δ 18 O of seawater was also zero, indicating that seawater is buffered by MOR hydrothermal circulation. Under steady state conditions the overall bulk 18 O fractionation (Δ) between the oceans and primary mid‐ocean ridge basalt magmas is calculated to be +6.1 ± 0.3, implying that seawater has had a constant δ 18 O≈−0.4 (in the absence of transient effects such as continental glaciation). Utilizing these new data on the depth of interaction of seawater with the oceanic crust, numerical modeling of the hydrothermal exchange shows that as long as worldwide spreading rates are greater than 1 km 2 /yr, 18 O buffering of seawater will occur. These conclusions can be extended as far back in time as the Archean (> 2.6 eons) with the proviso that Δ may have been slightly smaller (about 5?) because of the overall higher temperatures that could have prevailed then. Thus ocean water has probably had a constant δ 18 O value of about −1.0 to +1.0 during almost all of earth's history.

@article{doi101029jb086ib04p02737,
    author = "Gregory, Robert T. and Taylor, Hugh P.",
    title = "An oxygen isotope profile in a section of Cretaceous oceanic crust, Samail Ophiolite, Oman: Evidence for δ 18 O buffering of the oceans by deep (>5 km) seawater‐hydrothermal circulation at mid‐ocean ridges",
    year = "1981",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Isotopic analyses of 75 samples from the Samail ophiolite indicate that pervasive subsolidus hydrothermal exchange with seawater occurred throughout the upper 75\% of this 8‐km‐thick oceanic crustal section; locally, the H 2 O even penetrated down into the tectonized peridotite. Pillow lavas (δ 18 O = 10.7 to 12.7) and sheeted dikes (4.9 to 11.3) are typically enriched in 18 O, and the gabbros (3.7 to 5.9) are depleted in 18 O. In the latter rocks, water/rock ≤ 0.3, and δ 18 O cpx ≈ 2.9 + 0.44 δ 18 O feld, indicating pronounced isotopic disequilibrium. The mineral δ 18 O values approximately follow an exchange (mixing) trajectory which requires that plagioclase must exchange with H 2 O about 3 to 5 times faster than clinopyroxene. The minimum δ 18 O feld value (3.6) occurs about 2.5 km below the diabase‐gabbro contact. Although the gabbro plagioclase appears to be generally petrographically unaltered, its oxygen has been thoroughly exchanged; the absence of hydrous alteration minerals, except for minor talc and/or amphibole, suggests that this exchange occurred at T > 400°–500°C. Plagioclase δ 18 O values increase up section from their minimum values, becoming coincident with primary magmatic values near the gabbro‐sheeted diabase contact and reaching 11.8 in the diabase dikes. These 18 O enrichments in greenschist facies diabases are in part due to exchange with strongly 18 O‐shifted fluids, in addition to retrograde exchange at much lower temperatures. The δ 18 O data and the geometry of the mid‐ocean ridge (MOR) magma chamber require that two decoupled hydrothermal systems must be present during much of the early spreading history of the oceanic crust (approximately the first 10 6 years); one system is centered over the ridge axis and probably involves several convective cells that circulate downward to the roof of the magma chamber, while the other system operates underneath the wings of the chamber, in the layered gabbros. Upward discharge of 18 O‐shifted water into the altered dikes from the lower system, just beyond the distal edge of the magma chamber, combined with the effects of continued low‐ T hydrothermal activity, produces the 18 O enrichments in the dike complex. Integrating δ 18 O as a function of depth for the entire ophiolite establishes (within geologic and analytical error) that the average δ 18 O (5.7 ± 0.2) of the oceanic crust did not change as a result of all these hydrothermal interactions with seawater. Therefore the net change in δ 18 O of seawater was also zero, indicating that seawater is buffered by MOR hydrothermal circulation. Under steady state conditions the overall bulk 18 O fractionation (Δ) between the oceans and primary mid‐ocean ridge basalt magmas is calculated to be +6.1 ± 0.3, implying that seawater has had a constant δ 18 O≈−0.4 (in the absence of transient effects such as continental glaciation). Utilizing these new data on the depth of interaction of seawater with the oceanic crust, numerical modeling of the hydrothermal exchange shows that as long as worldwide spreading rates are greater than 1 km 2 /yr, 18 O buffering of seawater will occur. These conclusions can be extended as far back in time as the Archean (> 2.6 eons) with the proviso that Δ may have been slightly smaller (about 5?) because of the overall higher temperatures that could have prevailed then. Thus ocean water has probably had a constant δ 18 O value of about −1.0 to +1.0 during almost all of earth's history.",
    url = "https://doi.org/10.1029/jb086ib04p02737",
    doi = "10.1029/jb086ib04p02737",
    openalex = "W2143045284",
    references = "doi1010079783642666735, doi101007bf00371729, doi1010160012825272900384, doi101016001670377690051x, doi101029jb086ib04p02497, doi101029jb086ib04p02593, doi101086628195, doi101111j174754571996tb00520x, doi101126science177404352, doi101126science20343851073, doi101144gsjgs13360509"
}

The solidus comprises three curves, corresponding to subsolidus mineral assemblages with cusps at about 11 and 26 kbar. A thin layer of basalt was sandwiched between compressed blocks of powdered peridotite minerals and then was equilibrated with its host at melting temperatures. The basalt melt, was completely homogenized with the partial melt in the peridotite matrix within 24 hours. The role of K 2 O in the melting was investigated. Hypothesis of shallow-depth origin for MORBS is supported.--Modified journal abstract.

@article{openalexw1866460059,
    author = "Takahashi, Eiichi and Kushiro, Ikuo",
    title = "Melting of a dry peridotite at high pressures and basalt magma genesis",
    year = "1983",
    journal = "American Mineralogist",
    abstract = "The solidus comprises three curves, corresponding to subsolidus mineral assemblages with cusps at about 11 and 26 kbar. A thin layer of basalt was sandwiched between compressed blocks of powdered peridotite minerals and then was equilibrated with its host at melting temperatures. The basalt melt, was completely homogenized with the partial melt in the peridotite matrix within 24 hours. The role of K 2 O in the melting was investigated. Hypothesis of shallow-depth origin for MORBS is supported.--Modified journal abstract.",
    openalex = "W1866460059",
    references = "doi1010160012825268901475, doi101093petrology12121"
}

@article{doi1010160009254186900045,
    author = "Meschede, Martín",
    title = "A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb1bZr1bY diagram",
    year = "1986",
    journal = "Chemical Geology",
    url = "https://doi.org/10.1016/0009-2541(86)90004-5",
    doi = "10.1016/0009-2541(86)90004-5",
    openalex = "W2088496938",
    references = "doi1010160012821x70900580, doi1010160012821x7990013x, doi1010160016703778902223"
}

Precise new analyses of ferrous and total iron for 78 hand-picked mid-ocean ridge basalt (MORB) glasses constrain the redox states of MORB magmas, and the systematics of those redox states with respect to geography and chemistry. The data indicate that MORB magmas at the point of eruption include some of the most reduced terrestrial lavas yet analyzed. Irrespective of their tectonic setting, geographic setting or chemical type, quench glasses from the outer surfaces of MORB lavas have Fe3+/ΣFe ratios of 0.07 ± 0.03 (2σ), equivalent to relative oxygen fugacities 1–2 log10 units below the fayalite-magnetite-quartz buffer (FMQ). These reduced values contrast markedly with those of cogenetic whole rocks, even for samples from the same pillow. Pillow cores (including virtually all published whole rock analyses) typically have Fe3+/ΣFe close to 0.15, equivalent to oxygen fugacities close to FMQ. The post-eruptive oxidation responsible for this contrast apparently occurs rapidly, while the lava is still partially molten, most likely as a result of hydrogen loss. The striking contrast between glass and whole rock data suggests that two common assumptions with respect to treatment of MORB are inappropriate: (1) assumption of Fe3+/ΣFe close to 0.15 for calculating norms and magnesium numbers; and (2) assumption of FMQ conditions for experimental studies of MORB crystallization. Oxygen fugacities in the mantle source regions of MORB have also been assumed to be close to FMQ. It is likely that, redox states determined from wholly or partially crystalline lavas are generally not representative of magmatic values. The new data reported herein define a new and rigidupper limit for the oxidation state of the sub-oceanic mantle.

@article{doi1010160012821x86901950,
    author = "Christie, David M. and Carmichael, I. S. E. and Langmuir, C. H.",
    title = "Oxidation states of mid-ocean ridge basalt glasses",
    year = "1986",
    journal = "Earth and Planetary Science Letters",
    abstract = "Precise new analyses of ferrous and total iron for 78 hand-picked mid-ocean ridge basalt (MORB) glasses constrain the redox states of MORB magmas, and the systematics of those redox states with respect to geography and chemistry. The data indicate that MORB magmas at the point of eruption include some of the most reduced terrestrial lavas yet analyzed. Irrespective of their tectonic setting, geographic setting or chemical type, quench glasses from the outer surfaces of MORB lavas have Fe3+/ΣFe ratios of 0.07 ± 0.03 (2σ), equivalent to relative oxygen fugacities 1–2 log10 units below the fayalite-magnetite-quartz buffer (FMQ). These reduced values contrast markedly with those of cogenetic whole rocks, even for samples from the same pillow. Pillow cores (including virtually all published whole rock analyses) typically have Fe3+/ΣFe close to 0.15, equivalent to oxygen fugacities close to FMQ. The post-eruptive oxidation responsible for this contrast apparently occurs rapidly, while the lava is still partially molten, most likely as a result of hydrogen loss. The striking contrast between glass and whole rock data suggests that two common assumptions with respect to treatment of MORB are inappropriate: (1) assumption of Fe3+/ΣFe close to 0.15 for calculating norms and magnesium numbers; and (2) assumption of FMQ conditions for experimental studies of MORB crystallization. Oxygen fugacities in the mantle source regions of MORB have also been assumed to be close to FMQ. It is likely that, redox states determined from wholly or partially crystalline lavas are generally not representative of magmatic values. The new data reported herein define a new and rigidupper limit for the oxidation state of the sub-oceanic mantle.",
    url = "https://doi.org/10.1016/0012-821x(86)90195-0",
    doi = "10.1016/0012-821x(86)90195-0",
    openalex = "W1970548478"
}

Deep Sea Drilling Project hole 504B penetrates 1076 m into oceanic layer 2 and is the first hole to pass through the transition from pillow basalts altered at low temperatures into hydrothermally metamorphosed sheeted dikes. Alteration of the crust at site 504 occurred in four stages, related to the movement of the crust away from the spreading axis: (1) Dikes reacted with seawater (200–>300°C) in the upwelling zone of an axial convection cell at the spreading axis, resulting in the formation of greenschist facies parageneses in veins and host rocks. Mixing of the upwelling hydrothermal fluids with seawater circulating in the overlying more permeable pillow section occurred in the upper part of the lithologic transition zone, causing a steep temperature gradient at the base of the pillow section. Secondary minerals formed in the lower pillow section from the resultant reducing “mixed” fluids at temperatures of around 100°C. At the same time, the initial effects of “seafloor weathering” began in the upper 320 m of the pillow section at low temperatures (<50°C) and under conditions of open circulation of oxidizing seawater. (2) Following refracturing of the dikes, a second stage of axial upwelling occurred; hydrothermal fluids (200°–380°C) were probably similar to those presently sampled from spreading ridges on the seafloor. Mixing of these fluids with seawater in the lithologic transition zone caused deposition of quartz, epidote, and sulfides in veins and formation of a sulfide‐rich stockworklike zone within this transition zone. Alteration of the pillow section proceeded under the prior conditions, with the effects of seafloor weathering extending progressively downward into the crust. (3) Seawater recharge penetrated to depths of at least 1075.5 m subbasement and deposited anhydrite locally in veins. (4) Off‐axis alteration of the dikes was characterized by formation of zeolites, calcite, and prehnite in veins and host rocks from more highly evolved and lower temperature (100°–250°C) fluids. Alteration in the upper pillow section evolved from “seafloor weathering” conditions to more reducing and rock‐dominated, as cracks in the basalt were sealed with secondary minerals and the basement was covered with a layer of sediment. Zeolites and calcite were the last phases to form throughout the pillow section. Sealing of the crust to convective cooling also allowed conductive reheating of the crust from below. Calculations of seawater‐crustal chemical fluxes from whole rock data are complicated by the low recovery and heterogeneity of alteration effects but indicate that basalt‐seawater interactions are a sink for seawater Mg and K and a source for Si and Ca.

@article{doi101029jb091ib10p10309,
    author = "Alt, Jeffrey C. and Honnorez, José and Laverne, Christine and Emmermann, Rolf",
    title = "Hydrothermal alteration of a 1 km section through the upper oceanic crust, Deep Sea Drilling Project Hole 504B: Mineralogy, chemistry and evolution of seawater‐basalt interactions",
    year = "1986",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Deep Sea Drilling Project hole 504B penetrates 1076 m into oceanic layer 2 and is the first hole to pass through the transition from pillow basalts altered at low temperatures into hydrothermally metamorphosed sheeted dikes. Alteration of the crust at site 504 occurred in four stages, related to the movement of the crust away from the spreading axis: (1) Dikes reacted with seawater (200–>300°C) in the upwelling zone of an axial convection cell at the spreading axis, resulting in the formation of greenschist facies parageneses in veins and host rocks. Mixing of the upwelling hydrothermal fluids with seawater circulating in the overlying more permeable pillow section occurred in the upper part of the lithologic transition zone, causing a steep temperature gradient at the base of the pillow section. Secondary minerals formed in the lower pillow section from the resultant reducing “mixed” fluids at temperatures of around 100°C. At the same time, the initial effects of “seafloor weathering” began in the upper 320 m of the pillow section at low temperatures (<50°C) and under conditions of open circulation of oxidizing seawater. (2) Following refracturing of the dikes, a second stage of axial upwelling occurred; hydrothermal fluids (200°–380°C) were probably similar to those presently sampled from spreading ridges on the seafloor. Mixing of these fluids with seawater in the lithologic transition zone caused deposition of quartz, epidote, and sulfides in veins and formation of a sulfide‐rich stockworklike zone within this transition zone. Alteration of the pillow section proceeded under the prior conditions, with the effects of seafloor weathering extending progressively downward into the crust. (3) Seawater recharge penetrated to depths of at least 1075.5 m subbasement and deposited anhydrite locally in veins. (4) Off‐axis alteration of the dikes was characterized by formation of zeolites, calcite, and prehnite in veins and host rocks from more highly evolved and lower temperature (100°–250°C) fluids. Alteration in the upper pillow section evolved from “seafloor weathering” conditions to more reducing and rock‐dominated, as cracks in the basalt were sealed with secondary minerals and the basement was covered with a layer of sediment. Zeolites and calcite were the last phases to form throughout the pillow section. Sealing of the crust to convective cooling also allowed conductive reheating of the crust from below. Calculations of seawater‐crustal chemical fluxes from whole rock data are complicated by the low recovery and heterogeneity of alteration effects but indicate that basalt‐seawater interactions are a sink for seawater Mg and K and a source for Si and Ca.",
    url = "https://doi.org/10.1029/jb091ib10p10309",
    doi = "10.1029/jb091ib10p10309",
    openalex = "W2118168812",
    references = "doi1010160009254167900046, doi1010160012821x7990061x, doi1010160012821x82901613, doi1010160016703783901357, doi1010160016703785902224, doi1010160025322771900533, doi101029jb086ib04p02737, doi101126science20343851073, doi101146annurevea10050182001103, doi101180minmag197804232421, doi101180mono5"
}

Regional averages of the major element chemistry of ocean ridge basalts, corrected for low‐pressure fractionation, correlate with regional averages of axial depth for the global system of ocean ridges, including hot spots, cold spots, and back arc basins, as well as “normal” ocean ridges. Quantitative consideration of the variations of each major element during melting of the mantle suggests that the global major element variations can be accounted for by ∼8–20% melting of the mantle at associated mean pressures of 5–16 kbar. The lowest extents of melting occur at shallowest depths in the mantle and are associated with the deepest ocean ridges. Calculated mean primary magmas show a range in composition from 10 to 15 wt % MgO, and the primary magma compositions correlate with depth. Data for Sm, Yb, Sc, and Ni are consistent with the major elements, but highly incompatible elements show more complicated behavior. In addition, some hot spots have anomalous chemistry, suggesting major element heterogeneity. Thermal modeling of mantle ascending adiabatically beneath the ridge is consistent with the chemical data and melting calculations, provided the melt is tapped from throughout the ascending mantle column. The thermal modeling independently predicts the observed relationships among basalt chemistry, ridge depth, and crustal thickness resulting from temperature variations in the mantle. Beneath the shallowest and deepest ridge axes, temperature differences of approximately 250°C in the subsolidus mantle are required to account for the global systematics.

@article{doi101029jb092ib08p08089,
    author = "Klein, E. M. and Langmuir, C. H.",
    title = "Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness",
    year = "1987",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Regional averages of the major element chemistry of ocean ridge basalts, corrected for low‐pressure fractionation, correlate with regional averages of axial depth for the global system of ocean ridges, including hot spots, cold spots, and back arc basins, as well as “normal” ocean ridges. Quantitative consideration of the variations of each major element during melting of the mantle suggests that the global major element variations can be accounted for by ∼8–20\% melting of the mantle at associated mean pressures of 5–16 kbar. The lowest extents of melting occur at shallowest depths in the mantle and are associated with the deepest ocean ridges. Calculated mean primary magmas show a range in composition from 10 to 15 wt \% MgO, and the primary magma compositions correlate with depth. Data for Sm, Yb, Sc, and Ni are consistent with the major elements, but highly incompatible elements show more complicated behavior. In addition, some hot spots have anomalous chemistry, suggesting major element heterogeneity. Thermal modeling of mantle ascending adiabatically beneath the ridge is consistent with the chemical data and melting calculations, provided the melt is tapped from throughout the ascending mantle column. The thermal modeling independently predicts the observed relationships among basalt chemistry, ridge depth, and crustal thickness resulting from temperature variations in the mantle. Beneath the shallowest and deepest ridge axes, temperature differences of approximately 250°C in the subsolidus mantle are required to account for the global systematics.",
    url = "https://doi.org/10.1029/jb092ib08p08089",
    doi = "10.1029/jb092ib08p08089",
    openalex = "W1990814837",
    references = "doi101038242565a0, doi101111j1365246x1971tb02190x"
}

This Initial Reports volume covers Leg 111 of the cruises of the Drilling Vessel JOIDES Resolution, Bridgetown, Barbados, to Callao, Peru, Sites 504, 677, and 678, 16 August 1986–20 October 1986. Technical difficulties associated with deep penetration hampered earlier DSDP attempts to document the lithostratigraphy, alteration history, and geophysical properties deep within the oceanic crust and to test the validity of the inferred analogous relationship to ophiolites. Hole 504B, located in 5.9-Ma crust approximately 200 km south of the Costa Rica Rift, was a unique exception, where DSDP Legs 69, 70, and 83 cased through 274.5 m of sediment and cored 1075.5 m of the basement; 571.1 m of pillow lavas and minor flows of oceanic layers 2A and 2B underlain by a 209-m zone of transition into 295 m of sheeted dikes and massive units of layer 2C. During Leg 111, Hole 504B was deepened by 212.3 m to a total depth of 1,562.3 mbsf (1,287.8 m into basement), recovering slightly altered, phyric to highly phyric, fine- to medium-grained olivine tholeiitic basalts, chemically similar to basalt recovered from the shallower basement DSDP cores. Deep in the hole, the temperature gradient is linear, decreasing from 116°C/km in the pillow lavas to 61°C/km in the dikes. The chemical composition of sampled borehole waters is apparently controlled by vertical convection in the borehole and exchange of borehole water with the ocean bottom water that flows downhole into the upper 100-200 m of basement. Hole 504B was also logged with an extensive set of tools and, when calibrated against the properties of the recovered basalt, yielded a nearly continuous geophysical, geochemical, and lithological characterization of the basement, documenting that alteration products are tightly confined to fractures along boundaries between individual extrusive or intrusive events and that the boundary between pillow lavas and dikes is a relic of early listric faulting between pillows over the dikes in the rift valley. Sediment coring was also conducted at local heat-flow maximum and minimum sites near Hole 504B (Sites 678 and 677, respectively) to enable high-resolution studies of the Plio-Pleistocene biostratigraphy and chemical studies of the pore waters to differentiate advective from diffusive exchange between the ocean-bottom water and the basement through the sediment cover. The profiles of sediment pore-water composition versus depth differ greatly between these sites and indicate that ocean-bottom seawater flows down through the 300-m-thick sediment into basement at the low heat-flow site, whereas significantly altered seawater formed in basement upwells through the 180-m-thick sediment into overlying seawater at the high heat-flow site; rates of flows are estimated at a few mm/yr at both sites. The similarity in pore-water composition from basal alteration products at both sites suggests that the advective flow rates in sediment are negligible compared to those in basement.

@misc{becker1988proceedings,
    author = "Becker, K. and Sakai, H. and Party, The Leg 111 Science",
    title = "Proceedings of the Ocean Drilling Program Volume 111 Initial Reports: Costa Rica Rift, Sites 504, 677, and 678",
    year = "1988",
    publisher = "Ocean Drilling Program",
    abstract = "This Initial Reports volume covers Leg 111 of the cruises of the Drilling Vessel JOIDES Resolution, Bridgetown, Barbados, to Callao, Peru, Sites 504, 677, and 678, 16 August 1986–20 October 1986. Technical difficulties associated with deep penetration hampered earlier DSDP attempts to document the lithostratigraphy, alteration history, and geophysical properties deep within the oceanic crust and to test the validity of the inferred analogous relationship to ophiolites. Hole 504B, located in 5.9-Ma crust approximately 200 km south of the Costa Rica Rift, was a unique exception, where DSDP Legs 69, 70, and 83 cased through 274.5 m of sediment and cored 1075.5 m of the basement; 571.1 m of pillow lavas and minor flows of oceanic layers 2A and 2B underlain by a 209-m zone of transition into 295 m of sheeted dikes and massive units of layer 2C. During Leg 111, Hole 504B was deepened by 212.3 m to a total depth of 1,562.3 mbsf (1,287.8 m into basement), recovering slightly altered, phyric to highly phyric, fine- to medium-grained olivine tholeiitic basalts, chemically similar to basalt recovered from the shallower basement DSDP cores. Deep in the hole, the temperature gradient is linear, decreasing from 116°C/km in the pillow lavas to 61°C/km in the dikes. The chemical composition of sampled borehole waters is apparently controlled by vertical convection in the borehole and exchange of borehole water with the ocean bottom water that flows downhole into the upper 100-200 m of basement. Hole 504B was also logged with an extensive set of tools and, when calibrated against the properties of the recovered basalt, yielded a nearly continuous geophysical, geochemical, and lithological characterization of the basement, documenting that alteration products are tightly confined to fractures along boundaries between individual extrusive or intrusive events and that the boundary between pillow lavas and dikes is a relic of early listric faulting between pillows over the dikes in the rift valley. Sediment coring was also conducted at local heat-flow maximum and minimum sites near Hole 504B (Sites 678 and 677, respectively) to enable high-resolution studies of the Plio-Pleistocene biostratigraphy and chemical studies of the pore waters to differentiate advective from diffusive exchange between the ocean-bottom water and the basement through the sediment cover. The profiles of sediment pore-water composition versus depth differ greatly between these sites and indicate that ocean-bottom seawater flows down through the 300-m-thick sediment into basement at the low heat-flow site, whereas significantly altered seawater formed in basement upwells through the 180-m-thick sediment into overlying seawater at the high heat-flow site; rates of flows are estimated at a few mm/yr at both sites. The similarity in pore-water composition from basal alteration products at both sites suggests that the advective flow rates in sediment are negligible compared to those in basement.",
    url = "https://zenodo.org/doi/10.5281/zenodo.18470959",
    doi = "10.5281/zenodo.18470959",
    openalex = "W7152686680"
}

Dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of H 2 O in the production of magmas at convergent plate boundaries. The subduction of oceanic lithosphere, occurring with increasing pressures and rising temperatures, causes liberation of H 2 O from the slab. Amphibole, which can be stable to the highest PT conditions among hydrous phases in the slab, decomposes at around 90 km depth. It follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab‐derived H 2 O is not a direct trigger for the production of arc magmas. Instead, the H 2 O released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals (serpentine, talc, amphibole, chlorite, and phlogopite). This hydrated peridotite is dragged downward on the slab toward higher PT regions and releases H 2 O to shallower potential magma source regions in the mantle wedge. Combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge, it is concluded that those minerals decompose beneath the forearc region. On the other hand, high PT experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front. Phlogopite in the peridotite decomposes to release H 2 O at a deeper level (about 200 km). H 2 O liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites. Along with the migration of H 2 O through the above processes, subduction components, especially large ion lithophile elements, can be overprinted on the magma source region, which governs the geochemical characteristics of arc magmas.

@article{doi101029jb094ib04p04697,
    author = "Tatsumi, Yoshiyuki",
    title = "Migration of fluid phases and genesis of basalt magmas in subduction zones",
    year = "1989",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of H 2 O in the production of magmas at convergent plate boundaries. The subduction of oceanic lithosphere, occurring with increasing pressures and rising temperatures, causes liberation of H 2 O from the slab. Amphibole, which can be stable to the highest PT conditions among hydrous phases in the slab, decomposes at around 90 km depth. It follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab‐derived H 2 O is not a direct trigger for the production of arc magmas. Instead, the H 2 O released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals (serpentine, talc, amphibole, chlorite, and phlogopite). This hydrated peridotite is dragged downward on the slab toward higher PT regions and releases H 2 O to shallower potential magma source regions in the mantle wedge. Combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge, it is concluded that those minerals decompose beneath the forearc region. On the other hand, high PT experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front. Phlogopite in the peridotite decomposes to release H 2 O at a deeper level (about 200 km). H 2 O liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites. Along with the migration of H 2 O through the above processes, subduction components, especially large ion lithophile elements, can be overprinted on the magma source region, which governs the geochemical characteristics of arc magmas.",
    url = "https://doi.org/10.1029/jb094ib04p04697",
    doi = "10.1029/jb094ib04p04697",
    openalex = "W1997048572",
    references = "doi1010160009254180901072"
}

When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that the production of magmatically active rifted margins and the effusion of flood basalts onto the adjacent continents can be explained by a simple model of rifting above a thermal anomaly in the underlying mantle. The igneous rocks are generated by decompression melting of hot asthenospheric mantle as it rises passively beneath the stretched and thinned lithosphere. Mantle plumes generate regions beneath the lithosphere typically 2000 km in diameter with temperatures raised 100–200°C above normal. These relatively small mantle temperature increases are sufficient to cause the generation of huge quantities of melt by decompression: an increase of 100°C above normal doubles the amount of melt whilst a 200°C increase can quadruple it. In the first part of this paper we develop our model to predict the effects of melt generation for varying amounts of stretching with a range of mantle temperatures. The melt generated by decompression migrates rapidly upward, until it is either extruded as basalt flows or intruded into or beneath the crust. Addition of large quantities of new igneous rock to the crust considerably modifies the subsidence in rifted regions. Stretching by a factor of 5 above normal temperature mantle produces immediate subsidence of more than 2 km in order to maintain isostatic equilibrium. If the mantle is 150°C or more hotter than normal, the same amount of stretching results in uplift above sea level. Melt generated from abnormally hot mantle is more magnesian rich than that produced from normal temperature mantle. This causes an increase in seismic velocity of the igneous rocks emplaced in the crust, from typically 6.8 km/s for normal mantle temperatures to 7.2 km/s or higher. There is a concomitant density increase. In the second part of the paper we review volcanic continental margins and flood basalt provinces globally and show that they are always related to the thermal anomaly created by a nearby mantle plume. Our model of melt generation in passively upwelling mantle beneath rifting continental lithosphere can explain all the major rift‐related igneous provinces. These include the Tertiary igneous provinces of Britain and Greenland and the associated volcanic continental margins caused by opening of the North Atlantic in the presence of the Iceland plume; the Paraná and parts of the Karoo flood basalts together with volcanic continental margins generated when the South Atlantic opened; the Deccan flood basalts of India and the Seychelles‐Saya da Malha volcanic province created when the Seychelles split off India above the Réunion hot spot; the Ethiopian and Yemen Traps created by rifting of the Red Sea and Gulf of Aden region above the Afar hot spot; and the oldest and probably originally the largest flood basalt province of the Karoo produced when Gondwana split apart. New continental splits do not always occur above thermal anomalies in the mantle caused by plumes, but when they do, huge quantities of igneous material are added to the continental crust. This is an important method of increasing the volume of the continental crust through geologic time.

@article{doi101029jb094ib06p07685,
    author = "White, R. S. and McKenzie, Dan",
    title = "Magmatism at rift zones: The generation of volcanic continental margins and flood basalts",
    year = "1989",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that the production of magmatically active rifted margins and the effusion of flood basalts onto the adjacent continents can be explained by a simple model of rifting above a thermal anomaly in the underlying mantle. The igneous rocks are generated by decompression melting of hot asthenospheric mantle as it rises passively beneath the stretched and thinned lithosphere. Mantle plumes generate regions beneath the lithosphere typically 2000 km in diameter with temperatures raised 100–200°C above normal. These relatively small mantle temperature increases are sufficient to cause the generation of huge quantities of melt by decompression: an increase of 100°C above normal doubles the amount of melt whilst a 200°C increase can quadruple it. In the first part of this paper we develop our model to predict the effects of melt generation for varying amounts of stretching with a range of mantle temperatures. The melt generated by decompression migrates rapidly upward, until it is either extruded as basalt flows or intruded into or beneath the crust. Addition of large quantities of new igneous rock to the crust considerably modifies the subsidence in rifted regions. Stretching by a factor of 5 above normal temperature mantle produces immediate subsidence of more than 2 km in order to maintain isostatic equilibrium. If the mantle is 150°C or more hotter than normal, the same amount of stretching results in uplift above sea level. Melt generated from abnormally hot mantle is more magnesian rich than that produced from normal temperature mantle. This causes an increase in seismic velocity of the igneous rocks emplaced in the crust, from typically 6.8 km/s for normal mantle temperatures to 7.2 km/s or higher. There is a concomitant density increase. In the second part of the paper we review volcanic continental margins and flood basalt provinces globally and show that they are always related to the thermal anomaly created by a nearby mantle plume. Our model of melt generation in passively upwelling mantle beneath rifting continental lithosphere can explain all the major rift‐related igneous provinces. These include the Tertiary igneous provinces of Britain and Greenland and the associated volcanic continental margins caused by opening of the North Atlantic in the presence of the Iceland plume; the Paraná and parts of the Karoo flood basalts together with volcanic continental margins generated when the South Atlantic opened; the Deccan flood basalts of India and the Seychelles‐Saya da Malha volcanic province created when the Seychelles split off India above the Réunion hot spot; the Ethiopian and Yemen Traps created by rifting of the Red Sea and Gulf of Aden region above the Afar hot spot; and the oldest and probably originally the largest flood basalt province of the Karoo produced when Gondwana split apart. New continental splits do not always occur above thermal anomalies in the mantle caused by plumes, but when they do, huge quantities of igneous material are added to the continental crust. This is an important method of increasing the volume of the continental crust through geologic time.",
    url = "https://doi.org/10.1029/jb094ib06p07685",
    doi = "10.1029/jb094ib06p07685",
    openalex = "W2022648729",
    references = "alvarez1980extraterrestrial, doi1010160012821x78900717, doi101029jb082i005p00803, doi101029jb092ib08p08089, doi101029rg013i003p00001, doi101029rg018i001p00269, doi101038230042a0, doi101038274544a0, doi101038326143a0, doi101093petrology253713, doi101093petrology293625, doi101126science20844481095, doi101126science22746911161, doi101126science23848311237, doi101139e85009, doi101144gslmem19850100115, doi10130683d923ed16c711d78645000102c1865d, openalexw2989049194"
}

Summary The SW Indian and American-Antarctic Ridges are two of the world’s slowest spreading ocean ridges (less than 1 cm a −1), making them the low end-members for rate of ocean ridge magma supply. Two-thirds of the rocks dredged at the numerous large offset transforms along the ridges are residual mantle peridotites. Gabbroic rocks, however, representing layer 3 and possible palaeo-magma chambers are rare. This suggests a highly segmented crustal structure, with anomalously thin crust near fracture zones that may consist of only a thin veneer of pillow basalt erupted over mantle peridotite. The dredged peridotites underwent high degrees of melting, spanning the range believed to produce abyssal basalt. Their depleted compositions show that the melt was almost entirely removed. At the same time, the spatially associated basalts have a large range of compositions, similar to those from the rift valleys, requiring extensive shallow-level fractional crystallization. Since there is little evidence for magma chambers at these fracture zones, it is concluded that melts formed in the underlying mantle flowed laterally through the mantle beneath the crust towards a magmatic centre at the mid-point of an adjacent ridge segment. Magma was then subsequently intruded down the rift valley fissure system from the magmatic centre to erupt onto the fracture zone floor. Alternatively, the melt was drained from a mantle diapir beneath the midpoint of a ridge segment, prior to lateral flow of the residual peridotite beneath the ridge axis to the fracture zone. These processes suggest behaviour of the partially molten layer beneath ocean ridges analogous to Rayleigh-Taylor fluid instability, where a light less viscous fluid layer floating upwards in a denser medium goes unstable and drains at regularly spaced points into protrusions which rise rapidly to the surface. Evidence for such dynamically driven non-uniform melt flow in the mantle is seen in locally-abundant plagioclase peridotites, where the plagioclase crystallized from impregnated trapped melt. These rocks can contain up to 30% trapped melt, contrasting sharply with the typical abyssal peridotite which contains virtually none. Basalts erupted along these ridges provide a classic case of trace- and major-element decoupling during magma genesis. Despite trace-element and isotopic diversity, basalts from individual ridge segments were derived from primary magmas with similar major-element compositions. These observations can be explained if melt flows locally through the depleted mantle at the end of melting towards the midpoint of a ridge segment. This would cause melts originating at different points in an initially heterogeneous mantle to migrate through and equilibrate with the same section of mantle immediately prior to segregation—which, for the most part, would homogenize the melt’s major-element compositions. However, by virtue of the lever rule, this would have little effect on critical incompatible-trace-element or isotopic ratios of the migrating melts because of the very low incompatible-trace-element content of residual peridotite. Ocean ridges, then, appear to be marked by strings of regularly spaced volcanic centres overlying instability points in the partially molten upwelling asthenosphere much as has been postulated for arc volcanism and early continental rifting. Unlike arcs, the asthenosphere upwells to the base of the crust and the magmatic centres undergo continuous extension. Thus, large volcanoes are not constructed, and instead, ribbons of basaltic crust form parallel to the spreading direction. This is most evident at the SW Indian and American-Antarctic Ridges because of their highly attenuated magma supply. Where the magma supply is more robust and the magma chambers are correspondingly larger, the chambers may merge and eliminate the surficial morphological and chemical expression of punctuated magmatism at ocean ridges.

@article{doi101144gslsp19890420106,
    author = "Dick, H. J.",
    title = "Abyssal peridotites, very slow spreading ridges and ocean ridge magmatism",
    year = "1989",
    journal = "Geological Society London Special Publications",
    abstract = "Summary The SW Indian and American-Antarctic Ridges are two of the world’s slowest spreading ocean ridges (less than 1 cm a −1), making them the low end-members for rate of ocean ridge magma supply. Two-thirds of the rocks dredged at the numerous large offset transforms along the ridges are residual mantle peridotites. Gabbroic rocks, however, representing layer 3 and possible palaeo-magma chambers are rare. This suggests a highly segmented crustal structure, with anomalously thin crust near fracture zones that may consist of only a thin veneer of pillow basalt erupted over mantle peridotite. The dredged peridotites underwent high degrees of melting, spanning the range believed to produce abyssal basalt. Their depleted compositions show that the melt was almost entirely removed. At the same time, the spatially associated basalts have a large range of compositions, similar to those from the rift valleys, requiring extensive shallow-level fractional crystallization. Since there is little evidence for magma chambers at these fracture zones, it is concluded that melts formed in the underlying mantle flowed laterally through the mantle beneath the crust towards a magmatic centre at the mid-point of an adjacent ridge segment. Magma was then subsequently intruded down the rift valley fissure system from the magmatic centre to erupt onto the fracture zone floor. Alternatively, the melt was drained from a mantle diapir beneath the midpoint of a ridge segment, prior to lateral flow of the residual peridotite beneath the ridge axis to the fracture zone. These processes suggest behaviour of the partially molten layer beneath ocean ridges analogous to Rayleigh-Taylor fluid instability, where a light less viscous fluid layer floating upwards in a denser medium goes unstable and drains at regularly spaced points into protrusions which rise rapidly to the surface. Evidence for such dynamically driven non-uniform melt flow in the mantle is seen in locally-abundant plagioclase peridotites, where the plagioclase crystallized from impregnated trapped melt. These rocks can contain up to 30\% trapped melt, contrasting sharply with the typical abyssal peridotite which contains virtually none. Basalts erupted along these ridges provide a classic case of trace- and major-element decoupling during magma genesis. Despite trace-element and isotopic diversity, basalts from individual ridge segments were derived from primary magmas with similar major-element compositions. These observations can be explained if melt flows locally through the depleted mantle at the end of melting towards the midpoint of a ridge segment. This would cause melts originating at different points in an initially heterogeneous mantle to migrate through and equilibrate with the same section of mantle immediately prior to segregation—which, for the most part, would homogenize the melt’s major-element compositions. However, by virtue of the lever rule, this would have little effect on critical incompatible-trace-element or isotopic ratios of the migrating melts because of the very low incompatible-trace-element content of residual peridotite. Ocean ridges, then, appear to be marked by strings of regularly spaced volcanic centres overlying instability points in the partially molten upwelling asthenosphere much as has been postulated for arc volcanism and early continental rifting. Unlike arcs, the asthenosphere upwells to the base of the crust and the magmatic centres undergo continuous extension. Thus, large volcanoes are not constructed, and instead, ribbons of basaltic crust form parallel to the spreading direction. This is most evident at the SW Indian and American-Antarctic Ridges because of their highly attenuated magma supply. Where the magma supply is more robust and the magma chambers are correspondingly larger, the chambers may merge and eliminate the surficial morphological and chemical expression of punctuated magmatism at ocean ridges.",
    url = "https://doi.org/10.1144/gsl.sp.1989.042.01.06",
    doi = "10.1144/gsl.sp.1989.042.01.06",
    openalex = "W2080973789",
    references = "doi101007bf00300398, doi101086625580"
}

Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.

@article{doi101144gslsp19890420119,
    author = "Sun, Shen‐Su and McDonough, W. F.",
    title = "Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes",
    year = "1989",
    journal = "Geological Society London Special Publications",
    abstract = "Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1\% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.",
    url = "https://doi.org/10.1144/gsl.sp.1989.042.01.19",
    doi = "10.1144/gsl.sp.1989.042.01.19",
    openalex = "W2138522501",
    references = "doi1010160012821x7990013x, doi1010160012821x82901613, doi1010160012821x86900385, doi1010160016703768901087, doi1010160016703784904150, doi1010160031920186900932, doi1010160040195181902134, doi101038297391a0, doi101038309753a0, doi101093petrology193463, doi101093petrology253713, doi101098rsta19800224, doi101146annurevea14050186002425"
}

Geophysical evidence precludes the existence of a large, mainly molten magma chamber beneath portions of the East Pacific Rise (EPR). A reasonable model, consistent with these data, involves a thin (tens to hundreds of meters high), narrow (<1–2 km wide) melt lens overlying a zone of crystal mush that is in turn surrounded by a transition zone of mostly solidified crust with isolated pockets of magma. Evidence from the superfast spreading portion of the EPR suggests that the composition of the melt lens is mainly moderately fractionated ferrobasalt. These results have important implications for magmatic processes occurring beneath mid‐ocean ridges and are consistent with a model that effectively separates the processes of magma mixing and fractionation into different parts of a composite magma chamber. Magma mixing, as evidenced by disequilibrium relations between host liquids and included phenocrysts, is especially apparent in samples from low magma supply ridges and probably mainly arises from interactions between crystals of the mush zone and new injections of primitive magma rising out of the mantle. Magmatic differentiation beneath mid‐ocean ridges occurs in two parts. Migration of melts through the transition and mush zones can produce chemical trends consistent with in situ fractionation processes. Segregation of melt into molten horizons near the top of a composite magma chamber promotes the more extensive differentiation characteristic of fast spreading ridges. The optimum conditions for the formation of highly differentiated abyssal lavas is where small, discontinuous melt lenses occur, such as at intermediate spreading rates, in the vicinity of propagating rifts, and near ridge offsets at fast spreading ridges. Along‐axis homogenization of subaxial magma is inhibited by the thin, high aspect ratio of the melt lens and by the high viscosities expected in the mush and transition zones. Low magma supply ridges are unlikely to be underlain by eruptable magma in a steady state sense, and eruptions at slow spreading ridges are likely to be closely coupled in time to injection events of new magma from the mantle. Extensional events at high magma supply ridges, which are more likely to be underlain by significant volumes of low‐viscosity melt, can produce eruptions without requiring associated injection events. The critical magma supply necessary for the development of a melt lens near the top of a composite magma chamber is similar to that of normal ridges spreading at rates of about 50–70 mm/yr, a rate approximately corresponding to that marking an abrupt change in the morphology and gravity signal at the ridge axis. A composite magma chamber model can explain several previous enigmas concerning mid‐ocean ridge basalts, including why slow spreading ridges dominantly erupt a narrow range of relatively undifferentiated lavas, why magma mixing is most evident in lavas erupted from slow spreading ridges, why fast spreading ridges erupt a wide range of generally more differentiated compositions, why bimodal lava populations occur in the vicinity of some propagating rifts, and how along‐axis geochemical segmentation can occur at a scale shorter than the major tectonic segmentation of ridge axes.

@article{doi10102991jb02508,
    author = "Sinton, John M. and Detrick, R. S.",
    title = "Mid‐ocean ridge magma chambers",
    year = "1992",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Geophysical evidence precludes the existence of a large, mainly molten magma chamber beneath portions of the East Pacific Rise (EPR). A reasonable model, consistent with these data, involves a thin (tens to hundreds of meters high), narrow (<1–2 km wide) melt lens overlying a zone of crystal mush that is in turn surrounded by a transition zone of mostly solidified crust with isolated pockets of magma. Evidence from the superfast spreading portion of the EPR suggests that the composition of the melt lens is mainly moderately fractionated ferrobasalt. These results have important implications for magmatic processes occurring beneath mid‐ocean ridges and are consistent with a model that effectively separates the processes of magma mixing and fractionation into different parts of a composite magma chamber. Magma mixing, as evidenced by disequilibrium relations between host liquids and included phenocrysts, is especially apparent in samples from low magma supply ridges and probably mainly arises from interactions between crystals of the mush zone and new injections of primitive magma rising out of the mantle. Magmatic differentiation beneath mid‐ocean ridges occurs in two parts. Migration of melts through the transition and mush zones can produce chemical trends consistent with in situ fractionation processes. Segregation of melt into molten horizons near the top of a composite magma chamber promotes the more extensive differentiation characteristic of fast spreading ridges. The optimum conditions for the formation of highly differentiated abyssal lavas is where small, discontinuous melt lenses occur, such as at intermediate spreading rates, in the vicinity of propagating rifts, and near ridge offsets at fast spreading ridges. Along‐axis homogenization of subaxial magma is inhibited by the thin, high aspect ratio of the melt lens and by the high viscosities expected in the mush and transition zones. Low magma supply ridges are unlikely to be underlain by eruptable magma in a steady state sense, and eruptions at slow spreading ridges are likely to be closely coupled in time to injection events of new magma from the mantle. Extensional events at high magma supply ridges, which are more likely to be underlain by significant volumes of low‐viscosity melt, can produce eruptions without requiring associated injection events. The critical magma supply necessary for the development of a melt lens near the top of a composite magma chamber is similar to that of normal ridges spreading at rates of about 50–70 mm/yr, a rate approximately corresponding to that marking an abrupt change in the morphology and gravity signal at the ridge axis. A composite magma chamber model can explain several previous enigmas concerning mid‐ocean ridge basalts, including why slow spreading ridges dominantly erupt a narrow range of relatively undifferentiated lavas, why magma mixing is most evident in lavas erupted from slow spreading ridges, why fast spreading ridges erupt a wide range of generally more differentiated compositions, why bimodal lava populations occur in the vicinity of some propagating rifts, and how along‐axis geochemical segmentation can occur at a scale shorter than the major tectonic segmentation of ridge axes.",
    url = "https://doi.org/10.1029/91jb02508",
    doi = "10.1029/91jb02508",
    openalex = "W2107316430",
    references = "doi101007bf00371276, doi101029jb091ib01p00579, doi101146annurevea10050182001103"
}

Mid-ocean ridge basalts (MORBs) and ocean island basalts (QIBs) are derived by partial melting of the upper mantle and are marked by systematic excesses of thorium-230 activity relative to the activity of its parent, uranium-238. Experimental measurements of the distribution of thorium and uranium between the melt and solid residue show that, of the major phases in the upper mantle, only garnet will retain uranium over thorium. This sense of fractionation, which is opposite to that caused by clinopyroxene-melt partitioning, is consistent with the thorium-230 excesses observed in young oceanic basalts. Thus, both MORBs and QIBs must begin partial melting in the garnet stability field or below about 70 kilometers. A calculation shows that the thorium-230-uranium-238 disequilibrium in MORBs can be attributed to dynamic partial melting beginning at 80 kilometers with a melt porosity of 0.2 percent or more. This result requires that melting beneath ridges occurs in a wide region and that the magma rises to the surface at a velocity of at least 0.9 meter per year.

@article{doi101126science2615122739,
    author = "LaTourrette, Tom and Kennedy, Allen and Wasserburg, G. J.",
    title = "Thorium-Uranium Fractionation by Garnet: Evidence for a Deep Source and Rapid Rise of Oceanic Basalts",
    year = "1993",
    journal = "Science",
    abstract = "Mid-ocean ridge basalts (MORBs) and ocean island basalts (QIBs) are derived by partial melting of the upper mantle and are marked by systematic excesses of thorium-230 activity relative to the activity of its parent, uranium-238. Experimental measurements of the distribution of thorium and uranium between the melt and solid residue show that, of the major phases in the upper mantle, only garnet will retain uranium over thorium. This sense of fractionation, which is opposite to that caused by clinopyroxene-melt partitioning, is consistent with the thorium-230 excesses observed in young oceanic basalts. Thus, both MORBs and QIBs must begin partial melting in the garnet stability field or below about 70 kilometers. A calculation shows that the thorium-230-uranium-238 disequilibrium in MORBs can be attributed to dynamic partial melting beginning at 80 kilometers with a melt porosity of 0.2 percent or more. This result requires that melting beneath ridges occurs in a wide region and that the magma rises to the surface at a velocity of at least 0.9 meter per year.",
    url = "https://doi.org/10.1126/science.261.5122.739",
    doi = "10.1126/science.261.5122.739",
    openalex = "W2019884843",
    references = "doi1010160012821x77901947, doi1010160012821x80902149, doi1010160012821x85900019, doi1010160012821x86901950, doi101029jb095ib03p02661, doi101086627919, doi101093petrology323501, doi101093petrology3251021, doi101093petrology33342, openalexw592738002"
}

@article{doi101038375747a0,
    author = "Kelemen, P. B. and Shimizu, Nobumichi and Salters, Vincent J. M.",
    title = "Extraction of mid-ocean-ridge basalt from the upwelling mantle by focused flow of melt in dunite channels",
    year = "1995",
    journal = "Nature",
    url = "https://doi.org/10.1038/375747a0",
    doi = "10.1038/375747a0",
    openalex = "W2024828229",
    references = "doi101007bf00373711"
}

Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.

@article{doi101126science2725264991,
    author = "Hanan, B. B. and Graham, D. W.",
    title = "Lead and Helium Isotope Evidence from Oceanic Basalts for a Common Deep Source of Mantle Plumes",
    year = "1996",
    journal = "Science",
    abstract = "Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.",
    url = "https://doi.org/10.1126/science.272.5264.991",
    doi = "10.1126/science.272.5264.991",
    openalex = "W1974463006",
    references = "doi1010160012821x75900886, doi1010160012821x78900535, doi1010160012821x82901613, doi1010160012821x86900385, doi1010160012821x89900794, doi101029gl003i005p00249, doi101038309753a0, doi101098rsta19800224, doi101126science2565056517, doi101146annurevea14050186002425"
}

▪ Abstract Geophysical estimates of mid-ocean ridge axial heat fluxes (2–4 × 10 12 W) and of the total hydrothermal flux (9 ± 2 × 10 12 W) are well established. Problems arise in calculation of water fluxes because of uncertainties in (a) values of off-axis fluxes and (b) the partition of axial heat flow between high-temperature black smoker and lower-temperature diffuse flow. Of the various geochemical methods of estimating fluxes, 3 He/heat data are extremely variable, the Mg method is sensitive to flank fluxes, Sr isotopes agree with geophysical estimates only if flank fluxes are important, Li isotopes data are consistent with geophysical values, and Ge/Si ratios give low fluxes, which may reflect low-temperature processes not yet fully quantified. Estimates of hydrothermal heat and water fluxes derived from these approaches are presented as are hydrothermal chemical fluxes at the ridge axis, off axis, and as affected by hydrothermal plumes.

@article{doi101146annurevearth241191,
    author = "Elderfield, Henry and Schultz, Adam",
    title = "Mid-Ocean Ridge Hydrothermal Fluxes and the Chemical Composition of the Ocean",
    year = "1996",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "▪ Abstract Geophysical estimates of mid-ocean ridge axial heat fluxes (2–4 × 10 12 W) and of the total hydrothermal flux (9 ± 2 × 10 12 W) are well established. Problems arise in calculation of water fluxes because of uncertainties in (a) values of off-axis fluxes and (b) the partition of axial heat flow between high-temperature black smoker and lower-temperature diffuse flow. Of the various geochemical methods of estimating fluxes, 3 He/heat data are extremely variable, the Mg method is sensitive to flank fluxes, Sr isotopes agree with geophysical estimates only if flank fluxes are important, Li isotopes data are consistent with geophysical values, and Ge/Si ratios give low fluxes, which may reflect low-temperature processes not yet fully quantified. Estimates of hydrothermal heat and water fluxes derived from these approaches are presented as are hydrothermal chemical fluxes at the ridge axis, off axis, and as affected by hydrothermal plumes.",
    url = "https://doi.org/10.1146/annurev.earth.24.1.191",
    doi = "10.1146/annurev.earth.24.1.191",
    openalex = "W2157677644",
    references = "doi1010160012821x69900934, doi1010160012821x7990061x, doi1010160012821x89900174, doi1010160012821x92900676, doi1010160016703788903146, doi10102992jb01749, doi10102993jb02222, doi101029jz072i024p06261, doi101038326035a0, doi101126science20343851073"
}

@article{doi101016s0012821x97000186,
    author = "Kogiso, Tetsu and Tatsumi, Yoshiyuki and Nakano, Satoshi",
    title = "Trace element transport during dehydration processes in the subducted oceanic crust: 1. Experiments and implications for the origin of ocean island basalts",
    year = "1997",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/s0012-821x(97)00018-6",
    doi = "10.1016/s0012-821x(97)00018-6",
    openalex = "W2015396785",
    references = "doi1010160016703778902223, doi101029jb091ib10p10309"
}

@article{doi101038nature01073,
    author = "Saal, A. E. and Hauri, E. H. and Langmuir, C. H. and Perfit, M. R.",
    title = "Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle",
    year = "2002",
    journal = "Nature",
    url = "https://doi.org/10.1038/nature01073",
    doi = "10.1038/nature01073",
    openalex = "W1996000677",
    references = "doi101093oxfordjournalspetrologya037267, doi1015159781501508271"
}

@article{doi101038nature01215,
    author = "Dixon, J. E. and Leist, Loretta and Langmuir, C. H. and Schilling, Jean‐Guy",
    title = "Recycled dehydrated lithosphere observed in plume-influenced mid-ocean-ridge basalt",
    year = "2002",
    journal = "Nature",
    url = "https://doi.org/10.1038/nature01215",
    doi = "10.1038/nature01215",
    openalex = "W2006465451",
    references = "doi101126science2725264991"
}

▪ Abstract The recent recognition of a potentially vast, unexplored hot microbial biosphere associated with active volcanism along the global mid-ocean ridge network has fundamentally shifted concepts of how planets and life coevolve. Many processes intrinsic to the dynamics of the spreading center volcanic system provide partial or complete nutritional fluxes that support diverse microbial communities that thrive under extreme conditions on and beneath the seafloor. Mantle melting, volcanism, and fluid-rock reactions transport volatiles from the asthenosphere to the hydrosphere. Volcanic heat and exothermic reactions drive circulation of nutrient-rich fluids from which chemosynthetic organisms gain metabolic energy. In turn, many of these organisms symbiotically support macrofaunal communities that populate the vents. Long-term seafloor observatories will allow exploration of linkages between volcanism and this newly discovered biosphere. Such approaches may provide essential new information about our own planet while providing critically needed insights into how we can explore other planets for life.

@article{doi101146annurevearth30091201141331,
    author = "Kelley, Deborah S. and Baross, John A. and Delaney, John R.",
    title = "Volcanoes, Fluids, and Life at Mid-Ocean Ridge Spreading Centers",
    year = "2002",
    journal = "Annual Review of Earth and Planetary Sciences",
    abstract = "▪ Abstract The recent recognition of a potentially vast, unexplored hot microbial biosphere associated with active volcanism along the global mid-ocean ridge network has fundamentally shifted concepts of how planets and life coevolve. Many processes intrinsic to the dynamics of the spreading center volcanic system provide partial or complete nutritional fluxes that support diverse microbial communities that thrive under extreme conditions on and beneath the seafloor. Mantle melting, volcanism, and fluid-rock reactions transport volatiles from the asthenosphere to the hydrosphere. Volcanic heat and exothermic reactions drive circulation of nutrient-rich fluids from which chemosynthetic organisms gain metabolic energy. In turn, many of these organisms symbiotically support macrofaunal communities that populate the vents. Long-term seafloor observatories will allow exploration of linkages between volcanism and this newly discovered biosphere. Such approaches may provide essential new information about our own planet while providing critically needed insights into how we can explore other planets for life.",
    url = "https://doi.org/10.1146/annurev.earth.30.091201.141331",
    doi = "10.1146/annurev.earth.30.091201.141331",
    openalex = "W2153068522",
    references = "doi101007bf00300398, doi101007bf01140180, doi1010160016703793905425, doi1010160016703794902887, doi10102998jb00576, doi101029jb091ib10p10309, doi101038334609a0, doi101111j157469761997tb00325x"
}

@article{doi102138rmg2002478,
    author = "Graham, D. W.",
    title = "Noble Gas Isotope Geochemistry of Mid-Ocean Ridge and Ocean Island Basalts: Characterization of Mantle Source Reservoirs",
    year = "2002",
    journal = "Reviews in Mineralogy and Geochemistry",
    url = "https://doi.org/10.2138/rmg.2002.47.8",
    doi = "10.2138/rmg.2002.47.8",
    openalex = "W2098490586",
    references = "doi101029jb087ib07p05611, doi101126science2725264991"
}

Consideration of petrology, geochemistry, and mineral physics suggests that ancient subducted oceanic crusts cannot be the source materials supplying ocean island basalts (OIB). Melting of oceanic crusts cannot produce high‐magnesian OIB lavas. Ancient oceanic crusts (>1 Ga) are isotopically too depleted to meet the required values of most OIB. Subducted oceanic crusts that have passed through subduction zone dehydration are likely to be depleted in water‐soluble incompatible elements (e.g., Ba, Rb, Cs, U, K, Sr, Pb) relative to water‐insoluble incompatible elements (e.g., Nb, Ta, Zr, Hf, Ti). Melting of residual crusts with such trace element composition cannot produce OIB. Oceanic crusts, if subducted into the lower mantle, will be >2% denser than the ambient mantle at shallow lower mantle depths. This negative buoyancy will impede return of the subducted oceanic crusts into the upper mantle. If subducted oceanic crusts melt at the base of the mantle, the resultant melts are even denser than the ambient peridotitic mantle, perhaps by as much as ∼15%. Neither in the solid state nor in melt form can bulk oceanic crusts subducted into the lower mantle return to upper mantle source regions of oceanic basalts. Deep portions of recycled oceanic lithosphere are important geochemical reservoirs hosting volatiles and incompatible elements as a result of metasomatism taking place at the interface between the low‐velocity zone and the cooling and thickening oceanic lithosphere. These metasomatized and recycled deep portions of oceanic lithosphere are the most likely candidates for OIB sources in terms of petrology, geochemistry and mineral physics.

@article{doi1010292002jb002048,
    author = "Niu, Yaoling and O’Hara, Michael J.",
    title = "Origin of ocean island basalts: A new perspective from petrology, geochemistry, and mineral physics considerations",
    year = "2003",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Consideration of petrology, geochemistry, and mineral physics suggests that ancient subducted oceanic crusts cannot be the source materials supplying ocean island basalts (OIB). Melting of oceanic crusts cannot produce high‐magnesian OIB lavas. Ancient oceanic crusts (>1 Ga) are isotopically too depleted to meet the required values of most OIB. Subducted oceanic crusts that have passed through subduction zone dehydration are likely to be depleted in water‐soluble incompatible elements (e.g., Ba, Rb, Cs, U, K, Sr, Pb) relative to water‐insoluble incompatible elements (e.g., Nb, Ta, Zr, Hf, Ti). Melting of residual crusts with such trace element composition cannot produce OIB. Oceanic crusts, if subducted into the lower mantle, will be >2\% denser than the ambient mantle at shallow lower mantle depths. This negative buoyancy will impede return of the subducted oceanic crusts into the upper mantle. If subducted oceanic crusts melt at the base of the mantle, the resultant melts are even denser than the ambient peridotitic mantle, perhaps by as much as ∼15\%. Neither in the solid state nor in melt form can bulk oceanic crusts subducted into the lower mantle return to upper mantle source regions of oceanic basalts. Deep portions of recycled oceanic lithosphere are important geochemical reservoirs hosting volatiles and incompatible elements as a result of metasomatism taking place at the interface between the low‐velocity zone and the cooling and thickening oceanic lithosphere. These metasomatized and recycled deep portions of oceanic lithosphere are the most likely candidates for OIB sources in terms of petrology, geochemistry and mineral physics.",
    url = "https://doi.org/10.1029/2002jb002048",
    doi = "10.1029/2002jb002048",
    openalex = "W1985531665",
    references = "doi101126science2725264991"
}

Abstract A new species of the rare arietellid genus Scutogerulus is described from deep hyperbenthic waters off Okinawa, southwestern Japan. This is the second species of the genus. Phylogenetically significant characteristics known only on the basis of the type species are confirmed by the discovery of the new congener, in particular: (1) the genital system of the female exhibits the most plesiomorphic condition of any arietellid genus; (2) the well developed setae on the endopodal segments of the maxillae and maxillipeds are modified into ‘shield‐like setae’ similar to the ‘button setae’ in another arietelloidean family, the Augaptilidae; (3) the outer distal spine on the first exopodal segment of leg 1 is absent.

@article{doi101017s1477200004001331,
    author = "Ohtsuka, Susumu and Boxshall, Geoffrey A.",
    title = "A new species of the deep‐sea copepod genus Scutogerulus (Calanoida: Arietellidae) from the hyperbenthic waters of Okinawa, Japan",
    year = "2004",
    journal = "Systematics and Biodiversity",
    abstract = "Abstract A new species of the rare arietellid genus Scutogerulus is described from deep hyperbenthic waters off Okinawa, southwestern Japan. This is the second species of the genus. Phylogenetically significant characteristics known only on the basis of the type species are confirmed by the discovery of the new congener, in particular: (1) the genital system of the female exhibits the most plesiomorphic condition of any arietellid genus; (2) the well developed setae on the endopodal segments of the maxillae and maxillipeds are modified into ‘shield‐like setae’ similar to the ‘button setae’ in another arietelloidean family, the Augaptilidae; (3) the outer distal spine on the first exopodal segment of leg 1 is absent.",
    url = "https://doi.org/10.1017/s1477200004001331",
    doi = "10.1017/s1477200004001331",
    openalex = "W2124979281",
    references = "openalexw2271364307"
}

This paper presents the first comprehensive major and trace element data for ~ 130 abyssal peridotite samples from the Pacific and Indian ocean ridge-transforms systems. The data reveal important features about the petrogenesis of these rocks, mantle melting and melt extraction processes beneath ocean ridges, and elemental behaviours. While abyssal peridotite are serpentinized and have also experienced seafloor weathering, magmatic signatures remain well preserved in the bulk-rock compositions. The better inverse correlation of MgO with progressively heavier rare earth elements (REEs) reflects varying amounts of melt depletion. This melt depletion may result from recent sub-ridge mantle melting, but could also be inherited from fertile source histories. Light REEs in bulk-rock samples are more enriched, not more depleted, than in the constituent clinopyroxene (cpx) of the same sample suites previously studied. If the cpx light REEs record sub-ridge mantle melting processes, then the bulk-rock light REEs must reflect post-melting refertilization. The significant correlations of light REEs (e.g., La, Ce, Pr, Nd) with immobile high field strength elements (HFSEs, e.g., Nb and Zr) suggest that enrichments of both light REEs and HFSEs resulted from a common magmatic process. The refertilization takes place in the “cold” thermal boundary layer (TBL) beneath ridges where the ascending melts migrate through and interact with the advanced residues. The refertilization apparently did not affect cpx relics analyzed for trace elements. This observation suggests grain-boundary porous melt migration in the TBL. The ascending melts may not be thermally “reactive”, and thus may have only affected cpx rims, which, together with precipitated olivine, entrapped melt, and the rest of the rock, were subsequently serpentinized. The very large variations in bulk-rock Zr/Hf and Nb/Ta ratios are unexpected. The correlation between the two ratios is consistent with the observations in basalts that DZr/DHf <1 and DNb/DTa <1. Given the identical charges (5+ for Nb and Ta; 4+ for Zr and Hf) and essentially the same ionic radii (RNb/RTa = 1.000 and RZr/RHf = 1.006 ~ 1.026), yet a factor of ~ 2 mass differences (MZr/MHf = 0.511 and MNb/MTa = 0.513), it is hypothesized that mass-dependent Ds or diffusion/mass-transfer rates may be important in causing elemental fractionations during porous melt ascent in the TBL. It is also possible that some “exotic” phases with highly fractionated Zr/Hf and Nb/Ta ratios may exist in these rocks, thus having “nugget” effects on the bulk-rock analyses. All these hypotheses need testing by constraining the storage and distributions of all the incompatible trace elements. As serpentine contains up to 13 wt % H2O, and is stable up to 7 GPa before transformed to dense hydrous magnesium silicate phases that are stable at pressures of ~ 5 to 50 GPa, it is possible that the serpentinized peridotites may survive, at least partly, subduction-zone dehydration, and transport large amounts of H2O (also Ba, Rb, Cs, K, U, Sr, Pb etc. with elevated U/Pb ratios) into the deep mantle. The latter may contribute to the HIMU component in the source regions of oceanic basalts.

@article{doi101093petrologyegh068,
    author = "Niu, Yaoling",
    title = "Bulk-rock Major and Trace Element Compositions of Abyssal Peridotites: Implications for Mantle Melting, Melt Extraction and Post-melting Processes Beneath Mid-Ocean Ridges",
    year = "2004",
    journal = "Journal of Petrology",
    abstract = "This paper presents the first comprehensive major and trace element data for \textasciitilde\ 130 abyssal peridotite samples from the Pacific and Indian ocean ridge-transforms systems. The data reveal important features about the petrogenesis of these rocks, mantle melting and melt extraction processes beneath ocean ridges, and elemental behaviours. While abyssal peridotite are serpentinized and have also experienced seafloor weathering, magmatic signatures remain well preserved in the bulk-rock compositions. The better inverse correlation of MgO with progressively heavier rare earth elements (REEs) reflects varying amounts of melt depletion. This melt depletion may result from recent sub-ridge mantle melting, but could also be inherited from fertile source histories. Light REEs in bulk-rock samples are more enriched, not more depleted, than in the constituent clinopyroxene (cpx) of the same sample suites previously studied. If the cpx light REEs record sub-ridge mantle melting processes, then the bulk-rock light REEs must reflect post-melting refertilization. The significant correlations of light REEs (e.g., La, Ce, Pr, Nd) with immobile high field strength elements (HFSEs, e.g., Nb and Zr) suggest that enrichments of both light REEs and HFSEs resulted from a common magmatic process. The refertilization takes place in the “cold” thermal boundary layer (TBL) beneath ridges where the ascending melts migrate through and interact with the advanced residues. The refertilization apparently did not affect cpx relics analyzed for trace elements. This observation suggests grain-boundary porous melt migration in the TBL. The ascending melts may not be thermally “reactive”, and thus may have only affected cpx rims, which, together with precipitated olivine, entrapped melt, and the rest of the rock, were subsequently serpentinized. The very large variations in bulk-rock Zr/Hf and Nb/Ta ratios are unexpected. The correlation between the two ratios is consistent with the observations in basalts that DZr/DHf <1 and DNb/DTa <1. Given the identical charges (5+ for Nb and Ta; 4+ for Zr and Hf) and essentially the same ionic radii (RNb/RTa = 1.000 and RZr/RHf = 1.006 \textasciitilde\ 1.026), yet a factor of \textasciitilde\ 2 mass differences (MZr/MHf = 0.511 and MNb/MTa = 0.513), it is hypothesized that mass-dependent Ds or diffusion/mass-transfer rates may be important in causing elemental fractionations during porous melt ascent in the TBL. It is also possible that some “exotic” phases with highly fractionated Zr/Hf and Nb/Ta ratios may exist in these rocks, thus having “nugget” effects on the bulk-rock analyses. All these hypotheses need testing by constraining the storage and distributions of all the incompatible trace elements. As serpentine contains up to 13 wt \% H2O, and is stable up to 7 GPa before transformed to dense hydrous magnesium silicate phases that are stable at pressures of \textasciitilde\ 5 to 50 GPa, it is possible that the serpentinized peridotites may survive, at least partly, subduction-zone dehydration, and transport large amounts of H2O (also Ba, Rb, Cs, K, U, Sr, Pb etc. with elevated U/Pb ratios) into the deep mantle. The latter may contribute to the HIMU component in the source regions of oceanic basalts.",
    url = "https://doi.org/10.1093/petrology/egh068",
    doi = "10.1093/petrology/egh068",
    openalex = "W2113369720",
    references = "doi1010160009254194001404, doi1010160012821x86900385, doi1010160012821x8890132x, doi101016s0012821x6880010x, doi101016s0012821x9700040x, doi10102992jb02221, doi10102995rg01302, doi10103835084000, doi101038385219a0, doi101093petrology293625, doi1015159781400864874, doi102973odpprocsr1271281992, openalexw14108998, openalexw1624806571"
}

@misc{crossref2005basalt,
    title = "Basalt",
    year = "2005",
    booktitle = "Van Nostrand's Scientific Encyclopedia",
    url = "https://doi.org/10.1002/0471743984.vse0931",
    doi = "10.1002/0471743984.vse0931"
}

Picritic lava flows near Lijiang in the late Permian Emeishan flood basalt province are associated with augite-phyric basalt, aphyric basalt, and basaltic pyroclastic units. The dominant phenocryst in the picritic flows is Mg-rich olivine (up to 91.6 % forsterite component) with high CaO contents (to 0.42 wt %) and glass inclusions, indicating that the olivine crystallized from a melt. Associated chromite has a high Cr-number (73–75). The estimated MgO content of the primitive picritic liquids is about 22 wt %, and initial melt temperature may have been as high as 1630– 1690C. The basaltic lavas appear to be related to the picritic ones principally by olivine and clinopyroxene fractionation. Age-corrected Nd–Sr–Pb isotope ratios of the picritic and basaltic lavas are indistinguishable and cover a relatively small range [e.g. eNd(t) 1.3 to þ4.0]. The higher eNd(t) lavas are isotopically similar to those of several modern oceanic hotspots, and have ocean-island-like patterns of alteration-resistant incompatible elements. Heavy rare earth element characteristics indicate an important role for garnet during melting and that the lavas were formed by fairly small degrees of partial melting. Rough correlations of isotope ratios with ratios of alteration-resistant highly incompatible elements (e.g. Nb/La) suggest modest amounts of contamination involving continental material or a relatively low-eNd component in the source. Overall, our results are consistent with other evidence suggesting some type of plume-head origin for the Emeishan province. KEY WORDS: Emeishan; flood basalts; picrites; mantle plumes; late Permian

@article{doi101093petrologyegl034,
    author = "Zhang, Zhaochong",
    title = "Geochemistry of Picritic and Associated Basalt Flows of the Western Emeishan Flood Basalt Province, China",
    year = "2006",
    journal = "Journal of Petrology",
    abstract = "Picritic lava flows near Lijiang in the late Permian Emeishan flood basalt province are associated with augite-phyric basalt, aphyric basalt, and basaltic pyroclastic units. The dominant phenocryst in the picritic flows is Mg-rich olivine (up to 91.6 \% forsterite component) with high CaO contents (to 0.42 wt \%) and glass inclusions, indicating that the olivine crystallized from a melt. Associated chromite has a high Cr-number (73–75). The estimated MgO content of the primitive picritic liquids is about 22 wt \%, and initial melt temperature may have been as high as 1630– 1690C. The basaltic lavas appear to be related to the picritic ones principally by olivine and clinopyroxene fractionation. Age-corrected Nd–Sr–Pb isotope ratios of the picritic and basaltic lavas are indistinguishable and cover a relatively small range [e.g. eNd(t) 1.3 to þ4.0]. The higher eNd(t) lavas are isotopically similar to those of several modern oceanic hotspots, and have ocean-island-like patterns of alteration-resistant incompatible elements. Heavy rare earth element characteristics indicate an important role for garnet during melting and that the lavas were formed by fairly small degrees of partial melting. Rough correlations of isotope ratios with ratios of alteration-resistant highly incompatible elements (e.g. Nb/La) suggest modest amounts of contamination involving continental material or a relatively low-eNd component in the source. Overall, our results are consistent with other evidence suggesting some type of plume-head origin for the Emeishan province. KEY WORDS: Emeishan; flood basalts; picrites; mantle plumes; late Permian",
    url = "https://doi.org/10.1093/petrology/egl034",
    doi = "10.1093/petrology/egl034",
    openalex = "W2140136526",
    references = "doi101126science2725264991"
}

Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. The first known members of the Ediacara biota arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later.

@article{doi101126science1135013,
    author = "Canfield, Donald E. and Poulton, Simon W. and Narbonne, Guy M.",
    title = "Late-Neoproterozoic Deep-Ocean Oxygenation and the Rise of Animal Life",
    year = "2006",
    journal = "Science",
    abstract = "Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. The first known members of the Ediacara biota arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later.",
    url = "https://doi.org/10.1126/science.1135013",
    doi = "10.1126/science.1135013",
    openalex = "W1994160943",
    references = "doi101016jchemgeo200409003, doi10103835318, doi101038nature05345, doi101046j13653121200200408x, doi10108000241160500409223, doi101126science1078265, doi101126science1107765, doi101146annurevearth33031504103001, doi101146annurevearth33092203122519, openalexw2738937425"
}

Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., T P) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., T P = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties that we critically evaluate. A new evaluation is made of parental magma compositions that would crystallize olivines with the maximum forsterite contents observed in lava flows. These are generally in good agreement with primary magma compositions calculated using the mass balance method of Herzberg and O'Hara (2002), and differences reflect the well‐known effects of fractional crystallization. Results of primary magma compositions we obtain for mid‐ocean ridge basalts and various oceanic islands and plateaus generally favor the third type of model but with ambient mantle potential temperatures in the range 1280–1400°C and thermal anomalies that can be 200–300°C above this background. Our results are consistent with the plume model.

@article{doi1010292006gc001390,
    author = "Herzberg, Claude and Asimow, Paul D. and Arndt, N. T. and Niu, Yaoling and Lesher, C. Michael and Fitton, J. Godfrey and Cheadle, M. J. and Saunders, A. D.",
    title = "Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites",
    year = "2007",
    journal = "Geochemistry Geophysics Geosystems",
    abstract = "Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., T P) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., T P = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties that we critically evaluate. A new evaluation is made of parental magma compositions that would crystallize olivines with the maximum forsterite contents observed in lava flows. These are generally in good agreement with primary magma compositions calculated using the mass balance method of Herzberg and O'Hara (2002), and differences reflect the well‐known effects of fractional crystallization. Results of primary magma compositions we obtain for mid‐ocean ridge basalts and various oceanic islands and plateaus generally favor the third type of model but with ambient mantle potential temperatures in the range 1280–1400°C and thermal anomalies that can be 200–300°C above this background. Our results are consistent with the plume model.",
    url = "https://doi.org/10.1029/2006gc001390",
    doi = "10.1029/2006gc001390",
    openalex = "W2127503576",
    references = "doi101007bf00307281, doi101007bf00371276"
}

Recent diving with the JAMSTEC Shinkai 6500 manned submersible in the Mariana fore arc southeast of Guam has discovered that MORB‐like tholeiitic basalts crop out over large areas. These “fore‐arc basalts” (FAB) underlie boninites and overlie diabasic and gabbroic rocks. Potential origins include eruption at a spreading center before subduction began or eruption during near‐trench spreading after subduction began. FAB trace element patterns are similar to those of MORB and most Izu‐Bonin‐Mariana (IBM) back‐arc lavas. However, Ti/V and Yb/V ratios are lower in FAB reflecting a stronger prior depletion of their mantle source compared to the source of basalts from mid‐ocean ridges and back‐arc basins. Some FAB also have higher concentrations of fluid‐soluble elements than do spreading center lavas. Thus, the most likely origin of FAB is that they were the first lavas to erupt when the Pacific Plate began sinking beneath the Philippine Plate at about 51 Ma. The magmas were generated by mantle decompression during near‐trench spreading with little or no mass transfer from the subducting plate. Boninites were generated later when the residual, highly depleted mantle melted at shallow levels after fluxing by a water‐rich fluid derived from the sinking Pacific Plate. This magmatic stratigraphy of FAB overlain by transitional lavas and boninites is similar to that found in many ophiolites, suggesting that ophiolitic assemblages might commonly originate from near‐trench volcanism caused by subduction initiation. Indeed, the widely dispersed Jurassic and Cretaceous Tethyan ophiolites could represent two such significant subduction initiation events.

@article{doi1010292009gc002871,
    author = "Reagan, Mark K. and Ishizuka, Osamu and Stern, Robert J. and Kelley, K. A. and Ohara, Yasuhiko and Blichert‐Toft, Janne and Bloomer, Sherman H. and Cash, Jennifer and Fryer, P. and Hanan, B. B. and Hickey-Vargas, Rosemary L. and Ishii, Teruaki and Kimura, Jun‐Ichi and Peate, D.W. and Rowe, Michael C. and Woods, Melinda",
    title = "Fore‐arc basalts and subduction initiation in the Izu‐Bonin‐Mariana system",
    year = "2010",
    journal = "Geochemistry Geophysics Geosystems",
    abstract = "Recent diving with the JAMSTEC Shinkai 6500 manned submersible in the Mariana fore arc southeast of Guam has discovered that MORB‐like tholeiitic basalts crop out over large areas. These “fore‐arc basalts” (FAB) underlie boninites and overlie diabasic and gabbroic rocks. Potential origins include eruption at a spreading center before subduction began or eruption during near‐trench spreading after subduction began. FAB trace element patterns are similar to those of MORB and most Izu‐Bonin‐Mariana (IBM) back‐arc lavas. However, Ti/V and Yb/V ratios are lower in FAB reflecting a stronger prior depletion of their mantle source compared to the source of basalts from mid‐ocean ridges and back‐arc basins. Some FAB also have higher concentrations of fluid‐soluble elements than do spreading center lavas. Thus, the most likely origin of FAB is that they were the first lavas to erupt when the Pacific Plate began sinking beneath the Philippine Plate at about 51 Ma. The magmas were generated by mantle decompression during near‐trench spreading with little or no mass transfer from the subducting plate. Boninites were generated later when the residual, highly depleted mantle melted at shallow levels after fluxing by a water‐rich fluid derived from the sinking Pacific Plate. This magmatic stratigraphy of FAB overlain by transitional lavas and boninites is similar to that found in many ophiolites, suggesting that ophiolitic assemblages might commonly originate from near‐trench volcanism caused by subduction initiation. Indeed, the widely dispersed Jurassic and Cretaceous Tethyan ophiolites could represent two such significant subduction initiation events.",
    url = "https://doi.org/10.1029/2009gc002871",
    doi = "10.1029/2009gc002871",
    openalex = "W1593136970",
    references = "doi1010160012821x82901200, doi101111j14401738200500478x"
}

This chapter contains sections titled: Introduction Basic Theoretical Concepts Observations Modeling of Mantle Melting: Background and Previous Work New Quantitative Model for Mantle Melting Applications to Morb Data Trace Element Constraints Significance of Spreading Rate: A Key to Understanding the Local Trends? Conclusions Appendix A: Calculation of Feo, Mgo, Na2o and Tio2 During Adiabatic Melting Of The Mantle Appendix B: Olivine Liquid Partitioning as a function of Temperature, Pressure and Liquid Composition Appendix C: Modeling Complex Differentiation Processes

@incollection{doi101029gm071p0183,
    author = "Langmuir, C. H. and Klein, E. M. and Plank, Terry",
    title = "Petrological Systematics of Mid-Ocean Ridge Basalts: Constraints on Melt Generation Beneath Ocean Ridges",
    year = "2011",
    booktitle = "Geophysical monograph",
    abstract = "This chapter contains sections titled: Introduction Basic Theoretical Concepts Observations Modeling of Mantle Melting: Background and Previous Work New Quantitative Model for Mantle Melting Applications to Morb Data Trace Element Constraints Significance of Spreading Rate: A Key to Understanding the Local Trends? Conclusions Appendix A: Calculation of Feo, Mgo, Na2o and Tio2 During Adiabatic Melting Of The Mantle Appendix B: Olivine Liquid Partitioning as a function of Temperature, Pressure and Liquid Composition Appendix C: Modeling Complex Differentiation Processes",
    url = "https://doi.org/10.1029/gm071p0183",
    doi = "10.1029/gm071p0183",
    openalex = "W1561193515",
    references = "doi101007bf00371276, doi1010160012825268901475, doi1010160016703768901087, doi101016s0012821x6880010x, doi101038242565a0"
}

Abstract The mean composition of mid‐ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. “ALL MORB” is the total composition of the crust apart from back‐arc basins, N‐MORB the most likely basalt composition encountered along the ridge >500 km from hot spots, and D‐MORB the depleted end‐member. ALL MORB and N‐MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back‐arc spreading centers requires higher extents of melting and greater concentrations of fluid‐mobile elements, reflecting the influence of water on back‐arc petrogenesis. The average data permit a re‐evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 ± 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and 143 Nd/ 144 Nd ratio of all morb and N‐MORB provide constraints on the hypothesis that Earth has a non‐chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.

@article{doi1010292012gc004334,
    author = "Gale, A. and Dalton, C. A. and Langmuir, C. H. and Su, Yongjun and Schilling, Jean‐Guy",
    title = "The mean composition of ocean ridge basalts",
    year = "2012",
    journal = "Geochemistry Geophysics Geosystems",
    abstract = "Abstract The mean composition of mid‐ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. “ALL MORB” is the total composition of the crust apart from back‐arc basins, N‐MORB the most likely basalt composition encountered along the ridge >500 km from hot spots, and D‐MORB the depleted end‐member. ALL MORB and N‐MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back‐arc spreading centers requires higher extents of melting and greater concentrations of fluid‐mobile elements, reflecting the influence of water on back‐arc petrogenesis. The average data permit a re‐evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 ± 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and 143 Nd/ 144 Nd ratio of all morb and N‐MORB provide constraints on the hypothesis that Earth has a non‐chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.",
    url = "https://doi.org/10.1029/2012gc004334",
    doi = "10.1029/2012gc004334",
    openalex = "W1828329906",
    references = "doi1010160009254194001404, doi1010160012821x7990013x, doi1010160012821x86900385, doi1010160012821x8890132x, doi1010292001gc000252, doi1010292003gc000597, doi1010292008gc002332, doi10102994gl02118, doi101029jb092ib08p08089, doi101038309753a0, doi101093oxfordjournalspetrologya037267, doi101144gslsp19890420119"
}

@incollection{arndt2014basalt,
    author = "Arndt, Nicholas",
    title = "Basalt",
    year = "2014",
    booktitle = "Encyclopedia of Astrobiology",
    url = "https://doi.org/10.1007/978-3-642-27833-4\_153-3",
    doi = "10.1007/978-3-642-27833-4\_153-3",
    pages = "1-1"
}

@incollection{crossref2014basalt,
    title = "basalt",
    year = "2014",
    booktitle = "Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik",
    url = "https://doi.org/10.1007/978-3-642-41714-6\_20672",
    doi = "10.1007/978-3-642-41714-6\_20672",
    pages = "106-106"
}

@incollection{arndt2015basalt,
    author = "Arndt, Nicholas",
    title = "Basalt",
    year = "2015",
    booktitle = "Encyclopedia of Astrobiology",
    url = "https://doi.org/10.1007/978-3-662-44185-5\_153",
    doi = "10.1007/978-3-662-44185-5\_153",
    pages = "251-251"
}

The 24 papers in this volume, written in honor of A.F. Buddington, cover a wide range of topics and geographic areas. H.H. Hesss History of Ocean Basins perhaps the most famous paper in the volume, introduces the concept of seafloor spreading.

@incollection{doi101130petrologic1962599,
    author = "Hess, H. H.",
    title = "History of Ocean Basins",
    year = "2015",
    booktitle = "Geological Society of America eBooks",
    abstract = "The 24 papers in this volume, written in honor of A.F. Buddington, cover a wide range of topics and geographic areas. H.H. Hesss History of Ocean Basins perhaps the most famous paper in the volume, introduces the concept of seafloor spreading.",
    url = "https://doi.org/10.1130/petrologic.1962.599",
    doi = "10.1130/petrologic.1962.599",
    openalex = "W2486473486",
    references = "doi101029jz064i011p01967, doi101038scientificamerican106098, doi101073pnas40121096, doi101130001676061951621111ghosw20co2, doi101130001676061956671623ssotpo20co2, doi10113000167606195970291smitao20co2, doi101130spe62p391, doi1023071783259, doi1023071792199, doi102475ajs24411772"
}

@article{doi101038nature25009,
    author = "Stolper, Daniel A. and Keller, C. Brenhin",
    title = "A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts",
    year = "2018",
    journal = "Nature",
    url = "https://doi.org/10.1038/nature25009",
    doi = "10.1038/nature25009",
    openalex = "W2782454560",
    references = "doi1010292012gc004334, doi101029jb086ib04p02737, doi10103824839, doi101038nature06811, doi101038nature13068, doi101126science1135013, doi101130b304461, doi101146annurevearth241191, doi101146annurevearth33092203122711, doi1015159781400849079"
}

Fully characterising the exchange of volatile elements between the Earth’s interior and surface layers has been a longstanding challenge. Volatiles scavenged from seawater by hydrothermally altered oceanic crust have been transferred to the upper mantle during subduction of the oceanic crust, but whether these volatiles are carried deeper into the lower mantle is poorly understood. Here we present evidence of the deep-mantle Cl cycle recorded in melt inclusions in olivine crystals in ocean island basalts sourced from the lower mantle. We show that Cl-rich melt inclusions are associated with radiogenic Pb isotopes, indicating ancient subducted oceanic crust in basalt sources, together with lithophile elements characteristic of melts from a carbonated source. These signatures collectively indicate that seawater-altered and carbonated oceanic crust conveyed surface Cl downward to the lower mantle, forming a Cl-rich reservoir that accounts for 13–26% or an even greater proportion of the total Cl in the mantle.

@article{hanyu2019tiny,
    author = "Hanyu, Takeshi and Shimizu, Kenji and Ushikubo, Takayuki and Kimura, Jun-Ichi and Chang, Qing and Hamada, Morihisa and Ito, Motoo and Iwamori, Hikaru and Ishikawa, Tsuyoshi",
    title = "Tiny droplets of ocean island basalts unveil Earth’s deep chlorine cycle",
    year = "2019",
    journal = "Nature Communications",
    abstract = "Fully characterising the exchange of volatile elements between the Earth’s interior and surface layers has been a longstanding challenge. Volatiles scavenged from seawater by hydrothermally altered oceanic crust have been transferred to the upper mantle during subduction of the oceanic crust, but whether these volatiles are carried deeper into the lower mantle is poorly understood. Here we present evidence of the deep-mantle Cl cycle recorded in melt inclusions in olivine crystals in ocean island basalts sourced from the lower mantle. We show that Cl-rich melt inclusions are associated with radiogenic Pb isotopes, indicating ancient subducted oceanic crust in basalt sources, together with lithophile elements characteristic of melts from a carbonated source. These signatures collectively indicate that seawater-altered and carbonated oceanic crust conveyed surface Cl downward to the lower mantle, forming a Cl-rich reservoir that accounts for 13–26\% or an even greater proportion of the total Cl in the mantle.",
    url = "https://doi.org/10.1038/s41467-018-07955-8",
    doi = "10.1038/s41467-018-07955-8",
    number = "1",
    openalex = "W2906963232",
    volume = "10",
    references = "doi1010160012821x9290042t, doi101016jchemgeo200701014, doi101016jepsl200606014, doi1010292001gc000223, doi101038nature01073, doi101038nature13080, doi101038nature14876, doi101038nature16174, doi101111j1751908x2005tb00904x, doi1011300091761320030310481amgbpm20co2"
}

The seasonal cycle represents one of the largest signals of dissolved inorganic carbon (DIC) in the ocean, yet these seasonal variations are not well established at a global scale. Here, we present the Mapped Observation‐Based Oceanic DIC (MOBO‐DIC) product, a monthly DIC climatology developed based on the DIC measurements from GLODAPv2.2019 and a two‐step neural network method to interpolate and map the measurements. MOBO‐DIC extends from the surface down to 2,000 m and from 65°N to 65°S. We find the largest seasonal amplitudes of surface DIC in the northern high‐latitude Pacific (∼ 30 to >50 μ mol kg −1). Surface DIC maxima occur in hemispheric spring and minima in fall, driven by the input of DIC into the upper ocean by mixing during winter, and net community production (NCP) driven drawdown of DIC over summer. The seasonal pattern seen at the surface extends to a nodal depth of <50 m in the tropics and several hundred meters in the subtropics. Below the nodal depth, the seasonal cycle of DIC has the opposite phase, primarily owing to the seasonal accumulation of DIC stemming from the remineralization of sinking organic matter. The well‐captured seasonal drawdown of DIC in the mid‐latitudes (23° to 65°) allows us to estimate the spring‐to‐fall NCP in this region. We find a spatially relatively uniform spring‐to‐fall NCP of 1.9 ± 1.3 mol C m −2 yr −1, which sums to 3.9 ± 2.7 Pg C yr −1 over this region. This corresponds to a global spring‐to‐fall NCP of 8.2 ± 5.6 Pg C yr −1.

@article{doi1010292020gb006571,
    author = "Keppler, Lydia and Landschützer, Peter and Gruber, Nicolas and Lauvset, Siv K. and Stemmler, Irene",
    title = "Seasonal Carbon Dynamics in the Near‐Global Ocean",
    year = "2020",
    journal = "Global Biogeochemical Cycles",
    abstract = "The seasonal cycle represents one of the largest signals of dissolved inorganic carbon (DIC) in the ocean, yet these seasonal variations are not well established at a global scale. Here, we present the Mapped Observation‐Based Oceanic DIC (MOBO‐DIC) product, a monthly DIC climatology developed based on the DIC measurements from GLODAPv2.2019 and a two‐step neural network method to interpolate and map the measurements. MOBO‐DIC extends from the surface down to 2,000 m and from 65°N to 65°S. We find the largest seasonal amplitudes of surface DIC in the northern high‐latitude Pacific (∼ 30 to >50 μ mol kg −1). Surface DIC maxima occur in hemispheric spring and minima in fall, driven by the input of DIC into the upper ocean by mixing during winter, and net community production (NCP) driven drawdown of DIC over summer. The seasonal pattern seen at the surface extends to a nodal depth of <50 m in the tropics and several hundred meters in the subtropics. Below the nodal depth, the seasonal cycle of DIC has the opposite phase, primarily owing to the seasonal accumulation of DIC stemming from the remineralization of sinking organic matter. The well‐captured seasonal drawdown of DIC in the mid‐latitudes (23° to 65°) allows us to estimate the spring‐to‐fall NCP in this region. We find a spatially relatively uniform spring‐to‐fall NCP of 1.9 ± 1.3 mol C m −2 yr −1, which sums to 3.9 ± 2.7 Pg C yr −1 over this region. This corresponds to a global spring‐to‐fall NCP of 8.2 ± 5.6 Pg C yr −1.",
    url = "https://doi.org/10.1029/2020gb006571",
    doi = "10.1029/2020gb006571",
    openalex = "W3112856357",
    references = "doi1010160025322764900428"
}

@incollection{gawronska2023basalt,
    author = "Gawronska, Aleksandra J. and McLeod, Claire",
    title = "Basalt",
    year = "2023",
    booktitle = "Encyclopedia of Lunar Science",
    url = "https://doi.org/10.1007/978-3-319-14541-9\_135",
    doi = "10.1007/978-3-319-14541-9\_135",
    pages = "71-81"
}

Basalt fiber fabric (BFF) has gained extensive application in industrial, military, and aerospace fields due to its lightweight nature, chemical inertness, and mechanical durability. However, the inherent surface inertness and electrical insulation of BFs restrict their utilization in electromagnetic interference (EMI) shielding. In this work, we propose an innovative gradient functionalization strategy based on "plasma activation-ALD bridging-chemical plating-post annealing treatments" to fabricate polychromatic BFs with exceptional EMI and thermal shielding performance. Plasma pretreatment synergizes with ALD TiO2 to enrich hydroxyl groups, serving as atomic-scale "bridges" for anchoring dense Ni coatings. This process establishes interconnected conductive networks to reflect EM waves, while post annealing induces interfacial reconstruction, enhancing EMI shielding effectiveness (SE) through synergistic magnetic loss and interfacial polarization mechanisms. The optimized BFF demonstrates an outstanding EMI SE of 53.47 dB and maintains stable performance under high-temperature and cryogenic conditions. Additionally, vivid and uniform structural colors derived from thin-film interference were achieved on the fiber surface by modulating annealing temperatures. Notably, the high refractive index characteristics of TiO2, Ni, and NiO layers, coupled with their multiple refractive synergistic effects, lead to pronounced interfacial reflection of infrared radiation, which effectively reduces the radiation flux penetrating BFFs and significantly enhances overall shielding performance, underscoring their potential in thermal camouflage applications. This study establishes a groundbreaking strategy for designing multi-color BFFs with EM and thermal shielding capabilities, and provides novel insights for developing multifunctional shielding materials while expanding BFF's application horizons in chromatic engineering and radiation protection domains.

@article{doi101002exp270135,
    author = "Qiao, Sijie and Shi, Zhicheng and He, Annan and Huang, Zhiyu and Tong, Aixin and Wang, Binhao and He, Jun and Wang, Jiaxin and Ke, Wei and Yao, Na and Zhao, Shichao and Qin, Yong and Xu, Weilin and Chen, Fengxiang",
    title = "Collaborative Optimization of Electromagnetic Interference Shielding, Adaptive Multi-Color, and Thermal Camouflage of Basalt Fibers by Temperature-Induced Gradient Structure Control.",
    year = "2026",
    journal = "Exploration (Beijing, China)",
    abstract = {Basalt fiber fabric (BFF) has gained extensive application in industrial, military, and aerospace fields due to its lightweight nature, chemical inertness, and mechanical durability. However, the inherent surface inertness and electrical insulation of BFs restrict their utilization in electromagnetic interference (EMI) shielding. In this work, we propose an innovative gradient functionalization strategy based on "plasma activation-ALD bridging-chemical plating-post annealing treatments" to fabricate polychromatic BFs with exceptional EMI and thermal shielding performance. Plasma pretreatment synergizes with ALD TiO2 to enrich hydroxyl groups, serving as atomic-scale "bridges" for anchoring dense Ni coatings. This process establishes interconnected conductive networks to reflect EM waves, while post annealing induces interfacial reconstruction, enhancing EMI shielding effectiveness (SE) through synergistic magnetic loss and interfacial polarization mechanisms. The optimized BFF demonstrates an outstanding EMI SE of 53.47 dB and maintains stable performance under high-temperature and cryogenic conditions. Additionally, vivid and uniform structural colors derived from thin-film interference were achieved on the fiber surface by modulating annealing temperatures. Notably, the high refractive index characteristics of TiO2, Ni, and NiO layers, coupled with their multiple refractive synergistic effects, lead to pronounced interfacial reflection of infrared radiation, which effectively reduces the radiation flux penetrating BFFs and significantly enhances overall shielding performance, underscoring their potential in thermal camouflage applications. This study establishes a groundbreaking strategy for designing multi-color BFFs with EM and thermal shielding capabilities, and provides novel insights for developing multifunctional shielding materials while expanding BFF's application horizons in chromatic engineering and radiation protection domains.},
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC13094530/",
    doi = "10.1002/exp2.70135",
    pmcid = "PMC13094530",
    pmid = "42016749"
}

Enhanced silicate weathering (ESW) has shown promise for carbon dioxide removal (CDR) in dryland agriculture, yet its effectiveness in flooded rice paddies, particularly regarding the CDR pathways and microbial interactions, remains poorly understood. In this study, we quantified CDR in rice paddy amended with basalt and/or biochar. Basalt applied at 36 t ha-1 sequestered ∼11.3 t CO2 ha-1 through carbonate formation and increased rice yield by 20.7%. Co-applying with 18 t ha-1 of biochar further reduced CH4 and N2O emissions by 30.5% and 52.1%, respectively, leading to a 37.9% reduction in greenhouse gas intensity. This co-application also reshaped fungal community structure, enhanced fungal activity and diversity, and increased fungal necromass carbon by 21%. Moreover, it effectively reduced the accumulation of heavy metals in rice grains. Despite these co-benefits, its net CDR with greenhouse gas (GHG) mitigation but excluding organic carbon storage was only 8.8 t CO2 ha-1, roughly 25% lower than with basalt alone. These results indicate that co-applying basalt and biochar can substantially alter the biogeochemical processes governing CDR and crop productivity in paddy soils. To maximize CDR efficiency and grain yield, careful matching, dosage adjustment, and context-specific optimization of these amendments are essential.

@article{doi101016jjenvman2026129708,
    author = "Gong, Xueliu and Wu, Jiarong and Qin, Jingsong and Zhao, Jinkai and Zhu, Kai and Ye, Chenglong and Xia, Shaopan and Zheng, Jufeng and Qie, Wenkun and Li, Lianqing and Li, Zi-Bo and Bian, Rongjun",
    title = "Investigating the effects of co-applied basalt and biochar on carbon removal efficiency and grain yield in rice paddy.",
    year = "2026",
    journal = "Journal of environmental management",
    abstract = "Enhanced silicate weathering (ESW) has shown promise for carbon dioxide removal (CDR) in dryland agriculture, yet its effectiveness in flooded rice paddies, particularly regarding the CDR pathways and microbial interactions, remains poorly understood. In this study, we quantified CDR in rice paddy amended with basalt and/or biochar. Basalt applied at 36 t ha-1 sequestered ∼11.3 t CO2 ha-1 through carbonate formation and increased rice yield by 20.7\%. Co-applying with 18 t ha-1 of biochar further reduced CH4 and N2O emissions by 30.5\% and 52.1\%, respectively, leading to a 37.9\% reduction in greenhouse gas intensity. This co-application also reshaped fungal community structure, enhanced fungal activity and diversity, and increased fungal necromass carbon by 21\%. Moreover, it effectively reduced the accumulation of heavy metals in rice grains. Despite these co-benefits, its net CDR with greenhouse gas (GHG) mitigation but excluding organic carbon storage was only 8.8 t CO2 ha-1, roughly 25\% lower than with basalt alone. These results indicate that co-applying basalt and biochar can substantially alter the biogeochemical processes governing CDR and crop productivity in paddy soils. To maximize CDR efficiency and grain yield, careful matching, dosage adjustment, and context-specific optimization of these amendments are essential.",
    url = "https://pubmed.ncbi.nlm.nih.gov/41996914/",
    doi = "10.1016/j.jenvman.2026.129708",
    pmid = "41996914"
}

@misc{crossrefNonebasalt,
    title = "Basalt",
    year = "None",
    booktitle = "SpringerReference",
    url = "https://doi.org/10.1007/springerreference\_30559",
    doi = "10.1007/springerreference\_30559"
}