Subduction zones

@article{keith1971oceanfloor1,
    author = "Keith, M. L",
    title = "Ocean-floor convergence",
    year = "1971",
    journal = "A contrary view of global tectonics: Journal of Geology, v. 80, p. 249-276",
    note = "talkorigins\_source = {true}; raw\_reference = {Keith, M. L., 1971, Ocean-floor convergence: A contrary view of global tectonics: Journal of Geology, v. 80, p. 249-276.}"
}

Detailed studies of the seismicity of several subduction zones demonstrate that shallow-dipping thrust zones turn to steeper angles at depths of about 40 kilometers. An increased downward body force resulting from shallow phase changes in subducted oceanic crust may be the cause of this increased dip angle. In addition, the volume reduction associated with phase changes may produce sufficiently large stresses in neighboring rocks to cause the seismicity of the upper Benioff zone.

@article{pennington1983role,
    author = "Pennington, Wayne D.",
    title = "Role of Shallow Phase Changes in the Subduction of Oceanic Crust",
    year = "1983",
    journal = "Science",
    abstract = "Detailed studies of the seismicity of several subduction zones demonstrate that shallow-dipping thrust zones turn to steeper angles at depths of about 40 kilometers. An increased downward body force resulting from shallow phase changes in subducted oceanic crust may be the cause of this increased dip angle. In addition, the volume reduction associated with phase changes may produce sufficiently large stresses in neighboring rocks to cause the seismicity of the upper Benioff zone.",
    url = "https://doi.org/10.1126/science.220.4601.1045",
    doi = "10.1126/science.220.4601.1045",
    number = "4601",
    pages = "1045-1047",
    volume = "220"
}

@misc{pennington1983role2,
    author = "Pennington, W. D",
    title = "Role of shallow phase changes in the subduction of oceanic crust",
    year = "1983",
    howpublished = "Science, v. 220, p. 1045-1047",
    note = "talkorigins\_source = {true}; raw\_reference = {Pennington, W. D., 1983, Role of shallow phase changes in the subduction of oceanic crust: Science, v. 220, p. 1045-1047.}"
}

@article{kimura1995peeling,
    author = "Kimura, Gaku and Ludden, John",
    title = "Peeling oceanic crust in subduction zones",
    year = "1995",
    journal = "Geology",
    url = "https://doi.org/10.1130/0091-7613(1995)023<0217:pocisz>2.3.co;2",
    doi = "10.1130/0091-7613(1995)023<0217:pocisz>2.3.co;2",
    number = "3",
    pages = "217",
    volume = "23"
}

@article{prouteau1999fluidpresent,
    author = "Prouteau, G. and Scaillet, B. and Pichavant, M. and Maury, R. C.",
    title = "Fluid-present melting of ocean crust in subduction zones",
    year = "1999",
    journal = "Geology",
    url = "https://doi.org/10.1130/0091-7613(1999)027<1111:fpmooc>2.3.co;2",
    doi = "10.1130/0091-7613(1999)027<1111:fpmooc>2.3.co;2",
    number = "12",
    pages = "1111",
    volume = "27"
}

@incollection{gerya2011intraoceanic,
    author = "Gerya, T. V.",
    title = "Intra-oceanic Subduction Zones",
    year = "2011",
    booktitle = "Frontiers in Earth Sciences",
    url = "https://doi.org/10.1007/978-3-540-88558-0\_2",
    doi = "10.1007/978-3-540-88558-0\_2",
    pages = "23-51"
}

@article{bentham2014scattering,
    author = "Bentham, H. L. M. and Rost, S.",
    title = "Scattering beneath Western Pacific subduction zones: evidence for oceanic crust in the mid-mantle",
    year = "2014",
    journal = "Geophysical Journal International",
    url = "https://doi.org/10.1093/gji/ggu043",
    doi = "10.1093/gji/ggu043",
    number = "3",
    pages = "1627-1641",
    volume = "197"
}

Subduction zones are tectonic expressions of convergent plate margins, where crustal rocks descend into and interact with the overlying mantle wedge. They are the geodynamic system that produces mafic arc volcanics above oceanic subduction zones but high- to ultrahigh-pressure metamorphic rocks in continental subduction zones. While the metamorphic rocks provide petrological records of orogenic processes when descending crustal rocks undergo dehydration and anataxis at forearc to subarc depths beneath the mantle wedge, the arc volcanics provide geochemical records of the mass transfer from the subducting slab to the mantle wedge in this period though the mantle wedge becomes partially melted at a later time. Whereas the mantle wedge overlying the subducting oceanic slab is of asthenospheric origin, that overlying the descending continental slab is of lithospheric origin, being ancient beneath cratons but juvenile beneath marginal arcs. In either case, the mantle wedge base is cooled down during the slab–wedge coupled subduction. Metamorphic dehydration is prominent during subduction of crustal rocks, giving rise to aqueous solutions that are enriched in fluid-mobile incompatible elements. Once the subducting slab is decoupled from the mantle wedge, the slab–mantle interface is heated by lateral incursion of the asthenospheric mantle to allow dehydration melting of rocks in the descending slab surface and the metasomatized mantle wedge base, respectively. Therefore, the tectonic regime of subduction zones changes in both time and space with respect to their structures, inputs, processes and products. Ophiolites record the tectonic conversion from seafloor spreading to oceanic subduction beneath continental margin, whereas ultrahigh-temperature metamorphic events mark the tectonic conversion from compression to extension in orogens.

@article{zheng2016continental,
    author = "Zheng, Yong-Fei and Chen, Yi-Xiang",
    title = "Continental versus oceanic subduction zones",
    year = "2016",
    journal = "National Science Review",
    abstract = "Subduction zones are tectonic expressions of convergent plate margins, where crustal rocks descend into and interact with the overlying mantle wedge. They are the geodynamic system that produces mafic arc volcanics above oceanic subduction zones but high- to ultrahigh-pressure metamorphic rocks in continental subduction zones. While the metamorphic rocks provide petrological records of orogenic processes when descending crustal rocks undergo dehydration and anataxis at forearc to subarc depths beneath the mantle wedge, the arc volcanics provide geochemical records of the mass transfer from the subducting slab to the mantle wedge in this period though the mantle wedge becomes partially melted at a later time. Whereas the mantle wedge overlying the subducting oceanic slab is of asthenospheric origin, that overlying the descending continental slab is of lithospheric origin, being ancient beneath cratons but juvenile beneath marginal arcs. In either case, the mantle wedge base is cooled down during the slab–wedge coupled subduction. Metamorphic dehydration is prominent during subduction of crustal rocks, giving rise to aqueous solutions that are enriched in fluid-mobile incompatible elements. Once the subducting slab is decoupled from the mantle wedge, the slab–mantle interface is heated by lateral incursion of the asthenospheric mantle to allow dehydration melting of rocks in the descending slab surface and the metasomatized mantle wedge base, respectively. Therefore, the tectonic regime of subduction zones changes in both time and space with respect to their structures, inputs, processes and products. Ophiolites record the tectonic conversion from seafloor spreading to oceanic subduction beneath continental margin, whereas ultrahigh-temperature metamorphic events mark the tectonic conversion from compression to extension in orogens.",
    url = "https://doi.org/10.1093/nsr/nww049",
    doi = "10.1093/nsr/nww049",
    number = "4",
    pages = "495-519",
    volume = "3"
}

@article{chan2020hydrated,
    author = "Chan, Melanie",
    title = "Hydrated oceanic crust supports benign plate movement at subduction zones",
    year = "2020",
    journal = "Temblor",
    url = "https://doi.org/10.32858/temblor.105",
    doi = "10.32858/temblor.105"
}

@article{turner2022sediment,
    author = "Turner, Stephen J. and Langmuir, Charles H.",
    title = "Sediment and ocean crust both melt at subduction zones",
    year = "2022",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/j.epsl.2022.117424",
    doi = "10.1016/j.epsl.2022.117424",
    pages = "117424",
    volume = "584"
}

@inproceedings{schwarzenbach2025sulfur,
    author = "Schwarzenbach, Esther",
    title = "Sulfur cycling in oceanic lithosphere: from mid-ocean ridges to subduction zones",
    year = "2025",
    booktitle = "Goldschmidt2025 abstracts",
    url = "https://doi.org/10.7185/gold2025.29803",
    doi = "10.7185/gold2025.29803"
}

Boron has two stable isotopes, 10B and 11B, which are strongly fractionated during geological processes. They have been widely used to trace fluids in subduction zones. The temperature-dependent equilibrium boron isotope fractionation depends on boron coordination in the B-hosting minerals and fluids. In blueschist- and eclogite-facies high-pressure metamorphic rocks, omphacite (Cpx), amphibole and white mica are the dominant hosts of B. Yet, different crystallographic mechanisms of B substitution in Cpx have been proposed with first-order implications for B isotope fractionation during slab dehydration and eclogite formation. Hence, clarification of B coordination in clinopyroxene is desired, but a direct determination of boron coordination in silicates at the trace-element level is not technically possible. In this study, we have thus determined the B coordination in omphacite, glaucophane and mica by indirect means through the investigation of the B isotope fractionation in natural rocks.We investigated a set of six different tourmaline-bearing reaction zone rocks from the high-pressure (HP) mélange on the island of Syros formed at approximately 0.7 GPa, 430 °C. The rocks show the paragenesis tourmaline + phengite + omphacite + glaucophane in textural equilibrium, which offers the opportunity to determine equilibrium B isotope fractionation among these minerals. The proportions of trigonally and tetrahedrally coordinated B in omphacite, glaucophane and phengite was then estimated from the respective boron isotope fractionation against tourmaline. The B isotope fractionation between phengite and tourmaline is -14.7 ±0.6 ‰, and -12.4 ±0.8 ‰ between omphacite and tourmaline. B isotope composition in omphacite is 2.5 ±1.6 ‰ heavier than in phengite. No significant difference was found between glaucophane and phengite. From these results, we conclude that boron in omphacite is dominantly in tetrahedral coordination (84 ±6 % of the total B) with a minor amount of B in trigonal coordination (16 ±6 %).

@misc{xu2025boron,
    author = "Xu, Jie and Marschall, Horst R. and Gerdes, Axel",
    title = "Boron isotope fractionation during oceanic-crust dehydration in subduction zones: boron coordination in omphacite",
    year = "2025",
    abstract = "Boron has two stable isotopes, 10B and 11B, which are strongly fractionated during geological processes. They have been widely used to trace fluids in subduction zones. The temperature-dependent equilibrium boron isotope fractionation depends on boron coordination in the B-hosting minerals and fluids. In blueschist- and eclogite-facies high-pressure metamorphic rocks, omphacite (Cpx), amphibole and white mica are the dominant hosts of B. Yet, different crystallographic mechanisms of B substitution in Cpx have been proposed with first-order implications for B isotope fractionation during slab dehydration and eclogite formation. Hence, clarification of B coordination in clinopyroxene is desired, but a direct determination of boron coordination in silicates at the trace-element level is not technically possible. In this study, we have thus determined the B coordination in omphacite, glaucophane and mica by indirect means through the investigation of the B isotope fractionation in natural rocks.We investigated a set of six different tourmaline-bearing reaction zone rocks from the high-pressure (HP) m\&\#233;lange on the island of Syros formed at approximately 0.7\&\#160;GPa, 430 \&\#176;C. The rocks show the paragenesis tourmaline + phengite + omphacite + glaucophane in textural equilibrium, which offers the opportunity to determine equilibrium B isotope fractionation among these minerals. The proportions of trigonally and tetrahedrally coordinated B in omphacite, glaucophane and phengite was then estimated from the respective boron isotope fractionation against tourmaline. The B isotope fractionation between phengite and tourmaline is -14.7 \&\#177;0.6 \&\#8240;, and -12.4 \&\#177;0.8 \&\#8240; between omphacite and tourmaline. B isotope composition in omphacite is 2.5 \&\#177;1.6 \&\#8240; heavier than in phengite. No significant difference was found between glaucophane and phengite. From these results, we conclude that boron in omphacite is dominantly in tetrahedral coordination (84 \&\#177;6 \% of the total B) with a minor amount of B in trigonal coordination (16 \&\#177;6 \%).",
    url = "https://doi.org/10.5194/egusphere-egu24-19863",
    doi = "10.5194/egusphere-egu24-19863"
}