Ridges

Factors of importance in partial melting calculations are discussed. The thermal evolution of a geochemical and petrological model of the upwelling asthenosphere beneath a ridge crest is studied numerically. Partial melting, basalt eruption and differentiation of the upwelling asthenosphere is modelled. Melt distribution and density distribution in the top 100 km of the upper mantle are calculated. Partial melting takes place in a depth interval of 25—60 km below the ridge crest. The degree of partial melting is somewhat less than 20 %. About 2.5 times more liquid is produced by partial melting in the upwelling asthenosphere than is erupted at the ridge centre. This excess liquid solidifies in the lithosphere, off-ridge axis below the Moho. The calculated results are in agreement with the observations on the oceanic ridge basalt composition, its average eruption rate, and geochemical estimates of the degree of partial melting in the sub-ridge upper mantle.

@article{bottinga1978partial,
    author = "Bottinga, Y. and Allègre, Claude Jean",
    title = "Partial melting under spreading ridges",
    year = "1978",
    journal = "Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences",
    abstract = "Factors of importance in partial melting calculations are discussed. The thermal evolution of a geochemical and petrological model of the upwelling asthenosphere beneath a ridge crest is studied numerically. Partial melting, basalt eruption and differentiation of the upwelling asthenosphere is modelled. Melt distribution and density distribution in the top 100 km of the upper mantle are calculated. Partial melting takes place in a depth interval of 25—60 km below the ridge crest. The degree of partial melting is somewhat less than 20 \%. About 2.5 times more liquid is produced by partial melting in the upwelling asthenosphere than is erupted at the ridge centre. This excess liquid solidifies in the lithosphere, off-ridge axis below the Moho. The calculated results are in agreement with the observations on the oceanic ridge basalt composition, its average eruption rate, and geochemical estimates of the degree of partial melting in the sub-ridge upper mantle.",
    url = "https://doi.org/10.1098/rsta.1978.0031",
    doi = "10.1098/rsta.1978.0031",
    number = "1355",
    pages = "501-525",
    volume = "288"
}

@article{menard1984evolution,
    author = "Menard, H. W.",
    title = "Evolution of ridges by asymmetrical spreading",
    year = "1984",
    journal = "Geology",
    url = "https://doi.org/10.1130/0091-7613(1984)12<177:eorbas>2.0.co;2",
    doi = "10.1130/0091-7613(1984)12<177:eorbas>2.0.co;2",
    number = "3",
    pages = "177",
    volume = "12"
}

@misc{menard1984evolution1,
    author = "Menard, W. H",
    title = "Evolution of ridges by asymmetrical spreading",
    year = "1984",
    howpublished = "Geology, v. 12, p. 177-180",
    note = "talkorigins\_source = {true}; raw\_reference = {Menard, W. H., 1984, Evolution of ridges by asymmetrical spreading: Geology, v. 12, p. 177-180.}"
}

Mid‐ocean ridge axes are marked by segmentation of the axes and underlying magmatic systems. Fine‐scale segmentation has mainly been studied along fast‐spreading ridges. Here we offer insight into the third‐ and fourth‐order segmentation of intermediate‐spreading ridges and their temporal evolution. The Alarcón Rise and the Endeavour Segment have similar spreading rates (49 and 52.5 mm/year, respectively) but contrasting morphologies that vary from an axial high with a relatively narrow axial summit trough to an axial valley. One‐meter resolution bathymetry acquired by autonomous underwater vehicles, lava geochemistry, and ages from sediment cores is combined with available seismic reflection profiles to analyze variations in (1) geometry and orientation of the axial summit trough or valley, (2) seafloor depth near the axis, and (3) distribution of hydrothermal vents, (4) lava chemistry, and (5) flow ages between contiguous axes. Along both intermediate‐spreading segments, third‐ and fourth‐order discontinuities and associated segments are similar in dimension to what has been observed along fast‐spreading ridges. The Alarcón Rise and the Endeavour Segment also allow the study of the evolution of fine‐scale segmentation over periods of 300 to 4,000 years. Comparison between old and young axes reveals that the evolution of fine‐scale segmentation depends on the intensity of the magmatic activity. High magmatic periods are associated with rapid evolution of third‐order segments, while low magmatic activity periods, dominated by tectonic deformation and/or hydrothermal activity, are associated with little to no change in segmentation.

@article{lesaout2019evolution,
    author = "Le Saout, M. and Clague, D.A. and Paduan, J.B.",
    title = "Evolution of Fine‐Scale Segmentation at Intermediate‐Spreading Rate Ridges",
    year = "2019",
    journal = "Geochemistry, Geophysics, Geosystems",
    abstract = "Mid‐ocean ridge axes are marked by segmentation of the axes and underlying magmatic systems. Fine‐scale segmentation has mainly been studied along fast‐spreading ridges. Here we offer insight into the third‐ and fourth‐order segmentation of intermediate‐spreading ridges and their temporal evolution. The Alarcón Rise and the Endeavour Segment have similar spreading rates (49 and 52.5 mm/year, respectively) but contrasting morphologies that vary from an axial high with a relatively narrow axial summit trough to an axial valley. One‐meter resolution bathymetry acquired by autonomous underwater vehicles, lava geochemistry, and ages from sediment cores is combined with available seismic reflection profiles to analyze variations in (1) geometry and orientation of the axial summit trough or valley, (2) seafloor depth near the axis, and (3) distribution of hydrothermal vents, (4) lava chemistry, and (5) flow ages between contiguous axes. Along both intermediate‐spreading segments, third‐ and fourth‐order discontinuities and associated segments are similar in dimension to what has been observed along fast‐spreading ridges. The Alarcón Rise and the Endeavour Segment also allow the study of the evolution of fine‐scale segmentation over periods of 300 to 4,000 years. Comparison between old and young axes reveals that the evolution of fine‐scale segmentation depends on the intensity of the magmatic activity. High magmatic periods are associated with rapid evolution of third‐order segments, while low magmatic activity periods, dominated by tectonic deformation and/or hydrothermal activity, are associated with little to no change in segmentation.",
    url = "https://doi.org/10.1029/2019gc008218",
    doi = "10.1029/2019gc008218",
    number = "8",
    pages = "3841-3860",
    volume = "20"
}

@inproceedings{lissenberg2021magma,
    author = "Lissenberg, Johan and Loocke, Matthew and Cooper, George and MacLeod, Christopher",
    title = "Magma reservoir evolution at fast-spreading mid-ocean ridges",
    year = "2021",
    booktitle = "Goldschmidt2021 abstracts",
    url = "https://doi.org/10.7185/gold2021.5763",
    doi = "10.7185/gold2021.5763"
}

Lithospheric weakness is essential in subduction initiation. Spreading ridges are divergent plate boundaries which may represent lithospheric weakness and promote subduction initiation. Natural examples of ridge‐inversed subduction along spreading ridges have been proposed (e.g., the Proto‐South China Sea subduction). Although, the dynamic evolution of ridge‐inversed subduction has been investigated by geodynamical numerical modeling previously, it remains obscure, especially the influence of the thermal state and geometries of spreading ridges on subduction initiation and dynamic evolution. We establish two‐dimensional thermomechanical coupled numerical models to simulate the dynamic evolution of forced subduction along spreading ridges, and quantify the influence of four major parameters on subduction development (i.e., the spreading rate and cooling age of spreading ridges, forced convergence rate and asymmetric ridge geometry). Our model results suggest the following findings. (1) The cooling age of spreading ridges and the forced convergence rate are the most important parameters controlling ridge‐inversed subduction initiation, and the thresholds of the two parameters are revealed, that is, subduction may easily initiate with a cooling age less than ∼20 Myr and a forced convergence rate lager than ∼4 cm/yr. (2) The spreading rate of ridges prior to forced convergence and asymmetric ridge geometries play a secondary role in subduction development. (3) Ridge‐inversed subduction of the Proto‐South China Sea along the Palawan spreading ridge was proposed geologically, and our numerical modeling results support this scenario.

@article{qing2021dynamic,
    author = "Qing, Jiarong and Liao, Jie and Li, Lun and Gao, Rui",
    title = "Dynamic Evolution of Induced Subduction Through the Inversion of Spreading Ridges",
    year = "2021",
    journal = "Journal of Geophysical Research: Solid Earth",
    abstract = "Lithospheric weakness is essential in subduction initiation. Spreading ridges are divergent plate boundaries which may represent lithospheric weakness and promote subduction initiation. Natural examples of ridge‐inversed subduction along spreading ridges have been proposed (e.g., the Proto‐South China Sea subduction). Although, the dynamic evolution of ridge‐inversed subduction has been investigated by geodynamical numerical modeling previously, it remains obscure, especially the influence of the thermal state and geometries of spreading ridges on subduction initiation and dynamic evolution. We establish two‐dimensional thermomechanical coupled numerical models to simulate the dynamic evolution of forced subduction along spreading ridges, and quantify the influence of four major parameters on subduction development (i.e., the spreading rate and cooling age of spreading ridges, forced convergence rate and asymmetric ridge geometry). Our model results suggest the following findings. (1) The cooling age of spreading ridges and the forced convergence rate are the most important parameters controlling ridge‐inversed subduction initiation, and the thresholds of the two parameters are revealed, that is, subduction may easily initiate with a cooling age less than ∼20 Myr and a forced convergence rate lager than ∼4 cm/yr. (2) The spreading rate of ridges prior to forced convergence and asymmetric ridge geometries play a secondary role in subduction development. (3) Ridge‐inversed subduction of the Proto‐South China Sea along the Palawan spreading ridge was proposed geologically, and our numerical modeling results support this scenario.",
    url = "https://doi.org/10.1029/2020jb020965",
    doi = "10.1029/2020jb020965",
    number = "3",
    volume = "126"
}

It has long been recognised that spreading ridges are kept in place by competing subduction forces that drive plate motions. Asymmetric strain rates pull spreading ridges in the direction of the strongest slab pull force, which partially explains why spreading ridges can migrate vast distances. However, the interaction between mantle plumes and spreading ridges plays a relatively unknown role on the evolution of plate boundaries. Using a numerical model of mantle convection, we show that plumes with high buoyancy flux (>3000 kg/s) can capture spreading ridges within a 1000 km radius and anchor them in place. Exceptionally high buoyancy fluxes may fragment the overriding plate into smaller plates to accommodate more efficient plate motion. If the plume buoyancy flux wanes below 1000 kg/s the ridge may be de-anchored, leading to rapid ridge migration rates when combined with asymmetric plate boundary forces. Our results show that plume-ridge de-anchoring may have contributed to the rapid migration of the SE Indian Ridge from 43 million years ago (Ma) due to waning buoyancy flux from the Kerguelen plume, supported by magma flux estimates and radiogenic isotope geochemistry of eruption products. The plume-ridge de-anchoring mechanism we have identified has global implications for the evolution of plate boundaries near mantle plumes.

@article{doi101038s4146702453397w,
    author = "Mather, Ben and Seton, Maria and Williams, Simon and Whittaker, Joanne and Carey, Rebecca and Arnould, Maëlis and Coltice, Nicolas and Duncan, Robert",
    title = "Spreading ridge migration enabled by plume-ridge de-anchoring.",
    year = "2024",
    journal = "Nature communications",
    abstract = "It has long been recognised that spreading ridges are kept in place by competing subduction forces that drive plate motions. Asymmetric strain rates pull spreading ridges in the direction of the strongest slab pull force, which partially explains why spreading ridges can migrate vast distances. However, the interaction between mantle plumes and spreading ridges plays a relatively unknown role on the evolution of plate boundaries. Using a numerical model of mantle convection, we show that plumes with high buoyancy flux (>3000 kg/s) can capture spreading ridges within a 1000 km radius and anchor them in place. Exceptionally high buoyancy fluxes may fragment the overriding plate into smaller plates to accommodate more efficient plate motion. If the plume buoyancy flux wanes below 1000 kg/s the ridge may be de-anchored, leading to rapid ridge migration rates when combined with asymmetric plate boundary forces. Our results show that plume-ridge de-anchoring may have contributed to the rapid migration of the SE Indian Ridge from 43 million years ago (Ma) due to waning buoyancy flux from the Kerguelen plume, supported by magma flux estimates and radiogenic isotope geochemistry of eruption products. The plume-ridge de-anchoring mechanism we have identified has global implications for the evolution of plate boundaries near mantle plumes.",
    url = "https://pmc.ncbi.nlm.nih.gov/articles/PMC11484986/",
    doi = "10.1038/s41467-024-53397-w",
    pmcid = "PMC11484986",
    pmid = "39414825"
}

HYPOTHESIS: The depth of research into the mechanism of droplet impacting structured surfaces dictates the efficacy of their applications. The impact stress generated when a droplet impacts a surface is a pivotal factor influencing the efficiency of surface applications, ultimately determining the extent of surface wear. Despite the systematic examination of impact force, there remains a scarcity of research on impact stress and its mitigation strategies. Consequently, the objective of this study is to delve into the mechanisms that reduce maximum impact stress following the introduction of aerodynamic boundary layer and structural design. EXPERIMENTS AND SIMULATIONS: Based on experimental investigations, we examined the dynamic behavior of droplet impacting moving ridged surface with varying offset ratios across different tangential and normal Weber numbers. This study emphasizes the impact behavior phase diagram, droplet spreading length, and other relevant parameters. Furthermore, we systematically analyzed the evolution of the flow field and surface stress during the impact process benefit from a numerical simulation of a two-phase laminar flow model. FINDINGS: This study shows that the impact of droplets on moving ridged surfaces significantly influences stress reduction, with a focus on asymmetric droplet impacts. The research establishes a phase diagram for droplet impact behaviors across varying tangential Weber number (Weτ), normal Weber number (Wen) and offset ratio (χ), and some unified models about the maximum spreading diameter (Dmax) of the droplet are obtained based on the above variables. Besides, a model based on Prandtl's boundary layer theory emphasizes and proves the positive effect of the introduction of air layer on the reduction of maximum impact stress. Notably, the offset ratio significantly influences stress distribution, the maximum impact stress shows a non-monotonic change from increasing first to decreasing as χ increases considering the rotation of droplet. This research contributes valuable insights into surface design strategy for enhancing the resistance to droplet impact wear. These findings have broad implications for industrial applications where managing droplet impingement is crucial.

@article{doi101016jjcis202501020,
    author = "Yu, Wenlong and Wang, Wenhao and Cao, Damin and Wang, Yifei and Chen, Shuo and Zhao, Jiayi",
    title = "The droplet dynamics of asymmetrical impingement on moving ridged surface.",
    year = "2025",
    journal = "Journal of colloid and interface science",
    abstract = "HYPOTHESIS: The depth of research into the mechanism of droplet impacting structured surfaces dictates the efficacy of their applications. The impact stress generated when a droplet impacts a surface is a pivotal factor influencing the efficiency of surface applications, ultimately determining the extent of surface wear. Despite the systematic examination of impact force, there remains a scarcity of research on impact stress and its mitigation strategies. Consequently, the objective of this study is to delve into the mechanisms that reduce maximum impact stress following the introduction of aerodynamic boundary layer and structural design. EXPERIMENTS AND SIMULATIONS: Based on experimental investigations, we examined the dynamic behavior of droplet impacting moving ridged surface with varying offset ratios across different tangential and normal Weber numbers. This study emphasizes the impact behavior phase diagram, droplet spreading length, and other relevant parameters. Furthermore, we systematically analyzed the evolution of the flow field and surface stress during the impact process benefit from a numerical simulation of a two-phase laminar flow model. FINDINGS: This study shows that the impact of droplets on moving ridged surfaces significantly influences stress reduction, with a focus on asymmetric droplet impacts. The research establishes a phase diagram for droplet impact behaviors across varying tangential Weber number (Weτ), normal Weber number (Wen) and offset ratio (χ), and some unified models about the maximum spreading diameter (Dmax) of the droplet are obtained based on the above variables. Besides, a model based on Prandtl's boundary layer theory emphasizes and proves the positive effect of the introduction of air layer on the reduction of maximum impact stress. Notably, the offset ratio significantly influences stress distribution, the maximum impact stress shows a non-monotonic change from increasing first to decreasing as χ increases considering the rotation of droplet. This research contributes valuable insights into surface design strategy for enhancing the resistance to droplet impact wear. These findings have broad implications for industrial applications where managing droplet impingement is crucial.",
    url = "https://pubmed.ncbi.nlm.nih.gov/39798427/",
    doi = "10.1016/j.jcis.2025.01.020",
    pmid = "39798427"
}