Melt segregation and depletion during ascent of buoyant diapirs in subduction zones

dc.contributor.author Zhang, Nan
dc.contributor.author Behn, Mark D.
dc.contributor.author Parmentier, E. Marc
dc.contributor.author Kincaid, Christopher
dc.date.accessioned 2020-06-16T18:03:25Z
dc.date.available 2020-07-31T07:28:40Z
dc.date.issued 2020-01-31
dc.description Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Solid Earth 125(2), (2020): e2019JB018203, doi:10.1029/2019JB018203. en_US
dc.description.abstract Cold, low‐density diapirs arising from hydrated mantle and/or subducted sediments on the top of subducting slabs have been invoked to transport key chemical signatures to the source region of arc magmas. However, to date there have been few quantitative models to constrain melting in such diapirs. Here we use a two‐phase Darcy‐Stokes‐energy model to investigate thermal evolution, melting, and depletion in a buoyant sediment diapir ascending through the mantle wedge. Using a simplified 2‐D circular geometry, we investigate diapir evolution in three scenarios with increasing complexity. In the first two scenarios we consider instantaneous heating of a diapir by thermal diffusion with and without the effect of the latent heat of melting. Then, these simplified calculations are compared to numerical simulations that include melting, melt segregation, and the influence of depletion on the sediment solidus along pressure‐temperature‐time (P ‐T ‐t ) paths appropriate for ascent through the mantle wedge. The high boundary temperature induces a rim of high porosity, into which new melts are focused and then migrate upward. The rim thus acts like an annulus melt channel, while the effect of depletion buffers additional melt production. Solid matrix flow combined with recrystallization of melt pooled near the top of the diapir can result in large gradients in depletion across the diapir. These large depletion gradients can either be preserved if the diapir leaks melt during ascent, or rehomogenized in a sealed diapir. Overall our numerical simulations predict less melt production than the simplified thermal diffusion calculations. Specifically, we show that diapirs whose ascent paths favor melting beneath the volcanic arc will undergo no more than ~40–50% total melting. en_US
dc.description.embargo 2020-07-31 en_US
dc.description.sponsorship We thank careful reviews by Juliane Dannberg, Harro Schmeling, and Bernhard steinberger. This work is supported by NSF‐1316333 (MB & NZ), NSF‐1551023 (MB), NSF‐1316310 (CK), and by China's Thousand Talents Plan (2015) and NSFC‐41674098 funding to NZ. The public data repository of Deal.ii (www.dealii.org) is thanked for distributing the software and examples that are used in this study. Computational work was conducted in High‐performance Computing Platform of Peking University, Kenny cluster of WHOI, and Pawsey Supercomputing Centre of Western Australia. We thank Timo Heister and Juliane Dannberg for deal.II technical assistance. The data of mantle wedge thermal structure and diapir trajectories, and the source code to compute the model results are available in the Mendeley data (http://dx.doi.org/10.17632/73n8zkc68s.1). en_US
dc.identifier.citation Zhang, N., Behn, M. D., Parmentier, E. M., & Kincaid, C. (2020). Melt segregation and depletion during ascent of buoyant diapirs in subduction zones. Journal of Geophysical Research-Solid Earth, 125(2), e2019JB018203. en_US
dc.identifier.doi 10.1029/2019JB018203
dc.identifier.uri https://hdl.handle.net/1912/25871
dc.publisher American Geophysical Union en_US
dc.relation.uri https://doi.org/10.1029/2019JB018203
dc.subject Sedimentary diapirs en_US
dc.subject Subduction wedge en_US
dc.subject Melt migration en_US
dc.title Melt segregation and depletion during ascent of buoyant diapirs in subduction zones en_US
dc.type Article en_US
dspace.entity.type Publication
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relation.isAuthorOfPublication.latestForDiscovery de0c82ef-4a52-430e-8f43-8b3d71fcf5f4
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