气候变化领域集成服务门户(CCPortal): Limited Mantle Hydration by Bending Faults at the Middle America Trench

CCPortal

DOI	10.1029/2020JB020982
	Limited Mantle Hydration by Bending Faults at the Middle America Trench
	Miller N.C.; Lizarralde D.; Collins J.A.; Holbrook W.S.; Van Avendonk H.J.A.
发表日期	2021
ISSN	21699313
卷号	126 期号:1
英文摘要	Seismic anisotropy measurements show that upper mantle hydration at the Middle America Trench (MAT) is limited to serpentinization and/or water in fault zones, rather than distributed uniformly. Subduction of hydrated oceanic lithosphere recycles water back into the deep mantle, drives arc volcanism, and affects seismicity at subduction zones. Constraining the extent of upper mantle hydration is an important part of understanding many fundamental processes on Earth. Substantially reduced seismic velocities in tomography suggest that outer rise plate-bending faults provide a pathway for seawater to rehydrate the slab mantle just prior to subduction. Estimates of outer-rise hydration based on tomograms vary significantly, with some large enough to imply that, globally, subduction has consumed more than two oceans worth of water during the Phanerozoic. We found that, while the mean upper mantle wavespeed is reduced at the MAT outer rise, the amplitude and orientation of inherited anisotropy are preserved at depths >1 km below the Moho. At shallower depths, relict anisotropy is replaced by slowing in the fault-normal direction. These observations are incompatible with pervasive hydration but consistent with models of wave propagation through serpentinized fault zones that thin to <100-m in width at depths >1 km below Moho. Confining hydration to fault zones reduces water storage estimates for the MAT upper mantle from ∼3.5 wt% to <0.9 wt% H20. Since the intermediate thermal structure in the ∼24 Myr-old MAT slab favors serpentinization, limited hydration suggests that fault mechanics are the limiting factor, not temperatures. Subducting mantle may be similarly dry globally. © 2020. American Geophysical Union. All Rights Reserved. This article has been contributed to by US Government employees and their work is in the public domain in the USA.
英文关键词	outer-rise hydration; upper mantle anisotropy; upper mantle hydration
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187409
作者单位	U.S. Geological Survey, Woods Hole Costal and Marine Science Center, Woods Hole, MA, United States; Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, United States; Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States; Jackson School of Geosciences, University of Texas Institute for Geophysics, Austin, TX, United States
推荐引用方式 GB/T 7714	Miller N.C.,Lizarralde D.,Collins J.A.,et al. Limited Mantle Hydration by Bending Faults at the Middle America Trench[J],2021,126(1).
APA	Miller N.C.,Lizarralde D.,Collins J.A.,Holbrook W.S.,&Van Avendonk H.J.A..(2021).Limited Mantle Hydration by Bending Faults at the Middle America Trench.Journal of Geophysical Research: Solid Earth,126(1).
MLA	Miller N.C.,et al."Limited Mantle Hydration by Bending Faults at the Middle America Trench".Journal of Geophysical Research: Solid Earth 126.1(2021).