气候变化领域集成服务门户(CCPortal): Evidence for a Deep Hydrologic Cycle on Oceanic Transform Faults

CCPortal

DOI	10.1029/2019JB017751
	Evidence for a Deep Hydrologic Cycle on Oceanic Transform Faults
	Kohli A.H.; Warren J.M.
发表日期	2020
ISSN	21699313
卷号	125 期号:2
英文摘要	Oceanic transform faults represent abundant yet relatively unexplored components of the hydrologic cycle in the mantle lithosphere. Current models limit fluid circulation to 600 °C, the thermal limit of earthquakes recorded by teleseismic surveys. However, recent ocean-bottom seismic surveys have located earthquakes at depths corresponding to >1000 °C in modeled thermal structure. To constrain the depth extent of brittle deformation and fluid infiltration, we analyzed peridotite mylonites dredged from the Shaka Transform Fault, Southwest Indian Ridge. Samples range from high strain mylonites that preserve ductile microstructures to lower strain mylonites that are fractured and overprinted by hydrothermal alteration. Microstructural analysis of the high strain samples reveals brittle deformation of pyroxene concomitant with ductile deformation of olivine and growth of amphibole. Porphyroclasts preserve healed fractures filled with fluid inclusions, implying repeated episodes of fracture, fluid infiltration, and healing. The association of hydration features with brittle structures points to seawater, rather than melt, as the fluid source. Textural analysis indicates that strain localization was initiated by grain boundary pinning and that olivine grain size was reduced to ~1 μm in the presence of amphibole. Comparing the amphibole stability field to thermometry estimates for the limit of recrystallization suggests that fluid flow extended to ~650–850 °C. Our results indicate that the hydrologic cycle extends past the brittle-ductile transition and promotes strain localization via hydrolytic weakening and hydration reactions. We propose that seawater infiltration on oceanic transform faults is driven by the seismic cycle and represents a first order control on the rheology of the oceanic lithosphere. ©2019. American Geophysical Union. All Rights Reserved.
英文关键词	brittle-ductile transition; hydrologic cycle; oceanic transform faults; olivine rheology; peridotite mylonites; strain localization
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/188014
作者单位	Department of Geophysics, Stanford University, Stanford, CA, United States; Department of Geological Sciences, University of Delaware, Newark, DE, United States
推荐引用方式 GB/T 7714	Kohli A.H.,Warren J.M.. Evidence for a Deep Hydrologic Cycle on Oceanic Transform Faults[J],2020,125(2).
APA	Kohli A.H.,&Warren J.M..(2020).Evidence for a Deep Hydrologic Cycle on Oceanic Transform Faults.Journal of Geophysical Research: Solid Earth,125(2).
MLA	Kohli A.H.,et al."Evidence for a Deep Hydrologic Cycle on Oceanic Transform Faults".Journal of Geophysical Research: Solid Earth 125.2(2020).