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Title: A role for subducted super-hydrated kaolinite in Earth’s deep water cycle

Abstract

Water is the most abundant volatile component in the Earth. It continuously enters the mantle through subduction zones, where it reduces the melting temperature of rocks to generate magmas. The dehydration process in subduction zones, which determines whether water is released from the slab or transported into the deeper mantle, is an essential component of the deep water cycle. Here we use in situ and time-resolved high-pressure/high-temperature synchrotron X-ray diffraction and infrared spectra to characterize the structural and chemical changes of the clay mineral kaolinite. At conditions corresponding to a depth of about 75 km in a cold subducting slab (2.7 GPa and 200 °C), and in the presence of water, we observe the pressure-induced insertion of water into kaolinite. This super-hydrated phase has a unit cell volume that is about 31% larger, a density that is about 8.4% lower than the original kaolinite and, with 29 wt% H2O, the highest water content of any known aluminosilicate mineral in the Earth. As pressure and temperature approach 19 GPa and about 800 °C, we observe the sequential breakdown of super-hydrated kaolinite. The formation and subsequent breakdown of super-hydrated kaolinite in cold slabs subducted below 200 km leads to the release ofmore » water that may affect seismicity and help fuel arc volcanism at the surface.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCESNSFDOE-NNSAFOREIGN
OSTI Identifier:
1418045
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Geoscience; Journal Volume: 10; Journal Issue: 12
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES

Citation Formats

Hwang, Huijeong, Seoung, Donghoon, Lee, Yongjae, Liu, Zhenxian, Liermann, Hanns-Peter, Cynn, Hyunchae, Vogt, Thomas, Kao, Chi-Chang, and Mao, Ho-Kwang. A role for subducted super-hydrated kaolinite in Earth’s deep water cycle. United States: N. p., 2017. Web. doi:10.1038/s41561-017-0008-1.
Hwang, Huijeong, Seoung, Donghoon, Lee, Yongjae, Liu, Zhenxian, Liermann, Hanns-Peter, Cynn, Hyunchae, Vogt, Thomas, Kao, Chi-Chang, & Mao, Ho-Kwang. A role for subducted super-hydrated kaolinite in Earth’s deep water cycle. United States. doi:10.1038/s41561-017-0008-1.
Hwang, Huijeong, Seoung, Donghoon, Lee, Yongjae, Liu, Zhenxian, Liermann, Hanns-Peter, Cynn, Hyunchae, Vogt, Thomas, Kao, Chi-Chang, and Mao, Ho-Kwang. Mon . "A role for subducted super-hydrated kaolinite in Earth’s deep water cycle". United States. doi:10.1038/s41561-017-0008-1.
@article{osti_1418045,
title = {A role for subducted super-hydrated kaolinite in Earth’s deep water cycle},
author = {Hwang, Huijeong and Seoung, Donghoon and Lee, Yongjae and Liu, Zhenxian and Liermann, Hanns-Peter and Cynn, Hyunchae and Vogt, Thomas and Kao, Chi-Chang and Mao, Ho-Kwang},
abstractNote = {Water is the most abundant volatile component in the Earth. It continuously enters the mantle through subduction zones, where it reduces the melting temperature of rocks to generate magmas. The dehydration process in subduction zones, which determines whether water is released from the slab or transported into the deeper mantle, is an essential component of the deep water cycle. Here we use in situ and time-resolved high-pressure/high-temperature synchrotron X-ray diffraction and infrared spectra to characterize the structural and chemical changes of the clay mineral kaolinite. At conditions corresponding to a depth of about 75 km in a cold subducting slab (2.7 GPa and 200 °C), and in the presence of water, we observe the pressure-induced insertion of water into kaolinite. This super-hydrated phase has a unit cell volume that is about 31% larger, a density that is about 8.4% lower than the original kaolinite and, with 29 wt% H2O, the highest water content of any known aluminosilicate mineral in the Earth. As pressure and temperature approach 19 GPa and about 800 °C, we observe the sequential breakdown of super-hydrated kaolinite. The formation and subsequent breakdown of super-hydrated kaolinite in cold slabs subducted below 200 km leads to the release of water that may affect seismicity and help fuel arc volcanism at the surface.},
doi = {10.1038/s41561-017-0008-1},
journal = {Nature Geoscience},
number = 12,
volume = 10,
place = {United States},
year = {Mon Nov 20 00:00:00 EST 2017},
month = {Mon Nov 20 00:00:00 EST 2017}
}