skip to main content

DOE PAGESDOE PAGES

This content will become publicly available on November 20, 2018

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

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 in this paper 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% H 2O, 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 leadsmore » to the release of water that may affect seismicity and help fuel arc volcanism at the surface.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Yonsei Univ., Seoul (Republic of Korea). Dept. of Earth System Sciences
  2. Yonsei Univ., Seoul (Republic of Korea). Dept. of Earth System Sciences; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL); Chonnam National Univ., Gwangju (Republic of Korea)
  3. Yonsei Univ., Seoul (Republic of Korea). Dept. of Earth System Sciences; Center for High Pressure Science & Technology Advanced Research (HPSTAR), Shanghai (China)
  4. George Washington Univ., Washington, DC (United States). Dept. of Civil and Environmental Engineering
  5. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). High-Pressure Physics Group, Physics and Life Sciences
  7. Univ. of South Carolina, Columbia, SC (United States). NanoCenter & Dept. of Chemistry and Biochemistry
  8. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  9. Center for High Pressure Science & Technology Advanced Research (HPSTAR), Shanghai (China); Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Lab.
Publication Date:
Grant/Contract Number:
AC02-76SF00515; AC02-05CH11231; AC52-07NA27344; NA0001974; SC0012704; AC02-06CH11357; FG02-99ER45775; EAR-1345112; EAR-1447438; NRF-2016K1A4A3914691; NRF-2016K1A3A7A09005244; NA0002006
Type:
Accepted Manuscript
Journal Name:
Nature Geoscience
Additional Journal Information:
Journal Volume: 10; Journal Issue: 12; Journal ID: ISSN 1752-0894
Publisher:
Nature Publishing Group
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Element cycles; Geochemistry; Mineralogy; Seismology; Volcanology
OSTI Identifier:
1423465