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Title: Transport of water into the lower mantle: Role of stishovite

Abstract

When subjected to lower-mantle pressures and temperatures, natural 'anhydrous' basalt containing 0.2 wt.% H{sub 2}O forms a phase assemblage in which SiO{sub 2} stishovite is a significant carrier of hydrogen (up to 500 ppm H{sub 2}O by weight, as hydroxide), whereas the coexisting (Mg, Fe, Al, Ca)SiO{sub 3} perovskite appears to be not (upper bound of 50 ppm (wt) H{sub 2}O). Contrary to the devolatilization characteristically observed at lower pressures, we find that the abundance of H{sub 2}O in residual stishovite increases from {approx}100 to {approx}400 ppm by weight upon partially melting the high-pressure mineral assemblage at 28-60 GPa. We infer that the trace concentration of Al within residual stishovite increases upon partial melting, thereby increasing the coupled abundance of H in this crystalline phase. The 'anhydrous' component of subducted oceanic crust can thus recycle a significant amount of water into the lower mantle over the age of the Earth, with subducted stishovite potentially returning {approx} 10{sup 2} times the amount of water present in today's atmosphere.

Authors:
; ;  [1]
  1. Univ of Michigan
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1008781
Resource Type:
Journal Article
Journal Name:
J. Geophys. Res.
Additional Journal Information:
Journal Volume: 108; Journal Issue: (B1) ; 2003; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
ENGLISH
Subject:
08 HYDROGEN; ABUNDANCE; BASALT; DEVOLATILIZATION; HYDROGEN; MELTING; OCEANIC CRUST; PEROVSKITE; STISHOVITE; TRANSPORT; WATER

Citation Formats

Panero, W R, Benedetti, L R, Jeanloz, R, and UC Berkeley). Transport of water into the lower mantle: Role of stishovite. United States: N. p., 2010. Web.
Panero, W R, Benedetti, L R, Jeanloz, R, & UC Berkeley). Transport of water into the lower mantle: Role of stishovite. United States.
Panero, W R, Benedetti, L R, Jeanloz, R, and UC Berkeley). Wed . "Transport of water into the lower mantle: Role of stishovite". United States.
@article{osti_1008781,
title = {Transport of water into the lower mantle: Role of stishovite},
author = {Panero, W R and Benedetti, L R and Jeanloz, R and UC Berkeley)},
abstractNote = {When subjected to lower-mantle pressures and temperatures, natural 'anhydrous' basalt containing 0.2 wt.% H{sub 2}O forms a phase assemblage in which SiO{sub 2} stishovite is a significant carrier of hydrogen (up to 500 ppm H{sub 2}O by weight, as hydroxide), whereas the coexisting (Mg, Fe, Al, Ca)SiO{sub 3} perovskite appears to be not (upper bound of 50 ppm (wt) H{sub 2}O). Contrary to the devolatilization characteristically observed at lower pressures, we find that the abundance of H{sub 2}O in residual stishovite increases from {approx}100 to {approx}400 ppm by weight upon partially melting the high-pressure mineral assemblage at 28-60 GPa. We infer that the trace concentration of Al within residual stishovite increases upon partial melting, thereby increasing the coupled abundance of H in this crystalline phase. The 'anhydrous' component of subducted oceanic crust can thus recycle a significant amount of water into the lower mantle over the age of the Earth, with subducted stishovite potentially returning {approx} 10{sup 2} times the amount of water present in today's atmosphere.},
doi = {},
url = {https://www.osti.gov/biblio/1008781}, journal = {J. Geophys. Res.},
issn = {0148-0227},
number = (B1) ; 2003,
volume = 108,
place = {United States},
year = {2010},
month = {12}
}