Transport of water into the lower mantle: Role of stishovite

Journal Article · Wed Dec 01 04:00:00 EST 2010 · J. Geophys. Res.

OSTI ID:1008781

Panero, W R; Benedetti, L R; Jeanloz, R ^[1]

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1. Univ of Michigan

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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1008781
• Journal Information: J. Geophys. Res., Journal Name: J. Geophys. Res. Journal Issue: (B1) ; 2003 Vol. 108; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

08 HYDROGEN
ABUNDANCE
BASALT
DEVOLATILIZATION
HYDROGEN
MELTING
OCEANIC CRUST
PEROVSKITE
STISHOVITE
TRANSPORT
WATER