Stability of hydrous phases in subducting oceanic crust

Experiments in the basalt-H 2O system at 600–950°C and 0.8–3.0 GPa, demonstrate that breakdown of amphibole represents the final dehydration of subducting oceanic tholeiite at T≥650°C; the dehydration H 2O occurs as a free fluid or in silicate melt co-existing with an anhydrous eclogite assemblage....

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Bibliographic Details
Published in:Earth and planetary science letters 1996-09, Vol.143 (1), p.161-171
Main Authors: Liu, Jun, Bohlen, S.R., Ernst, W.G.
Format: Article
Language:English
Subjects:
basalts
Marine
oceanic crust
phase transitions
subduction
water
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Summary:Experiments in the basalt-H 2O system at 600–950°C and 0.8–3.0 GPa, demonstrate that breakdown of amphibole represents the final dehydration of subducting oceanic tholeiite at T≥650°C; the dehydration H 2O occurs as a free fluid or in silicate melt co-existing with an anhydrous eclogite assemblage. In contrast, about 0.5 wt% of H 2O is stored in lawsonite at 600°C, 3.0 GPa. Our results suggest that slab melting occurs at depths shallower than 60 km for subducting young oceanic crust; along a subduction zone with an average thermal gradient higher than 7°C/km, H 2O stored in hydrated low-potassium, metabasaltic layers cannot be subducted to depths greater than 100 km, then released to generate arc magma.
ISSN:0012-821X
1385-013X
DOI:10.1016/0012-821X(96)00130-6