Complete miscibility between silicate melts and hydrous fluids in the upper mantle: experimental evidence and geochemical implications

作者: Hélène Bureau , Hans Keppler

DOI: 10.1016/S0012-821X(98)00266-0

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摘要: The phase relationships between silicate melts and hydrous fluids were studied by direct visual observation in an externally heated diamond-anvil cell. Complete miscibility of melt water was observed for a wide range compositions, including nepheline, jadeite, dacite, haplogranite Ca-bearing granite. Some evidence complete also the system basalt–H2O. critical temperatures all systems decrease rapidly with pressure. At 15 kbar, temperature nepheline is around 550°C, jadeite 800°C granitic compositions it close to 900°C. In general, appear increase silica content system. Our results suggest that there most upper mantle, except at very shallow depths. This means water-saturated solidus cannot be defined any more deeper parts mantle. Very silica-rich inclusions found spinel lherzolites associated fluid inclusion are probably result unmixing supercritical containing comparable amounts components. decomposition amphibole subducted slab occurs conditions where gap not yet closed, while phengite lawsonite far beyond curve. Accordingly, released breakdown these minerals should have different properties. Highly mobile, little dissolved produced breakdown, will lead much silicate-rich less mobile phases.

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