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Published December 1982 | public
Journal Article

Phase relationships in the system KAlSiO_4-Mg_2SiO_4-SiO_2-H_2O as a model for hybridization between hydrous siliceous melts and peridotite

Abstract

The system KalSiO_4-Mg_2SiO_4-SiO_2-H_2O includes model representatives of (1) hydrous siliceous magma from subducted oceanic crust — the eutectic liquid in KalSi_3O_8-SiO_2-H_2O, and (2) the overlying mantle peridotite — the assemblage forsterite+enstatite (Fo+En). In a series of partly schematic isobaric isothermal sections, the products of hybridization between the model materials at pressures between 20 and 30 kbar have been determined. The liquid dissolves peridotite components with little change in composition. Hybridization is not a simple mixing process, because of the incongruent melting of peridotitic assemblages with phlogopite (Ph). Hybridization causes solidification of the liquid, with products a sequence of three mineral assemblages: Ph, Ph+quartz (Qz), and Ph+En. The products represent an absolute geochemical separation and local concentration of all potassium from the liquid. Hybridization is accompanied by H_2O-saturation of melts, and evolution of aqueous fluid. Although there are significant differences between the melt composition and that of the magma rising from subducted oceanic slab, and between Fo+En and the mantle rock, extrapolation of the results suggests that the conclusions can probably be extended to mantle conditions with sodium in the melt, and jadeitic clinopyroxene included in the hybrid products.

Additional Information

© 1982 Springer-Verlag. Received February 23, 1982; Accepted May 13, 1982. This research was supported by the Earth Sciences Section of the National Science Foundation, NSF Grant EAR 76-20413 and NSF Grant EAR 81-08626.

Additional details

Created:
August 22, 2023
Modified:
October 17, 2023