REDOX STATE OF ECLOGITES AND PERIDOTITES FROM SUB-CRATONIC UPPER MANTLE AND A CONNECTION WITH DIAMOND GENESIS

Abstract

Pressure-Temperature- fO2 conditions and fluid compositions estimated for mineral parageneses from inclusions in diamonds, diamond-bearing and diamond-free xenoliths using a garnet-clinopyroxene-silica oxygen barometer data indicate that the upper mantle is zoned, with a relatively oxidized lithosphere and a reduced asthenosphere. Calculations in the C-O-H system indicate that eclogite inclusions within diamonds and xenoliths have formed mainly in equilibrium with water-rich fluids. © Springer-Verlag 2006.