MINERALOGY AND T-P CONDITIONS OF CRYSTALLIZATION OF EARLY ARCHAEAN GRANULITES FROM QIANXI COUNTY, NE CHINA

This paper presents new wet chemical analyses of proxeue, garnet, amphibole and bio-tite from the Early Archaean granulites of Qianxi county, NE China. The mineralogy anddistribution coefficients of Fe and Mg between coexisting ferromagnesian minerals are discussedin detail. The narrow K_D(Fe) range and the close clustering of the intersections on the Wo-Enjoin for the pyroxene pairs may be suggestive of the attainment of uniform equilibrium condi-tions. From petrographic observations and geothermobarometric calculation, it is concluded thatthe P-T conditions of metamorphic recrystallization of the granulites are 11--13 Kb and800--850℃ during an intermediate pressue granulite facies metamorphism at a geothermalgradient of 18--23℃/km.