High-pressure metamorphism in kyanite-bearing schists from the original Jingangku Formation of the Wutaishan

摘要

There arc four types of kyanite-bearing schists in the original north Jingangku Formation of the Wutai Group. One of them is called kyanite-gedrite schist which mainly consists of gedrite and kyanite. There is a coronitic texture in the rocks, some minerals form a rim around the kyanite grains and develop as a result of reaction between the gedrite and enclosed kyanite. There is more than one rim which consists of an inner rim of staurolite, corundum and chlorite with an outer rim of cordierite. The development of coronitic texture in the kyanite-gedrite schist implies a direct transition trom an assemblage typical of high pressure and moderite temperature to an assemblage typical of moderite pressure and temperature. The obvious decompression implies that the rocks have experienced a related subduction-uplift process along coverging plate boundaries.