THE CHARACTERISTICS OF THE KANGDING GROUP AND ITS IMPLICATION FOR THE EVOLUTION OF THE YANGTZE PLATFORM BASEMENT

The basement of the Yangtze platform consists of two structural layers. The old one is the Kangding Group （crystalline basement） and the young one the Huili Group （folded basement）. The Kangding Group is composed of three parts: the tholeiitic series in the lower, the calc-alkali series in the middle and the sedimentary series in the upper, totalling over 10000 m in thickness. They have all undergone regional metamorphism and migmatization to different degrees. Two terranes can be recognized in the crystalline basement, i.e. the gneiss-granulite terrane and the granite-greenstone terrane. Based on the distribution, protolith formation sequence and geochemistry, the Kangding Group is considered as the early Precambrian greenstone belt.