THE CHARACTERISTICS OF PRE-SINIAN METAMORPHIC ROCKS IN THE HUILI-MIYI-YANBIAN AREA,SICHUAN PROVINCE,AND THEIR AGE

There is a sequence of miea-schist, mica-quartz schist and albite quartzite with small amount of greenschist,granulitite and dolomite marble containing such diagnostic minerals as silimanite,staurolite,andalusite and almandine in the Huili-Miyi-Yanbian area,Sichuan Province.The authors name this sequence of metamorphic rocks the Xiacun Grnup and divide it from below upwards into the Gongshan,Wujiagou,Huanglian and Hetaowan Formations. A detailed correlation is made between it and the Huili,Yanbian,Hekou and Kangding Groups established by the predecessors in respect to the rock associations,sedimentary formations,metamorphism and isotopic ages.The authors consider that the Xiacun Group lies above the Kangding Group and below the Huili and Yanbian Groups,with an age range between 2000 and 1700 Ma.Its relationship with the Hekou Group awaits further study.