THE FORMATION AGE OF GRANITOIDS IN THE BAIIYUZHONGDIAN AREA, WESTERN SICHUAN

Since 1985, the author and his colleagues have collected eight samples for whole-rock Rb-Sr isochron age determination, four samples for zircon U-Pb Wrych concordia age determination and Six samples for ⁴⁰Ar/³⁹Ar fast neutron dating. The ages of granitoids exposed widely in the area can be determined and checked by several methods. The granitoids in the area were determined to be Caledonian—Himalayan in age, and the peak periods for the rock formation are middle and late Indosinian and late Yanshanian-early Himalayan.