Study of Environment and Chronology of Late Triassic Intrusive Rocks in East Nalinggele River of Qinghai

The Late Triassic intrusive rocks existing in east Nalinggele river are the mineralizing parent rocks for numerous skarn-typeiron or edeposits in the study area. Using five groups of graphic method proposed by Maniar and Piccoli(1989) for discriminating tectonic environment, we conclude that the intrusive rocks are the post-orogenic granitoids (POG type), which is in good accordance with regional data. The U-Pb test results show that the emplacement age of the intrusive rocks is between 214.2±1.3Ma, and 225.2 ±1.2 Ma and is resulted from the magmatic activity in late Indo-Chinese epoch. The study of petrology, genesis, and emplacement ageprovides a way for determining the agewhen the east Kunlun-Hercinian-Indo-Chinese orogenic cycle was in the stretching and collapsing process in late Triassic. In addition, the study is also significant for furt her studying the geological settings and for mineral resources exploration in this area.