Geochemical Characteristics of Nianbo Formation at Cuoqin County, Tibet and its Geotectonic Significance

Nianbo formation of Lingzizhong group is the stratum of Eocene Epoch, which mainly consists of a set of intermediate-acid volcana lava and pyroclastic rock, and partly contains fresh water limestone. The field geological investigation and the synthetic research on petrology, lithogeochemisty and so on show they are calc-alkalic rock and that.incompatible K,Rb,Ba,and Th are intensely concentrated and Nb,Sr,P,Ti evidently lost in them, and that they are evidently controlled by deep faults and have close relationship with the regional structure evolution.