Abstract: The Pana volcanic rocks of the Linzizong Group in Zhaxue area, Linzhou County, Tibet are mainly composed of rhyolitictrachy lavas and volcanoclastic rocks. Its geochemical characteristics (14.55% of Al₂O₃ 8.78% of K₂O+Na₂O, 5.77% of K₂O, K₂O/Na₂O=2.07) suggest that the Pana Formation volcanic rocks belong to highAl, highK calcalkalineshoshonite series. LREE in the volcanic rocks were slightly enriched with moderate to strong Eu anomalies. In the volcanic rocks, Rb and Th were intensively enriched, Ta, Ba and U moderately enriched while Y, Yb and Sr relatively depleted. The lithogeochemical study suggests that the Pana Formation volcanic rocks were formed about 40 Ma by anatexis of the thickened continental crust in the postcollision process between Indo plate and Eurasia plate.

Key words: lithogeochemistry, partial melting, postcollision, Tibet