Enriched upper mantle and eclogitic lower crust in north Qiangtang, Qinghai-Tibet Plateau: petrological and geochemical evidence from the Cenozoic volcanic rocks.

Using the petrological and geochemical method, the Cenozoic volcanic rocks collected from north Qiangtang, Qinghai-Tibet plateau were dealt with in th is paper. The research results indicate that the Tertiary volcanic rocks ca n be devided into two different associations: alkaline (shoshonitic) series and high-potassium calc-alkaline series. They originated from a special in homogeneously enriched upper mantle and a eclogitic lower crust, respective ly. It shows that the north part of Qinghai-Tibet plateau develops a enrich ed mantle source and a eclogitic lower crust in Cenozoic period at the spec ific tectonic setting of plates collision. This recognization is significan t for further discussions about the uplift mechanism and continental dynami cs of the Qinghai-Tibet plateau.