Petrogenesis of Cenozoic Adakit Volcanic Rocks of Western Yudaishan In Qiangtang of Northern Tibet

The characteristics of petrology and elemental geochemistry indicated that there is one belt of high—K and high—Mg calc—alkaline series Cenozoic volcanic rocks in the western of Yanzihu—Yudaishan Qiangtang of northern Tibet.They are rich in LREE and LILE,while depleted in incompatibility elements (Cr,Ni,etc.),their geochemical characteristics imply that they have clear geochemical characteristics of Adakite.The petrogenesis is restricted by fractional crystallization and the provence contamination by the upper crust in source.The high—K and high—Mg calc—alkaline series volcanic rocks result from the India/Eurasia collusion zone,forming a hybridized melt successively fractionated to evolve different adakit esuites distinguished as the calc—alkaline rocks.