Petrogenesis of the Cenozoic volcanic rocks from the northern part of the Qinghai-Tibet Plateau
青藏高原北部新生代火山岩的成因机制

Based on the electron probe analyses result of the minerals and the bulk rock composition of the Cenozoic volcanic rocks from Yumen and Hoh Xil lithodistricts on the Qinghai-Tibet Plateau, the forming conditions including temperature and pressure of those rocks are studied.According to the thermodynamics calculation result of the mineral-melt equilibrium,the depth of the asthenosphere superface (about 75～130km) for the northern part of the Qinghai-Tibet Plateau during Cenozoic era is suggested. Finally, this paper indicates that the Cenozoic volcanic rocks in the northern part of the Qinghai-Tibet Plateau mainly consist of shoshonite series.Their forming temperature is 630～1039℃ and forming pressure is between 2.3～4.0 GPa and formed in the intracontinental orogenic belt,where the primary magma was originated from a particular enriched upmantle and accreted crust-mantle belt or directly originated from asthenosphere superface by partial melting of pyrolite.