Petrogenesis of the Cenozoic volcanic rocks from the northern part of Qinhai-Xizang (Tibet) plateau |
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Authors: | Shaocong Lai |
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Institution: | (1) Department of Geology, Northwest University, 710069 Xi’an, China |
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Abstract: | Based on electron probe analyses of the minerals and bulk composition of the Cenozoic volcanic rocks from Yumen and Hoh Xil
lithodistricts, Qinghai-Xizang plateau, the forming conditions including the temperature and pressure of those rocks are studied
in this paper. According to the thermodynamic calculation results of mineral-melt equilibrium, the depth of the asthenosphere
superface (about 75 – 130 km) for the northern part of the Qinghai-Xizang plateau during the Cenozoic is suggested. Finally,
this paper indicates that the Cenozoic volcanic rocks in the northern part of the Qinghai-Xizang plateau mainly consist of
shoshonite series. Their forming temperature is 630 – 1039°C and forming pressure is between 2.3 – 4.0 GPa. The rocks were
formed in the intracontinental orogenic belt, of which the primary magma was originated from a particular enrichment upper
mantle and accreted crust-mantle belt or directly from asthenospheric superface as a result of partial melting of pyrolite.
The project was supported by the National Natural Science Foundation of China (No. 49234080), the Geological Sectional Foundation
of MGMR (No. 8506201, 8506207) and the Science Foundation of Northwest University (97NW23). |
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Keywords: | Qinghai-Xizang plateau Cenozoic volcanic rock petrogenesis |
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