Geochemistry and petrogenesis of core samples from Baishan molybdenum deposit, East Tianshan Mountains, Xinjiang.

Samples from deep drill holes show that the mineralized granitic rocks related to Baishan molybdenum deposit, East Tianshan Mountains, Xinjiang are moyite, biotite-plagiogranite and granitic porphyry. The collected samples were used to investigate their geochemical features and petrogenesis for these rocks. All of the rocks are characterized by high Al2O3 and Na2O and Sr contents, but low MgO, Y and Yb contents and high Sr/Y and La/Yb ratios, similar to the geochemical characteristics of adakitic rocks. These signatures suggest that the magmas of these rocks were derived from a deep garnet-bearing source. Evidence of rock ages and geochemical tectonic-discrimination-diagrams show these rocks were formed in post-orogenic environment. Based on the geochemical characteristics, we proposed that the magmas of these adakitic rocks (drill hole core samples) may have been formed by partial melting of the thickened lower crust. The mineralization of Baishan molybdenum deposit should be related to adakitic magma activity. The high Mo abundance of the crustal source, the fluid release from the magmas and high oxygen fugacity environment during the magmatic process may be the key factors for the molybdenum mineralization.