Geochemical Characteristics and its Tectonic Significance of Quartz Diorite in Baimashan Gold Field,Southern Qinling Mountains

Baimashan small rock,related to the gold deposit in spacial,is located in the Baimashan gold deposit area,the South Qinling ore-forming sub-belt.It is dominanted by the granodiorite and minor biotite monzonite at the marginal part.Geochemical characters indicate that Baimashan quartz diorite belong to the high K calc-alkalic series,however,they also have more similar geochemical characters to theCtype adakite than theOtype adakite.The tectonic nature of lithosphere in South Qinling was characterized by transition from compression to extention in the Early-Middle Triassic period.The granites of adakite in the South Qinling area may resulted from partial melting of the mafic lower crust(basalts)in the thickened lower crust,and mixing with the mafic magma,due to the lithospheric stretching and the asthenosphere upwelling,which can provide some clues to the collision between the North China Plate and the Qinling micro-plate,and also direct copper-gold prospecting.