Petrogenesis of the Baimashan C-type adakite in Western Qinling: Constraints from their geochemistry and Sr-Nd-Pb isotopic compositions

The Baimashan small rock body, relatedto gold deposit in space, is located in the Baimashan gold mining field, western Qinling metallogenic belt. This study conducted geochemical characteristics analysis of main elements, trace elements and rare earth elements, and Sr-Nd-Pdisotopic composition so as to understand its petrogensis. The results indicate that these rocks belong to high K calc-alkalic series and have geochemical compositions similar to the C-type adakite. Sr-Nd-Pb isotopic compositions show thattherock body is characterized by enrichment of radiogenic Pb, with initial(⁸⁷Sr/⁸⁶Sr)_t of 0.706, negative εNd_(t) of -6.75, and T_DM of1.53Ga, implying that the magmas should derive from lower continental crust andgeochemically similar to the mafic rocks of the Yaolinghe Group. It can be concluded that the rock might result from partial melting of thickened mafic lower crust, with residual phase being amphibole eclogite.