Metallogenic Tectonic Setting And Ore-Finding Potential Of Xitieshan Massive Sulfide Lead-Zinc Deposit: Evidence From Lithochemistry And Geochemistry Of Ore-Hosted Volcanic Strata, Tanjianshan Group.

Recent research of submarine massive sulfide deposit (MSD) showed that the MSD generation was closely related to some processes of tectonic structure and volcanism, which occurred in a special period of tectonic evolution and generally ore-forming time-span within several million years. The Xitieshan deposit, located in the northern margin of the Qaidam basin, Qinghai Province, is the largest MSD in the northwest of China. Based on systematic petrochemical and geochemical research of ore-hosting volcanic rocks, named the Tanjianshan Group, it can be stated that, (1) petrochemistry and geochemistry of volcanic rocks of the Tanjianshan Group indicate that the magmas were originated from an identical source, evolving from acidic to mafic and thus generating various volcanic rocks with a transitional petrochemical and geochemical trend. (2) Attributes of REE and trace elements, and tectonic discrimination diagrams collectively display that the tectonic settings for generating the Tanjianshan Group volcanic had been evolved continuously from continental magmatic arc, through transitional arc, to oceanic basin. (3) The magma evolution and Rb-Sr isotope systematics imply that the tectonic setting of the Xitieshan MSD might be a continental back-arc basin similar to Okinawa tough in the southwest Pacific. (4) As to the mineral prediction, it is concluded that, the volcanic-sedimentary successions within the bimodal volcanic sequence formed during the early back-arc extension, are believed to be the important target in the Xitieshan orefield and its vicinities, but the upper stratigraphic successions of the Tanjianshan Group are not favorable in finding MSD mineralization.