The exploration breakthrough of the Tiegelongnan superlarge porphyry Cu（Au）deposit, Bangong Lake arc, Tibet, and its significance

Abstract: Based on detailed analysis of regional metallogenic geological background and conditions, it is held that the Duolong ore district of the West Bangong Lake arc has metallogenic prospecting and resources potential for porphyry Cu-Au deposits. Through the exploration in 2013, the authors made a breakthrough in Tiegelongnan. Copper reserves of the Tiegelongnan ore district has reached a superlarge ore deposit, and this deposit has thus become the largest porphyry Cu（Au） ore deposit in the Duolong ore district as well as the major exploration breakthrough in 2013. The deposit is located in early Cretaceous Meiriqiecuo formation of the middle Duolong ore district, and has a close temporal relationship with early Cretaceous intrusive granodiorite porphyry, granite porphyry and concomitant hydrothermal mineralization breccia. The orebodies mainly occur in the lower middle Jurassic Sewa Formation feldspar quartz sandstone, lithic sandstone intercalated with dark gray to deep black silty slate and mineralized porphyry. Orebodies exhibit concealed dome and are characterized by great downward extension in the forms of network veins, veinlets, and disseminations. Hydrothermal alteration is well developed, with obvious zonation, strong silicification, sericitization, and widely superimposed advanced argillic alteration. The denudation degree of the ore district is very low. The surface only develops limonite and clay, with no copper mineralization. Alteration and mineralization increased gradually downward, and the mineralization extension reaches one thousand kilometers at depth without closure. The upper copper mineralization is of chalcocite-digenite-enargite association, exhibiting characteristics of the Cu-S system, which gradually changes into bornite and chalcopyrite characteristics of the Cu-Fe-S system. Copper mineralization is associated with Au, Ag mineralization and assumes positive correlation. Compared with other porphyry Cu-Au ore deposits in the Duolong ore district, this deposits is poor in gold. The exploration breakthrough of the deposit provides a good example for the exploration work of the mining company and also has significance for regional ore-prospecting.