Constraints on tectonic, fluid and metallogenic system evolution for the formation of Sareke sandstone copper deposit in northwestern Tarim block

There exist close relationships between tectonics, fluid evolution and formation of copper ore in the Sareke sandstone deposit in northwestern Tarim block, which constitute an integrated system. The δD values of inclusion water in the calcite of diagenetic stage are in the range of -65.3‰~-99.2‰, and the δD values of inclusion water in the quartz of metallogenic epoch are in the range of -65.3‰~-99.2‰, the δ¹⁸O_H2O values of the ore-forming fluid in the diagenetic stage are in the range of -3.22‰~1.84‰, and the δ¹⁸O_H2O values of the ore-forming fluid in the metallogenic epoch are in the range of-4.26‰~5.14‰, suggesting that the ore-forming fluid in the diagenetic stage and transformation period of the Sareke copper deposit mainly originated from the atmospheric water in the Mesozoic period and basin brine evolved from the water-rock interaction of the rainfall. The δ³⁴S values of the chalcocite in the ore are in the range of-15.4‰~-24.7‰, suggesting that most of the sulfur originated from the bacteria and reduced organic carbon in the strata, with the addition of minor organic sulfur. The evolution of the tectonics and ore-forming fluid controlled the formation of sandstone copper deposits. In the early period of the basin development, the strong uplift movement caused the erosion of the basement and Paleozoic strata in the periphery of Sareke basin, which offered abundant provenance to the formation of copper-rich source layer. Toward the late period, i.e., Late Jurassic epoch, large amounts of ore-forming fluid after long-term evolution was concentrated in the agglutinate and fissures of conglomerate in Kuzigongsu Formation, forming sandstone copper deposits with economic value in Sareke basin.