Abstract:

Derni massive sulfide Cu(Zn-Co) deposit is mainly wrapped by ophiolite in East Kunlun Mountains, and 8 massive sulfide ores give an isochronal age of (295.5±7.2)Ma by Re-Os isotope, which is a little later than zircon U-Pb age (308.2±4.9) Ma of the basalt in the mining area. The diagenesis and metallogenic epoch is between Late Carboniferous and Early Permian. It is older than the Indo-Chinese epoch granite in the north side of the mining area, suggesting no direct genesis relationship between granite and Derni Cu(Zn-Co) ore deposit. According to the texture and structure of the ores, mineral compositions and various geochemistry data, the genesis of Derni Cu(Zn-Co) ore deposit can be summarized as submarine exhalation-sedimentary mineralization and experienced later hydrothermal superimposition, which is similar to Cyprus-type VMS deposit by tectonic setting and mineral compositions. From mapping and borehole logging, the main ore bodies of Derni Cu(Zn-Co) ore deposit lay in brecciaous serpentinite or between brecciaous serpentinite and carbonaceous Fe-Si rock, which is different from any other VMS deposits in the world, and the special phenomenon may be caused by quick spreading of Late Paleozoic Tethyan middle ocean ridge, lack of enough mafic magma replenishment, accompanied by rapid ascending of meta-peridotite.

Key words: massive sulfide deposit, Re-Os isotope dating, ophiolite, Derni, East Kunlun Mountains