Study Of Geological Characteristics And Enrichment Regularities Of Mineralization Of Kalangu,Tamu Lead-Zinc Deposits, West Kunlun, Xinjiang Province

Western Kunlun Orogenic Belt which locates in the northwestern part of China is one of the lowest level of geological research for restrict of natural condition. It was located at the junction of Pale-Asian and Tethyan tectonic domain and has experienced a complicated geological evolution including many events of magma and tectonic movements, which is considered to be of great ore-forming potential. The late-Paleozoic Oytage-kurliang fissure basin is a very important Lead-Zinc ore-forming zone in the northern part of Western Kunlun Orogenic Belt, it also experienced a complicated geological evolution and exists with a special ore-forming background.In pre-sinian, Qaidam massif,West Kunlun massif and Pamirs massif were formed by the breaking up of the earth's crust. In Caledonian, Original Tethyan ocean crust began to subduce under West Kunlun massif from north to south while the magmatic arc of the middle of Western Kunlun Orogenic Belt was formed. In the late Paleozoic, the middle of Western Kunlun Orogenic Belt is considered to be late-Paleozoic magmatic arc because of the influence of breaking up of the Paleo-Tethyan ocean, at the same time, Kusilapu-Talong region was located at the position of back arc and later developed into late- Paleozoic back arc fissure(also named late-Paleozoic Oytage-kurliang fissure basin). This fissure belongs to the sedimentary formation of late Paleozoic and formed a suit of Reef Carbonate—Biolithite Limestone,Dolomite,Carbonate Siltstone which riched in ore-forming elements such as: Pb,Zn and Cu , it provided materials for metallogenisis. It is also considered to be an important Lead-Zinc ore-forming belt which contains many ore-forming occurrence such as Kalangu,Tamu and so on. The late-Paleozoic Oytage-kurliang fissure basin which experienced the process of late-Paleozoic sediment and magma,tectonic movements of Heroynian,Indosinian,Yanshan Period and Ximalaya Period creates many favorable conditions for metallogenisis.Kalangu and Tamu Lead-Zinc deposits are located in the north of late- Paleozoic Oytage-kurliang fissure basin. The main emerged stratum in ore district consist of lower Carboniferous, the lithology is mainly Limestone,Dolomitie,a little Carbonate Siltstone and Sandstone; the ore bodies are mainly reached in the lithological segment of C11-3kl. Those two deposits are strictly controlled by some interbeded fragmentation and minitype structural bands, with the ore bodies presented"feather"type,vein type,layer type and layer like type. Some dolerite veins are found in the ore district and the nearby. Some mineralization phenomena occurred very closely to the dolerite veins , which made us believe that the mineralization of the two deposits maybe has close relationship with the dolerite veins. Dolerite veins maybe provide the heat source for the metallogenisis, but they can't provide enough heat-drive force for large scale deposits because of the limitation of scale of dolerite veins.Kalangu and Tamu Lead-Zinc deposits have the same ore characteristics, Ore mineral are mainly composed of galenite,phalerite,pyrite and chalcopyrite; gangue mineral are mainly consisted of dolomite,calcite and quartz; ore texture are mainly automorphic and hypidiomorphic,polilitic and replacement dissolved texture; ore structure are mainly disseminated,veinlet and massive structure. Kalangu and Tamu Lead-Zinc deposits also have the same characteristics of fluid inclusions, it is proved that metallogenic fluids of those two deposits are of low salinity(〈8wt%NaCl) and low density(〈1g/cm3); the homogeneous temperatures of fluid inclusions are 160 oC～180 oC with 233 oC individually, which indicate that the ore-forming temperatures reach middle category. The study of hydrogen-oxygen isotope indicates that metallogenic fluids are mainly precipitation of atmosphere. The wall rock and ore have the same characteristics of Pb/Zn, which indicates that metallogenic materials mainly come from the wall rock. But Kalangu gives priority to Pb and Tamu gives priority to Zn according to the content of Pb and Zn.It is believed that Kalangu and Tamu Lead-Zinc deposits which controlled by tectonics,magmatic rocks and stratum are hydrothermal vein deposits of middle-low temperature. It, firstly, had been undergoing a sedimentation process in the shallow sea which existed in the southern margin of Qaidam massif, enriching process of Pb and Zn since the beginning of late Paleozoic. It provided materials for metallogenesis. And later hydrothermal fluids had been eluviating rock layers and schlepping Pb and Zn to somewhere favourable to precipitate and to form deposit.Kalangu and Tamu Lead-Zinc deposits are not Mississipi Valley Type deposits, the reasons are as follows:①,ore bodies of the former are strictly controlled by faults, the shape of it is more complicated, and ore bodies of the later are controlled by lithology and lithofacies with the shape simple;②,metallogenic fluids of the former are mainly precipitation of atmosphere which is of low salinity and low density, and the later is mainly formation water with high salinity and high density;③,sulphur isotopes of the former are not the same as those of the later which mainly come from the vaporing sulphate of sea facies;④,there are some dolerite veins which are found in the ore district and the nearby of the former , those veins are considered to have close relationship with metallogenesis, but the later goes without this phenomena.Based on the systemic study of the Geological Characteristics,Enrichment Regularities and Metallogenesis, we believe that Kalangu and Tamu Lead-Zinc deposits also have biggish potential of prospecting; the region of the two deposits is of great ore-forming condition, which made it have more chances to find hydrothermal vein Lead-Zinc deposits of middle-low temperature.