Geological Characteristics And Ore Genesis Of The Nixintage Iron Deposit In The Western Tianshan Mountains, Xinjiang, NW China

Nixintage iron deposit is situated at east Awulale metallogenic belt, western Tianshan Mountains,Xinjiang. Several large-sized and medium-sized iron deposits have been found in this belt and their genetictype and the contact between them has become a hotspot in this area. A series of systematic research hasbeen done after conscientiously study the comprehensive previous achievements to discuss the volcanicrocks and ore genesis and then reveal the mineralization process. We can proposed several points asfollows: The ore body is hosted in the third part of the Lower Carboniferous Dahalajunshan Formation（C1d3）and the volcanic rocks exposured in the studied area consist of tephrite, basaltic trachyandesite,trachyandesite and pyroclastic rocks. They are all characterized by rich in alkali and titanium and belong tothe alkali basalt series. These volcanic rocks and the ore deposit yield an U-Pb age of343.2±2Ma（MSWD=1.8）and it says that they were formed in the VeasonAge of the early Carboniferous Epoch. Theiron orebodies are all concealed orebodies which are hosted in basaltic trachyandesite, trachyandesite andpyroclastic rocks and appear in bedded and Stratoid forms On the basis of the study of ore fabric andparagenetic association of minerals, the metallogenic stages of Nixintage iron deposit can be devided intotwo period: magmatic metallogenic period and hydrothermal metallogenic period. Petrological andgeochemical characters show that the orebodies and its wall rocks are homologous and the the magmasource area shall be the metasomated depleted mantle wedge above the subducting plate. During the courseof moving upward the primary magma had assimilated a considerable quantity of crust materials andexperienced some extent of fractional crystallization. The study of petrography demonstrates that theore-forming parental magma of the magmatic ore is probably the alkalic basaltic magma which is rich inNa. The stable isotopes geochemitry reveal that the metallogenic hydrothermal solution is derived fromvolcanic hydrothermal solution and The metallogenic substance mainly comes from the basaltic magmawhich is formed under the environment of active continental margin. To sum up, Nixintage magnetic irondeposit is the product of basaltic magma differential evolution which is formed under the environment ofactive continental margin during the Carboniferous period. The genetic type of this magnetic iron oredeposit is belongs to volcanic magmatic-hydrothermal compound type.