新疆阿吾拉勒地区查岗诺尔铁矿床铜矿化的成因探讨

Study on the Cu-mineralization of the Chagangnuoer Fe-deposit in the Awulale area,Xinjiang

与西天山阿吾拉勒石炭纪火山活动有关的铁矿床普遍发育含铜的方解石脉,在局部地段构成伴生或独立铜矿体.钻孔揭露显示,查岗诺尔铁矿体内含铜方解石脉穿插在磁铁矿、石榴石、阳起石和绿帘石中,其形成明显晚于铁矿化.流体包裹体研究显示,查岗诺尔铁矿床后期铜矿化的成矿流体应为CO2-CaCl2-NaCl-H2O体系的超临界流体.这种富含CO2的超临界流体不但具有较强的渗透性,而且对铜等成矿元素具有较高的溶解度,可以携带巨量成矿元素进行长距离迁移.由于体系的温度及CO2和H2S等挥发分含量降低,铜等成矿元素在流体中的溶解度明显下降并沉淀成矿.碳、氧位素分析结果显示,查岗尔铁矿床晚期铜矿化与区内早二叠世的钾质-超钾质岩浆活动有关.

The Cu-bearing calcite veins, usually in association with the accessory or independent Cu mineralization, were widespread in Fe deposits associated with Carbonaceous volcanics in the Awulale Mountains, western Tianshan. The drillings show that the calcite veins occurred significantly later than the Fe mineralization, with cutting across the magnetite, garnet, actinolite and epidote. This study investigated the fluid inclusions forming after the Fe mineralization in the Chagangnuoer deposit. The results suggest that the Cu-mineralization fluid was a supercritical fluid of CO2 CaCI2--NaCI--HeO, Such CO2-rich fluid was of high permeability and solubility in Cu, and of high ability to transfer abundant ore-forming elements over a long distance. As the temperature down to 280 ℃-240 ℃, the fluid would change into sault solution. The solubility would drop and the ore-forming elements would precipitate, since the deerease of temperature and violates of CO2 and H2S. C--O isotopes indicate that the Cu-mineralization related fluids of the Chagangnuoer Fe deposit were derived from the Permian potassic and shoshonitic magmatisims.