青海铜峪沟铜矿区含黄铜矿硅质岩及其地质找矿意义
Genesis of the Chalcopyritebearing Silicalite in the Tongyugou Copper Ore District, Qinghai Province and Its Geological Prospecting Significance

摘要： 位于东昆仑与西秦岭衔接转换部位的青海铜峪沟是鄂拉山成矿带上一处重要的大型铜矿床，矿山增储和外围找矿问题突出，硅质岩可能是重要找矿标志之一。铜峪沟铜矿区硅质岩呈层状、似层状及条带状整合产于中—下三叠统中，由微晶-细晶石英组成，含少量绢云母、黄铜矿及磁黄铁矿等。硅质岩主微量元素特征，如Al2O3-TiO2图解、Fe-Mn-(Cu+Ni+Co)×10三角图解和P2O5-Y图解，以及硅氧同位素特征等方面显示出典型热水沉积地球化学特征；同时岩石Si/Al比值、U/Th比值及稀土元素特征等表明热水沉积体系遭受了少量陆源物质的影响。此外，硅质岩Al2O3/(Al2O3+Fe2O3) -Fe2O3/TiO2图解、Ti/V-V/Y图解、(La/Ce)N-Al2O3/(Al2O3+Fe2O3)图解及稀土元素特征等均显示其形成于大陆边缘环境。区域上，随着阿尼玛卿洋由南向北俯冲，早—中三叠世铜峪沟一带属弧后盆地环境，盆地内发生喷流沉积作用使大量成矿物质预富集形成矿胚层，此为重要成矿期，而硅质岩作为该过程的重要地质记录，同时指示区域上错扎玛和塔东等地有较好的找矿前景。
Abstract: The Tongyugou area, located in the conjunction between the East Kunlun and West Qinlin orogenic belts, is one of the most important copper deposits in the Ela mountain metallogenic belt. Further resource prospecting at the area faces great challenges, and the silicalite might be one of the clues. The silicalite in the Tongyugou copper ore district occurs as bedding and banded structure, and is mainly hosted in conformity within LowerMiddle Triassic rocks. It is mainly made up of microfine crystalline quartz grain with less sericite, chalcopyrite and pyrrhotine, however, no biological related texture has been observed. The Al2O3TiO2 and FeMn(Cu+Ni+Co)×10, P2O5Y diagrams and SiO isotope signature suggests that the silicalite was formed by hydrothermal sedimentary processes. Its Si/Al and U/Th values and rare earth element geochemical characteristics also imply that the hydrothermal sedimentary system has been affected by some terrigenous material. Based on the examination in Al2O3/(Al2O3+Fe2O3)Fe2O3/TiO2, Ti/VV/Y and (La/Ce)NAl2O3/(Al2O3+Fe2O3) discrimination diagrams, the silicalite is proved to be formed at continental margin setting. Accompanying with the northward subduction of the Anyemaqen ocean in the EarlyMiddle Triassic, the Tongyugou area appears to be a backarc basin. In the basin, exhalative sedimentation occurred and also resulted in a lot of oreforming minerals to form protore beds. The silicalite is an important recorder to preserve the information of the mineralization event. Also, this study suggests that the Cuozama and Tadong may be important targets for the exploration of VMS type deposits