WANG Xiao-juan1,2,3，LIU Yu-ping2*，YE Lin2，MIAO Ying-li4，ZHANG Qian2
(1. Henan Institute of Geological Survey, Zhengzhou 450001, China;
2. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
3. Henan Key Laboratory of Ground Water Pollution Control And Rehabilitation, Zhengzhou 450001, China;
4. Yunan Hualian Mineral Resource Exploration Lt. Co., Qujing 655000, China)
Abstract: The Dulong tin-zinc ploymetallic deposit is one of the largest cassiterite-sulfide deposits in China. Due to the complexity of the tectonic, geological, and metallogentic activities, the genesis of the deposit has been greatly debated for a long time. This has restricted mineral exploration in depth and peripheral areas of the deposit to a certain extent. In this paper, based on the field observation of geological characteristics of the deposit, geochemical characteristics of major and trace elements of the skarn mineral - pyroxene have been studied systematically. The analytical results of major elements using electron probe and trace elements using LA-ICP-MS show that the formation of skarn is closely related to the concealed granite body in depth. The end member compositions of pyroxenes are changed regularly from Di- Hd, to Di, and then to Di-Hd with their sampling locations changed from deep to shallow levels. It is speculated that the pH value and redox environment of the fluids were changed obviously, from a relatively reduced acidic environment in the early stage to a relatively oxidized alkaline environment, a suitable precipitation environment for the common mineralization of polymetallic elements, in the late stage of the formation process of skarn in the deposit.The results of trace element analysis show that the pyroxenes contain relatively high contents of metallogenic metal elements such as Zn, In, Sn. Compared with the Laojunshan granite, the hidden rock mass of the deposit is obviously depleted in the ore-forming elements, indicating indirectly that the formation of skarn in the Dulong deposit could be controlled by the Yanshanian Laojunshan granite. At the same time, the major elements analytical results show that the pyroxene composition can be used to judge if its formation is closely related to the mineralization or not. The space with distance range of 50-300m away from the hidden granite could have obvious mineralization and should be a favorable one to find mineral resources of Sn, Zn, Cu, W, and other metallic elements.
Keywords: pyroxene; geochemistry; ore deposit gemesis; exploration; Dulong Sn-Zn ploymetallic deposit
ACTA MINERALOGICA SINICA Vol. 40, No.6, 2020, page 664-676
