青海省同仁县夏布浪铜铅锌矿床安山岩SHRIMP锆石U-Pb定年及其对成矿时代的制约

青海省同仁县夏布浪铜铅锌矿是近年来在秦祁昆结合部新发现的VMS型铜铅锌多金属矿床之一。该矿床为小型铜铅锌矿, 矿体规模变化较大, 呈浸染状、网脉状、条带状赋存于三叠系火山岩中;主要的金属矿物有黄铜矿、黄铁矿、辉锑矿、方铅矿、闪锌矿;围岩蚀变有绿泥石化、碳酸盐化、硅化等, 其中硅化蚀变与成矿作用关系最为密切, 且蚀变带范围随矿体厚度变化而变化。含矿安山岩SHRIMP 锆石U-Pb年龄为240.1±2.4 Ma(MSWD=0.31), 说明夏布浪矿区内安山岩形成时代为中三叠世。结合前人对区域内三叠纪岩浆活动的研究成果, 认为该矿的形成与火山活动密切相关, 其成矿时代与安山岩形成时代一致, 且该矿床形成于古特提斯洋在中三叠世向北俯冲过程中的大陆边缘弧环境。

SHRIMP zircon U-Pb dating of andesite and its constraint on mineralization age in Xiabulang Cu-Pb-Zn deposit,Tongren County,Qinghai

The Xiabulang Pb-Zn deposit is one of the newly discovered VMS-type Cu-Pb-Zn small-scale polymetallic deposit in the juncture of Qinling, Qilian and Kunlun orogens. The ore body occurred as disseminated, net veined and stripped in andesite, and was coexistent with chalcopyrite, pyrite, stibnite, galenite and sphalerite. The ore-bearing rock had experienced strong alterations such as chloritization, carbonatization, silicification, and the major ore-related alteration is silicification. The width of alteration was varied as the thickness of the ore body changing. Based on field geological survey, the SHRIMP zircon U-Pb dating of ore-hosting andesite yielded age of 240.1±2.4 Ma(MSWD=0.31), indicated that rock-forming time might have been the product of Middle Triassic volcanic activities, also represent the forming age of the Xiabulang Cu-Pb-Zn deposit. The mineralization of the Xiabulang Cu-Pb-Zn deposit was closely related with the massive intermediate to acidic magmatism of Qinling-Qilian-Kunlun region in the Middle Triassic under continent margin arc environment resulted from the northward subduction of paleotethyan ocean.