南祁连乙什春基性-超基性岩体LA-ICP-MS锆石 U-Pb年龄及其地质意义

研究区位于中祁连地块南缘, 青海湖南- 古雷深大断裂南侧，是祁连成矿带铜镍矿找矿最有利地区。铜镍矿矿体产于
同源同期侵入的基性- 超基性岩体内, 铜镍矿化无论在时间上和空间上都与岩体的侵位密切相关。本次研究对乙什春基性-
超基性岩体中的锆石进行了阴极发光(CL) 成像观察, 结合Th/U比值特征，显示其为岩浆成因；并应用LA-ICP-MS 对锆石微
区U-Pb 年龄进行了测定，获得乙什春含矿岩体中锆石加权平均年龄为（455.1±1.7） Ma，表明其含矿岩体的侵位及矿化作
用发生于晚奥陶世，成岩成矿的动力学背景为陆缘裂谷构造环境。

Zircon U-Pb Dating of the Yishichun Mafic-Ultramafic Complex From Southern Qilian and its Geological Significance

The study area is located at the southern margin of the Middle Qilian, south of the Qinghai Lake-GuLei deep fault
belt, which is a favorable area for copper-nickel deposits in Qilian metallogenic belt. Yishichun Copper-nickel ore occurs within the homologous and contemporaneous basic-ultrabasic intrusions, and copper-nickel mineralization is spatially and temporally related to the intrusive rocks. The cathodoluminescence (CL) images and the Th/U ratios of zircons from the basic-ultramafic rocks suggest that zircon crystals are of magmatic origin; The LA-ICP-MS U-Pb dating of these zircons yields a weighted mean age of 455.1±1.7 Ma. Therefore, the ore-bearing rock emplacement and copper-nickel mineralization occurred during the late Ordovician, and the metallogenic dynamic process was probably related to an ancient continental margin rifting.