广西大厂矿区锡矿床成矿物质来源：铅同位素证据

摘要

为了揭示广西大厂锡多金属矿床的成矿物质来源，利用黄铁矿、磁黄铁矿、闪锌矿以及方铅矿等金属硫化物单矿物，开展铅同位素分析与研究。根据经典铅同位素判别模型，探讨矿质来源及其特点。结果表明，铅同位素比值206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为17.478~18.638、15.440~15.858和37.556~39.501。根据Zartman铅构造模式，矿石铅含有上地壳成分；然而，并非所有的铅都由花岗岩提供，还存在其他的铅来源形式。显然，该矿床属于壳−幔联合作用的产物，原岩与岛弧物质具有一定的相似性；而且上地壳和下地壳中的远源可能与俯冲岛弧或洋壳有关。幔源物质在源区发挥着重要作用；同时，基于铅同位素三维拓扑投影向量，矿石铅主要集中于A区域，表明其具有扬子铅同位素省的特征，也暗示了可能与扬子板块具有一定的亲缘关系。%For revealing the ore sources of the Dachang tin−polymetallic ore deposit, the lead isotopes were analyzed systematically by using the single minerals of sulphides, including pyrite, pyrrhotite, sphalerite, and galena. Then, the mineral sources and their characteristics were discussed based on the classical lead isotope discriminating model. The results show that the lead isotope ratios of206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb range from 17.478 to 18.638, 15.440 to 15.858, and 37.556 to 39.501, respectively. According to Zartman lead model, the ore lead contains the upper crust composition; however, the granite does not provide all ore leads, and other material sources exist. Obviously, the ore deposit belongs to the result of the combined effect of crust−mantle. The source rocks are characterized by a certain degree of similarity with the island arc material. Moreover, its distant origin in the upper and lower crusts may be related to the subduction island arc material or oceanic crust. The mantle-derived material may have a certain status in the source region. Meanwhile, based on the lead isotope three-dimensional topology projection vectors, the ore leads are concentrated in zoneA, which indicates the characteristics of Yangtze lead isotope province and a possible genetic relationship with Yangtze block.