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天桥铅锌矿床位于川-滇-黔铅锌成矿带中东部,为黔西北地区铅锌矿床的典型代表之一。长期以来,对该矿床的成因认识存在较多争议,前人的研究主要集中在分散元素的富集规律、稀土元素及同位素对成矿流体来源的指示意义等方面,对天桥矿床中闪锌矿的微量元素特征缺乏系统的研究。本文应用ICP-MS对天桥矿床中闪锌矿的微量元素进行测试分析,研究结果表明,该矿床中闪锌矿的微量元素具有富Ge、Ga贫Mn、In、Sn、Cd的特征,其微量元素富集规律明显与夕卡岩型、喷流沉积型及岩浆热液型铅锌矿床不同,而与典型MVT型矿床(如勐兴、牛角塘等矿床)非常类似,仅其中Cd含量较低(均值为1282×10-6),该特征与川滇黔地区MVT型铅锌矿床(会泽和杉树林)中闪锌矿微量元素组成一致。总体上,本矿床闪锌矿富集Ge和Ga等低温成矿元素,其In/Ga比值中等,Zn/Cd比值较高,暗示其形成于中温环境。综合前人研究成果及矿床产出地质特征,我们认为天桥铅锌矿床属于MVT型铅锌矿床。
The Tianqiao Pb-Zn deposit is located in the middle and eastern part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic belt and is one of the typical representatives of the lead-zinc deposits in the northwestern Guizhou. For a long time, there is much controversy about the genesis of the deposit. The predecessors’ research mainly focused on the enrichment of dispersed elements and the indication significance of rare earth elements and isotopes on the source of ore-forming fluid. The trace element characteristics of the lack of systematic research. In this paper, the trace elements of sphalerite in Tianqiao deposit were tested and analyzed by ICP-MS. The results show that the trace elements of sphalerite in this deposit are characterized by Mn, In, Sn and Cd rich in Ge and Ga, The element enrichment law is obviously different from the skarn, jet sedimentary and magmatic hydrothermal Pb-Zn deposits, and is very similar to the typical MVT deposits (such as Mengxing and Niujintang deposits). Only the Cd content is lower (Average 1282 × 10-6), which is consistent with the trace elements of sphalerite in MVT-type lead-zinc deposits (Huize and Cedar forest) in Sichuan, Yunnan and Guizhou provinces. In general, the ore-bearing sphalerite is enriched in low-temperature ore-forming elements such as Ge and Ga. The In / Ga ratio is medium and the Zn / Cd ratio is high, suggesting that it is formed in a moderate temperature environment. Based on the previous research results and the geological characteristics of the output of the deposit, we believe that the Tianqiao Pb-Zn deposit belongs to the MVT type lead-zinc deposit.