塔西南MVT型铅锌矿床成矿作用机制研究--以卡兰古铅锌矿为例

塔里木板块演化过程可以划分为：前寒武纪陆核增生－地块形成，早古生代这缘裂解－开合拼贴，晚古生代裂谷叠加－板块统一，中新生代盆山耦合－地貌定型4个阶段。而它的边缘部分则经历了新元古代－古生代－中生代的陆核增生和相邻洋壳的消亡几个阶段。并且由于地壳发展的不均衡，形成了一些裂谷和裂陷槽。卡兰古MVT型铅锌矿床位于塔里木地块的西南缘－西昆仑造山带与塔木板块交接部位的晚古生代乌依塔格－库尔良型陷槽北段，属于西昆仑地区库斯拉甫－他龙铅锌成矿带的一部分，是区内最重要的、最典型的MVT型铅锌矿床之一。通过对该矿床野外考察和综合室内测试、岩矿鉴定研究分析，认为卡兰古铅锌矿是一种碳酸盐岩容矿的低温热液型矿，其成矿地质背景、控矿岩石、矿物组合、矿石结构构造等，均与密西西比河谷型铅锌矿极为相似；该矿床的成矿机制可能是由于深层液体与油田卤水两种不同性质流体的混合而形成的。特别是通过对塔木、卡兰古等铅锌矿区的矿物流体包裹体研究表明：矿物流体包裹体类型简单，多为液相，成矿流体是具有低温、高盐度、高密度等特征；与此同时还富含Ca^2 、Mg^2 、Na^ 离子及有机烃类物质和硫化氢气体的热卤水。这些特征均与北美典型的密西西北河谷型铅锌矿非常相似。它代表了塔里木西南缘该类型铅锌矿的成矿机制。其成矿物质主要来源于地层之中，没有地幔物质成分的参与。在成矿作用过程中，成矿金属（铅锌）以硫氢配合物形式迁移。喜马拉雅期逆冲推覆褶皱作用所引发的大规模热卤水运移、循环，导致了矿物质的进一步富集、沉淀。

MINEROGENETIC MECHANISM OF LEAD-ZINC DEPOSITS IN SOUTHWESTERN TARIM

The history of the crustal evolution of Tarim can be divided into 4 periods: Precambrian continental accretion, early Paleozoic continental margin rifling-accretion, late Paleozoic rift superposition-plate reunification and Meso-Cenozoic mountain-basin coupling-shaping. Kalangu MVT-type lead-zinc deposit is located in southwestern Tarim. It belongs to the northern part of late Palaeozoic Oytag-Kurliang rift, as part of the West Kunlun's Kusilafu-Talong lead-zinc-copper belt. Detail field investigation and rock-mineral analysis suggest that minerals are sourced from Pre-Devonian rocks. The enrichment and precipitation of minerals are caused by deep hot brine mixed with oil brine. Thrusting and folding during the Himalayan orogeny led to the circulation of deep hot brine. Kalangu Lead-zinc deposit is a low-temperature carbonate-hosted one similar to Mississippi Valley type lead-zinc deposit in terms of geologic setting, ore-controlling rocks, mineral assemblage, texture and structures of ores. Ore fluid inclusion's chemical composition shows that ore fluid inclusion is simple, mostly liquid inclusions, with low-temperature, high-salinity and high-density features. The Pb isotopic age (508 Ma) suggests that materials are sourced from existing rocks, not from magmatic process. Another evidence is from a similar REE partition pattern of both ores and country rocks. The S isotopic analysis indicates a close relation with hot brine. A V-shaped basin-and-range coupling relationship between west Kunlun Mts and Tarim basin, revealed from seismic profiles, is favorable for formation of similar prospects in the region.