滇西兰坪—思茅钴矿带钴富集过程与就位机制

Cobalt is a strategic critical metal and the main deposit types include primary magmatic deposits, nickel-rich lateritic deposits, and hydrothermal deposits. Among them, the basin brine related hydrothermal cobalt deposits have contributed 60% of the world’s mine production, suggesting that the basin brine has an important role in the enrichment of cobalt. Recently studies are focused on the famous Central African copper and cobalt belt that formed during Neoproterozoic times. However, the metallogenic model is hotly debated as the primary ore-forming structures were strongly modified by later deformation and metamorphism. The Lanping-Simao cobalt belt was formed as a result of Indo-Asian collision during Cenozoic. The cobalt is hosted in cobaltite together with tetrahedrite, galena, barite, and calcite. All of this makes the Lanping-Simao cobalt belt ideal natural laboratories for investigation of the enrichment of cobalt. This application focus on the metallic source, migration of cobalt-bearing fluids, and emplacement of orebodies for the Baiyangping, Liziping, and Shuixie cobalt polymetallic deposits within the Lanping-Simao cobalt belt. The orebodies emplacement mechanism will be studied by field structure and alteration mapping. The source of cobalt will be traced by in situ Pb isotopic analysis of sulfide and further evaluation by mass balance calculation. The migration and precipitation of cobalt will be deduced by quantitative elemental analysis of sulfide and phase equilibrium calculation. Finally, the huge amounts of cobalt accumulation process in the Lanping Co deposit will be established. This proposal will obtain new insights into the source(s) and enrichment mechanism of cobalt for basin brine related hydrothermal cobalt deposits.

钴是一种战略性关键金属，其矿床类型主要包括岩浆型、风化型和热液型等。其中，盆地流体有关热液钴矿床的储量和产量都首屈一指，显示地壳内的后期热液过程对钴富集成矿具有重要作用。目前相关研究主要集中在中非铜钴矿带，但因其成矿时代老，后期叠加改造明显，相关成矿模型存在很大争议，钴的富集机制与就位过程还未揭示。云南兰坪—思茅钴矿带具有形成时代新，钴共生矿物组合丰富等特征，是研究盆地流体有关钴矿床成因的理想对象。本申请选择该带内白秧坪、李子坪和水泄三个典型矿床，以成矿作用的“源—运—储”为主线，通过构造—蚀变填图和构造应力场分析，阐明矿体就位机制；通过原位微区铅同位素组成测定，示踪钴来源，并结合质量迁移计算估算钴贡献量；利用矿物共生组合热力学计算与相平衡模拟，反演钴迁移沉淀过程；综合对比分析，阐明盆地流体作用下钴富集过程与就位机制。研究有望在完善钴成矿理论和阐明钴成矿规律方面获得创新认识。

钴是一种战略性关键金属，其矿床类型主要包括岩浆型、风化型和热液型等。其中，盆地流体有关热液钴矿床的储量和产量都首屈一指，显示盆地流体对钴富集成矿具有重要作用。但盆地流体中钴的富集机制与就位过程还未揭示。云南兰坪—思茅钴矿带是研究盆地流体有关钴矿床成因的理想对象。本申请选择该带内白秧坪、李子坪和水泄三个典型矿床，通过构造—蚀变填图和构造应力场分析，阐明矿体就位机制；通过原位微区铅同位素组成测定，示踪钴来源；利用矿物共生组合热力学计算与相平衡模拟，反演钴迁移沉淀过程。研究发现：（1）始新世时，俯冲印度板片在26°N附近发生了E-W向撕裂。这一撕裂作用显著降低了该区域的岩石圈强度，为随后的陆块旋转提供了有利条件。（2）始新世末-中中新世，斜向碰撞阶段，陆块差异性旋转造成裂隙张开，形成控矿裂隙系统。（3）成矿金属来源于三叠纪火山岩或者侏罗纪—始新世红层，被中高盐度、氧逸度和硫逸度、中低温度的盆地流体活化并迁移。盆地流体在裂隙系统排泄，体系温度降低或者与围岩反应，导致硫化物沉淀，形成盆地流体有关的钴多金属矿床。由此阐明了盆地流体作用下钴富集过程与就位机制。（4）盆地流体有关热液钴矿床具有造山带脉状矿化和盆地内层状矿化的二元结构。欧亚大陆南缘存在一条上万公里长的特提斯碰撞钴矿带。该带具有得天独厚的金属源区、流体运移和金属沉淀等成矿条件，成矿潜力重大。这些研究为创新钴成矿理论、揭示钴成矿规律提供了重要支撑资料。项目发表标明资助的文章11篇，其中SCI论文5篇。项目负责人入选自然资源部科技领军人才。