黔西南卡林型金矿中黄铁矿mapping及其对成矿作用的指示：以水银洞和烂泥沟金矿为例

Most Carlin-type gold deposits in China are located in southwestern Guizhou Province, part of the large-area epithermal mineralization province in southwestern Yangtze Massif. There are two styles of Carlin-type gold mineralization in the region: strata-bounded mineralization and fault-controlled mineralization. The strata-bound gold deposits are controlled by anticlines and hosted in late Permian bioclastic limestones, whereas the fault-controlled gold deposits are localized at fault zones in early or middle Triassic siltstones and mudstones. Previous studies demonstrate that the two types of deposits were formed at different time. The origin and genetic model of such large-scale Carlin-type gold mineralization are still not well constrained, largely due to the lack of systematic understanding on the compositions, origins and evolution histories of the ore-forming fluids. ..In this proposal, we plan to conduct systematic studies on the typical strata-bound Shuiyindong deposit and fault-controlled Lannigou gold deposit in the region, which formed at different time, and occur in different tectonic units. The newly developed LA-ICP-MS elemental mapping and SIMS elemental/isotopic mapping techniques will be utilized in this study. The morphology and texture, elemental and isotopic composition of pyrites will be obtained, in order to constrain the source of metals, and composition and evolution histories of ore-forming fluids. Furthermore, we attempt to compare the origins and dynamics of two different types of Carlin-type gold mineralization to search for possible linkage of these two different ore-forming systems. Achievements attained in this project will enhance our understanding of Carlin-type gold mineralization in the large-area epithermal mineralization province in southwestern Yangtze Massif.

我国的卡林型金矿床主要集中在扬子西南缘大面积低温成矿省的黔西南地区。在该区卡林型金矿床具有层控型和断裂型两大类：断裂型金矿床产于断裂中，赋矿层位一般为中-下三叠统地层，容矿岩石主要是泥质粉砂岩和粉砂质泥岩；而层控型金矿床主要产于上二叠统生物碎屑灰岩，受背斜控制。这两个矿床的成矿时代也有一定差异。由于缺乏系统的成矿流体成分和演化的对比研究，制约了对大面积卡林型金矿化成矿动力学模型的总结。本项目拟以层控型水银洞金矿和断裂型烂泥沟金矿这两个典型矿床为研究对象，选择近年发展起来的LA-ICP-MS和SIMS元素和同位素mapping技术，通过对两个矿床中黄铁矿的形貌学、元素和同位素mapping分析，精细限定成矿物质来源、成矿流体组成和演化及其控制因素。在此基础上，通过对不同时间、不同空间的两个矿床成矿流体物质组成、流体演化过程及动力学机制的对比，厘清两类矿床之间的成因联系，总结扬子西南缘低温成矿

硫化物元素和同位素变化能够很好的记录成矿流体性质和演化过程。该项目建立了基于LA-ICP-MS的硫化物微区原位元素分析和硫化物定量元素mapping分析方法，形成自动数据处理软件IDPRO一套。采用硫化物mapping分析等方法，对右江盆地的水银洞和烂泥沟两个卡林型金矿和吉尔吉斯斯坦的中亚造山带中Togolok和Jangart两个花岗岩有关矿床中的黄铁矿开展了对比研究。矿物学、形貌学、元素和同位素组成显示水银洞和烂泥沟金矿的黄铁矿形成具有四个期次。其中第一期是沉积过程中形成的，后三期具有热液成因。虽然不同期次的黄铁矿具有不同的微量元素含量和硫同位素组成，显示了右江盆地卡林型金矿成矿流体具有多个来源，但是这些矿床的含金黄铁矿均具有富Pb、As和Sb等元素富集的特征，说明岩浆热液可能在这些矿床金成矿过程中起了重要作用。

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