陕西煎茶岭金矿成矿元素富集机理与成矿模型

The Jianchaling Au deposit in the Qinling Orogen, with the measured reserves of 52 t Au at an average grade of 5 g/t, is the largest Au deposit in the Mianxian-Lueyang-Yangpingguan triangle block. The deposit has attracted several investigations due to their particularity, i.e., the structural position and hostrocks. However, the mechanism of metals mobilization and precipitation, the character of the ore-forming fluids, and the timing of the mineralization are poorly understood. In this proposal, we aim to systematically analyze contents and in situ distributions of trace elements in sulfides, to identify some available parameters of mobilization of the gold deposit, and further analyze the source of gold and activation of the migration process and mechanisms. Combined with fluid inclusions study, we attempt to clarify the ore genesis of Jianchaling deposit. Then, we will further study the ore-forming ages by analyzing the Ar-Ar ages of hydrothermal fuchsite, combined deposit geology to explore the coupling of mineralization and Qingling orogenic belt. Combining these results, we aim to fullfill the metallogenetic process, and finally provide guide to explorations of the Jianchaling gold deposits.

煎茶岭金矿位于秦岭造山带，金储量为52吨，平均品位5g/t，为勉（县）-略（阳）-阳（平关）三角区最大的金矿床，因其构造位置及产于超基性岩等特殊性，受到地质学家的高度关注。但其成矿机理、成矿流体特征、成矿时代以及与造山作用的耦合关系是前人研究的薄弱环节。本项目以煎茶岭金矿为例，利用各阶段不同类型的黄铁矿原位LA-ICP-MS测定其微量元素含量与相关参数，查明金的赋存状态，深入剖析金的来源以及活化迁移过程与迁移机制；通过测定不同阶段流体包裹体温度、成分，反演成矿流体性质与来源；并利用铬云母Ar-Ar定年，确定其成矿作用时代，结合矿床地质特征，探讨成矿作用与秦岭造山作用的耦合关系。研究成果将详细刻画煎茶岭金矿的成矿作用过程，为进一步寻找煎茶岭式金矿提供新的思路。

本项目研究了陕西省略阳地区储量最大的煎茶岭金矿，采取Ar-Ar同位素地质年代学、流体包裹体地球化学、碳氧硫稳定同位素和锶钕铅放射性同位素进行了系统研究。本研究取得了重要成果有，利用铬云母Ar-Ar年龄测得煎茶岭金矿的成矿年龄为198Ma，为早侏罗世，也为限定了勉略阳地区陆陆碰撞的时间提供了有利证据；根据矿床地质和流体包裹体地球化学研究，揭示了煎茶岭金矿的成矿流体为中温（200°~250 °C℃）、低盐度（1.1% ~ 12.4%），且富含CO2的变质流体，计算的第1阶段的成矿压力117~354MPa，形成断层阀模式的静岩-净水压力转换，形成深度约12km；根据碳氧同位素研究，进一步证明了变质流体特征，而硫、锶、钕、铅同位素显示成矿物质来自围岩断头崖组和下伏的碧口群。通过系统研究，煎茶岭属于印支期末特提斯洋闭合过程中，陆陆碰撞体制下形成的造山型金矿。