新疆萨热克铜矿床沉积-构造热叠加成矿过程研究

The Sareke copper deposit, located at the coupling areas of the western edge of the Tarim basin with the southwestern Tianshan range, is one of newly discovered large-scale deposits. The copper mineralization mainly developed in Mesozoic conglomerates, showing a typical sediment-hosted deposit. It’s geological and metallogenic characteristics, ore-forming material source and genesis have been well studied, showing that there are at least two types (phases) of copper mineralization, such as sedimentation-related and tectono-thermal superposition-related Cu-mineralization. However, the ore-forming age, especially the differences between two types (phases) of copper mineralization and the coupling relationship between the ore-forming fluid inside the basin and the tectono-thermal superposition are still remain controversial. Here, the S-Pb isotopic compositions of sulfides from ore-bodies in the south ore best will determined in order to discuss the source of ore-forming material, and then we propose a new project using micro infrared spectroscopy, Laser Raman spectrum analysis, and in-situ analysis techniques to reveal the composition, source and evolution of ore-forming fluids. Multiple dating methods are also adopted to constrain the regional tectono-thermal superposition and ore-forming age, in order to better recover the detailed ore-forming process of the copper migration, sedimentation and enrichment, and further to discuss the metallogenic mechanism. Our study is not only a typical case study of the sediment-hosted Cu deposit for its ore-forming dynamics, but also can provide scientific guidance to the exploration of sediment-hosted Cu deposits in the western edge of the Tarim basin and southwestern Tianshan range.

新疆萨热克铜矿床位于塔里木盆地西缘、西南天山之中，铜矿化主要产于中生界砂砾岩中，是近年来我国铜矿找矿的重大突破，具有超大型矿床前景。前人对其矿床地质特征、成矿物质来源和成因进行了初步探讨，发现该铜矿发育两类（期）铜矿化，一类与沉积作用有关，一类（期）与构造-热作用（基性脉岩侵入）有关。但对成矿时代，尤其是两类（期）铜矿化的形成机制、成矿动力学过程以及盆地成矿流体与构造-热作用的耦合关系等仍不清晰。本申请拟采用同位素示踪研究深部与铜矿化相关的铅锌成矿物质来源；采用显微红外光谱、激光拉曼光谱和微区原位分析等技术研究萨热克铜矿床的成矿流体组成、性质、来源及其演化；采用多方法联合测年手段，确定区域构造-热作用时限和铜矿化时代；精细恢复铜迁移、沉淀-富集成矿过程，进而探索萨热克铜矿床成矿机理，为沉积岩容矿型铜矿床研究提供典型实例，为塔里木盆地西缘中生界铜矿床勘探提供科学依据。

新疆萨热克铜矿床位于塔里木盆地西缘、西南天山之中，铜矿化主要产于中生界砂砾岩中。本次对铜矿化的形成机制、区域构造-热作用以及盆地成矿流体与构造-热作用的耦合关系等进行了研究。初步查明了区域前寒武纪浅变质岩的形成时代及其含铜丰度，云母Ar-Ar坪年龄介于276.0Ma到256.2Ma之间，表明至少在早-晚二叠世，区域经历了一段缓慢冷却过程。区域前寒武纪浅变质岩Cu元素丰度略显异常。获得了矿区内辉绿岩Ar-Ar年龄，集中在75-90Ma之间，暗示矿区在75-90Ma发生了一期或多期构造-热事件，对成矿产生了影响，至少在辉绿岩形成同期发生了铜矿化事件。研究了含矿层位岩石地球化学特征，得出：上侏罗统库孜贡苏组上段灰绿色砾岩地层和含矿砾岩的稀土元素配分曲线大致相互平行，表明区域地层沉积具有同源性，推断盆地中的沉积物来源于周缘的沉积地层。初步调查表明，萨热克盆地边缘构造变形强烈，而盆内构造变形强度相对较弱。认为萨热克铜矿区以压扭性断裂和右旋走滑断裂为主，反映了研究区南东和北西侧长城系地层逆冲推覆（对冲）对矿区的强烈影响。在区域挤压应力影响下，构造驱动形成了大规模的盆地含矿流体运移。ESR年龄显示萨热克铜矿床断层的活动时间均在更新世-全新世，表明成矿后区域内较为强烈的构造活动，对早期形成的矿体造成了一定的破坏。综合研究认为：萨热克铜矿床发育于中生代陆相沉积盆地内，铜矿体产出严格受层位控制，砾岩中碎屑颗粒间隙是其主要容矿空间，成矿方式表现为硫化物交代砾岩中胶结物后生成矿，尤其是矿石矿物以辉铜矿为主，与典型陆相砂岩型铜矿一致。区域有构造-热叠加成矿事件发生或成矿过程中有其它或深部物质加入。部分矿体或矿石中可见沥青等油气残留物，暗示油气等烃类物质积极参与了金属元素的成矿过程。本次研究丰富了沉积岩容矿型铜矿研究案例，将会有助于区域类似矿床勘查。