绿泥石和绿帘石矿物学对东天山叠加成矿作用的指示

The Tuwu-Yandong Cu deposit and the Honghai VMS Cu-Zn deposit, located in the Dananhu-Tousuquan island belt of the Eastern Tianshan mountains, are the economically most important Cu deposits in the Xinjiang province at present, containing ~650 million tons grading 0.46 percent and ~20 million tons grading 1.49 percent, respectively. Since their discovery, many studies have been undertaken on these two deposits to characterize the geology, alteration, Cu mineralization, geochemistry and geochronology of intrusions and volcanic rock, timing of mineralization, and ore-forming fluids. These studies show that these two deposits both have experienced overprinting alteration and mineralization after their formation..This project is planned to investigate these two deposits and do a three-dimensional alteration mapping and area sampling. Based on the studies of hydrothermal alteration and mineralization for these two deposits, we will do physical and chemical research on chlorite and epidote at different stages of these two deposits, by using electron probe, LA-ICP-MS, Mossbauer spectromete, scanning electron microscope, X-Ray diffraction, transmission electron microscopy, short wavelength infrared and laser Raman spectrometer. We will discuss chlorite and epidote trace element changes at different distances (lateral and vertical) for these two deposits and obtain the physical and chemical conditions of hydrothermal fluid at different periods, especially the overprinting alteration and mineralization period. Finally, we will discuss the physical and chemical conditions for migration and concentration of elements at these two deposits and reveal the mechanism of the overprinting alteration and mineralization in the Eastern Tianshan mountains.

土屋-延东铜矿和红海VMS型铜锌矿床是东天山地区目前最有经济价值的铜矿床，分别含有铜资源储量约270万吨和30万吨。自发现以来，这两个矿床的矿床地质特征、含矿岩体年代学和地球化学、成矿年代学以及成矿流体和成矿物质来源等方面，开展了较为详细的研究工作。这些研究表明，这两个矿床形成之后，都经历了后期的叠加改造作用。.本项目以土屋-延东铜矿和红海VMS型铜锌矿床为研究对象，从矿物的微结构和表面特征入手，对不同蚀变矿化阶段分布广泛的绿泥石和绿帘石，用X射线衍射仪、穆斯堡尔谱分析仪、透射电子显微镜和激光拉曼分析仪等分析它们的物理结构，用电子探针和激光剥蚀电感耦合等离子体质谱仪测试它们的化学成分；查明绿泥石和绿帘石物理结构和化学成分特征以及在空间上的变化规律，得到不同期次热液流体的物理化学条件和组成，特别是叠加改造期流体的物理化学信息，探讨这两个矿床元素迁移及富集机理，揭示东天山地区叠加改造作用机制。

土屋铜矿（成矿年龄为320 Ma左右）位于吐哈盆地南缘，东天山大南湖-头苏泉岛弧带上，位于康古尔断裂以北约1–4 km。已探明铜资源储量接近70万吨，铜平均品位为0.46%，并伴生有金、钼和银等，是目前新疆最有经济价值和规模最大的铜矿之一。本项目以土屋铜矿为研究对象，在野外考察的基础上，对土屋铜矿钻孔和地表样品进行编录。根据脉次穿插关系、蚀变矿物组合、矿物共生关系以及蚀变矿物SWIR分析，在结合前人研究成果基础上，重新划分了土屋铜矿的成矿期次，从早到晚依次为：斑岩成矿期、叠加改造期和表生期，其中斑岩成矿期又可以分为钾化、青磐岩化和绢英岩化三个阶段，绿泥石在青磐岩化和叠加改造期都广泛发育。对这两期绿泥石进行电子探针和LA-ICP-MS分析，发现土屋铜矿青磐岩化阶段绿泥石地球化学特征与年轻斑岩系统青磐岩化阶段绿泥石一致。相对于青磐岩化阶段的绿泥石，土屋叠加改造阶段的绿泥石亏损Mg和K，富集Fe和Al。存在两种不同特征的绿泥石，与土屋铜矿存在两期铜矿化一致。与变质绿泥石进行对比，土屋青磐岩化阶段的绿泥石更加富集Mg和K，而亏损Fe、Al和As，这表明绿泥石的地区化学成分可以区分不同来源的绿泥石。此外，该项目还开展了围岩对斑岩系统绿泥石地球化学成分影响的相关工作，发现绿泥石Al、Ga和Ti的含量不受前驱体矿物成分的控制，而与其形成温度呈正相关关系，可以用来指示斑岩矿床热液矿化中心。