东天山卡拉塔格铜矿床成矿条件和矿床成因研究

Volcanogenic massive sulfide (VMS) deposits always formed in the arc-basin system, and provide huge amounts of economic metals. The eastern Tianshan orogen are closely related to the long-term evolution of the arc-basin systems and have enormous exploration potential of VMS deposit, but there has been lack of large VMS deposit until the discovery of Kalatage. Thus, the new discovered early Paleozoic Cu-Zn deposits in Kalatage, eastern Tianshan would give us a new insight into the metallegenic theory and exploration of the copper deposits in north Xinjiang. In this proposal, we aim to select the Honghai and Hongshi copper-zinc deposit in kalatage. We will focus on systematically analyze Fe-Cu-Zn isotopes and in situ distributions of trace elements in sulfide, to delineate the sources of the metallogenic material and metallogenic mechanism of the deposit. The results may help us to better understanding the mechanism of Fe-Cu-Zn isotopic variability in the hydrothermal ore mineralization. This work will help to clarify the ore genesis and establish the metallogenetic model of Kalatage copper deposit, and finally provide guide for the explorations of the VMS deposits in the eastern Tianshan orogen.

VMS矿床主要形成于弧盆系统，具有巨大的工业价值。东天山发育复杂的长期演化的弧盆系统，但一直缺乏重要的VMS矿床。卡拉塔格早古生代铜锌矿床的发现，为东天山乃至北疆地区铜成矿理论研究和找矿勘查展示了一个重要方向。本项目拟选择卡拉塔格红海铜锌矿床和红石铜矿床，重点开展不同矿物组合和成矿阶段的硫化物LA-ICP-MS微量元素和Fe-Cu-Zn同位素联合研究，探索不同成矿阶段硫化物元素和同位素组合差异的原因和机理，建立矿床Fe-Cu-Zn同位素示踪标志，厘定卡拉塔格早古生代铜锌矿床成因类型，建立成矿模式，为东天山寻找VMS矿床提供新的思路。

本项目以东天山新发现的古生代铜矿床为研究对象，通过典型矿床解剖和区域对比研究相结合，确定了东天山早古生代岛弧斜坡带是VMS矿床形成的有利环境。主要进展包括：厘定卡拉塔格矿集区存在3套早古生代火山-沉积岩建造，即中晚奥陶世大柳沟组、早志留世红柳峡组和卡拉塔格组，地球化学特征显示均形成于岛弧背景。识别了东天山早古生代与洋壳俯冲有关的成矿系统遗迹，即VMS矿床（红海黄铜矿铼锇年龄为434.2±3.9Ma）、斑岩矿床（玉带石英闪长玢岩铀铅年龄为432±3Ma）和浅成低温热液矿床（红石黄铜矿铼锇年龄为431.8±2.7Ma）；确证了东天山存在早古生代VMS矿床，发现伴生的自然金和碲银矿；识别出早古生代浅成低温热液矿床，可能为新疆北部最古老的浅成低温热液矿床。揭示卡拉塔格存在四期铜成矿作用，即450-430Ma、400-380Ma、300Ma和280Ma，且早期VMS矿床经受了后期热液叠加改造，导致卡拉塔格呈叠加成矿特色。初步建立叠加成矿模式，尝试绿泥石等蚀变矿物地球化学研究和铜锌同位素研究，根据元素或同位素比值的变化规律，为找矿勘查提供指导。建议进一步瞄准“古VMS矿床/斑岩矿床叠加改造精细过程和机制”科学问题深入研究，有望取得矿床学理论的创新。