西天山卡特巴阿苏金矿床物质来源和成矿机制研究

Numerous world-class and giant orogenic gold deposits in western Tien Shan from Uzbekistan to Kyrgyzstan occur in a typical accretionary geodynamic setting; however, the large-scale gold mineralization in this region is principally associated with collisional orogenic processes. The reason and mechanism for this issue remain unclear. Although the Xinjiang western Tien Shan shares the similar tectonic setting with its Central Asian part, the prospecting potential of gold in this region is still unknown. All of these are significant geological and exploration problems and have received extensive attention. The newly discovered Katebasu large gold deposit in Xinyuan County, Xinjiang offers an important opportunity to shed light on the above mentioned questions. The current application focused on the ore and gangue minerals with various occurrences, textures, stages and generations from the Katabasu deposit, using a combined study of microscopic observation, fluid inclusion and in-situ trace element and sulfur isotope analysis, in order to understand the source and mechanism of gold mineralization in the deposit. Based on the study of the following three aspects: (1) the occurrence of gold and its relationship with gold-bearing minerals; (2) hydrothermal alteration and ore-forming fluid processes and (3) sources for ore formation and mechanism of ore precipitation, this application aims to understand the source and mechanism in forming the Katebasu gold deposit, and provides additional nutrients in the knowledge of orogenic gold formation and also serves for the continues breakthrough of gold prospecting in Xinjiang western Tien Shan.

天山西段，乌兹别克斯坦和吉尔吉斯斯坦境内东西向呈带状产出的众多世界级和大型-超大型造山型金矿床虽主体产在典型的增生造山环境，但大规模金成矿却多与碰撞造山地质过程有关，这其中的原因和机制是什么？与中亚天山背景相似、矿带相连的新疆西天山金矿找矿重大突破潜力怎样？都是颇受关注的地质和找矿问题。最近在新疆新源县新发现的卡特巴阿苏大型金矿床为认识这些问题提供了良好机遇。项目拟针对卡特巴阿苏金成矿物质来源不明和成矿机制不清关键问题，以矿区不同产状、组构、矿化阶段和世代的矿石和脉石矿物为对象，通过显微岩相矿相学观测、流体包裹体、微区原位微量元素和硫同位素等方法，开展金赋存状态及与载金矿物关系、热液蚀变和流体演化过程、成矿物质来源及富集机理三方面研究，旨在揭示卡特巴阿苏金成矿物质来源和成矿机制，丰富造山型金成矿认识，并为新疆西天山金矿找矿持续突破提供新参考。

天山是世界最典型增生造山带，但其中大规模金成矿却多与碰撞地质过程有关，区别于世界各地增生造山有关金成矿，增生造山环境中碰撞造山型金成矿机理是颇受关注的科学问题。项目选择新疆西天山新发现的卡特巴阿苏大型碰撞造山型金矿床开展研究，构造解析和构造应力场反演联合揭示了金矿田构造过程，通过精细矿物学和硫化物微区地球化学揭示了金赋存状态、成矿物质来源和与富集机制，利用低温热年代学和热史模拟刻画了成矿后的剥露历史和保存条件。研究表明，卡特巴阿苏金矿床经历了晚石炭世自南向北逆冲作用（D1）、二叠纪右行走滑活动(D2期)、新生代变形(D3期)三期矿田构造过程，金矿体受D1期碰撞造山过程导致N-S向缩短及其伴生一系列韧脆性断裂-裂隙构造系统控制。金矿化强度与断裂-裂隙构造系统的密集程度和硅化-绢英岩化热液蚀变强度密切相关，自然金呈裂隙金、晶间金和包裹金三种形式产于自形-半自形晶（Py1）和他形碎裂状（Py2）两个世代黄铁矿，不可见金以次显微固溶体金形式赋存在黄铁矿晶体内。大规模金成矿是深部/变质流体晚石炭世碰撞造山构造体质驱动下，沿密集断裂-裂隙构造系统不断萃取中天山地块火山-侵入岩系中的成矿物质并迁移至浅部地表，最终在低角度逆冲向高角度逆冲剪切兼右行走滑构造体制转换过程中成矿。矿床形成后经历了晚石炭世–早二叠世快速剥露作用和二叠纪以来缓慢稳定的地表侵蚀过程，模拟计算显示成矿后~4.75 km厚的盖层物质被构造剥蚀。项目丰富了造山型金矿床研究内容，对指导新疆西天山、尤其那拉提-额尔宾山一带金矿找矿勘查有实用价值。