新疆东天山三岔口铜矿成矿流体演化与成矿机制研究

Porphyry copper deposits are the most significant sources of world’s Cu resources, which have long been paid much attention by ore deposit scientists. The rapid development of high-precision analytical methods and techniques has significantly improved our understanding about those deposits in recent years. The Sanchakou Cu deposit is located in eastern section of the eastern Tianshan orogenic belt, Xinjiang, and is of porphyry and hydrothermal vein types. As a little research on this deposit, the geological characteristics and genetic mechanism of the Sanchakou Cu deposit still remain unclear. Compared with research on the Tuwu-Yandong-Chihu porphyry Cu deposits, the project focuses on quartz from ore-bearing porphyries as well as the ore and gangue minerals with various stages and textures from the Sanchakou deposit, utilizing fluid inclusion and isotope geochemistry, molybdenite Re-Os geochronology, and in-situ trace element analyses. The project aims to (1) understand the characteristics of mineralization and alteration and the ore-forming conditions of the Cu deposit, and constrain the ore-formation age; (2) discuss the sources of ore-forming materials and fluids, and the evolution of ore-forming fluids; (3) explain the mechanism of ore enrichment and precipitation; and (4) deduce the Cu ore-forming mechanism in the Sanchakou deposit. This study is very important both to promote metallogenic theory of porphyry Cu deposits and to provide guidelines for regional porphyry Cu exploration in eastern Tianshan.

斑岩铜矿作为世界上铜金属的最重要来源，受到国内外矿床学家的长期关注。特别是近年来高精度测试技术和高新仪器的不断发展和成熟，为进一步探究斑岩成矿理论提供新契机。新疆三岔口铜矿是东天山造山带在东段的找矿突破，兼具有斑岩型和热液脉型的特点，其地质特征和成矿机制研究较为薄弱。本项目拟以三岔口铜矿为主要研究对象，结合对比中段土屋-延东-赤湖铜矿带，综合运用流体包裹体及同位素地球化学、辉钼矿Re-Os年代学及微区原位微量元素分析等先进测试技术，对矿区含矿斑岩体中石英斑晶、不同矿化阶段和组构的矿/脉石矿物开展研究，重点查明铜矿化-蚀变特征及形成条件，厘定铜成矿作用时代；探讨成矿物质来源、成矿流体来源及其演化过程，深刻理解铜金属富集沉淀机理，揭示研究区铜矿成矿机制。本项目对于丰富东天山斑岩铜成矿理论，指导研究区斑岩铜矿找矿突破都具有重要意义。

斑岩铜矿作为世界上铜金属的最重要来源，受到国内外矿床学家的长期关注。新疆三岔口铜矿是东天山造山带在东段的找矿突破，其地质特征和成矿机制研究薄弱，矿床成因存在争议。本项目以东天山三岔口铜矿为研究重点，结合对比区内著名斑岩铜矿（土屋-延东）和全球典型斑岩矿床，开展了系统的岩石-岩相-矿相学、成岩年代学、流体包裹体和同位素地球化学方面研究。取得以下认识：1）三岔口矿床含铜矿物主要为黄铜矿和斑铜矿，其次为硫钴铜矿（Cu0.89Fe0.02Co1.87Ni0.05S4）、蓝辉铜矿和铜蓝，呈浸染状和脉状赋存于闪长质岩体中；发育斑岩型蚀变—早期钾化（磁铁矿-黑云母蚀变组合）、弱绢英岩化和广泛青磐岩化，以及叠加的沸石蚀变；2）岩石地球化学和S-Pb同位素结果显示，矿区内石英闪长岩和花岗闪长岩提供了重要的铜金属和硫等成矿物质，闪长质熔体来源于板片流体交代的地幔楔物质的部分熔融；3）成矿流体以岩浆热液为主（中高温、中低盐度H2O–NaCl体系），有部分大气降水和少量高盐度卤水加入；4）年代学数据结果和前人资料统计分析，认为志留纪和石炭纪是东天山铜成矿作用的重要时期。基于以上认识和研究成果，本项目提出三岔口铜矿形成于与俯冲作用相关的岛弧环境，为早古生代改造的斑岩型矿床，特殊的沸石蚀变及相关的脉体与矿化很可能与区域构造事件相关。本项目识别的三岔口斑岩矿床成矿模式为发展斑岩成矿理论及相似矿床的找矿勘查可提供重要参考。项目实施过程中，在国际主流期刊发表国际SCI论文4篇。已毕业硕士研究生1人，在读博士研究生1人，在读硕士研究生1人。