新疆谢米斯台地区斑岩型铜矿成矿构造环境及成矿作用

Early Paleozoic mafic-acidic volcanic rocks, subvolcanic rocks and intermediate-acidic intrusive rocks are mainly generated in the Xiemisitai area, which is located in the north margin of Kazakhstan - Junggar plate. A porphyry copper mineralization with certain scale has been found in the subvolcanic rocks in this area recently. This research focuses on the scientific problems of "metallogenic tectonic setting, metallogenic process and conditions", carrying out the studies of regional metallogenic geology, geochemistry and geochronology in the existing mineralization areas and key section and the comparison with its adjacent metallogenic belt and determining the tectonic setting and evolution features of Xiemisitai area in Paleozoic. Meanwhile, magma dynamics mechanism and source characteristics, the constraints of tectonic evolution and the restriction of crust mantle exchanging to the ore source supplying, ore-forming material migration and location of ore deposits, and the control of regional tectonic, alteration zoning to orebody location during the oceanic crust subduction period are also discussed based on plate tectonic evolution and mineralization features, regional metallogenic theory and thinking method of comparative mineral deposit geology. What’s more, this study will find out the metallogenic tectonic environment, metallogenic conditions and main control factors of porphyry copper deposit in the area, discovering the mechanism of element enrichment and the process of mineralization. Finally, a metallogenic dynamics model for porphyry copper in Xiemisitai area will be established, which may give a great contribution to analysing the metallogenic potential, enriching and developing the porphyry copper metallogenic theory and the prospecting evaluation.

谢米斯台地区位于哈萨克斯坦-准噶尔板块北缘，主要发育早古生代基性-酸性火山岩、次火山岩和中酸性侵入岩，新近在该区内次火山岩中发现具有一定规模的斑岩型铜矿化。立足于板块构造演化与成矿特点，运用区域成矿学理论和比较矿床学思维方法，围绕谢米斯台地区“成矿构造背景、成矿条件及成矿过程”这一科学问题，在已有矿化区和重点区段开展区域成矿地质、地球化学和年代学研究以及与相邻成矿带的对比研究，确定谢米斯台地区古生代构造背景及其演化特征，探讨洋壳俯冲时期岩浆形成的动力学机制和源区特征、构造演化和壳幔物质交换对矿源供给、成矿物质迁移和矿床定位的制约以及区域构造、蚀变分带对矿体定位的控制，查明区内斑岩型铜矿的成矿构造环境、成矿条件和主要控制因素，探讨元素富集机理和成矿过程。最终建立谢米斯台地区斑岩铜矿成矿动力学模型，分析成矿潜力，丰富和发展斑岩型铜矿成矿理论，指导找矿评价。

项目承担者前期在新疆谢米斯台地区发现斑岩型铜矿化。本项目在前人工作基础上，以谢米斯台地区斑岩型铜矿成矿构造环境、成矿条件及成矿作用和成矿后变化为主要研究内容，在详细野外地质调研的基础上，开展地质学、年代学、地球化学等综合研究，取得以下主要研究结果：.1、谢米斯台地区大面积出露的火山岩、侵入岩的形成时限为晚奥陶世-晚泥盆世（452Ma~370Ma），形成于俯冲背景下的陆缘弧构造环境，与古亚洲洋壳的俯冲作用密切相关，岩浆源区为新生下地壳。弧岩浆作用经历了四个阶段，早志留世-早泥盆世（434Ma~398Ma）为岩浆活动的高峰时期。区内弧火山活动一直延续至晚泥盆世（370Ma），而非前人认为的仅发育于志留纪。.2、谢米斯台地区早古生代构造-岩浆演化控制着区内斑岩型矿化的类型及其特征，区内斑岩型铜（金）矿化与中志留世（430Ma）花岗闪长斑岩关系密切，斑岩型铜矿化与早志留世（434Ma）和晚志留世（423Ma）次火山岩关系密切。谢米斯台地区具有良好的斑岩型矿床成矿构造条件、岩浆条件、物源条件和流体条件，有利于斑岩型铜矿床的形成。.3、布拉特斑岩型铜矿主成矿期经历了三个成矿阶段。第一阶段成矿温度＞475℃，主要形成黄铜矿-斑铜矿固溶体和黄铁矿；第二阶段成矿温度为430~290℃，主要形成黄铜矿、斑铜矿、黄铁矿等硫化物；第三阶段成矿温度为242~154℃，主要形成黄铜矿、斑铜矿、黄铁矿等。成矿物质、流体主要来自岩浆，随成矿作用演化，地壳硫、大气降水参与度增高。.4、谢米斯台地区矿床保存条件良好，具有很好的深部找矿潜力；与早古生代岩浆活动相关的斑岩型铜（金）矿化是谢米斯台地区后续找矿突破的主要矿化类型。.上述研究成果可以为完善区内火山岩地层时代划分、探讨谢米斯台地区古生代构造演化提供新的资料，为区内早古生代斑岩型铜矿的进一步找矿勘查提供理论指导。