中国及境外天山铅锌成矿作用与找矿方向

中国及境外天山铅锌矿床多有发现,如哈萨克斯坦Tekeli、Shalkiya和Achisai,乌兹别克斯坦Kurgashinkan和Uchkulach,塔吉克斯坦Altyntopkan,中国新疆乌拉根、彩霞山、阿齐山、阿尔恰勒等大型—超大型铅锌矿床,构成了天山巨型铅锌成矿带。这些铅锌矿床形成于怎样的地球动力学背景?铅锌成矿的基本地质特征是什么?有哪些重要成矿类型?受何要素控制?未来找矿突破方向在哪里?这些都是颇受关注的地质找矿问题。在广泛矿产地质调查和综合分析前人研究成果的基础上,将中国及境外天山作为整体,综述了天山造山带构造演化和重要铅锌成矿环境、典型矿床特征与成矿系统/成矿类型,总结了天山地区铅锌成矿演化过程,并分析了区域铅锌成矿特点与找矿突破方向。结果表明:天山造山带经历了前寒武纪古陆形成、洋-陆俯冲增生、陆-陆碰撞造山和陆内成盆4个地球动力学过程,先后出现了元古宙古陆边缘裂陷盆地、古生代洋-陆俯冲增生岛弧、晚古生代陆-陆碰撞造山与中—新生代山前/山间盆地4类重要铅锌成矿环境。在元古宙古陆边缘裂陷盆地环境,主要受同生断层、还原性细碎屑岩-碳酸盐岩建造等控制,形成了古陆边缘裂陷盆地铅锌成矿系统与SEDEX型铅锌矿床;在古生代洋-陆俯冲增生岛弧环境,主要受弧岩浆活动、断裂构造、地层等控制,形成了增生岛弧铅锌成矿系统与矽卡岩型、斑岩型、岩浆热液脉型、VMS型铅锌矿床;在晚古生代陆-陆碰撞造山环境,主要受被动陆缘海相碳酸盐岩、张性开放空间、逆冲推覆构造等控制,形成了碰撞造山铅锌成矿系统与MVT型铅锌矿床;在中—新生代山前/山间盆地环境,主要受盆地三元结构、油气运移与红层“漂白”、硫酸盐岩等控制,形成了山前/山间盆地铅锌成矿系统与砂岩型铅锌矿床。由此可见,天山地区存在多种铅锌成矿环境和不同铅锌成矿系统与成矿类型,其铅锌成矿表现出长时间、多期次、多类型叠合成矿和一定继承性的演化特点。尽管沉积岩容矿铅锌矿床(包括SEDEX型、MVT型和砂岩型)在全球铅锌矿产资源中占据主导地位,而在天山地区增生岛弧铅锌成矿系统则占有更为重要的地位,特别是北天山岛弧带,哈萨克斯坦—伊犁板块南、北缘和中天山地块应该给予高度重视。与此同时,哈萨克斯坦—伊犁板块北缘与东天山中天山地块元古界SEDEX型铅锌找矿、境外中天山地块北缘与南天山造山带古生代被动陆缘碳酸盐岩地层MVT型铅锌找矿、新疆西南天山山前/山间盆地砂岩型铅锌找矿前景良好,也仍值得持续关注。

Zn-Pb Metallogeny and Prospecting Orientation of Tianshan in China and Abroad

There are many Zn-Pb deposits in Tianshan of China and abroad,forming a giant Zn-Pb metallogenic belt.Why so many Zn-Pb deposits are located here?how geodynamic setting results in their formation?What is the regional ore-forming types and the key to the Zn-Pb metallogeny?Where is the future prospecting orientation?All these significant geological and exploration problems are attracted much more attentions.Based on investigating the regional geology and Zn-Pb deposits in Tianshan and consulting various references,the important metallogenic environments,geological characteristics of typical Zn-Pb deposits and their ore-forming types were demonstrated,and tectonic-metallogenic evolution of Tianshan orogen and prospecting direction of Zn-Pb mineral resources were then discussed.The results show that Tianshan orogen experiences four geodynamic processes,namely the formation of Precambrian continent,ocean-continent subduction accretion,continent-continent collision orogeny,and intraplate deformation,and four corresponding metallogenic environments,including Proterozoic paleo-continent margin rift basin,Paleozoic ocean-continent subduction accretion island arc,Late Paleozoic continent-continent collision orogeny and Meso-Cenozoic depression basin.Accordingly,four important metallogenic systems and ore-forming types are formed as follow.The SEDEX Zn-Pb deposits are formed in Proterozoic paleo-continent margin rift basin environment,and controlled by contemporaneous faults and reduced fine-grained clastic rocks or carbonate rocks.The skarn,magmatic hydrothermal vein and VMS Zn-Pb deposits are formed in island arc of Paleozoic ocean-continent subduction accretion environment,and controlled by arc-related magmatism,faults and favorable strata.The MVT Zn-Pb deposits are formed in Late Paleozoic continent-continent collision orogeny environment,and controlled by marine carbonate in passive margin,extensional faults and thrust nappe structures.The sandstone-hosted Zn-Pb deposits are formed in Meso-Cenozoic depression basin environment,and controlled by basinal structure,infilling of oil and gas,bleaching of red beds,and sulfate.The Paleozoic subduction accretion island arc Zn-Pb system and skarn,magmatic hydrothermal vein and VMS types play a more important role in Zn-Pb mineral resources of Tianshan orogen compared to other parts of the world,which should be paid more attentions.North Tianshan island arc belt,the northern and southern margins of Kazakhstan-Yili block and central Tianshan block are all favorable for Paleozoic subduction accretion island arc Zn-Pb system,and show promising potential for ore prospecting of more large-scale Zn-Pb deposits.Meanwhile,the northern margin of Kazakhstan-Yili block and central Tianshan massif of East Tianshan for Proterozoic paleo-continent margin rift basin Zn-Pb system and SEDEX type,the northern margin of foreign central Tianshan and South Tianshan orogen for Late Paleozoic continent-continent collision orogenic Zn-Pb system and MVT,and the piedmont/intermontane basins along South Tianshan orogen for Meso-Cenozoic depression basin Zn-Pb system and sandstone-hosted type are all favorable,which should continue to be concerned about.These results may provide reference and indication for regional Zn-Pb metallogenic understanding and future Zn-Pb ore exploration.