逆冲褶皱系富硅型碳酸盐岩容矿铅锌矿床成因：以伊朗马拉耶尔-伊斯法罕铅锌成矿带为例

The metallogenesis of carbonate-hosted MVT Pb-Zn deposits in thrust-fold belt setting cannot be explained by the previous classic model of worldwide MVT deposits, which made it be an urgent unanswered question. Recent studies indicate that three types of carbonate-hosted deposits could form in the thrust-fold belt setting, which include the carbonate-rich, fluorite-rich and quartz-rich types. The first two types have been found a relative long time ago and received more attention. The gneisses of them are nearly clear. However, the last type, the quartz-rich carbonate-hosted Pb-Zn deposits is just found recently and the understanding of them is nearly black. The Zagros collisional orogen locating in the west of the Eastern Tethyan metallogenic domain have produced big thrust-fold system in it. Many large quartz-rich carbonate-hosted Pb-Zn deposits formed in the thrust-fold system and built the famous Malayer-Esfahan Pb-Zn metallogenic belt. Therefore, the project will focus on this belt and choose Irankuh and Emarat quartz-rich carbonate-hosted Pb-Zn deposits as targets to investigate the metallogenesis of the quartz-rich type deposits. Structure-lithology-mineralization-alteration mapping, fluid inclusion analysis, geochemical investigations and dating will be performed on these deposits. The aims for these works are elucidating sources, migration and concentration of ore-forming fluid, sources and precipitation mechanism of ore-forming materials, and the relationship between the ore-forming process and the thrust-fold deformation in the region. A genetic model for the quartz-rich carbonate-hosted Pb-Zn deposits in thrust-foldbelt setting will be established at last. The research will provide important information to improve the existing genetic model for carbonate-hosted Pb-Zn deposits located in thrust-fold belt setting and be valuable to understand theworldwide MVT Pb-Zn deposits and the metallogenesis of collisional orogen.

逆冲褶皱系背景碳酸盐岩容矿铅锌矿成矿作用难以用已有MVT铅锌成矿模型解释，成因机制亟待解决。研究表明，产于逆冲褶皱系的MVT铅锌矿由富碳酸盐型、富氟型和富硅型三种类型组成。其中，前两种发现较早，有一定研究认识，后一种新近发现，研究极为薄弱。地处东特提斯域西段的伊朗扎格罗斯造山带，发育新生代逆冲褶皱系，其中产出众多大型富硅型碳酸盐岩容矿铅锌矿，构成著名的马拉耶尔-伊斯法罕铅锌成矿带。项目以该带Irankuh和Emarat两个富硅型铅锌矿为主要研究对象，以矿床形成的源-运-储研究为主体思路，通过典型矿区大比例尺填图、流体物理化学性质分析、地球化学示踪、成矿年龄直接测定等技术，查明带内成矿流体和物质的来源、迁移、汇聚作用，再塑成矿与区域构造耦合过程，揭示区带铅锌成矿机理。研究将在逆冲褶皱系背景碳酸盐岩容矿铅锌矿成因机制方面取得原创性成果，对增进MVT铅锌矿和大陆碰撞造山成矿作用的理解具重要作用。

本项目在2018.1-2021.12期间执行，主要开展伊朗马拉耶尔-伊斯法罕铅锌成矿带褶冲系富硅型碳酸盐岩容矿铅锌矿床成矿作用研究。执行期间，项目开展了区域地质考察、矿区地表填图和平硐编录、流体包裹体测温和惰性气体同位素-卤素含量分析、H-O-S-Pb同位素分析、并与区域成矿作用进行了对比。本次研究发现，马拉耶尔-伊斯法罕铅锌成矿带内富硅型碳酸盐岩容矿铅锌矿床形成于新生代初期（65Ma左右），发育在阿拉伯板块-欧亚大陆板块碰撞造山阶段，和区域上逆冲-走滑断层等压扭性构造密切相关，受与逆断层相关的次级断层、岩性分界面等要素控制。这套矿床矿种组合以Zn-Pb为主，少量矿区出现Cu。硫化物主体为闪锌矿、方铅矿、黄铁矿，非硫化物以石英、白云石、方解石、重晶石为主。矿化以脉体充填或热液矿物交代充填为主要形式，强硅化和白云石化为主要蚀变特征。成矿流体为低温高盐盆地卤水来源和中温高盐的岩浆水-大气水混合流体来源，生物还原或有机质热还原赋矿碳酸盐岩地层封存水中溶解的早白垩世海相硫酸盐为主要还原硫来源，成矿金属物质来自于带内经历了“造山”作用的上地壳岩石。总体来看，这套富硅型碳酸盐岩容矿铅锌矿床是一套发育在构造、岩浆活动极为复杂的褶皱逆冲带中的铅锌矿床，其成因类型可归纳为有岩浆作用远程参与的碳酸盐交代类型。这些矿床的成矿过程和其东邻的“三江”成矿带MVT铅锌成矿发育过程有相似之处，但流体来源更为复杂，具体为：斜向碰撞、岩浆作用和压扭性构造发育、盆地卤水和岩浆水迁移——流体汇聚，圈闭、有机质、细菌准备——硫酸盐被还原、还原硫形成，应力松弛——流体排泄，流体混合——金属沉淀，区域富岩浆岩地层准备、成矿流体温度快速下降——富硅矿物组合形成。项目发表论文21篇（SCI论文11篇），培养研究生3名；相关成果首次回答了褶冲带内富硅型碳酸盐岩容矿铅锌矿床的成因，为理解特提斯域巨型碳酸盐岩容矿铅锌成矿带区域成矿规律提供了原创性认识。