陆–陆碰撞褶皱逆冲带内MVT铅锌成矿作用：青藏高原与扎格罗斯造山带对比研究

Mississippi Valley-type (MVT) Pb-Zn deposits mainly occur in forelands and fold-thrust belts of convergent orogens. Based on the studies of the Ouachita orogen, previous work has established the metallogenic model for MVT deposits in forelands. However, this model cannot explain the metallogenesis for MVT deposits in fold-thrust belts. Abundant MVT Pb-Zn deposits in fold-thrust belts in the continent-continent collisional zones of the Tethyan tectonic domain, the world’s most important MVT metallogenic domain, provide a good opportunity for establishing the MVT metallogenic model in such a tectonic setting. .This proposal focuses on four important MVT deposits and their two fold-thrust belts in the eastern Tibetan and Zagros orogens which have different tectonic evolution histories. The proposal plans to study regional structural deformation, ore controls, and Pb-Zn mineralization ages, in order to understand the tectonic setting for ore formations; through analyzing regional structural deformation and associated fluid records, and ore fluid-transmitting faults at deposits, this study tries to recover the ore-forming fluid flow history and pattern; the proposal will pay more attentions on the controls of salt diapiric structure on two MVT deposits and then summarize typical ore controls; the roles of hydrocarbon fluids on the MVT ore formations will be investigated, in order to understand the process of sulfide precipitation. By comprehensive comparisons, the study attempts to illustrate the key factors and process for the MVT ore formations in the fold-thrust belts and establish a metallogenic model. This study may obtain new insights into the genesis of MVT deposits in fold-thrust belts and the metallogenesis of continent-continent collision setting.

密西西比河谷型（MVT）铅锌矿床主要形成于汇聚造山带的前陆带和褶皱逆冲带内，西方学者基于北美Ouachita造山带的研究，建立了前陆带内MVT成矿模型，但其无法解释褶冲带内MVT矿床成因。特提斯域是全球最重要的MVT矿床发育区，其陆-陆碰撞褶冲带内发育大量MVT矿床，为创建相关成矿模型提供了天然实验室。.本申请聚焦青藏高原和扎格罗斯造山带中两个处于不同构造演化阶段的褶冲带及其内四个典型矿床，通过区域构造和控矿构造分析、矿床定年，揭示区域构造与成矿耦合关系；开展区域构造-流体分析和导矿断裂研究，揭示成矿流体在褶冲带内运移特征；通过控矿构造、特别是盐底劈构造控矿研究，厘定褶冲带内构造控矿式样；以油气流体参与成矿过程为研究重点，阐明矿质沉淀过程。开展综合对比，凝练出控矿关键要素和成矿源-运-储一般过程，构建成矿模型。研究有望在完善MVT矿床成矿理论及理解特提斯域陆-陆碰撞与成矿方面获得创新认识。

本项目聚焦青藏高原和扎格罗斯造山带褶皱-逆冲带内MVT铅锌成矿作用，意在阐明褶冲带内MVT铅锌成矿过程，结合综合对比，揭示特提斯域MVT铅锌矿床巨量发育的内在因素。项目通过4年研究，1）厘定金顶和Angouran矿床形成于新生代陆-陆汇聚环境，结合区域对比，揭示特提斯域褶冲带内MVT铅锌成矿主要发生在陆-陆汇聚环境，但成矿发生区域挤压逆冲晚期或之后的走滑或伸展阶段；2）确定金顶和伊朗Angouran超大型铅锌矿床的盐底辟构造控矿特征，揭示特提斯域陆-陆汇聚褶冲带内MVT铅锌矿床主要储集于盐底辟构造、碳酸盐岩和蒸发岩岩溶构造、高孔隙度白云岩等储矿构造中；3）在金顶矿床发现方解石交代石膏/硬石膏、且方解石具有低的碳同位素组成，精细定年证明油气活动远早于铅锌成矿，为“油气流体还原硫酸盐为铅锌成矿提供还原硫”这一认识提供了关键证据，进一步系统阐明“还原”的特提斯是域内MVT铅锌大规模成矿的关键；4）初步构建了褶冲带内MVT铅锌“挤压成储、油气成藏、转换成矿”三阶段成矿模型，提出特提斯域的大陆汇聚和原、古、新特提斯洋长期处于低纬度区演化是导致域内MVT铅锌巨量富集的本质因素。项目发表第一、二资助论文11篇（SCI 8篇），1人获“杰青”基金、1人获“优青”基金资助，圆满地完成了各项任务目标。