滇西兰坪盆地蒸发岩系发育规律及盐构造解析

The Lanping Mesozoic-Cenozoic basin is one of the important salt basin in our courtry, where is the Jinding Superlarge Pb-Zn deposit located.The closely relationship between evaporite or salt structures and Pb-Zn mineralization. Preliminary studies have shown that massive evaporite gathered before metal mineralization in Lanping basin, and formed different deformation style and stage of salt structures. The large-scale salt dome formed in the early which provide salt for Jinding orebody, under nappe extrusion, produced puncture and spray salt tectonics which associated metal mineralization. But the Lanping basin evaporite development pattern, material composition, deformation characteristics and mechanism of salt structures is unclear. On the basis of detailed field geological survey, the project will adopt systems petrology , mineralogy, major and trace elements, isotope geochemistry and fluid inclusions analysis, by the modern salt tectonics theory, to study material composition and developmental characteristics of evaporates, deformation stage and formation mechanism as the study entry point, explore evaporite formation age, depositional environment and development law,which is relate with Jinding deposit. Reveal the ore-forming fluids of the nature, origin and accumulation law, determine the relationship between salt deformation stages and mineralization. Reshape the history and relationship between salt tectonics and the Jinding mineralization. The completion of this study not only to investigate the mechanism of salt tectonics mineralization and rich " Jinding " type mineralization theory.

兰坪中新生代盆地是我国重要含盐盆地之一，是金顶超大型铅锌矿床所在地。蒸发岩及盐构造与铅锌成矿关系密切，前期研究发现兰坪盆地在金属成矿前发生过大规模的蒸发岩聚集，形成不同变形样式及变形期次的盐构造，早期形成的大型盐丘体，为金顶成矿提供盐源，经后期推覆挤压形成穿刺型和盐推覆等盐相关构造并伴生大量金属成矿。但是兰坪盆地蒸发岩的物质组成、发育规律、盐构造变形特征及机制等问题尚不清楚，本项目拟在详细野外地质调查基础上，以最新盐构造理论为指导，通过系统的岩石学、矿物学、主微量元素和同位素地球化学以及流体包裹体分析，研究蒸发岩物质组成、发育规律、盐构造变形特征及形成机制，探讨兰坪盆地中与金属矿床有关的蒸发岩形成时代、沉积环境及发育规律，揭示成矿流体性质、来源及聚集规律，确定盐构造变形期次与成矿关系，重塑盐构造与金属成矿作用的历史和联系。该项研究对探讨盐构造成矿机理、丰富"金顶式"成矿理论具有重要意义。

本项目研究了兰坪盆地的蒸发盐发育规律及盐构造特征。项目组对蒸发岩进行了详细的野外地质调查，结合地球化学分析，确定了兰坪盆地蒸发岩的层位、形态，及其盐构造变形特征及期次。四年的研究工作基本上是按照项目申请书中所制定的研究内容和研究计划进行的，研究工作基本完成，申请书中的研究目标也基本达到，相关研究成果已陆续发表。主要取得如下几点认识：（1）布在古近世云龙组呈层状的黑色石膏和指状侵入的灰绿色、灰白色膏泥为古近世云龙组蒸发岩体；分布在云龙组地层中呈蘑菇状、指状侵入的厚层块状石膏为晚三叠世三合洞组蒸发岩体。（2）兰坪盆地发育的盐构造类型有盐枕、盐背斜、盐焊接、盐穿刺、盐推覆、盐岩滑脱－断层相关褶皱组合等多种盐构造变形样式。（3）盐构造形成机制主要受到推覆挤压缩短作用、基底断层作用和塑性流动汇聚作用、盐下和盐上层断裂滑脱作用等控制，其主要沿推覆断裂构造带呈串珠状分布。（4）兰坪盆地盐构造变形期次主要分为两期: 一期为古新世-始新世挤压－拗陷层内变形阶段，而形成盐枕、隆升较低的盐背斜等整合型盐构造；另一期为渐新世的逆冲推覆－盐岩滑脱阶段，受强烈的挤压推覆作用而形成盐墙、盐株等盐刺穿型构造。盐构造不同阶段的变形演化对金属元素富集成矿起到关键作用，其流动变形而形成的盐构造圈闭促使了金属聚集成矿。