铅锌超常富集成矿过程的高温高压实验—以会泽超大型富铅锌矿为例

The Huize super-large Pb-Zn deposit，located in the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic belt is characterized by "rich, large, strong, high” and so on. Among them, "lead and zinc supernormal enrichment" is the greatest features. Previous studies have been conducted to study the formation mechanism by isotope, trace elements and fluid inclusions tracing, which is not yet able to explain the metallogenic mechanism of ore deposits satisfactorily. The dynamics experimental of high temperature and high pressure has not been reported, which will be an effective means for the study of the metallogenic process. This study focuses on the scientific problem of fluid migration and precipitation kinetics mechanism of Pb-Zn abnormal enrichment. Based on the new ideas of regarding as " water rock reaction-fluid properties-lead and zinc hydrolysis-complex instability” an organic whole which is constantly changing, pay attention to the characteristics of different ore-forming stages of mineral assemblage, sphalerite crystal structure and morphology were changed, in order to study the dynamic process of migration and precipitation of lead and zinc under the conditions of open - flow - far from equilibrium by evolution perspective. By using the improved stack reactor and continuous stirred tank reactor, the hydrolysis kinetics experiments under different temperature and pressure, pH, concentration and water-rock reaction conditions and fluid mixing dynamics experiment in 4 mineralization stages will be carried out. The mechanism of metallogenic dynamics of lead and zinc abnormal enrichment will be revealed. The research can not only deepen the understanding of the geochemical behavior of lead and zinc in hydrothermal system, but also is of great significance to innovate the metallogenic theory of this type of ore deposit and the high temperature and high pressure experimental technology of the hydrothermal system.

位于川滇黔接壤区的会泽超大型富铅锌矿具有“富、大、强、高”等特点，其中铅锌超常富集是最大特色。前人多从同位素、微量元素和流体包裹体等方面研究，尚不能圆满解释矿床成矿机制。基于成矿过程的有效研究手段的高温高压动力学实验也未见报道。本研究围绕“铅锌超常富集成矿过程中流体运移、沉淀动力学机制”的科学问题，从“水岩反应-流体性质-铅锌水解-络合物失稳”视为有机整体的新思路出发，针对不同成矿阶段矿物组合，闪锌矿形貌、晶体结构改变的特点，以动态演化的视角研究在（半）开放-流动-非平衡下铅锌运移、沉淀的动力学过程。采用改进的叠层反应器和全混流高压釜，开展不同温压、pH、浓度和水岩反应条件下的水解动力学实验和两类流体混合成矿动力学实验，揭示铅锌超常富集成矿动力学机制。该研究对深化热液体系中铅锌地球化学行为的认识，创新该类矿床成矿理论及热液体系高温高压实验技术均具有重要意义。

位于川滇黔接壤区的会泽超大型富铅锌矿具有“富、大、强、高”等特点，其中铅锌超常富集是最大特色。前人多从同位素、微量元素和流体包裹体等方面研究，尚不能圆满解释矿床成矿机制。基于成矿过程的有效研究手段的高温高压动力学实验是解决上述问题的最佳方式之一。项目通过开展高温高压下的水解实验和水岩相互作用实验，取得以下成果：随着温度升高，铅锌水解被抑制，高温下铅锌在运移过程中水解较弱甚至不水解，利于流体不断萃取围岩中铅锌元素且长距离大规模运移，形成富矿流体；碳酸盐岩能明显促进铅锌水解，且其促进程度远大于其它抑制铅锌水解条件的影响。其原因是碳酸盐岩可以不断消耗水解反应生成的H+，从而使水解反应的平衡向右移动；流速过快会导致流体与围岩接触有限，利于运移，容易形成范围较小而品位相对较高的矿床，如川滇黔的HZT型矿床；而流速较慢的流体能与围岩充分反应，不利于金属元素的长距离大规模运移，运移途中容易水解而沉淀下来，形成的矿床范围较大但品位较低，如MVT型矿床。上述高温高压下开展的实验结果进一步验证了MVT和HZT 两类矿床品位悬殊的主要原因是pH、运移驱动力和水解程度的不同。该研究对深化热液体系中铅锌地球化学行为的认识，创新该类矿床成矿理论及热液体系高温高压实验技术均具有重要意义。