沉积岩型铅锌矿床的成矿系统研究

Study of metallogenic systems of sediment-hosted lead and zinc deposits

沉积岩型铅锌矿床是铅锌矿床中重要类型之一。在系统论述沉积岩型铅锌矿床成矿背景、地球化学和矿床类型的基础上,分别阐明了沉积喷流型(SEDEX)、密西西比型(MVT)和砂岩型(SST)3个成矿系统的成矿要素、作用过程、矿床和异常组合以及成矿模式。对3个铅锌成矿系统作了全面对比,获得一些认识:(1)SST矿床的矿化表现为对构造和高孔隙度有利岩性而不是地层层位的依赖性;(2)云南会泽碳酸盐型铅锌矿(MVT)成矿物质除热卤水沉淀来源外,还有火山岩系的提供,属后生混合流体成矿作用;(3)沿古陆边缘同生断裂构造发生的海底热水喷流沉积作用为SEDEX型铅锌成矿奠定了物质基础;裂谷伸展期常有“双峰式”火山活动,提供部分矿源、热源、水源;同生断层长期活动提供热水循环通道和矿质沉积场所;(4)风化剥蚀的变质基底为三者提供了成矿物质,成矿热卤水在盆地中经过了演化过程。

Sediment-hosted lead and zinc deposits are economically important types of ore deposits. These ore deposits are typically located at the edge of stable continent cratons. The study of sediment-hosted lead and zinc metallogenic system focuses on the relationship between time-space and ore-forming events. In our study, we examined the links in the sequence of events that lead from ore-forming stages, to ore emplacement and preservation. This method can find out the ore distribution, ore suppliers, genesis, ore-forming mechanism, and guide the scientific ore-searching. Sediment-hosted lead and zinc deposit can be divided into three types ： 1） Sedimentary Exhalative （SEDEX）, 2） Mississippe-Valley type （MVT） and 3） Sandstone-hosted type （SST）. In our study of the three types of sediment-hosted metallogenic systems, we came to the following conclusions： （1） In the case of SST deposits, porosity and permeability of the host sandstone are the most important ore controls. For example, the Jinding Pb-Zn deposit is only controlled mainly by structure and the highly porous character of the host rock rather than the sedimentary strata per se. （2） The Huizhe Zn-Pb MVT deposit, the ore metals were precipitated from hot saline fluids associated with volcanic systems. The genesis is epigenesis of mixing solution ore-forming process. （3） SEDEX Pb-Zn deposits, are spatially associated with syngenetic faults which provided the path and space for deposition of metals, volcanic activity during the rifting stage. SEDEX deposits are formed during syngenetic and epigenetic processes. （4） To some extent, the weathered and metamorphic basement rocks provide the metal source for all three types of sediment-hosted Pb-Zn deposits.