| This article detailedly studies characteristics of dolomite, the lead-zinc deposits mineralization, and their coupling rules with Sedimentology, Sedimentary geochemistry, Mineralogy, Petrology, Mineral deposits, Modern metallogenic theory and System theory of Sinian Dengying Formation in Hanyuan region, Sichuan Province, China. At last, this article puts forward indicator and metallogenic regularity of lead-zinc deposits with dolomite surrounding rocks.On the basis of a large number of regional geological data, this article clears and figures out division scheme of Dengying Formation, plate movement history, regional tectonic evolution history, present tectonic framework, nature and evolutionary stages of sedimentary basins, lithofacies paleogeographic characteristics and evolution of Dengying Formation and regional distribution characteristics of lead-zinc deposits in the study area.This article renewedly clarifies a genetic classification scheme of dolomite, and then recognizes six kinds of dolomite genetic types of Dengying Formation, such as primary dolomite, contemporaneous dolomite, penecontemporaneous dolomite, diagenetic dolomite, epigenetic dolomite and supergene dolomite, with profile observation, thin section observation, scanning electron microscopy (SEM) analysis, cathodoluminescence (CL) analysis, geochemical analysis and mineralogical analysis. Primary dolomite includes microbial dolomite. Contemporaneous dolomite includes mainly mimetic dolomite. Penecontemporaneous dolomite includes mainly evaporating pump dolomite and mimetic dolomite. Diagenetic dolomite includes mainly powder crystal dolomite, fine crystal dolomite and siliceous dolomite. Epigenetic dolomite includes mainly saddle dolomite. Supergene dolomite includes mainly powder crystal dolomite caused by meteoric fresh water leaching of grape-shaped dolomite and dolomicrite. The recognition of microbial dolomite and mimetic dolomite is of great significance, and can compare with others studys.This article studies the features of geophysical, geochemical, geology of ore deposits, geochemistry of ore deposits and mineralogenetic epoch of key lead-zinc deposits of Dengying Formation, such as Tangjia, Tuanbaoshan, Heiqu, Xuqu. The results show that the study area is located in the conversion parts of Hanyuan-Ebian fault uplift and Liangshan fault depression; is enriched Lead, zinc, silver, iron, phosphorus, magnesium, barium, cadmium, germanium, gallium, sulfur, and other elements; has geology of hydrothermal (hot water) ore deposits of dolomite and fault ore-controlling in the low temperature metallogenic domain; is mainly low temperature hot brine and submarine exhalation genesis in the background of cratonization crust, orogenic belt and mature island arc; has mainly two ore source beds, such as folded and crystalline basement (granite Jinning period) under the Dengying Formation and dolomite of Dengying Formation; has three metallogenic stage or mineralogenetic epoch, such as metallogenic stage â… -1and â… -2(the Late Sinian to the Early Cambrian), metallogenic stage â…¡ (the Late Cambrian to the Devonian) and metallogenic stage â…¢ (the Permian to the Triassic). On the basis of the results, the lead-zinc deposit of Dengying Formation is classified as SEDEX type and MVT type according to the new reclassify classification scheme of the lead-zinc deposit. In addition, this article also probes into the paragenetic and associated assemblage relationship between the lead-zinc deposits and pyrite, phosphate rock and magnesite.And then this article summarizes and puts forward the evolution rules of dolomite genetic types of Dengying Formation in the study area. There are some unique combinations of genesis and structure types in the each geological history, and each genetic type of dolomite has evolutions of genesis and species in the different geological history. In the deposit-diagenetic process of dolomite of Dengying Formation, there are mainly primary dolomite, contemporaneous dolomite, penecontemporaneous dolomite and diagenetic dolomite, and also have epigenetic dolomite formed by tectonic and hydrothermal process and supergene dolomite formed by Tongwan movement. After Qiongzhusi stage, there are mainly epigenetic dolomite and supergene dolomite.This article also summarizes and puts forward the evolution rules of the lead-zinc deposits mineralization of Dengying Formation in the study area. The main metallogenic period is from the Late Sinian to the Early Cambrian. There are (near) SEDEX type and MVT type lead-zinc deposit in the2th and3th member of Dengying Formation period in the Tangjia and Tuanbaoshan. There is SEDEX type lead-zinc deposit in the4th member of Dengying Formation period in the Heiqu and Xuequ. The (near) SEDEX type is the precursor or prelude of the SEDEX type. The MVT type is closely related to the SEDEX type, and they have genetic, time and sparce relationships. The two secondary metallogenic periods is from the Late Cambrian to the Devonian and from the Permian to the Triassic. There is MVT type lead-zinc deposit or reforming early lead-zinc deposit and secondary mineralization in the2th,3th and4th member of Dengying Formation period.This article compares the evolution rules of dolomite genetic types of Dengying Formation with the evolution rules of the lead-zinc deposits mineralization of Dengying Formation, and summarizes and puts forward their coupling rules and indicator of lead-zinc deposits. The grape-shaped dolomite, laminar dolomite and clotted dolomite of contemporary and penecontemporary period provide ore source bed, organic matter, geochemical barrier and reservoir space for lead-zinc deposits mineralization, and the (pene)contemporaneous and hydrothermal breccia dolomite and aperture of bedding provide migration channel and reservoir space, in which there are the (near) SEDEX type of metallogenic stage â… -1and the MVT type of metallogenic stage â… -2, â…¡ and â…¢. The saddle dolomite, the massive silicalite dolomite and the hydrothermal breccia dolomite of diagenetic and epigenetic period are indicator and product of lead-zinc deposits mineralization, near which there are SEDEX type of metallogenic stage â… -2and the MVT type of metallogenic stage â… -2, â…¡ and â…¢. These can also be concluded that the indicators of lead-zinc deposits of the2th and3th member of Dengying Formation are the (pene)contemporaneous and hydrothermal breccia dolomite, the saddle dolomite and the massive silicalite dolomite in the grape-shaped dolomite, the laminar dolomite and the clotted dolomite, near which there are tubular, big vein and plural vein MVT type lead-zinc deposit and stratiform and stratoid (near) SEDEX type lead-zinc deposit; the indicators of lead-zinc deposits of the4th member of Dengying Formation are near the massive silicalite dolomite, the hydrothermal breccia dolomite and the saddle dolomite, under phosphate rock body and shale and siltstone of Qiongzhusi Formation, where there are stratiform and stratoid SEDEX type lead-zinc deposit.Finally, this article comprehensively puts forward the’ before the mineralizationâ†'metallogenic stage â… â†'1â†'metallogenic stage â… -2â†'metallogenic stage â…¡â†'metallogenic stage â…¢â†'after the mineralization’ metallogenic regularity and metallogenic model of lead-zinc deposits with dolomite surrounding rocks of Dengying Formation in the study area. |
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