The Genesis Of Dolomite And Its Relations To The Deposits In Panlong Pb-Zn Mine Area,Guangxi Province

Panlong Pb-Zn Mine is located in Panlong Village,Wuxuan County,Guangxi Province.It is a typical large-scale Pb-Zn deposit in the Central Guizhou area.It has been proven that the amount of Pb-Zn metal exceeds 1 million tons,reaching a large scale,and its associated barite resources are also Large.At present,there are two kinds of arguments for the genetic type of Panlong Pb-Zn mine:MVT type and SEDEX type.Regardless of the type of genetics,the objective fact is that the Panlong Pb-Zn mine is produced in the Early Devonian Upper Lun Dolomite and is closely related to the evolution of the white cloud.This study is based on the regional Devonian sedimentary environment and lithofacies paleogeographic evolution.The basic characteristics of the Shanglun Dolomite,the basic characteristics of the Panlong Pb-Zn deposit and its relationship with dolomite,and the study on the genesis of dolomite and its contribution to the mineralization of the Panlong Pb-Zn deposit,the following preliminary conclusions are drawn.:1.Detailed geological survey and petrographic studies show that although the Panlong Pb-Zn deposit has some characteristics of SEDEX deposits,such as layered ore bodies and particulate structures,it lacks important jet sedimentary rocks and jet structures.Before there is more evidence,the Panlong Pb-Zn deposit is defined as a low-temperature packed layered Pb-Zn deposit?MVT type?.2.Shanglun dolomite is formed by limestone dolomite in the deep burial state,although the compaction and further cementation in the diagenetic period caused the primary pores to be destroyed and filled to some extent,but buried the white clouds.The dolomite formed by lithification has strong anti-compaction ability,and the original intercrystalline pores formed in the early stage of diagenesis are preserved,which is conducive to further modification of the later dissolution,resulting in further increase of porosity and great reservoir performance.Improvement,the reservoir capacity is obviously improved.When encountering hydrothermal fluids containing Pb and Zn,Pb-Zn ore bodies are formed in pores or fissures under certain conditions with changes in temperature and pressure conditions.3.Sedimentary environment and paleogeographic studies show that the Wushen Devonian is in the process of coastal-semi-open-open-open platform evolution,seawater gradually invades from the southwest,forming the sedimentary sequence of the Wuxuan Basin,and the Wuxuan Basin is protected by the south side of Pingxiang-Dali.In the fault-controlled fault basin,on the one hand,the Pingxiang-Dali fault controls the formation and evolution of the basin.On the other hand,the fault controls the rise of ore-forming hydrothermal fluid and hot brine,and becomes the channel of ore-forming hydrothermal fluid.Mine structure.4.Shanglun Dolomite should belong to the product of the early two pond limestones beingreplaced by hot brine.The diagenetic temperature of dolomite in Shanglun Dolomite is 80.36¹12.77°C,the diagenesis depth is 1678-2660 m,the value of ?¹⁸O is between-6.53^-11.75,and the dolomite genetic type is buried dolomite.5.The data of ?¹³C shows that the dolomitization of the Upper Dolomite in the study area is formed by microbial fermentation.The data of fluid inclusions show that the diagenesis?or dolomite?temperature of the Shanglun dolomite is in the range of 150-154 °C,indicating that the dolomite depth is 3636-3758 m,which is characterized by buried dolomite.For the early limestone in the Ertang period,the formation environment of the original rock is an open platform phase.6.From the results of the study of strontium isotope,the original rock of the Shanglun dolomite diagenesis is partly derived from the land source,and some may come from seawater.The trace element Sr,the composition is very low,and the Na component is also low,indicating that dolomitization is formed by the formation of mixed water.The Fe composition is high and the Mn component is also high,indicating that dolomitization is formed by burial.7.The southern margin of the Wuxuan Basin,along the Pingxiang-Dali fault zone,is a layered Pb-Zndeposit?represented by the Panlong Pb-Zn mine,including Pengcun,Boji,Shilu,Daduan,Tongqiao?.The ore deposit belongs to the MVT-type deposit,and its ore-forming geological body is Shanglun dolomite.The ore-forming structure is dolomite layer.The Pingxiang-Dali fault not only controls the formation of the basin,but also provides the channel for the ore-forming ore-forming hydrothermal fluid.The deep buried hot brine provides thermal power.8.Dolomiteization prepares the necessary ore-forming space for mineralization.From the perspective of basin system fluid dynamics,the thermal fluid from the deep part of the Pingxiang-Dali fault zone provides power for dolomitization and provides ore-forming structures for mineralization.Therefore,the Pingxiang-Dali fault zone controlled basin?main fault at the edge of the faulted basin?,the ore-conducting?the ore-forming structure of the layered Pb-Zn deposit?,the controlled rock?the dolomite process controlled by the thermal fluid?,and the ore-bearing?Integration of dolomite lithification and metallogenic processes?,the fusion of ore-forming geological bodies?Shanglun dolomite?and layered Pb-Zndeposits is finally realized.The high temperature buried depth dolomitization has a spatial coupling with the Panlong Pb-Zn ore series mineralization,and the consistency process of genesis.