| As one of the most widely used inorganic fillers,heavy calcium carbonate is widely used in rubber,plastics and other industries.At present,with the rapid development of the heavy calcium downstream extension industry,the domestic demand for heavy calcium resources is increasing.However,due to various reasons,the domestic research on the genesis of the heavy calcium mineral resource-calcite deposit is relatively lagging behind.The Shangfang in the West Zhejiang is located in the eastern section of the Gan-Hang structural belt,close to the structural suture zone of the Yangtze plate and the Huaxia plate.Calcite deposits are widely distributed in the area,and it is an important heavy calcium resource base in my country.The predecessors have carried out a series of geological surveys in the study area,but the research on the genesis of calcite deposits in the area is relatively few.To this end,this paper takes the Shangfang calcite deposit in the above as the research object,clarifies the occurrence and distribution of the ore body through field geological survey,and determines the mineralogy of the ore by scanning electron microscope(SEM)and X-ray powder diffraction(XRD)analysis Characteristics,through elemental and stable isotope(C-O)geochemical analysis to reveal the geochemical composition of the ore,through the zircon U-Pb chronology to limit the time period of metallogenesis,on this basis to explore the metallogenesis,for the exploration of calcite deposits for heavy calcium and use to provide important theoretical basis.The research in this thesis mainly achieved the following understanding:1)According to petrographic characteristics,the ore of the calcite deposit in the upper town can be divided into two types: marble and marbled limestone.The main minerals of the two types of ore are calcite.Among them,calcite of marble has a higher degree of crystallinity and more regular grain shape than calcite of marbled limestone,and its XRD shows consistent characteristics of calcite map,showing that the mineral composition of marble is single;Limestone shows obvious dissolution and metasomatism.The XRD patterns of some samples show that it contains a small amount of impurity components.2)The main components of marble and marble petrified limestone are Ca O,followed by Mg O.Among them,marble has a higher Ca O content,which is consistent with the mineral composition characteristics;trace element results show that marble and marble petrified limestone In addition to the high Sr and Ba content,the other content is less,showing the characteristics of hydrothermal activity.In addition,both of them show right-dip features on the diagram of the rare earth distribution model after chondrite normalization,while the rare earth standardized in North American shale The partition diagram shows a slightly leftward or near-horizontal characteristic,and δEu are positive anomalies,indicating that magmatic hydrothermal fluids may be involved in the formation of two types of ores;C-O isotope composition shows that marble and marble petrification are mainly located in marine carbon In the area of acid rock,the range of carbon isotope variation is relatively narrow,while the range of oxygen isotope variation is large,suggesting that the ore-forming materials are derived from marine carbonate rocks,and the mineralization is the result of late hydrothermal activity.3)The zircon U-Pb dating of the granite porphyry in the mining area indicates that it was formed in the Early Cretaceous(135 Ma),which is consistent with the time limit of large-scale magmatism in the region.The magmatism in this period may restrict the formation of calcite deposits in the upper town.4)Comprehensive studies suggest that the calcite deposit in the Shangfang was formed by Carboniferous marine carbonate deposits,which were formed by contact metamorphism with the participation of magmatic hydrothermal fluids. |
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