The Geological Characteristics, Genesis And Metallogenic Prediction Of Dachang Tin-polymetallic Ore Field, Guangxi

Guangxi Dachang mineral field is famous around the world for its giant resources of Sn and other metals, and it is significant to study it geological characteristics and mineralization rules. Based on the metallogenic series theory, polygenetic compound ore deposit, mineralization prediction on composit information, mineralization theory on combination of different geological conditions, mineralization on geological anomalies theory, combined with detailed field work, the bulk of this dissertataion is focused on deposit geological, geochemical characteristics, ore deposit genetic model, the main controlling factors of Dachang Sn polymetallic deposit, with the research of the geological background of the Dachang mineral field. By comprehensively summarizing the mineralization rules of the Dachang area, the metallogenic work had been carried out.The evolution history of sedimentary facies and paleogeography within the Danchi basin had been studied, and further work had been put on the main stratigraphies, formation and evolution of litho-facies; so, with this kind of work, the understanding of the mineralization background goes a bit deeper.By analysis the latest geophysical, geochemical and exploration results, the geological properties of mineralization within Dachang mineral field had been re-organized systemetically, the relationship between the mineralization rules and ore bodies spacial distribution been analyzed; while, the re-classification of the mineralization layers is helpful for the metallogenic works.A new metallogenic model is summarized. The metal sources are from the basement, and the basement had experienced strong miveralizaiton stage. The brine, carrying the ore-forming materials, stored in the stable areas and formed high-density ore-forming fluid. The Sedex-type mineralization in the early Devonian had formed layered ore bodies. The ore-forming materials remobilized and concentrated in the stress concentration areas during the Variscan. While with the motivation from granite in Yanshanian, the magmatic water and ore-forming fluid, carrying the ore-forming materials, precipitated at stress relief areas, and this kind of mineralization procedure repeated multiple. It is believed that the Dachang mineral field is a consequence of mineralization procedure with multiple stages and multiple genesis.In this dissertation, it is the first time being mentioned that the combination of uplift structure and containing structure dominating the mineralization. It is a inovation for the metallogenic research relating to endogenic granite deposit. The containing structure can conduct the ore-forming fluid to the uplift structure and form bigger deposits. While, the extension structure can destroy the aggregation of ore-forming fluid and decentralize the fluid, and lead to the destruction of favorable ore-forming conditions.Based on the zonation of mineralization, different types of deposit models had been summarized, and, combined with the geophysical and geochemical models, the ore prediction model is upgraded to the latest comprehensive, more practical model.It is the first time using a new technology on comprehensive research, mathematical geology and geophysical-geochemical information to summarize a3-D model that would be suitable for deep blind ore prediction in mature area. With the help of this technology, the exploration had abtained a breakthrough, and the new finding Zinc reource would be classified as a giant deposit. And the exploration depht had been deepened from600m below surface to1000-1500m below surface. The exploration potential had been expanded, and the understanding of Dachang mineralization had been improved.