The Geological Setting And Genisis Of Xikuangshan Super-Giant Antimony Deposits, Hunan, China

This is a Ph. D. dissertation of regional metallogeny for Xikuangshan super—giant antimony ore deposits, Hunan province, China. The geotectonic enviroment, regional geological feature and deep—geological basement of the central Hunan were systematically outlined. The regional circulating system of paleo—ground water (paleo—hydrothermal solution) and the geotemperature distribution during Mesozoic era within the central Hunan were rebuilt, their relationships with the antimony mineralization occurences were discussed. A new concept of antimony—enriched geochemical block existed in central Hunan were proposed as the geochemical enviroment for the formation of Xikuangshan deposits as well as the antimony ore concentrated area of central Hunan. Xikuangshan deposit was reclassifed as that of beded—breccia type based on the re—analyses of ore—controlling structures. The ore depositing conditions (and/or enviroments) were. outlined in Xikuangshan area. A Sm—Nd isochron age of 156.36±4.63Ma was obtained which indicats that the antimony mineralization took place in Jurassic period. A great quantity of fluid inclusion and stable isotopic (H, O, S, C, Pb) data combined with experimental geochemical data of stibnite solubility demonstrate that the ore—forming fluid is a kind of paleo—hydrothermal solution (hot ground water) with a mixed origin. Ore—forming elements such as antimony and sulfur :may originated from the base strata system. The regional comparision of chemical compositions of fluid inclusion and lead isotopic data from various antimony ore deposits illustrate that the Xikuangshan deposit bear similarity in genesis and relativeness in the origin of ore—forming materials with other Sb, Sb—Au as well as Sb—Au—W deposits in the central Hunan. At last, the Xikuangshan antimony deposit is genetically considered as one related to the circulating and discharging of paleo—hydrothermal solution, a mineralization pattern of cycling and inner—discharging of paleogeofluid was constructed. Some basic geological and hydro—geological conditions which controlled the deposition of ore elements in exceptional quantities for super—giant deposits were concluded, and a clue to prospect such kind of deposits is also given finally.