Characteristics And Origin Of The Dongguashan Stratabound Skarn Cu Deposit In Tongling, Anhui Province

Tongling area in Anhui Province is an important part of the Middle-lowerYangtze River polymetallic metallogenic belt. Dongguashan copper deposit is one ofrepresentative stratabound skarn Cu deposits in Tongling, Anhui Province. It is typicaldue to its large scale, high grade and remarkable geologic feature. A comprehensivepetrographical, mineralogical and geochemistry study has been carried out on theDongguashan copper deposit, with a focus on analyses of ore texture and structureand mineral composition.The following are major achievement obtained in this thesis.1. Field investigation and microscopic observation indicate occurrence ofsedimentary, thermally metamorphic, and hydrothermal metasomatic textures andstructures in ores from the deposit.2. Compositional analyses of minerals support formation of pyrrhotite in themain ore body of the Dongguashan copper deposit by desulfurization of pyrite in theearly laminated ore body during the Yanshanian intense metamorphism. A slowcooling process occurred during its formation, locally with a rapid cooling process.3. A mineralographical and isotopic research shows derivation of Cu in theDongguashan copper deposit possibly from the Yanshanian magmatic fluid.4. Two periods of mineralization are responsible for the formation of theDongguashan Cu deposit. The early mineralization of the late Carboniferoussubmarine exhalative and sedimentation led to formation of many copper sources bedswith S and Fe in the basement of the deposit. In contrast, the late mineral of theYanshanian magmatic activity resulted in formation of stratabound skarn Cu depositthrough variation of physicochemical conditions in the metallogenic system andsuperimposed reformation of early sources beds by the magmatic fluid.