Metallogenic Regularities And Ore-prospecting Direction Of Manaoke Gold Deposit In Sichuan Province

As a typical representative of the fine-disseminated gold deposits related with the tectonic alteration zone, Manaoke Gold Deposit is located in the northwestern Sichuan province. Geotectonically, the Manaoke Gold Deposit lies in the junction of North China Plate, Yangtze Plate and Indian Plate, where the spatial distribution of the Manaoke brittle-ductile shear zone is controlled by the regional Maqu-Lueyang deep fractured zone.The location of ore bodies are controled by the multi-stage fracture, cracks and joints of different directions, and the tectonic alteration zone is the mainly favorable parts for bonanza ores.In the past, the research on the connection between the mineralization and the fluid derived from the depth of the Earth is ignored for a long time, as a result of manacle by the traditional idea of the stratabound deposit theory. Recently, research has found that the deposits of this type is close in space with the tectonic-magmatic activities and the deep fluid.Based on the Project of Superseding Resources Exploration for the State Crisis Mine-"Superseding Resources Exploration to the Manaoke Gold Deposit in Jiuzhaigou County, Sichuan Province" and the cooperative item of "Comprehensive research on the Metallogenic Regularities and Ore-prospecting Direction of Manaoke Gold Deposit in Sichuan Province" from Manaoke Gold Mine Development Co., LTD in Jiuzhaigou County, Sichuan Province, this doctoral dissertation intends to introduce the theory and research method of the deep fluid mineralization. With systematically study on the stable isotopes and the geochemistry of the trace and rare earth elements, the source of the ore-forming fluid and the mineralization are identified on basis of the study of the geological feature of deposit, the metallogenic regularities the deposit are summarized, and prospecting orientation is outlined.The doctoral dessertation achieves the following main results and understanding:(1) Manaoke Gold Deposit has certain layer-controlled characteristics. No matter in regional or in isolated areas, the gold-rich ore bodies tend to locate in a special combination of different stratums, which shows that the mineralization is related to the stratum. Outside the abundance and the occurrence state of the metallogenic elements, stratums combination of different physicochemical properties should assume more responsibility for this. In profile, the lithology association is rhythm of sandstone and slate, which help to form superimposed relationship and ordered arrangement of competent (permeable barrier) and incompetent (impermeable barrier). Almost all of the gold ore bodies occur in transfer sites between competent and incompetent, that is the contact belt of sandstone and slate.(2) Manaoke Gold Deposit is primarily controlled by the structure. The location of ore bodies are controled by the multi-stage fractures, cracks and joints of different directions in the Manaoke brittle-ductile shear zone, and the tectonic alteration zone is the mainly favorable part for bonanza ores. Without strict restriction by the stratum, the gold ore (mineralized) bodies, where the expansion and shrinkage with branching complex are a familiar phenomenon, occur mainly as nervation, net nervation, podiform in the tectonic alteration zone. For the first time, the compound positions of polytectonic faults, which is the mainly favorable parts for bonanza ores, is presented in this paper. Although the occurrence of the ore bodies are mainly NW, the compound positions of the NNE, NW and NS structures are the favorable position to find the rich and large ore bodies.(3) The geological and geochemical characteristics of Manaoke Gold Deposit show obvious difference with the traditional "Carlin-type Au deposit". The tectonic-magmatic activities play an important role in controlling ore bodies, as well as obvious signs of deep source fluid involved in metallogenesis. The geochemistry of trace and rare earth elements in hydrothermal minerals, such as quartz, calcite, etc. indicate that the ore forming materials and ore forming hydrothermal solution have multi source, part from the deep through the deep and large faults, part from the shallow through the transformation of sedimentary formations. The formation of ore bodies is closely related to the Mixed metamorphic ore-forming fluid and superposition by the magmatic hydrothermal fluid. Manaoke Gold Deposit belongs to a large scale medium-low temperature hydrothermal gold deposit of polygenetic compound characteristics.(4) With favorable geological mineralization setting, favourable metallogenetic conditions and significant mineralization information, the Manaoke Gold Deposit, whose depth and periphery are enormously potential for ore prospecting, possesses the prerequisite of super large ore concentration area of the microfine disseminated gold deposits. The west and east of the Manaoke brittle-ductile shear zone, as the prospecting direction and targets of the periphery, have a good exploration prospect. The North of the ore area, where the F1fracture is adjacent to the northern Yangbuliangzi fault, with the features of intense tectonic movements and fluids, are prospecting potential. Near the east Manaoke metallogenic belt and adjacent to Heye fault, with the similar metallogenic characteristics and favourable geochemical prospecting anomaly, the Badui, Xiaoshengou and Raolagou area, where magmatism are obviously more violent and gold occurrences (mineralized points) have been found, is the key place for prospecting henceforth. A great effort for ore prospecting for the deep large orebody in Manaoke gold ore field is the main prospecting object for the future.