The Metallogenesis And Space-time Structure Of Copper And Gold In Jiurui District, Jiangxi Province

Jiurui metallogenic belt is located in the north of Jiangxi Province. It’s an important part of Middle to Lower Yangzi River metallogenic belt. The Jiurui metallogenic belt is rich in metal mineral resources, such as copper, sulfur, molybdenum, gold, silver, lead and zinc. There are two large scale copper deposits, three middle scale copper-gold deposits, five small scale copper deposits and ten ore showings of gold and copper in this belt. The main ore deposit types include skarn copper deposit, massive sulfide polymetallic deposit, porphry copper-gold deposit and gossan-type gold deposit. Resently, important advances on the deep exploration oresearch has been made. Exploration breakthroughs in both depth and width around in Wushan and Chengmenshan deposits have been made. Furthermore, the large scale porphry copper, gold and molybdenum mineralized bodies are found in Xiangutai district, which shows the great potential of copper and gold in the area. The geochemical analyses and isotopic dating are carried out in this paper. Based on field survey and indoor microscopic study, effects of the strata, magmatite and structure on the mineralization are discussed. This paper focus on the relationship of regional magmatism and mineralization which can generally describe the copper-gold enrichment mechanism in Jiurui district, Jiangxi province.The strata and magmatite outcroping in the Jiurui Copper polymetallic ore field are Yanshanian intrusive granodiorite and Lower Triassic to Upper Paleozoic sediments. The Upper Devonian Wutong formation sandstone, Upper Carboniferous-Lower Permian Huanglong formation dolomitic limestone and Middle Permian Wangjiapu coalbeds constituted a favorable sandwich structure type, in which the stratiform massive sulfide copper deposits in Chengmenshan southern belt and Wushan northern belt occurred. Carboniferous-Permian strata favorable for the formation of ore are formed under late Paleozoic sedimentary basin environment.Mesozoic igneous rocks are of deep-seated huge batholith, intermediate-depth batholith, shallow magma column and near-surfacial small magmatic body in vertical direction from deep to shallow, roughly corresponding to ore belt, ore field and deposit,respectively. Ore bodies are intimately related to with plutons. There are4types of ore, i.e. porphyry copper ore body and skarn ore body in porphyry and xenoliths, respectively, skarn ore body in contact zone, interlay sulfide type ore body outside contact zone and disseminated-veinlet ores. There is a sequence of Moâ†'Cuâ†'Cu-Au(Mo-W-Pb-Zn)â†'Pb-Zn-Ag(Cu-S-Au) from the center of porphyry to outside. The magmatic rocks show zonal spacial distribution, and from north to south5structural-magmatic belt can be identified. They are NEE-trending tectonic-magmatic belt, NWW-trending tectonic-magmatic belt which is controlled by Yangtze River faults(Jiujiang-Guangji fault), tectonic-magmatic belt controlled by NNE and NW-or NWW-trending basement faults and their joints, and tectonic-magmatic belt controlled by NW-and NEE-trending covering strata faults and their joints (controlling shallow magmatic rocks and deposits).The copper and gold orebodies are mainly controlled by "four zones and one surface ", which includs the contact zone between magmatic rocks and surrounding rock, interlaminar broken zone, fractured zone, fault zone, and different lithological interface or sedimentary discontinuous surface. The contact zone and interlaminar broken zone is a typical structural zones controlling the occurrence of ore bodies.The ore deposits in this metallogenetic belt are characterized by multi-type.The two periods of mineralization can be identified. The first is Hercynian submarine exhalative hydrothermal mineralization system forming early Carboniferous stratabound S, Fe, Cu, Au deposits. The second is Yanshan magmatic hydrothermal superimposition-transformation metallogenic system which is related to the large-scale porphyry type Cu-Mo mineralization and skarn type Cu-Mo (W)-Au mineralization. The zircon LA-ICP-MS U-Pb dating for Dingjiashan, Yangjishan, Baoshan, Tongling and Dalang granites related to Cu-Au mineralization were carried out. The zircon U-Pb age of Dingjiashan quartz diorite is145.4±1.2Ma, Yangjishan quartz diorite144.8±1.3Ma, granodiorite porphyry in Baoshan143.6±1.2Ma, Tongling granodiorite porphyry141.2±1.3Ma, and Dalang quartz dioriteis146.4±1.2Ma. They are Yanshanian and represent the formation ages of the garanite. The comprehensive studies indicate that the ore-forming process of Cu-Au deposits in the Jiurui ore belt can be described as the follows:the first phase of mineralization is the Hercynian seafloor exhalative mineralization between the345Ma～328Ma; The second is Yanshanian magmatic-hydrothermal superimposition-transformation mineralization,.The second phase can be further divided into two stages.The early mineralization between148Ma～143Ma occurs mainly in the central region, such as Wushan-Dalang magmatic rock subzone (148Ma) and Dingjiashan-Yangjishan Mountain magmatic subzone (145Ma～143Ma). Late mineralization occured mainly during143Ma～138Ma and dominantely in the Tongling-Xiacao magmatic subzone(142Ma～141Ma), Fengshandong～Dongleiwan magmatic rock subzone and Xintang-Chengmenshan magmatic subzones(142Ma～138Ma).In conclusion, the temporal-spacial evolution of mineralizations of Jiurui area is not only constrained by the tectonics of Middle to Lower Yangtze River metallogenic belt, but also controlled by regional tectonic setting of eastern China. Meantime Jiurui metallogenetic belt also displays its unique features in temporal-spacial evolution. The metallogenetic tectonic setting in Jiurui probably closely is related to theinteraction of Yangtze plate, North China plate and paleo-pacific plate and crust-mantle interaction.