Geological Setting Of Ore-forming Process Of Luchun-Mojiang Region, Yunnan Province

The strata is relatively abundant in Luchun-Mojiang Region, which is located in the western Yunnan Province, southwestern China, part of the"south Sanjiang metallogenic belt", at the junction of Ailaoshan Orogen and Changdu-Simao Basin, including from the Silurian to Cretaceous,especially the Triassic, and the Waigucun Formation of Triassic is an important ore-bearing strata. Magmatic rocks scatters, as apophyse,dike and small-scale stock,among which intermediate-acidic hypabyssal rocks are dominated and intermediate,mafic rocks are subordinate. The acidic porphyry and lamprophyre play an important role in the formation of gold deposit.The distribution of metamorphic rocks is only in the Silurian strata, wall rocks, fault zones.Study region is front-edge faults of Ailaoshan orogen which consist of Luoen Slice,Niukong-Huangcaoling Fault, Niukong Slice, Datou Fault, Dashuigou Slice, Dazhang-Erya Fault, Baliu Fault and Amojiang Fault from east to west.The typical minerals are gold, copper, manganese, coal, etc., and there are some cinnabar, titanium, chromium and vanadium, lead and zinc anomalous area and high points which were found by previous geochemical work. There is diversity of the geological setting of ore-forming process in differert slice, so do the mineral types.Niukong gold deposit is located in Niukong Slice.According to previous work and field survey, based on the location of orebodies, magmatic characteristics, wall rock alteration and ore characteristics , it is judged as a tectonoclastic zone altered rock type Gold deposit. The ore-controlling factors are:NW to nearly EW extending fault,especially the convergence zone with the SN extending fault; tectonoclastic zone intruded by the intermediate-acidic porphyry and lamprophyre;the Waigucun Formation of the Triassic.By contrast to the Ailaoshan gold belt,it is inferred that the formation of the deposit may be in the late Yanshan stage to early Himalayan stage.Mina copper mine is located in Baliu Slice,and ore bodies are bound to grey sandstone in Waigucun Formation.So it is judged as a sandstone copper ore.According to the characteristic of ore district and the ore-controlling factors,it is inferred the formation of deposit experience two phase——forming the primary ledge in Triassic;hydrothermal that come from NNW extending fault having the copper enriched and forming ore bodies.Bafu manganese mine is located in Niukong Slice,and the ore body exist in the relatively thick layers which contain manganese in Waigucun Formation.Based on the characteristic of the ore body and ore,it is regard as a weathering-leaching manganese mine.The formation of deposit also experience two phase——forming the primary ledge in Triassic; forming ore bodies in Quaternary.Two coal mine points located in Dashuigou Slice,and the seam exist in Xiamidi Formation and Xianrendon Formation,respectively. Moreover, Yangbazhai Formation, Waluba Formation and Maichuqing Formation all possess coal lines.The characteristics of ore-controlling factors in study region are:minerals are obviously controlled by the Up Triassic Series, especially the Waigucun Formation, which show the areal geology——Sanjinag metallogenic belt feather; minerals are controlled by nearly SN extending to NW extending fault in Baliu Slice, by NW extending to nearly EW extending fault in others,which show the tectonic ore-formation is periodical and divisional; hypabyssal and ultra-hypabyssal intermediate-acidic magma and the mantle-derived alkaline lamprophyre facilitate the enrichment and formation of gold deposit.Based on the analysis of ore-controlling factors, the relationship between mineralization and geological processes is discussed. In the end,it is recommended that NW to nearly EW extending fault in Waigucun Formation in Niukong Slice and the Triassic in Baliu Slice are two most potential prospecting area for gold ore and copper ore,respectively; Luoen Slice and NW extending fault in Up Permian Series in Baliu Slice are two potential prospecting area for gold ore,and on both sides of Niukong Fault are potential prospecting area for copper ore.Moreover, perspective area of copper arsenic ore,coal and manganese ore are also recommended.