The Ore-Forming Fluids Features And Origin Of The Misha Vein-type Pb-Zn-Cu-Ag-Au Deposits In Jianchuan Country, Western Yunnan Province

Misha area is located within the Fujing-Shanglan-Misha strong deformation and uplift zone in the eastern margin of Lanping basin, western Yunnan, SW China, and belongs to the middle and south edge of the Sanjiang orogenic belt. The geotectonic history includes the Paleo-Tethys close to Paleozoic period, and the collision between the Indian plate with the Asian-European continent during early Cenozoic. A series of vein-type lead, zinc, copper, silver and gold deposits are formed under these tectonic setting, hosted within the strongly deformed formations from the early Permian to late Triassic. On the western edge of the Lanping basin, there are several vein-type Cu deposits including Wudichang, Xiaogela, Kedengjian, Jingman and Liancheng copper deposits with the same genesis/rock types. These deposits and their surrounding rocks in the eastern and western edge of the Lanping basin show that they are the basinal basement, whether there are some contacts with some large-scale deposits in the basin, such as Baiyangchang Cu deposit, Jinding Pb-Zn deposit. Meanwhile, the orogenic deposit has good prospects for development, and it also has a great economic value doing this research during the current resource constraints.This research results show that:(1) Geological survey carry out from Misha-Xiangtu-Yongxiang in the middle stratum of the basin, exposed that in this area mainly are the upper Permian Shanglan formation (P2S); the lower-middle Triassic Pantiange formation (T1-2p); the upper Triassic Sanhedong formation (T3s); the upper Triassic Maichuqing formation (T3m), the upper Cretaceous Nanxin formation (K2n), the Paleocene Yunlong formation (Eiy) and Quaternary (Q).(2) Through detail geological field work, and microscopic scale studies the tectonic deformation in the area can be divided into four periods, Di:controlled by the squeeze from east-west, showing N-S to the dense cleavage; D2:formation in Di phase structure under the action of progressive deformation, forming a series of sheath (shear) fold, fold cleavage, D3:wear cut D1, D2, tensile fracture; D4:fracture. And found four types of orebody to match the defomation:Chunyiping Cu deposit, Chunyiping Au deposit, Baliqiao Fe (Au)-Pb deposit, Yandong Pb-Zn deposit.(3) From the Field and the microscopic observations, the above four types of mineralization associated with gangue minerals, and through the analysis of the inclusions by laser Raman microscopic measuring temperature of fluid inclusions and stable isotope analysis found the fluid property shows:(1) Chunyiping copper deposit exposed in the middle of P2s which the host rock is deep purple sandstone, the deposit is strictly controlled by the regional cleavage action. It’s lack of fluid inclusions. The homogenization temperature is 190□ with salinity of 9.76 wt% NaCl.δ18O value in quartz is 2.98‰, while δ D value is-121.5‰; (2) Chunyiping Au deposit exposed in the bottom of the P2s which the host rock is dark gray phyllite. Orebody where a strong split physicochemical, deformation structures shear fold, pleats cleavage and with "S-C" fabric and so on. The fluid is full of inclusions and the homogenization temperature is 300.4 ℃ with salinity of 5.14 wt% NaCl; while the homogenization temperature of the later stage fluid is 331℃ with salinity of 6.4 wt% NaCl.δ18O value in quartz is 8.7‰, while δ D value is-129.1‰; (3) Baliqiao iron (±old)-lead deposit exposed in the upper part of P2s in the border of the underlying strong deformation phyllite junction site and the slate within thin interbedded limestone. The fluid is full of inclusions and the homogeniza-tion temperature is 330℃ with salinity of 3.72 wt% NaCl.δ18O value in quartz is 9.08‰, while δ D value is-125.9‰; (4) Yandong lead-zinc deposits located at the junction of T3S and T3m formation. The ore output stability, with weak deformation of the surrounding rocks, only has some fragmentation after the main mineralization. The homogenization temperature of the fluid inclusions is 180℃,δ18O value in quartz is 2.9‰, while δ D value is-98.2‰;(4) Compare with the current status of orogenic deposits and the characteristics of regional mineralization fluids, we can conclude that the deposit belongs to orogenic deposit, and it is formed due Paleo-Tethys ocean crust subduction and subsequent plate during the later Permian.(5) Knowing the achievements mentioned above for the deep understanding of orchid basin base Polymetallic deposit mineralization, metallogenic theory provides a new basis for perfecting orogenic belts, as well as provide new ideas to the regional resource evaluation and exploration.