Magmatic Intrusive Structure-fracture Structure And Metallogenic Relationship In Yisikeshu Mining Area,Yunnan Province

Dongchuan Copper Mine in Yunnan Province is located in the northeast of Yunnan Province.Its tectonic location is located in the western margin of the Yangtze Plate.It is a faulted-constrolled basin at the eastern part of Huili-Dongchuan rift trough.The occurrence location of the deposit is obviously controlled by the fault in the basin and is closely related to magmatic rocks.Based on the theory of magmatic intrusive tectonic system,this paper makes a detailed data analysis,field geological survey,petrography,tectonic geology,mineral geochemistry and other research on magmatic intrusive structure-fracture structure in Yisikeshu mining area,and achieves the following understandings and achievements:1.During the upwelling and emplacement of magma-hydrothermal fluid,the physical and chemical conditions might have been constantly changing,with their corresponding characteristic minerals.On the whole,the change of magma-hydrothermal evolution environment is that the temperature,pressure and oxygen fugacity are all reduced,and the mineralization sequence of amphibole,biotite and chlorite were formed.Copper mineralization occurs in the chloritization stage.Its formation environment might be low temperature,low oxygen fugacity and high sulfur fugacity?T=203?,lgf?O₂?=-48.00,lgf?S₂?=-8.32?.2.In the process of magma upwelling and emplacement,the surrounding rock is squeezed by mechanical penetration,and the released thermal fluid leads to hydraulic fracturing of the surrounding rock,forming the fracture system and related fractured rock facies zones.In the process of magma emplacement,dissolution flow separates and forms high temperature fluid.In the process of rising and cycling along fracture-fracture,mixed formation water extracts mineralizing materials from Yinmin Formation,Luoxue Formation and basement slip formation,and forms ore-bearing hydrothermal fluid.Driven by heat provided by magma or energy provided by tectonics,it moves continuously from rock mass to contact between intrusive rock and surrounding rock.In joints and fractures of belts and surrounding rocks,material and energy are exchanged with surrounding rocks continuously,resulted in copper-bearing hydrothermal breccia and layered"fracture ore".3.Magmatic intrusive structure-fracture structure enriched and reformed the original sedimentary deposit in Yisikeshu mining area.Cataclastic lithofacies is one of the most important deposit structures.Fracture system provided a good migration channel and storage space for copper sulfide precipitation.The surrounding rock near the intrusive rock mass is divided from inside to outside into strong fractured lithofacies zone fractured lithofacies zone weak fractured lithofacies zone,and the grade of copper ore is also changed from high to low.Fracture survey shows that there are three stages of ore-bearing fractures in the direction of near EW,near NS and NEE,respectively.Near EW trending bedding fissures are the main ore-bearing fissures in the Luoxue Formation.In the places where cracks?joints?expand and intersect,cracks are densely developed,especially in the places where cataclastic rocks developed and where multiple groups of fractures intersected with stromatolites bedding,copper enrichment and mineralization are the most significant.