Geological Characteristics And Metallogenic Model Research Of The Fe-Cu Deposit In Dahongshan,yunnan Province

The Dahongshan iron-copper deposit in Yunnan province is located in the southwestern margin of the Kangdian Axis,belonging to the central Yunnan synclise between the Honghe and Luzhijiang deep fault.This deposit is hosted in the Mesoproterozoic Dahongshan Group comprising sedimentary volcanic eruption,which has unique ore-forming geological features,abundant iron,copper metal resources and important research significance.However,the metallogenic pattern of the deposit has been disputed for many years.The selection of this doctoral dissertation are based on the research project(12120113094900)by the author's supervisor.Based on previous studies,systematically study the geological background of the deposit by field investigation sampling and indoor analysis and comprehensive study.Discuss the metallogenic model of Dahongshan Fe-Cu deposit through the geological characteristics,origin of ore-forming elements,source of ore-forming fluid,geochronology of mineralization process etc.This study gets the following understanding:(1)Hongshan Fm.of the Dahongshan group is a single geological body and continental volcanic altered rock,mainly lithology is hidden explosive breccia,surrounded by dolerite.(2)The U-Pb age of dolerite is 1643±19Ma,represents magma intrusion age.Age of variable sodic lava of Hongshan formation is 1656±16Ma.Age of the quartz albitophyresi intrusion is 1673±20Ma.Age of metamorphic zircon of gabbro is 748.9±5.7Ma which represents the regional metamorphism time.(3)Re-Os dating of chalcopyrite reaches isochron age of 1143 ± 72 Ma,which represents the age of Late vein copper deposit of the Dahongshan.(4)The predecessors have done a lot of C,O,S,Pb isotope studies of Dahongshan deposit,combined with Re-Os isotope study and geochemical characteristics of rare earth elements,indicates that the source of the mineralresources is crust mantle mixture and the involvement of mantle fluid mineralization,which is the important condition of forming the Dahongshan's large Fe-Cu deposit.(5)Dahongshan Fe-Cu deposit is the product of continental volcanic-subvolcanic magmatic system,it is probably formed in the spatial superposition by rich iron and copper(gold)ore-forming fluid.The relationship of magnetite body and copper body is abrupt contact with nearly forming time.The main body of the Fe-Cu deposit is formed by ultra high pressure fluid including iron fluid,carbonate fluid,sodium melting magma,sulfide fluid and volatile components injecting along with the magma channel or structure weak belt in late evolution of deep magma chamber in Columbia supercontinent breakup event(1.8~1.6Ga).Late chalcopyrite vein is formed by the overprinting on early Fe,Cu orebody by the Cu fluid injecting along with the early faults in Grenville orogenic event,aggregating of Rodinia continent(1.1~1.0Ga).