Geochemical Characteristics Of Hongtoushan Copper Deposit

Hongtoushan copper deposit originated in Qingyuan granite-greenstone granite belt,is one of the largest copper deposits of northeast China,and is a tipical copper benthonic volcanic-hosted massive sulphide deposit of Archean.In this artical,we use the theory of ore deposit geochemistry,and the way of Field investigation,sampling,rock identification,rock geochemistry,trace element geochemistry,stable isotope geochemistry and fluid inclusion research methods to study the tectonic background and the geochemical characteristics of Hongtoushan copper deposit.Based on the analyzing and discussion,we worked out conclusions:1)Fe and other metals significantly enrich in ore and deplete in the rock,and Si and Al enrich in the rock of Hongtoushan Copper Deposit.The analysis of the original rock shows that the original rock of Hongtoushan group is a series of basic to sub alkaline series of volcanic rocks.The tectonic environment of Hongtoushan group was an active continental margin arc and back arc basin near the mainland.2)The rocks and ores of Hongtoushan copper deposit had no obvious fractionation and had aenrichment LREE distribution type,and showed the same material sources,the latter long deformation and metamorphism makes the individual elements appear a certain degree of depletion and enrichment.The rocks and ore sample dispersion degree have good correlation,showed that the rocks and ore of Hongtoushan belonged to the same rock metallogenic system.3)The analysis of lead and sulfur isotope results that,the sulfur and lead isotopes of ore have the characteristics of mantle material,studies of lead isotope can be directly drawn into minerals from the mantle and upper crust,combined with lead isotope age calculation,we can obtained,the source of minerals of Hongtoushan copper deposit and the source of metamorphic rocks are consistent,they both from Archean volcanic eruption of mantle material,and process by the lower crust contamination during eruption.4)The study of fluid inclusion in the Hongtoushan copper deposit shows that the temperature of ore is 174-274 ?,and the peak value is 210?220 ?.The salinity of fluid inclusion in ore is 15.35?33.65wt%NaCl,and the peak value falls to 22?25%.The mineral density range is 1.02-1.15g/cm3,which reflects the characteristics of high salinity and medium density.5)Analysis of oxygen isotope show that,the mixed hydrothermal ore-forming fluid of Hongtoushan copper deposit is mainly mix by meteoric water and magmatic water.The results show that the ore-forming fluid has the characteristics of weak acid,rich in H2S,medium salinity and low density.Therefore,it may be a mixture of magma water,atmospheric water and sea water.6)Comprehensive research concluded that the metallogenic model of Hongtoushan massive sulfide deposits:fluid and sea water formed the two fluid's main source of ore-forming process,plays an important role in deposition of fluid mixing effect on metal sulfide accumulation and mineralization,the ore-forming fluid is high in salinity,medium in density and rich in reduction,it is erupted into the sea during the acidic volcano rock eruption gap,and mixed with seawater,went through a volcano or fault system infiltration cycle on flow,deposition in suitable seafloor depressions finally formed the layered ore body.Because of the differences in temperature,salinity,and chemical composition of hydrothermal eruption from the volcano and the sea water turbulence degree,the formation of the ore composition and chemical composition of massive sulfide deposits are different.In the process of deformation and metamorphism,morphology and the ore-forming material distribution of deposit was transformed and minerals has partly depleted and enriched.