Study On Ore-forming Fluids And The Genesis Of Zhongzui Copper Deposit In Liwu Copper Orefield

Zhongzui Copper deposit is located in the north west of Jianglang fornix,which is one of important coppet-rich deposits in Liwu copper orefield.Liwu copper orefield has received much concern and been studied deeply since it was discovered,however,considerable differences still exist in genetic type and mineralization.This paper carried out research on stratigraphy and magmatic zircons,Re-Os isotope of chalcopyrite,and fluid inclusion,which was based on the study of geological characteristics of the deposit.Finally combining thise with S and H-O isotopic datas,the genesis of Zhongzui copper deposit in Liwu copper orefield was tried to be discussed.This paper get following understandings:(1)The study on deposit geology indicates that,deposit is controlled by shear zones,closely related to alteration,with filling and replacement features.Fluid action and mineralization accompanied the evolution of shear bands,which correspond to different stages of the evolution of shear bands.(2)U-Pb zircon dating results show that,ages of Jianglang group which have diagenetic significance distribute between 537-2925 Ma,the mean age of 6 new ages is 548 Ma,with a peak around 552 Ma.Ages of Liwu group which have diagenetic significance distribute between 504-3191 Ma,the mean age of 6 new ages is 555 Ma,with a peak around 556 Ma.Both have similar age distribution and younger zircons age,which shows they have homologous sedimentary characteristics,and they are both formed in the Neoproterozoic sedimentary.Zircons of acid intrusive rocks in the north east of fornix have a mean age 159Ma,which is its diagenetic age.Mean age of minority is 133Ma,reflects a tectonic event.(3)There are two Re-Os chalcopyrite isochron age 149Ma and 346Ma.The former is close to granite zircon ages(159Ma)and altered mica ages(143?132Ma),reflects the close ties between magmatism,fluid action,and mineralization.The latter near the age of regional mafic intrusive rocks 294?363 Ma,implies that there may be a mineral accumulation.(4)Laser Raman analysis shows ore-forming fluids as H2O-NaCl-CH4(-CO2)system.Fluid inclusions Microthermometry of two mineralization stages shows that:in the dip-banded mineralization stage,homogenization temperature is 181-375?,salinity is 5.26?16.99wt%;In the massive bonanza stage,homogenization temperature is 142-343?,salinity is 5.41?21.19wt%.Which shows forming fluids as medium-high temperature,medium salinity fluids.(5)Hydrogen and oxygen isotope and sulfur isotope datas indicate that ore-forming fluids are mainly metamorphic water and magmatic water,added with formation water.Sulfur comes from formation and magmatic rocks.Those show the characteristics of multiple sources of minerals and fluids.In summary,the Zhongzui copper deposit is a shear zone controlled high temperature hydrothermal deposit.