Study on the characteristics of fluid inclusions and metallogenic evolution of Jinchang gold deposit,Heilongjiang Province

Jinchang gold deposit is a superlarge one with three different kinds of mineralization,which are cryptoexplosive breccia pipe type,bedded micro-fine vein disseminated type as well as fault-controlled quartz-vein and altered rock type respectively.This paper carried out a comparative study on fluid inclusions occurred in quartz of the three-type ores from petrography,microthermometry,compositional and hydrogen-oxygen isotope analyses as well as SEM/EDS analysis of daughter minerals etc.aspects,the results show that the ore-forming fluids of the three-type mineralization posed different geochemical features.The ore-forming fluids of the cryptoexplosive pipe type mineralization belong to magmatic-hydrothermal transitional fluids;that of the micro-fine vein disseminated type mineralization belong to highly saline solutions with a complex composition;whereas the ore-forming fluids of the fault-controlled quartz-vein and altered rock type mineralization belong to highly saline NaCl-H2O solutions.The composition of hydrogen-oxygen isotopes of fluid inclusions reveal that they all came from magmatic activities.Combined with the occurrences of ore bodies and geochronological data existed,the conclusion was made that the metallogenic evolution sequence in the mining district is cryptoexplosive breccia pipe type→ bedded micro-fine vein disseminated type→ fault-controlled quartz-vein and altered rock type and Jinchang gold deposit is the result of superimposition of mimeralization of magmatic fluids at different phases.