The Type,Metallogenic Characteristics And Regularity Of Gold Deposits In The Mid-eastern Part Of Heilongjiang Province

The research area is located in the middle-eastern part of Heilongjiang province,its south and north part respectively adjacent to the northern part of Jilin Province and the Russian far east.The area is a complex tectonic region that has different periods of Rodinia supercontinent evolution,Paleo Asian ocean evolution and mesozoic and cenozoic shore pacific evolution,geological effect of multi-period has become an important area of the gold deposit.So far,four large gold deposits have been found in the area?Laozuoshan,Dongan,Jinchang and Dongfengshan?.There are more than ten medium-sized gold deposits?Daanhe,Pingdingshan,Sishanlinchang?,twenty small-scale gold deposits and more than thirty gold mineralized spot in area.For a long time,the types and characteristics of gold deposits in the area,especially the regional metallogenic regularity and prospecting potential,have attracted much attention and researched by scholars both home and abroad.However,there are great controversies about the genetic types and metallogenic regularities of deposits.In the paper,we have discussed for the deposit geology,fluid inclusions and chronology of various typical gold deposits in this area,we have achieved the following achievements.1.On the basis of systematic research for geological features of deposit,the main genetic types of endogenic gold deposits in this area are divided into five categories:mesothermal gold deposit,contact metasomatism/skarn gold deposit,epithermal gold deposit porphyry gold deposit and sedimentary metamorphic hydrothermal gold deposit.At the same time,the epithermal hydrothermal gold deposit is divided into two subcategories,which are high sulfuration and low sulfuration gold deposits of epithermal hydrothermal.2.By the research of fluid inclusions for the typical deposit,the metallogenic fluid properties of different types of deposits in the study area.The gold deposits of medium temperature hydrothermal fluids have the characteristics of medium temperature,medium salinity and low density.The fluid inclusions are mainly CO2 and H2O,which belong to the CO2-H2O-NaCl magmatic fluid system.Contact metasomatic/skarn gold deposits have properties of high temperature,medium salinity and medium density,The composition of the metallogenic fluid is mainly CO₂-CH₄-H₂O,and it has the properties of magmatic hydrothermal fluid.Epithermal and low-sulfidation ore fluid has the properties of middle and low temperature,low salinity and low density,belongs to H₂O-NaCl magmatic fluid system.Epithermal and high-sulphidation and porphyry gold deposits have the properties of the middle temperature,medium density and low salinity,belong to H₂O-NaCl magmatic fluid containing CO₂.The fluid of the sedimentary metamorphic hydrothermal gold deposit has the characteristics of middle-low temperature,middle-low salinity and low-medium density,the gas phase composition of the metallogenic fluid is major CO₂,and contains a certain amount of N₂,H₂O,CH₄ and so on.3.The data of the isotopes of S-Pb-H-O of fluid inclusions in quartz reveal,the metallogenic material of the mesothermal gold deposit is mainly derived from the lower crust,and the ore fluid is magmatic fluid,and a large amount of atmospheric precipitation has been added to the metallogenic process.The metallogenic materials of contact metasomatic hydrothermal gold deposits are mainly derived from the upper crust or young crustal source.The metallogenic fluid is a meso hydrothermal fluid.The composition of the fluid is the interaction between magma and strata,and there is also precipitation in the metallogenic process.Porphyry,epithermal gold copper deposit and epithermal high sulfidation and low sulfide gold deposit metallogenic materials have crust mantle mixed source characteristics.However,the former two metallogenic fluids have high oxidation fluid properties or magmatic hydrothermal properties,there are different degrees of atmospheric precipitation in the metallogenic process.The latter epithermal metallogenic fluid of low sulfur type gold deposit dominated by meteoric water and magmatic water accounts for a smaller proportion.4.Combined the Single Zircon U-Pb isotopes with the ³⁹Ar/⁴⁰Ar isotopes of alt-ered minerals,the gold deposits in this area are divided into three mineralization periods:the Middle Jurassic?262Ma?,the late Triassic?219-182Ma?and the early Cret-aceous?119-110Ma?.The empithermal and low sulfide gold deposit and the porp-h yry copper gold deposits were concentrated in the early Cretaceous,while the mes othermal gold deposits were formed in late Triassic?219-182Ma?and the early Cret aceous?119-110Ma?.5.From the point of view of fluid evolution,we have obtained the metallogeni c mechanisms of different genetic types of gold deposits:Contact metasomatic hydro thermal gold deposits have experienced fluid immiscibility or boiling to form low s-alinity and high salinity,then skaring in the metasomatism of high temperature or e liquid with gas phase,with temperature higher than 350?.Unloaded Fe,As,Au a-nd other elements in medium high temperature,and unloaded quartz and calcite fro m the final ore containing fluid and precipitation.The mesothermal gold deposit is f-ormed under the condition of reduced and closed ore-forming fluids,unloading an-d precipitating gold and silver and other minerals with the decrease of temperature and pressure and the process of atmospheric water entry.The epithermal and low s-ulfide gold deposits are low temperature and low salinity,which are the main ele-ments of the filling and crystallization and the precipitation and unloading of gold and other metallogenic elements.The epithermal and high sulfide gold copper deposi-ts and porphyry/porphyry mineralization processes are the mineralization of high o-xidation fluids with strong immiscibility and boiling.The mineralization of the sedi-mentary metamorphic hydrother-mal gold deposits experienced early deposition and superimposed metamorphism and metamorphic deformation,and a certain degree re ceived later magmatic hydrothermal transformation.6.From the point of diagenesis and mineralization,the diagenetic and metallogenic geological models of the above-mentioned contact metasomatism type?skarn type?,mesothermal type,epithermal and low sulphide type gold deposit and porphyry-epithermal high sulfide gold copper deposit have been established.It provides scientific basis for further research on regional metallogenic theory and prospecting.7.Combining the regional geological background with the metallogenic geologic al features,It is pointed out that skarn type gold deposits and sedimentary metam-orphic gold deposits should be found on the Jiamusi massif.But there is a great p-otential of epithermal and low sulphide gold deposits in the Mesozoic basin.The early Cretaceous granite area developed in the granitic complex uplift are to find t he epithermal high sulphide type and porphyry type.8.From the perspective of regional metallogenic geology background,geochemical characteristics of exploration elements and the temporal and spatial distribution of gold deposits,The gold deposits in the study area are redivided into 5 metallogenic series,6metallogenic subseries and 11 ore deposits.The metallogenic units are divided into 2metallogenic domains:Ancient Asia and the Pacific Ocean,1 metallogenic provinces,3third level metallogenic belts,34 grade IV metallogenic belts,or metallogenic perspective areas,6 grade V ore fields or mineralization concentrated areas.