Geological Characteristics And Prospecting Direction Of The Pingdingshan Deposit, Heilongjiang Province

Pingdingshan gold deposit lies in the northern part of Jiamusi block, the north ofcontacting section between Jiamusi uplift and Songnen block, which also belongs tothe east part of Central Asina Orogenic Belt. The factors such as superior naturalgeographical conditions, well supplied water and power resources, convenienttransportation, sufficient labor forces of the study area are conductive to its mineralexploitation.Polyphase mineralization stack and breaking occurred near the gold orebodies. Alterations of wall rocks are mainly silication, sericitization, pyrophyllite、pyritization. The content of sulfide is low. Ore mineral are mainly electrum，theassociated minerals include pyrrhotite, arsenopyrite and so on. Secondary mineralconclude sphalerite and galena. Ore structures have disseminated structure, stratifiedstructure and ore frames have euhedral-granual, hypidiomorphic-granual texture andfilling-metasomatic texture. Gangue minerals mostly is quartz, there are few calcite、sericite and hydromica ect.The granites in the Pingdingshan gold deposit are composed of earlierlight-colored medium-grained monzogranite and slightly later fine-grained biotitemonzogranite with zircon U-Pb ages at271.7±2.3Ma and249.8±3.3Ma,respectively. The εHf(t) values for these two episodes of magmatism are at-4.17~-0.58and-4.98~-0.49, which correspond to Hf two-stage model ages of1432Ma and1457Ma, respectively, suggesting that their parent magmas derived from the partial melting of Mesooproterozoic crust. Both earlier and later monzogranitesare characterized by high Al2O3, K2O+Na2O, LREE and LILE (Rb, Ba, Th, U and K),and low MgO, HREE and HFSE (Nb, Ta, P and Ti). They are chemically high-Kcalc-alkaline rock series, and represent volcanic arc/syn-collision I-type granites.Combined with the evolution history of the eastern segment of the Central-AsianOrogenic Belt, we consider that the granites in the Pingdingshan deposit formed fromthe subduction and collision of songnen block with Jiamusi block. The results showthat fluid inclusions in quartz are well developed mainly in gas-liquid phase. The fluidof main ore-forming phase is characterized by medium-low temperature(142.2~267.3℃), low salinity(1.39~5.25%NaCl) and low density (0.78~0.97g/cm3).The gas phase compositions of the ore-forming fluid mainly are H2O, CH4and CO2,the liquid phase is H2O and CH4.Comprehensive studies show the Pingdingshan golddeposit belongs to medium-low temperature hydrothermal vein type gold deposit.According to the geological characteristics, combined with the study of thesurrounding deposits, the Ping dingshan deposit is a typical medium-low temperaturehydrothermal vein type gold deposit, the metallogenic geologic condition ofPingdingshan deposit is superior, major ore-control structure includes the NE andNNE structure, ore bodies occur mainly within the interlaminar fractures. Accordingto the geological background in the study area and different types of ore-prospectingcriteria, we consider that the Pingdingshan deposit has a good ore-forming geologicalconditions and prospecting potential.