Geology,Geochemistry And Metallogenic Regularity Of The Suolong Gold Deposit,Gansu Province

The Suolong gold deposit is located in the central part of the Min-Li metallogenic belt in the western Qinling Mountains,which is controlled by lithology and tectonics and belongs to a small-sized gold deposit.The deposit is hosted in the Lower Permian strata,the mineralization can be divided into hydrothermal mineralization and supergenetic oxidation periods.The hydrothermal mineralization period can also be divided into less sulfide-quartz???,arsenic-pyrite-quartz???,polymetallic sulphide-quartz-calcite???,and carbonate late???stages,of which stage?is the early ore-forming stage.Stage?and?are the main ore-forming stages,and stage?is the late ore-forming stage.The ore minerals of the Suolong gold deposit are mainly pyrite,arsenic-pyrite,arsenopyrite,pyrrhotite,and chalcopyrite.The gangue minerals consist mainly of quartz and calcite.The homogenization temperature of the fluid inclusions ranges from 140°C to395°C,while the salinity ranges from 0.35%to 18.30%and the density ranges from0.52 to 0.95.The trapping pressure ranging from 8.6 to 49.3 MPa indicates the gold mineralization formed at depth of 0.3 to 1.9 km.There are two main types of fluid inclusions which are the CO₂-H₂O-NaCl and the H₂O-NaCl inclusions.Fluid inclusions analyses show that the liquid and gas phases are mainly composed of H₂O and the gas phase contains CO₂ and minor CH₄.In general,the ore-forming fluids of the Suolong gold deposit are characterized by medium-low temperature,medium-low salinity,low density,weak acidity,and weak reduction state.Trace and rare earth elements features indicate that the metallogenic materials are mainly from the wall rocks and partly from the magmtic rocks.H,O,C,S,and Pb isotopic analyses indicate that the ore-forming fluid was mixture of meteoric,magmatic and metamorphic water.Carbon isotope of the hydrothermal calcite was mainly derived from the granitoids,but also experienced hybridization of marine carbonate rocks and certain effects of the late low temperature alteration at the same time.Sulfur isotope was mainly derived from ore-bearing strata,but also mixed a certain degree of magmatic sulfur.Lead isotope is characterized by the source of upper crust and also shows signature of crust-mantle mixing.Based on the comparison of the metallogenic characteristics of the Suolong gold deposit with the Carlin-Carlin-like type disseminated gold deposit,it is considered that is the Carlin-like type disseminated gold deposit.The major indicators for gold deposit are limonite-quartz veins or pyrite-quartz veins,NNE-NE-trending tectonics,main ore-forming stage pyrite-arsenopyrite-quartz mineral assemblage,and the comprehensive anomaly of Au,As,Hg,and Sb.