| The Heihainan gold deposit is located in Bukadaban-amne Variscan metallogenic belt,in Qin-Qi-Kun metallogenic megaprovince.Previous studies on the Heihainan gold deposit are mainly focused on the geological characteristics features of the deposit,and the relative lack of the characteristics and origin of ore-forming fluid,source of ore-forming materials and the ore genesis of the deposit.Accordingly,based on the geological investigation and laboratory analysis,mainly worked on microscopy identification,fluid inclusion and stable isotope geochemistry of the Heihainan deposit,the genetic type of the deposit has been determined and a metallogenic model has been preliminary established.The strata in the mining area is simple,and the structure is mainly of the North West to the fault,the igneous rock is mainly acid rocks.Ore bodies are almost layered or bedded occurred in the contact area and the surrounding rock of the shallow metamorphic clastic rock strata and the tectonic fracture zone.Ore bodies trinity controlled by a series of NW and NNW secondary faults of Kunnan fracture.Extension and tension-shear fracture in the area provides a better ore matching and ore hosting structure for ore forming.The quartz veins in the mining area are divided into three stages according to their mutual relations,and quartz veins of the second stage are the main gold-bearing quartz veins.The formation of the ore bearing strata dominated by clastic rocks provides favorable conditions for the formation of surrounding rocks.The wall rock alteration includes silicification,pyritization,sericitization,chloritization and carbonatization etc.Two types of ore are altered rock type and quartz vein type.Ore textures basically contain euhedral granular texture,xenomorphic granular texture,reaction rim texture,replacement remnant texture and replacement mesh texture,etc.Ore structures are mainly vein structure,veinlet disseminated structure,massive structure and main ore structure,etc.Ore minerals mainly pyrite,arsenopyrite,limonite,etc.;non metallic minerals is mainly quartz,sericite,feldspar,calcite,etc.Fluid inclusion study shows that the fluid inclusions in minerals are mainly gas-liquid two-phase inclusions and CO2-H2O three phase inclusions,and the ore-forming fluid is rich in CO2.Generally,fluids belong to medium and low temperature,low salinity and medium density system.On the basis of fluid inclusion petrography and microthermometry computational studies combined with the geological characteristics of the mine,that fluid immiscibility was occurred in the area and is suggested to be the main metallogenic mechanism of gold in this deposit.The study of hydrogen and oxygen isotope shows that the ore-forming fluid of the Heihainan gold deposit is mainly metamorphic water,and it has been mixed with meteoric water since the mineralization period.Sulfur isotopic study shows that the sulfur in the ore-forming material shows the characteristics of sedimentary sulfur in the strata.Lead isotopic study shows that the ore lead is the mantle-crust source.The characteristics of ore controlling factors,the relationship of mineral assemblages,the structural characteristics of the ore,the alteration of the surrounding rock,the characteristics and origin of the ore-forming fluids reveal that Heihainan gold deposit is similar to the typical orogenic gold deposit. |
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