Characteristics Of Fluid Inclusions And The Formation Cause Of Heishan Gold Deposit In Hami,Xinjiang

The Hami Heishan gold deposit is located in the Zhongtianshan block on the south side of the Aqikekuduk-Shaquanzi fault in the eastern Tianshan area of Xinjiang.The Zhongtianshan block has undergone many structural-magmatic transformations,and the structural style is extremely complicated,and magmatic rocks are relatively developed.Only iron ore,lead-zinc ore,copper-nickel ore,tungsten ore,rare metal ore and non-metallic ore have been found in the Zhongtianshan block.But no reports have been found of gold deposits with mining value in the Zhongtianshan block.In recent years,Heishan gold mine is a large-scale gold mine with mining value,which was discovered in the zhongtianshan block by the author's team(Geological Survey Center of nonferrous metals).The predecessors only used the Heishan Gold Mine as a mine site to briefly describe its output status,mineralization alteration type,geophysical characteristics,and geochemical characteristics.There are few studies on the ore-controlling structural characteristics,mineralization alteration characteristics,ore-forming fluid characteristics and ore-forming material sources of Heishan Gold Mine,which are closely related to the genesis of the deposit.The main exposed strata in the mining area are the Upper Paleozoic-Lower Proterozoic metamorphic rock strata and the Middle Proterozoic metamorphic rock strata.The Upper Paleozoic-Lower Proterozoic stratigraphy is dominated by quartz schist and marble.the Middle Proterozoic metamorphic rock stratigraphy are dominated by marble.The mining area experienced large-scale magmatic activities in the Late Paleozoic,forming a large number of magmatic rocks.The east-west or northeast-trending fault developed in the mining area is a secondary fault of the Archik Kuduk-Shaquanzi fault.The northeast-trending fault and thefoliated zone developed on the fault zone have an extremely important position in the Heishan Gold Mine.They are the ore-controlling structures of the Heishan Gold Mine and controls the output of the Heishan Gold Mine.By referring to the predecessors'geological data about the Achikokuduk-Shaquanzi fault and the Zhongtianshan block,the tectonic environment of the Heishan gold mining area is analyzed.According to predecessors and scholars,the Late Carboniferous is an important structural transition period of collision and post-collision in this area,and the Late Carboniferous-Early Permian is the extension stage of post-collision.The extensional tectonic stress environment is a favorable environment for the formation of gold deposits.Through the 1:10,000 geological mapping of Heishan gold mining area,drilling core cataloging,sampling test analysis and other methods,the favorable ore-controlling structure,the type of mineralization and alteration in Heishan gold mining area were studied in detail.The Heishan gold deposit is mainly controlled by the NNE trending faults in the mining area and the foliation developed on the fault zone.The main alterations developed include silicification,Pyritization,carbonateization,sericinization and propylitization.gold is deposited in pyrite minerals,the fissures of the quartzs and the fissures of pyrite minerals in the quartz veins.Through the fluid inclusion experiment,it can be obtained that the homogenization temperature of fluid inclusions in Heishan gold deposit is 163-216°C,the salinity is 3.05-5.09wt%Na Cl.Therefore,the ore-forming fluid of Heishan gold deposit is medium low temperature and low salinity fluid.Characteristics of Pb isotopic composition of pyrite in ores measured by Pb isotopic test experiment(²⁰⁶Pb/²⁰⁴Pb value is 18.5365-18.7465,²⁰⁷Pb/²⁰⁴Pb value is 15.6033-15.6294,²⁰⁸Pb/²⁰⁴Pb value is 38.4035-38.6851)suggesting metallogenic material of Heishan gold deposit come from the magmatism of the subduction zone and upper crust.Through the 1:50,000 rock debris geochemical survey in Shaquanzi,it is found that the metamorphic rocks of the monzonite granite and the Tianhu rock group in the mining area have gold-related low-temperature anomalous combinations.In addition,the gold element mineralization coefficient(f)of these two geological units is the highest in the mining area This shows that the ore-forming materials of the Heishan Gold Deposit are likely to come from metamorphic rocks of the monzonite granite and Tianhu rock group.Through geological mapping,drilling,geochemical exploration,fluid inclusion Fluid inclusion test experiment and Pb isotope Fluid inclusion test experiment,etc.,a more detailed study of the Heishan gold deposit was conducted.The metallogenic regularity of the Heishan gold deposit was summarized,and the ore genesis was summarized.The understanding gained is as follows:1.The main metal minerals in the ores of the Heishan gold deposit are pyrite,pyrrhotite,chalcopyrite,arsenopyrite,etc.Non-metallic minerals include quartz,calcite,mica,tremolite,etc.Gold is deposited in pyrite minerals,the fissures of the quartzs and the fissures of pyrite minerals in the quartz veins.2.In the middle of the mining area,the ore-controlling structure of the Heishan gold deposit is the NE trending fault and the foliation zone developed on the NE trending fault zone.3.The temperature measurement of fluid inclusions of Heishan gold deposit shows that the metallogenic temperature of Heishan gold deposit is between 163 and 216?,and the estimated metallogenic depth is between 1.61 and 2.11km.The developed belt-shaped alterations from the center to both sides are the silicification+carbonation zone,the sericition zone+carbonation zone,and the propylitization zone.Therefore,the author believes that the Heishan gold deposit should be classified as a epithermal gold deposit.4.The ore-forming materials of the Heishan Gold Deposit originate from metamorphic rocks in the upper subgroup of the Tianhu Rock Group and late Carboniferous-Early Permian monzonite granites.According to the Pb isotope characteristics of pyrite in Heishan Gold Mine,the ore-forming materials are derived from the upper crust and the subduction zone Pb(magmatism)of the upper crust and the mantle.In addition,the geochemical survey data of 1:50,000 soil(rock fragments)in the Shaquanzi district in Jingxia area of the East Tianshan metallogenic belt shows that an abnormal combination of Au+As+Sb was found on the Tianhu Rock Group in the mining area.And Bi+CD+Au+Ag abnormal assemblage of Monzogranite in the mining area.Their anomalous combination characteristics are related to medium-low temperature hydrothermal activities.In addition,the gold element mineralization coefficient(f)of these two geological units is the highest in the mining area.The above combined evidence of Pb isotope tracing and low-temperature abnormal assemblages indicate that the material source of the Heishan gold deposit is the Tianhu rock group and late Carboniferous-Early Permian Monzogranite.5.The formation of Heishan gold deposit is closely related to the strata-magma-structure of the Zhongtianshan block.Heishan gold deposit is located in the Zhongtianshan block where the Tianhu group metamorphic rocks,Late Paleozoic magmatic rocks and NE trending faults all developed.In order to find this type of gold deposit in Zhongtianshan block,it is necessary to pay attention to the areas where the metamorphic rocks,Late Paleozoic magmatic rocks and NE trending faults are well developed.6.The strong silicification,calcitization and pyritization in Heishan gold deposit is an obvious prospecting indicator,and the propylitization developed in the periphery of the mineralization belt can be used as an indirect prospecting indicator.