Geological And Geochemical Characteristics And Causes Of Formation Of The Gongguan Hg-Sb Deposit,Shaanxi Province,China

The Gongguan Hg-Sb deposit is a typical middle-low temperature hydrothermal stratabound deposit,which is located at the western dip end of Gongguan-Huilong anticlinoria in the south of the east Qinling mountains,and at the west of the south and north wings of the anticline,and at the north side of the Nanyangshan fault in Xunyang County,Ankang City,Shaanxi Province.Through and collection of a large number of predecessors'research results and related geological foundation data,In combination with the work of the field geological survey and indoor experiment test and analysis,Hg-Sb deposits in Xunyang residence of ore-forming materials,ore-forming material sources was studied in detail,analyzes the formation mechanism of the ore deposit.Through rock specimen and microscope observation,scanning electron microscope,in situ S-Pb isotope composition test analysis,total rock trace element content test analysis.Come to the following knowledge:1)The mineral composition of Gongguan Hg-Sb deposit is relatively simple.The metallic minerals mainly include stibnite,cinnabar and a small amount of pyrite.Nonmetallic minerals are mainly quartz,dolomite,calcite and a small amount of barite.The metallogenic stage can be divided into three stages:The early stage was dominated by quartz and dolomite;The middle stage is dominated by stibnite and cinnabar;Large amounts of calcite were formed in the late stage.The ore structure is dominated by allocrystalline structure,Automorphic-semi-automorphic crystal structure,metasomatic filling structure and double crystal structure inside the crystal.Ore structure is mainly disseminated,block,vein,breccia and crystal cave structure.2)the S isotope composition of the main metal mineral stibnite,cinnabar and pyrite shows that the overall?³⁴S values ranges from 3.4‰to 10.5‰,indicates that the sulfur of the deposit mainly comes from the sedimentary sulfide;The Pb isotopes composition of stibnite and pyrite shows that the ²⁰⁶Pb/²⁰⁴Pb ratio is 18.006¹8.362,the ²⁰⁷Pb/²⁰⁴Pb ratio is 15.445¹5.610,the ²⁰⁸Pb/²⁰⁴Pb ratio is 37.871³8.288,indicates that the lead in this deposit has the characteristics of deep source lead.3)Based on the comparative analysis of the differences of trace and rare earth elements between dolomite surrounding rock and ore,it is inferred that the two may have different material sources,and the addition of deep material in the mineralization process,which is less likely to originate from surrounding rock.4)The occurrence,size and shape of the deposit are controlled by strata,lithology,lithofacies and structure,which belong to the sedimentary-superimposed transformation type of middle-low temperature hydrothermal stratigraphic deposit.Most of the ore-bearing bodies in this mining area occur in the dolomite of the Devonian Gongguan Formation.Under favorable formation lithology,the fracture structure is the main controlling factor for this mercury-antimony deposit.