Geological And Geochemical Characteristics Of Xinwu Au-Deposit In Yangchun Basin,Guangdong

Based on the geological survey of China Geological Survey,"Special Mapping and Technology Application Demonstration Prospecting Research in Guangdong Yangchun Copper Polymetallic Mining Exploration Area"?No.12120114015801?,systematic researches have been made with summary and in-depth analysis of existing information.The main achievements and understandings of the regional geology,geological and geochemical characteristics of the Xinwu gold deposit in Yangchun basin,Guangdong are as follows:1.Xinwu gold deposit is located in the structural fracture zone,which has obvious control over Au-mineralization.Quartz-sulfide veins are mineralized veins.The majority of ore-bearing veins are quartz-pyrite?arsenopyrite?veins.2.Alteration is well developed in Xinwu area,mainly,silicification,pyritization,arsenopyritization and sericitization,among which silicification,pyritization and arsenopyritization are closely connected with Au-mineralization.3.According to the trace element geochemical characteristics of Xinwu deposit,quartz-sulfide veins strongly linked to the mineralization have a principal hypothermal-sulfide assemblage:Pb-Cd-Sb-Bi-Ag-As-Au-Re.The great and obvious enrichment of trace elements of packsand,metamorphic quartz sandstone are quite consistent with that of quartz-sulfide veins.Their curve patterns are fairly similar in trace element cobweb chart,indicating a certain genetic relationship between them.4.The correlation analysis of ores and mineralized rocks shows that Pb,Cu,Ag,As and Ta are positively related to Au,indicating that their very analogous material resources and geochemical mineralization process.5.In the light of REE geochemical characteristics,REE distribution patterns of quartz-sulfide veins are LREE-rich and HREE-poor and gently inclined to the right,with negative Eu anomaly and weak-negative Ce anomaly for the majority.REE distribution patterns of packsand and metamorphic quartz sandstone are quite consistent with that of quartz-sulfide veins,furhter explaining their certain genetic relationship.6.On the grounds of the study on fluid inclusions,the ore-forming temperatures of Xinwu Au deposit predominately range from 167?to 319?,correspondingly,the ore-forming depth range is 0.47⁰.88km,and the pressure range is 139.84²64.47×10⁵Pa,the density range is 2.97⁹.98 wt%Nacl,which are coincident with the characteristics of typical epithermal gold deposits,so that Xinwu Au Deposit belongs to epithermal gold deposits.7.The study on hydrogen and oxygen isotopes shows that the value of?D_V-SMOW is-68.5‰^-89.4‰,with the average of-77.57‰;and the value of?¹⁸O_waterater is 0.70‰⁶.75‰,with the average of 3.10‰,indicating that the water in the ore-forming fluids is the mixture of magmatic water and formation water,with the addition of late-period precipitation.About S isotope,?³⁴S in pyrite and arsenopyrite ranges from 3.2‰to 0.8‰,averaged-0.59%,stating that S in ore-forming fluids of Xinwu Au deposit is mainly derived from the mantle.