Geological Characteristics And The Genesis Of Touzha Ag-Pb-Zn Deposit,Guigang,Guangxi

The Touzha Ag-Pb-Zn polymetallic deposit in Guangxi is located in the Dayaoshan uplift in the southwestern part of the Qinhang metallogenic belt.A series of deposits with certain element zoning regularity are formed around the Dapingtianshan intrusion.Touzha Ag-Pb-Zn deposit is located near the outer contact zone of Dapingtianshan rock mass and adjacent to the large Longtoushan gold deposit.The study of its genesis will help to further understand the characteristics and metallogenic regularity of this magmatic hydrothermal metallogenic system and provide theoretical basis for geological prospecting.This research took Touzha Ag-Pb-Zn deposit as the main research object,combining with the study of surrounding rock mass,using LA-ICP-MS zircon U-Pb dating,zircon Hf isotope,inclusion microthermometry combined with laser Raman analysis and stable isotope analysis,the age of the intrusions,geological characteristics of deposits,rock geochemical characteristics,characteristics of ore-forming fluids and source of ore-forming materials were preliminarily studied.Step by step,the main achievements are as follows:?1?The ore-bearing strata of the deposit are mainly mudstone-siltstone in the lower part of the Huangdongkou Formation of Cambrian.The ore bodies are obviously controlled by lithology and structure,and can be divided into vein-like and layered orebodies according to their occurrence.Vein orebodies are filled along faults and joints in the North-South direction.Layered ore bodies are mainly skarn type with five layers.The orebodies are influenced by Cambrian limestone strata and folds.The formation of the deposit mainly goes through contact thermal metamorphism stage,skarn stage,quartz-sulfide stage and quartz-calcite stage,in which quartz-sulfide stage is the main mineralization stage.?2?Zircon LA-ICP-MS analysis shows that the ages of the intrusive rocks in the Dapingtianshan area are similar,mainly concentrated in 90-100 Ma,belonging to the late Yanshanian period.The geochemical characteristics of the intrusive rocks are similar,all of them are high-K calc-alkaline series;the distribution patterns of trace elements are identical,enriching Rb,K,Ba,Th and other elements,and depleting Nb,Sr,P and Ti elements;the distribution patterns of rare earth curves are identical,right-inclined,with negative europium anomaly,light rare earth is obviously enriched and heavy rare earth is depleted.Zircon Hf isotope characteristics are similar.The ratio of ¹⁷⁶ Hf to ¹⁷⁷ Hf ranges from 0.281935 to 0.282814,and the total value of ?Hf?t?ranges from-7.5 to 0.7,mostly negative.The second-order model age of TDM2 ranges from 1112 to 1974 Ma,reflecting that they are mainly crustal-derived materials,possibly with a small amount of mantle-derived contamination.All rocks are of the same origin and belong to a magmatic hydrothermal system.?3?Comprehensive fluid inclusion characteristics: homogeneous temperature peak of main metallogenic stage is 270-370? with medium to high salinity;C-H-O isotopic characteristics: ?¹³C_V-PDB values range from-7.3-0.7 ‰,? C_V-PDBW‰ values range from-79^-61‰ and?¹⁸O_V-SMOW‰ values range from 15.6-17.2‰;S isotopic characteristics: ?³⁴S_V-CDT?‰?ranges from 0.98-3 ‰,indicating that ore-forming fluid and material derived from magmatic fluid.It reflects that the orebody is related to the Dapingtianshan rock mass.Compared with the previous research results,other deposits in the surrounding area are also closely related to intrusive rocks,indicating that these deposits belong to the same magmatic hydrothermal metallogenic system controlled by the Dapingtianshan rock mass.