Geological Characteristics And Genesis Of Luohedong Gold Deposit In Danba Area,Sichuan Province

The Luohedong gold deposit is located in Danba County,Sichuan Province.It is located in the north-south structure of Kangdian,the curved structure of Xiaojin and Jintang,and the northwestward tectonic interface of Xianshui River.It belongs to the deposit in the caprock of the Daduhe gold metallogenic belt.According to previous studies,the Luohedong gold deposit has a large mineralization and a high grade of Au,but the degree of research is very low.In this paper,through the detailed observation and systematic sampling of the surface and underground of the Luohedong gold deposit,combined with the study of petrography,fluid inclusions,isotope geochemistry and trace element geochemistry,the ore-forming fluids and ore-forming materials are discussed.Combined with regional ore-forming geological background,analyzes the genesis of the deposit.The study achieved the following main results and understanding:1.The gold ore body of the Luohedong gold deposit is mainly vein and lenticular.It is produced in the upper inter-layer fracture zone of the second group?Sm²?of the Maoxian Group of the Silurian system.It is nearly north-south,tending to the east,and the dip angle is 37°-67.°.The ore is composed of metal minerals and gangue minerals.The metal minerals are mainly pyrite,and the gangue minerals are mainly quartz.The surrounding rock alteration of the ore body mainly includes silicification and pyrite mineralization.2.The fluid inclusions in the Luohedong gold deposit can be divided into four types:CO₂-rich three-phase inclusions,gas-liquid two-phase inclusions,liquid inclusions and gas inclusions.The temperature of the fluid inclusions was found to be between 160°C and 360°C by temperature measurement,and the salinity was calculated to be between 4.44 wt%and 6.71 wt%.3.Through the rare gas isotope tracing of quartz and pyrite in the Luohedong gold deposit,it is found that there are two main sources of fluid,namely mantle and crust,and the crust fluid dominates the ore-forming fluid.The analysis of the S and Pb isotopes of pyrite indicates the involvement of the mantle and crustal materials.The trace element analysis of quartz and pyrite shows that the Luohedong gold deposit has the ore-forming characteristics of superimposed metamorphic hydrothermal fluid.The analysis of rare earth elements in quartz and pyrite indicates that the physicochemical conditions for the formation of ore-forming fluids in the Luohedong gold deposit may be relatively reducing environments,suggesting that the ore-forming fluids of the deposit may belong to medium-high temperature hydrothermal fluids.4.The metallogenic geological characteristics of the Luohedong gold deposit are analyzed and the ore-forming geochemical data is analyzed,and compared with the Daduhe gold metallogenic belt and typical deposits.It is preliminarily believed that the Luohedong gold deposit belongs to the orogenic metamorphic hydrothermal deposit.