Discussion On The Characteristics Of Ore-forming Fluids And Genesis Of Erdaogou Gold Deposit In Liaoning

The Erdaogou gold deposit is located on the north side of the eastern part of the Inner Mongolian axis in the northern margin of the North China Craton.The North China Craton is the main mineralization area in China,and the Erdaogou gold deposit is a typical deposit in the Chifeng-Chaoyang deposit area.Although the deposit has been mining for a long time,and many scholars have studied it,the characteristics of ore-forming fluids and the genesis of the deposit have been controversial.This article uses fluid inclusions,rock geochemistry,independent geological thermometers and isotope geochemistry to test and discuss the characteristics of the deposit fluid and the genesis of the deposit.The main conclusions obtained in this article are as follows:?1?The syenite porphyry is widely distributed in the Erdaogou gold deposit.It has the characteristics of silicon-rich,alkali-rich,high-potassium,over-aluminum and high degree of differentiation,and belongs to alkaline granite.The wavy ore-bearing British veins and UST single-phase consolidation structure are developed in the rock mass,indicating that hydrothermal dissolution occurred after the porphyry magma emplaced.The main types of fluid inclusions in porphyry are gas-liquid two-phase and daughter-crystal three-phase inclusions,and occasionally CO₂-containing three-phase inclusions.The uniform temperature and salinity are"bimodal",indicating that the dissolved magmatic hydrothermal fluid may be Boiling occurred.The distribution pattern of the rare earth elements in the ore is similar to that of the positive porphyry,and they are all right-dipping,with weak negative europium anomalies and slight positive Gd anomalies.It is inferred that the Erdaogou gold deposit and syenite porphyry have a close genetic relationship.?2?The fluid inclusions in the ore-bearing veins of the Erdaogou Gold Mine are mainly gas-liquid two phases,free of CO₂.The main ore-forming stage?medium?has a uniform temperature between 250 and 350?.It belongs to medium-high temperature,low salinity NaCl-H₂O metallogenic system This is different from the IRGD?intrusion-related gold deposit?on the northern margin of the North China Craton.The research of H-O isotope shows that the ore-forming fluid is mainly magma water,and a small amount of atmospheric water is mixed in.The S and Pb isotopes indicate that the ore-forming materials mainly come from the lower crust and mantle.Comparative studies of lead isotopes and rare earth elements in the ore body and rock body show that the ore-forming materials in the Erdaogou gold deposit may come from syenite porphyry.?3?The Erdaogou gold deposit may be a gold deposit related to alkaline rocks.The metallogenesis is related to the syenite porphyry.The metallogenic age is close to that of the syenite porphyry.The metallogenic depth is relatively shallow between 1.0 and3.3km.A large amount of copper was also found during the mineralization stage,and the deposit may be Au?Cu?deposits related to alkaline rocks.