Study On Geological Characteristics And Genetic Mechanism Of The Guocheng-Liaoshang Gold Deposits In Northeast Margin Of The Jiaolai Basin

The Guocheng-Liaoshang super-large gold deposits is located in the northeast margin of the Jiaolai basin of the Jiaodong Peninsula,are an important part of MupingRushan gold belt.The orebodies,hosted in Paleoproterozoic Jingshan Group and Paleoproterozoic Muniushan granite,are mainly controlled by NE trending faults.Based on the previous research,the genetic mechanism of the Guocheng-Liaoshang gold deposits is analyzed in this paper studies by using the ore characteristics,genetic mineralogy and C-H-O-S isotopes.Finally,the regional gold metallogeny of the northeast margin of the Jiaolai basin is discussed by comparison of the northwest Jiaodong gold area.Most gold minerals in Guocheng-Liaoshang gold deposits are native gold,which are closely associated with pyrite,dolomite and quartz.Pyrite is the main gold-bearing mineral in Guocheng gold deposit,while pyrite and dolomite are the main gold-bearing minerals in Liaoshang gold deposit.The thermoelectric test of pyrite in Guocheng-Liaoshang gold deposits shows that N-type pyrite appears earlier and higher temperature,while P-type pyrite appears later and lower temperature.The occurrence rate of P-type pyrite is positively correlated with gold grade.The temperature of pyrite in Guocheng gold deposit is concentrated in 250 ~ 350 ?,P-pyrite is main type,and the denudation degree of orebodies is about 50%.The temperature of pyrite in Liaoshang gold deposit is concentrated in 330 ~ 350 ?,N-pyrite is main type,and the denudation degree is close to 70%.GuochengLiaoshang gold deposits are intermediate temperature deposit.Hydrogen and oxygen isotopes show that the ore-forming fluid of GuochengLiaoshang gold deposits comes from the mixing of primary magmatic and metamorphotic water,which is greatly affected by meteoric water.Carbon and oxygen isotopes show that the fluid comes from the mixing of deep mantle and crust source fluid and combines the matter in the ore-bearing surrounding rock Jingshan Group.Sulfur isotope shows that the sulfur source is consistent with the whole Jiaodong gold deposits,which sulfur isotope is mixed into Jingshan Group or the sedimentary rocks of the Jiaolai basin.In summary,the Guocheng-Liaoshang gold deposits are a medium temperature hydrothermal structural filling gold deposit controlled by Guocheng fault and its secondary fault structure,where rainwater and crust-mantle mixed fluid are involved in mineralization.