The Study Of The Metallogenic Characteristics And Genesis Of The Naoniushan Cu-Au Deposit, Middle Part Of The Da Hinggan Mountains, China

Naoniushan copper-gold deposit is a hydrothermal deposit with subvolcanic activities closely connected, which is located in the middle of Da Hinggan Mountains metallogenic belt. In this paper, through the study of regional geological characteristics, ore deposit geological features, rock and ore deposit geochemical study in the Naoniushan copper-gold deposit, we get the following understanding:(1) This study uses the LA-ICP-MS zircon U-Pb dating to research the chronology of granite porphyry which closely associated with mineralization in the mining area, get two pieces of granite porphyry age were 133.7±1.5Ma, 132.4±1.4 Ma, the average is about 133 Ma±1.5 Ma, show that granite porphyry formed in the early cretaceous and is a product of late yanshanian magmatic activity, tests also found a small amount of the captured zircon in the granite porphyry which age were 231.5 Ma, 243.6 Ma and is early-middle Triassic indo-Chinese epoch product of magmatic activity. Therefore, the Naoniushan copper-gold deposit formation is closely associated with early-middle Triassic magmatic activity and the early cretaceous yanshanian magmatic activity. And the late yanshanian magmatic activity plays a leading role in the formation of this deposit, speculated that main metallogenic stage of Naoniushan copper gold deposit should be later than granite or similar in age, that is the ore-forming age should be in the early cretaceous, belongs to yanshan metallogenic peak of Da Hinggan Mountains.(2) The study of fluid inclusions in quartz and calcite samples show that inclusion types have mainly two-phase fluid inclusions, the pure liquid inclusions and contain the son mineral polyphase inclusions, gas-liquid two phase inclusions microscopic measurement results show that the Naoniushan copper gold deposit ore-forming fluid is medium temperature fluid, and the fluid is characterized by medium-low salinity, deposit formed in the shallow, middle-low pressure environment.(3) Hydrogen-oxygen isotopic study indicate that the ore-forming fluid of Naoniushan copper gold deposit has the characteristics of magmatic water and meteoric water mixed each other. The ore-forming fluid mainly magmatic water in the early days. Accompanying with the ongoing mineralization, the ore-forming fluid is the mixture of atmospheric precipitation and precipitation dominated in the process of upward migration of the late ore-forming fluid along the tectonic fissures.(4) Sulfur-lead isotope research make it clear that Sulfur isotope fractionation basically achieve the balance in metallogenic period, and δ34S value of the Naoniushan deposit range is small, indicates that the source of sulfur in ore deposit is relatively uniform, may come from deep source magma, and has the characteristics of mantle source sulfur and meteorites. The isotopic composition of lead characteristics show that ore lead is the normal causes radioactive lead, and the ore-forming material of lead mainly comes from the mantle, there is a small amount of the earth’s crust lead contamination in the process of the ore deposit formation.