Geological, Fluid Inclusion, H-O-S-Pb Isotope Constraints on the Genesis of the Erdaogou Gold Deposit, Liaoning Province

Abstract

The Erdaogou gold deposit is located in the conjuncture of North China Carton and Xingmeng orogenic belt. The ore-forming process of Erdaogou gold deposit is divided into three stages (I to III), which are quartz-pyrite stage (stage I), quartz-polymetallic sulfide stage (stage II) and quartz-calcite stage (stage III). Two types of fluid inclusions is distinguished in the ore-forming stage, i.e., aqueous type (W-type) and aqueous-carbonic type (C-type) inclusions. From the stage I to III, the homogenization temperature of fluid inclusions are respectively 334–395, 214–364 and 172–272 °C, with salinities of 7.72 wt.%–11.23 wt.% NaCl equiv., 0.20 wt.%–23.18 wt.% NaCl equiv., and 0.35 wt.% to 5.25 wt.% NaCl equiv. The ore-forming fluids of the Erdaogou deposit have the characteristics of medium-low temperatures, moderate salinities and low densities. And the fluids belong to the CO2-H2O-NaCl system. The values of δ34SV-CDT in sulphide samples at different stages (stages I to III) are between −2.2‰ to 2.3‰, indicating sulfur source from magma volatiles or subvolcanic rock leaching. The lead isotopes suggest that ore-forming metals may be derived from a mixture of lower crust and mantle materials. Oxygen and hydrogen isotope data at Erdaogou indicate that magmatic fluid and meteoric water may both be involved in the hydrothermal system. Based on the geological characteristics, fluid inclusion results, stable and radiogenic isotope results of Erdaogou gold deposit, we believe that the temperature decrease, fluid boiling are the key factors leading to the ore precipitation and the genetic type of Erdaogou gold deposit is low-sulfidation epithermal deposit.