Abstract
The Haigou gold deposit is one of the largest known lode gold deposits in the JiapigouâHaigou gold belt of the Yanbian area of NE China. Although this area contains a significant amount of gold mineralization, identifying new resources has been problematic. Here, we present the results of a systematic study of the ore geology and fluid inclusion characteristics of deepâseated mineralization in this area, as compiled from previous research. We use these data to determine the genetic processes that formed these deposits and outline the key criteria that should be used for future exploration. The Haigou deposit is hosted by a monzonitic granite (monzonite) with mineralization present within quartz veins. The gold mineralization is associated with silicification, and four stages of mineralization have been identified: milky quartz, pyriteâquartz, quartzâpolymetallic sulphides and quartzâcarbonate. The second and third stages host the majority of the mineralization. Three main types of fluid inclusion are present within the deposit: CO2âH2O, aqueous and pure CO2. The early milky quartz vein stage of mineralization hosts CO2âH2O and aqueous inclusions, whereas the main stages of mineralization are associated with all three types of fluid inclusions, which are randomly distributed but are especially well developed within pyriteâquartz veins. These stages of mineralization are also associated with clusters of CO2âH2O inclusions that coexist with large but variable amounts of aqueous phase fluid inclusions. The only fluid inclusions associated with the later stages of mineralization are aqueous inclusions within calciteâquartz veins. Microthermometric data indicate that the inclusions associated with metallogenesis homogenize at 145â410 °C and contain mediumâ to lowâsalinity fluids (<11.93 wt.% NaCl equivalent). The mineralization in this area formed during the Middle Jurassic (163â161 Ma), as evidenced by40Ar/39Ar dating of hydrothermal sericite from the main stage of mineralization. Integrated CâHâOâSâPb isotope analysis indicates that the initial oreâforming fluid was derived from CO2ârich magmas produced by the anatexis of lower crustal material. This fluid is then mixed and underwent fluid immiscibility during ore formation. The Haigou gold deposit is a typical mediumâ to lowâtemperature quartz lode gold deposit that formed after the collision of continental terranes during the transition from compressive to extensional tectonics. The data presented here indicate that this area has significant potential for deepâseated mineralization; an area that should be the focus of future exploration. Copyright Š 2016 John Wiley & Sons, Ltd.
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