Wallrock Alteration And Its Relation With Gold Mineralization In The Herenping Albite-quartz Lode Gold Deposit In Western Hunan

Abstract:The Xiangxi (western of Hunan) is famous for its abundant mineral resources including native gold, antimony and tungsten. Generally, gold-bearing quartz veins are widespread and quartz lode gold deposits are the most important type throughout western Hunan. However, gold-bearing albite-quartz veins are widely distributed in the Liulincha region in western Hunan, where pink albite can reach30-40percent in amount in ore veins. These albite-quartz gold deposits are relatively unique, but they are poorly constrained. This dissertation applies different discipline methods including mineralogy, petrology, economic geology and geochemistry on the Herenping albite-quartz lode gold deposit in this area. In order to reveal the sources of the ore-forming materials, mineralization process and ore-forming fluid of this deposit, wall-rock alterations of the Herenping deposit in this region are systematically studied in this dissertation, and the relationship between wallrock alterations and gold mineralization is discussed. The main achievements are obtained in this study as follows:(1) The Herenping gold deposit belongs to the albite-quartz lode gold deposit, pink albite acts as an important gold-bearing mineral. Ore veins are typically stratiform in shape, concordant with the host strata(2) The main alterations in the studied deposit include decolorization, pyritization, carbonatization and chloritization. Among them, decolorization is the most widespread and can be severed as an effective indicator for prospecting in the studied area.(3) A mass balance calculation reveals that, Na2O, W, Sr, V, Cr, Nb, Ag and some volatiles (S, CO2, H2O) were added to the wallrock, and SiO2, TFeO, CaO, MgO, Zn, Cu, Pb, As, Sb, Ni, Ba and REE were removed from the host strata. The migration intensity of these active components predominately depends upon the degree of hydrothermal alteration.(4) Cu, Pb, Zn, As, Sb and Fe were removed from the wall rock, these changes are ascribed to the formation of pyrite, sphalerite, halcopyrite, tetrahedrite, galena and arsenopyrite, gold is often intergrown with these ore minerals.(5) The Na and Al for albite in ore veins are not derived from the host strata, whereas the host wallrock contributes a part of Si for quartz in ore veins.