Gold mineralization in phyllonites at the Haile Mine, South Carolina

Abstract

Gold mineralization at the Haile mine is hosted by a sequence of high-strain rocks (phyllonites) characterized by intense pressure solution reactions including conversion of chlorite to sericite and loss of original quartz. The margins of these high-strain zones are silicified and pyritized. The high-strain rocks are themselves mineralized with pyrite and minor molybdenite. Gold is found in close association with sulfides in both the phyllonites and the silicified zones.Textural features are used to show that the high-strain rocks and the silicified zones arose through alteration during deformation of the hosting tuffaceous argillite.The rocks hosting the mineralization are considered to have arisen through initially pure shear-dominated deformation with migration of elements released through pressure solution reactions. Later deformation involved a component of simple shear with influx of fluids from outside the high-strain zones.Anastomozing shear zones of the type seen at the Haile mine will exhibit varying fluid flow regimes as they anastomoze with respect to the principal compressive stress. Some areas will be zones of fluid outflow and dominated by pressure solution, whereas elsewhere dilation, simple shear, and fluid influx will predominate. Movement of fluid through rock piles in this way may represent a means of leaching and precipitating ore components.The recognition that epigenetic gold deposits related to ductile shear zones occur in the southern Appalachians is of great importance for exploration in the area because it highlights major fault zones as potential hosts for gold mineralization.