Vein mineralization at the Damang Gold Mine, Ghana: controls on mineralization

摘要

Two distinct styles of Au mineralization occur at the Damang Gold Mine; Palaeoproterozoic sediments of the Tarkwaian Group host both. One style of mineralization is stratabound within quartz-lithic conglomerates of the Banket Series. The second style of mineralization is associated with an extensive low-displacement, fault-fracture mesh that formed in a compressional stress regime late in the deformational history and after the peak metamorphism. Regional deformation within the Tarkwaian involved initial NW-SE directed shortening (D_1). A major NNE-trending F_1 anticline hosts the Damang orebody. Broadly N-S shortening during D_2 resulted in the formation of E-W-trending thrusts with small displacements. The D_3 shortening direction was similar to that of D_1. Steep D_1 faults were reactivated and a new set of low angle thrusts and associated flat-lying extension veins were formed. The bulk of the mineralization observed at Damang is associated with the low displacement D_3 fault fracture mesh. The presence of flat-lying extensional veins and the reactivation of some misoriented D_1 structures is indicative of periodic episodes of supralithostatic fluid pressures, low differential stress and fault-valve behavior towards the end of the deformation history.