VMS and epithermal-style ore deposits in the Archean Murchison volcanic arc, South Africa

摘要

The Archean Murchison greenstone belt, Northern Province, South Africa, represents a rifted volcanic arc sequence. The close spatial and temporal association of Au-As-Sb-Hg and base metal deposits suggest penecontemporaneous and premetamorphic epithermal-style mineralization and hydrothermal convection with the formation of VMS deposits. These occur within highly fractionated porphyritic rhyolites in a suggested supra-subduction zone setting. Subsequent deformation during collision and accretion of the arc led to intense remobilization of metals and the formation of regional shear zones along areas of premetamorphic alteration. The Murchison belt shares many similarities with recent arc-back-arc systems in the SW-Pacific which are favorable settings for the origin of shallow submarine hydrothermal systems.