Metamorphism of sulfide ores from the Aggeneys-Gamsberg base metal deposits, South Africa

摘要

Four major stratiform base metal deposits occur in the Aggeneys-Gamsberg area that are part of the poly-deformed and medium- to high-grade metamorphosed Namaqualand Metamorphic Complex of South Africa. The host rocks and the individual sulfide ore minerals have been intensely affected by several metamorphic and deformational events, resulting in almost total obliteration of primary textures and the formation of a range of structural, textural and mineralogical modifications typical of metamorphosed base metal deposits. Large-scale dislocation and reconcentration of the original disseminated mineralization as discordant ore pegmatites and massive sulfide segregates suggest extensive involvement of metamorphic fluids in the mobilization process during peak metamorphic conditions. Although the preserved fabric is predominantly of a retrograde character, the overall structural and textural relationships favor a syn-sedimentary origin of the mineralization over syntectonic emplacement during the main phase of deformation.