Abstract

The Pikwe Ni-Cu orebody is an Archean stratabound massive sulfide deposit associated with amphibolite host rocks of troctolitic composition. A small ultrabasic pod in the host amphibolite contains dumbbell-shaped sulfide blebs demonstrating that the ore was emplaced as an immiscible sulfide magma. The orebody was subsequently involved in a series of high-grade tectono-metamorphic events during the evolution of the Limpopo orogenic belt (2,660 to 2,000 m.y.). During the first metamorphic event sulfide/silicate reactions resulted in textural and mineralogical changes in the host amphibolite, the most notable of which is the development of large almandine-rich garnets.Polyphase deformation produced a sequence of ore textures including contorted-inclusion sulfide, foliated sulfide, and breccia sulfide. Detailed study of the regional structural geology has enabled the ore textures to be related to regional structural and metamorphic events. The orebody appears to have partially retained its pretectonic morphology despite its complex structural history.

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