Geology of part of the central Damara Belt around the Tumas River, South West Africa

Abstract

Abstract provided by author:

Two tectonic events were responsible for the regional structure. An early F1 episode produced east-west oriented overturned folds and was followed by an intense F2-episode of isoclinal folding which is responsible for the dominant northeast - southwest regional fabric. The interference of these folds in the proximity of the underlying basement produced the complex dome and basin structures seen in the central and western parts of the area. An F3 episode of minor importance was also recognized

The presence of continental basement rocks in this central part of the Damara belt is evidence for formation of the orogen by in-situ deformation rather than continental collision

The metamorphic grade increases westwards from medium grade to high grade. In the east, the metapelites contain andalusite, and coexisting muscovite and quartz. This indicates that temperatures of 600 C at 3, 5 - 4 kb pressure were attained. In the west, coexisting wellastonite and anorthite in the Khan gneisses indicate pressure-temperature conditions of 720 C at 4, 5 - 5 kb