Title:

The intracratonic branch of the Damara Orogen in South West Africa II. Discussion of relationships with the Pan-African mobile belt system

Author(s):
Publication Year:
1977
Abstract:

In Part I the conclusion was reached that the intracratonic branch of the Damara orogen cannot be explained by a plate-tectonics continent/continent collision model. The intracratonic branch is connected with the coastal branch and also with the Zambezi belt. There is a direct stratigraphic and structural connection with the coastal branch which shows some features suggestive of a continental margin geosyncline, and, by inference, an orogeny caused by subduction. Such an interpretation would make it possible to regard the intracratonic branch as a failed arm of a hypothetical triple junction situated to the west of the present-day coast. The evidence for this attractive hypothesis must, however, remain inconclusive because the greater part of the coastal belt is hidden underneath the Atlantic Ocean. The hypothetical ocean arm cannot have been broad and did probably not extent northwards beyond Gabon. The connection with the Zambezi belt and the Lufilian arc is covered by younger deposits. The Zambezi belt is composed of tectonically and thermally reconstituted Archaean basement. It contains no structure which could be interpreted as a continent/continent collision suture. This is also true for the Mozambique belt which is structurally connected with the Zambezi belt. The join between the two can therefore not be regarded as a triple junction in the plate tectonic sense. The Lufilian arc contains a “miogeosynclinal” sequence  which is stratigraphically very similar to the Damara Supergroup, but it is still uncertain whether the two are strictly contemporaneous. In these belts vertical movements and transcurrent faults seem to have played a greater role than compressive shortening. The evolution of these belts was to a considerable degree guided by the older Irumide structures which seem to be connected with the approximately contemporaneous Rehoboth-Sinclair igneous province delimiting the southern margin of the Damara belt. A geodynamic model is proposed for the evolution of grabens, aulacogens, ensialic geosynclines and regions with tectono-thermal overprinting interpreting these structures as different reactions of the heterogeneous crust to mantle diapirs of different sizes.

Publication Title:

Precambrian Research

Volume:
5
Issue:
4
Pages:
339-357
Item Type:
Journal Article
Language:
en

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