Title:

Multiple deformation patterns in the Otjosondu manganese mining area, eastern Damara Belt, Namibia

Publication Year:
1991
Abstract:

In the southern Central Zone of the western part of the inland branch of the Damara Orogen, early fold phases are difficult to identify because of intense D2 and D3 overprinting. In the east, however, at Otjosondu, the D3 event is much less intense; early fold generations are therefore more easily identified. The D1 phase of deformation in the study area is accompanied by an appreciable component of simple shear, and a poly harmonic suite of F1 folds has developed. Recumbent to inclined as well as upright tight and upright open folds have been recognized. The variation in orientation and style of D1 folds and the angle of 40-60° between the D1 and the D2 shortening directions result in contrasting styles of superposed fold patterns between these two generations. The superposition of D2 folds on recumbent D1 folds led to the development of dome-crescent mushroom interference patterns. In contrast, depending on the interlimb angle of upright D1 fold morphologies, these D1 folds either preserved their original D1 trend or have been reactivated and reorientated to differing extents by fold hinge migration during D2 deformation. The orthogonal superposition of D3 warping on D2 folds led to distorted dome-and-basin interference fold patterns. Brittle deformation fabrics have been observed as a conjugate set of sinistral and dextral arrays of shear fractures. A set of horizontal stress-release fractures developed predominantly in quartzitic lithologies. D2 and D3 folds are correlated with obvious fold patterns developed throughout the Central Zone. The D1 phase has only been recognized close to the Okahandja Lineament. Elsewhere in the inland branch this reactivation of 01 folds by the D2 deformation phase may explain why the identification of D1 folds has been difficult.

Publication Title:

Communications of the Geological Survey of Namibia

Publisher:
Geological Survey of Namibia
Volume:
7
Pages:
15-19
Item Type:
Journal Article
Language:
en
Keywords:

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