Geologisch-mineralogische Untersuchungen am Donkerhoek-Granit, Karibib-Distrikt, Südwestafrika

Abstract

Abstract taken from published version of thesis:

The Donkerhoek Granite, a large granite complex in the eugeosyncline of the late Precambrian Damaran Orogenic belt, is proved to be a post-tectonically intrusive, homogeneous biotite-muscovite monzogranite (isotopic age: 420 ± 20 m. y.). Its relation to the surrounding geological setting represented by high-grade metamorphic sediments of the eugeosynclinal filling having undergone two folding processes and its mechanism of intrusion (stoping, sheeting) are described. The type locality of the Donkerhoek Granite has been mapped in this respect. Geological, petrographical and petrological investigation was carried out to trace the intrusional history of the Donkerhoek-Granite: from the initiation of the granitic magma (by anatexis of a eugeosynclinal sediment during metamorphism), its passive ascent (by gravity Inversion over a few kilometers), to the active emplacement of the magma (at a depth of 14-15 km accompanied by the deformation of the country rock), which closed with the intrusion of pegmatites supplied by the Donkerhoek-Granite. Their mechanism of intrusion (network-like dikes and plugs) is pointed out. The characteristic features of the stock-like Achas Granite - early post-tectonically intruded - are presented comparatively