Abstract
M.Sc.
This study has served to expand the geological map of surroundings of the Venetia Mine
(Limpopo Province, South Africa) incorporating the area lying south of the kimberlite
deposit and bounded in the south by the Dowe-Tokwe fault. The most significant
structural conclusion stemming from this mapping project is that the Venetia Synform
seems to be tectonically separate from the surrounding area and actually forms a klippe
(shallowly dipping thrust) against the Krone Metamorphic terrane and the Gotha
Complex. Petrographic descriptions of quartzofeldspathic lithologies found in the Krone
Metamorphic Terrane to the west of the Venetia klippe (Mellonig, 2004) are identical
suggesting that they belong to the Gotha igneous complex.
There are no differences in geochemical compositions of monzogranite to granodiorite,
tonalite and quartz diorite from Farms Gotha and Venetia. The rocks are I-type
granitoids that generally form in continental magmatic arcs. The amount of U and Th in
the igneous rocks of the Farms Gotha and Venetia (contained in minerals found within
quartz, plagioclase, amphibole and K-feldspar crystal boundaries and the magmatic
zircons of the Farm Gotha samples) and the pattern produced by heat producing
elements (Council for Geoscience Radiogenic Map), indicate that that the unexpectedly
high concentration of these elements are not the result of regional metamorphism, but is
the remnant of the final crystallisation phase of the magma of the area. REE plots of the
Venetia Mine samples show negative Eu anomalies, indicating the presence of
plagioclase and K-feldspar in the magma source of the Venetia mine samples. The
assumption is, that most samples retained their original chemical compositions having
experienced only weak deuteric alteration and no dynamic metamorphism.