Abstract
M.Sc. (Geology)
This study presents the first detailed major- and trace element geochemical and geochronological studies of the Molopo Farms Complex (MFC), situated in the Northern Cape Province, South Africa and south eastern Botswana. The rocks of the MFC are gabbro, serpentinite, pyroxenite and intrudes into sedimentary host rocks, these rocks are medium- to coarse grained. The mafic igneous rocks of the MFC are dominantly sub-alkaline tholeiitic in composition and characterized as basaltic andesite. The MFC is completely covered by Cenozoic sediments of the Kalahari Formation and it is only known through intersection in exploration drill core and geophysical data. It is thought that the MFC has intruded the sedimentary succession of the Paleoproterozoic Transvaal Supergroup.
Unlike other layered complexes (Bushveld Complex, Stillwater Complex, etc.), no detailed geochemical studies have been done on the MFC. At present, the available age is the poorly constrained at 2044±24 Ma (Rb-Sr errorchron age) and for that reason, and the fact that it is a layered igneous complex it has been correlated with Bushveld Complex. However, this age and correlation are poorly constrained. This study provides additional data on the geochemical composition of the igneous rocks to fully understand the geochemical signature of the igneous rocks of the MFC, a baddeleyite age on a gabbro from the complex and also detrital zircon age data on the sedimentary country rocks.
The geochemical signature of the MFC has been compared to that of other magmatic events (Bushveld Complex, Moshaneng dykes and Post Waterberg sills) to evaluate the similarities in composition. The MFC is characterized by an enrichment in LREE relative to the HREE and shows negative Eu, Nb(Ta), P, Ti and positive K, Pb and U anomalies. This geochemical signature compares well with that of the B1-magma of the Bushveld Complex.
An age of 2052±16 Ma, obtained from U-Pb baddeleyite dating, has been interpreted to be the emplacement age of the MFC. This age is within error with the 2054.4±1.3 Ma accepted age of the Bushveld Complex. The maximum age of sedimentary country rock into which MFC intrudes has been better constrained by U-Pb detrital zircon dating. The youngest concordant zircon ages obtained are between 2018±39 and...