Mode of Occurrence and Origin of Iron Ore Deposits of Ga-Nchabeleng Area, Sekhukhune District, Limpopo Province, South Africa

Abstract

The study area falls under the Sekhukhune District Municipality of the Limpopo province within Rustenburg layered suite of the Bushveld Igneous complex. The aim of the study was to investigate the petrological and mineralogical characteristics of gabbronorite and iron ore as well as to establish the geological environment of the ore formation so as to ascertain the mode of occurrence and origin of the iron ore deposit. Geological mapping was conducted so as to confirm the host rocks and establish the relationship between the host rocks and orebodies. The map revealed the distribution of the rocks within the study area and the geological setting of the iron ore. The iron ore was found to be localized within gabbronorite. Iron ore occurred as veins, veinlets, stockworks, stringers, and finger-like structures. The geological structures acted as conduits for the ferruginous melts that finally formed the iron ore. Petrographic study revealed the presence of feldspar, mainly plagioclase in gabbronorite, and minor concentration of oxides mainly magnetite. Some rock specimens revealed a high concentration of magnetite especially those located near the host rock-orebody contact. Reflected light microscopy was done to establish the mineralogy of iron ore and to ascertain the relationship of the ore minerals. The main ore minerals were magnetite and hematite with minor ilmenite. The XRD results revealed high content of magnetite (92 %), followed by hematite (61%), then ilmenite (12%). The XRF results revealed gabbronorite with minimum and maximum FeO3 wt% of 1.31% and 44.22% respectively, while minimum and maximum values of FeO3 wt% in magnetite ore samples were found to be 43.38% and 54.55% respectively with an average value of 52.36%. The magnetite registered high concentration values of Zn (221 ppm), Ni (225 ppm), Co (163 ppm), Cr (503 ppm) and V (8981 ppm). The study concluded that the iron ore is hosted by intermediate to felsic igneous rocks which were found to be gabbronorite. Ore bodies formed stockworks that were randomly oriented as veins, veinlets, and stringers associated with fractional crystallization of the layered complexes. The magnetite ore within the study area was of good grade with average values above 50% and rich in V, Cr, Ni, Zn and Co. The study recommends further detailed exploration of iron ore in the area, applying techniques such as geophysical methods and borehole drilling leading to resource evaluation.