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The Bushveld Complex, South Aftrica – The First Hundred Years / A Tribute to Tony Naldrett
October 22, 2020 @ 12:00 pm
THE BUSHVELD COMPLEX, SOUTH AFRICA – THE FIRST HUNDRED YEARS
a tribute to Professor Tony Naldrett
One hundred years on, the Bushveld Complex is still one of the greatest ore deposits on Earth and still has undeveloped and unexplored resources. The Bushveld intrusion was first shown on a map in the late 1860’s although the first use of the term Bushveld Complex was in 1901. However, it was the discovery of the platinum–bearing horizon by Andries Lombaard and confirmed by Merensky, in the Eastern Bushveld in 1924 that was really the beginning of the bonanza that the Bushveld Complex was to become. Within three years, Merensky had traced the reef that was named after him, all the way around the eastern, western and northern limbs of the Complex. Mining of platinum in the northern and western limb soon followed.
Chromium, was first noted in 1865 but wasn’t mined until 1924. Three groups of chromitites were defined with decreasing chromium content upwards from a Lower Group of six chromitites (LG), through the Middle Group of four chromium-rich layers (MG) to the Upper Group of two or three chromitites (UG), with the LG6 being the thickest and most amenable chromitite for mining. All chromitites contain platinum group elements (PGE), with increasing PGE grade upwards. A game changer in the late 1970’s was the development of the methodology for extracting PGE from chromitite layers. As the UG2 was the richest, and had been left unmined because of its low Cr content, it has now become a greater PGE resource than the Merensky Reef. Naldrett provided a detailed PGE profile through each of the chromitites layers showing how PGE ratios change through the horizons.
Just as the fortunes of the Bushveld Complex might have appeared to be waning, over the last decade the discovery of two Tier 1 deposits in the northern limb, the sub-horizontal Flatreef mineralization located downdip of the exposed Platreef, and the discovery of the palladium-dominant Waterberg Ni-Cu-PGE deposit under cover north of the exposed northern limb, have been game changers especially as the mineralization in the latter is at different stratigraphic levels to that in the other limbs. Naldrett noted the similarity of the upper part of the Platreef with that of the Merensky Reef – a correlation that has now become widely accepted with the discovery of the Flatreef.
This talk, given as a tribute to Professor Tony Naldrett, will take a look at the whole Bushveld Complex, new ideas, new developments and include some of Tony’s vast contribution to research on this huge Complex.
Professor Judith Kinnaird has recently retired as Director of the Economic Geology Research Institute in the University of the Witwatersrand, Johannesburg but remains as co-director of a National Centre of Excellence (CIMERA) for Minerals and Energy Research Analysis, funded by the South Africa government.
She has an Honours BSc degree from the University of London and an MSc and PhD from the University of St. Andrews in Scotland. She has worked on the tin-bearing granites in Nigeria and South Africa, Li-Be-Sn-Nb-Ta and gem-bearing pegmatites in Namibia, Nigeria and Somaliland and uraniferous deposits in Namibia, South Africa and Malawi. At the University of the Witwatersrand she leads research on the Northern limb of the Bushveld Complex and also works on various projects related to Critical Metals especially lithium, germanium and platinum group elements.
This seminar will be via Zoom. An invitation to join the event will be emailed to the Earth Sciences “Seminars” and “Everyone” list serves.