Platinum in Malawi
By Grain Malunga FIMMM Mineral Resources and Environmental Management Expert
Platinum metals exploration in Malawi has been associated with mafic to ultramafic rocks, sometimes associated with arnothosites. These rocks have been metamorphosed and it is possible that lateroregenic events triggered magmatisation of buried intrusive bodies. These are associated with irumide orogeny. This paper tries to documents target areas for exploration of platinum minerals including nickel, copper and chrome.
The platinum group metals are characterised by their denseness, hardness, high reflectivity and resistance to tarnishing. They have electrical conductivity and conduct heat. They promote chemical reactions. They have three main occurrences as follows:
- Platinum-bearing nickel-copper, copper, or copper-cobalt sulphides that are related genetically to basic or ultrabasic rocks. This group does not show magmatic separation or segregation.
- Platinum-bearing nickel-copper ores that are magmatically disseminated or concentrated in gabbroic and ultrabasic rocks. Pyroxenite and anorthosite host rocks are commonly associated with norite and all of these may have the outlines of dikes, sills, pipes, lenses, or schlieren.
- Native alloys of the platinum metals that are magmatically disseminated in peridotites and if concentrated, they are commonly intergrown with chromite. Most of these deposits are in dunites may partly alter to serpentinite.
- Placer deposits of native platinum metals consist mainly of two principal alloys known as “platinum” and “osmiridium.” Osmiridium consists dominantly of iridium and osmium and hosts minor metals of ruthenium, rhodium, and platinum.
- Platinum in bedrock lodes may have gold, silver and some base metals which act as cations in combination with elements such as arsenic, antimony, bismuth,sulphur, tellurium and oxygen.
Platinum in Malawi
Platinum and associated minerals in Malawi have showings in mafic and ultramafic rocks. A series of pyroxenitic and gabbroic rocks with serpentenite alterations have been found to contain Ni – Cr – Cu – Pt sulphide mineralisation. There is high potential to discover economic deposits in Karonga –Chitipa area, Kasungu – Mchinji – Lilongwe plain, Ntcheu – Mwanza area and Blantyre-Chikwawa (Shire Highlands) area. Table 1 documents what was obtained in previous exploration works while Figure one shows the localities of these minerals.
- Bloomfield, K. and Garson, M. S. 1965. The geology of the Kirk Range-Lisungwe Valley area. Bull. Geol. Surv. Malawi, 17.
- Malunga G. W. P. 1997. Mineral Potential of Malawi, Unpublished Report.
- Paterson, Grant and Watson Ltd. 187. Interpretation of Airbone geophysical survey results. UNDP Project Mlw/80/030.
- Peters, E. R. 1969. The geology of the Kasungu area. Bull. Geol. Surv. Malawi, 25.
- Thatcher, E. C. and Wilderspin, K. E. 1968. The geology of the Mchinji-Upper Bua area. Bull. Geol. Surv. Malawi, 24.
This was initially published in Malawi’s Mining & Trade Review Issue Number 48 (April 2017).