A brief review of the Precambrian metallogeny of peninsular India, Madagascar and eastern/southern Africa
|Location||International Geological Congress,oslo 2008|
|Holding Date||11 October 2008|
The Precambrian shield areas of India, Madagascar and Southern and eastern Africa are endowed with numerous economically important mineral deposits and prospects. By re-assembling the Pan-African continent of Gondwana, one can compare the metallogeny across India, Sri Lanka, Madagascar and the Seychelles, and eastern and southern Africa. The mineral deposits and/or occurrences included in this review are only those whose age of mineralization is believed to be Precambrian to early Cambrian. A variety of commodities, including gold, base metals, diamonds, iron, manganese, tintungsten± molybdenum, tantalum-niobium, gemstones, platinum group metals, uranium, graphite, gemstones etc., are found. Only selected commodities will be discussed.
In India, Madagascar and East Africa, primary gold deposits and/or occurrences commonly occur in greenstone belts, mainly of Archaean age and to a lesser extend in greenstone belts of Proterozoic age. The gold mineralization is generally structurally
controlled, hosted in a variety of lithologies and mainly epigenetic vein / lode type. Banded iron formations (BIF’s) host most of the iron-ore deposits in India and Madagascar, whilst the economic deposits of Tanzania are hosted in titaniferous magnetite bodies associated with anorthositic gabbro; BIF’s do occur. Precambrian-aged diamondiferous Kimberlite pipes have been found in India and East Africa. In India, diamond deposits are also found in lamproites and Neoproterozoic to early Palaeozoic conglomerates and sandstones. Currently, kimberlites found in Madagascar have not yielded diamonds. Chromite (± platinum group metals) occurs in ultramafic complexes and/or as podiform ore bodies throughout the area. Mineralization associated with pegmatites is common throughout the area. This includes significant tungsten (± tin ± molybdenum) deposits and to a lesser extent, niobium-tantalum deposits. Good quality gemstones are also found in all areas (i.e., India, Madagascar and East Africa), and include, amongst others, ruby, sapphire, emerald, amethyst, tourmaline etc.
From preliminary work, certain similarities in types and styles of mineralization have been observed across the map area, however there are also some noticeable differences. The crustal evolution of Madagascar and Mozambique is being revisited due to the availability of new age data pertaining to the Archaean and Proterozoic terrains in these areas. It is hoped that the final results will contribute towards a better understanding of the Precambrian metallogeny and crustal evolution (tectonic history) of India,Madagascar and East/South Africa.