Greenstone belt
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- This article is about zones of mixed sedimentary and volcanic rock sequences that often contain minable concentrations of gold, silver, copper, zinc and lead. For other meanings, see Greenstone (disambiguation).
Greenstone belts are so called because of the green hue imparted by the chlorite minerals within the rocks. Greenstone belts are mainly found in Australia, southern Africa, and Canada, and may be found included within igneous and metamorphic rock such as basalt, granite and gneiss.
The best known greenstone belt in the world is the South African Barbeton Greenstone belt, which led to the first discovery of gold in South Africa. The Barbeton Greenstone belt was first uniquely identified by Prof Annhauser at the University of the Witwatersrand, Johannesburg, South Africa. His work in mapping and detailing the characteristics of the Barbeton Greenstone belt has been used a primer for other greenstone belts around the world.
He noted the existence of pillow lavas, indicating a lava being rapidly cooled in water, as well as the spinifex textures created by crystals formed under rapidly cooling environments, namely water.