What is a greenstone belt in geology?

Greenstone belts are zones of metamorphosed mafic/ultramafic volcanic rocks with associated sedimentary rocks that occur in narrow basins within the Precambrian granite and gneiss bodies.

What causes greenstone belts?

Greenstone belts are primarily formed of volcanic rocks, dominated by basalt, with minor sedimentary rocks inter-leaving the volcanic formations. By the Phanerozoic, extensive continental cover and lower heat flow from the mantle has seen greater preservation of sediments and greater influence of continental masses.

What type of rock is greenstone belt now?

Basalt was a common rock then as it is today. Greenstone belts get their very name from this prominent rock, which served as protolith for the low-grade metamorphic rock called greenstone. Then, as now, basalt erupted as mafic lava onto or near Earth’s surface, cooling rapidly to make a fine-grained igneous rock.

Where are greenstone belts deposited?

Greenstone belts, which are remnants of Archean oceanic crust emplaced in the suture zones (convergent plate boundaries), contain most of South America’s known large gold deposits, such as those located near Belo Horizonte, Brazil. Two major cycles of crustal deformation occurred in the Precambrian, widely…

How did the greenstone belt get its name?

They get their name because of their green color that is caused by the chlorite minerals that are largely present in the rock layer. They are rock formations that underwent a metamorphosis as volcanic sequences acted upon sedimentary rocks. Greenstone belt layers are most likely to be found between granite and gneiss layers of rock.

What kind of rocks are the greenstone belts made of?

The greenstone belts are typically sandwiched between large bodies of crustal rocks such as granite and gneiss. Not all greenstone belts are Archean; some are also known from the Proterozoic. But the Proterozoic’s tectonic record is more diverse, so for the sake of this case study, we will focus on the Archean.

Where is the Barberton greenstone belt in South Africa?

The Barberton Greenstone Belt, also known as the Makhonjwa Mountains, is situated on the eastern edge of Kaapvaal Craton in South Africa. It is known for its gold mineralisation and for its komatiites, an unusual type of ultramafic volcanic rock named after the Komati River that flows through the belt.

What can be extracted from a greenstone belt?

Many times gold mining companies will sell other bi-products that are present in the gold mines, as there are a variety of profitable minerals that can be extracted from most greenstone belts.