Why are greenstone belts important?
Greenstone belts host important ore deposits of metals such as gold, Cu–Zn, Ni, and Fe. Well-known examples include the Abitibi and Flin Flon belts in Canada, the Norseman-Wiluna belt in Australia and the Barberton belt in South Africa.
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 are greenstone belts and how do they form?
Greenstone belts have been interpreted as having formed at ancient oceanic spreading centers and island arc terranes. Greenstone belts are primarily formed of volcanic rocks, dominated by basalt, with minor sedimentary rocks inter-leaving the volcanic formations.
Where is the greenstone belt located?
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…
Is greenstone a granite?
The granite-greenstone association is characterized by supra-crustal successions comprised dominantly of mafic volcanic rocks, known as “greenstone belts,” engulfed in a sea of granitic rocks. This association dominates in Archean provinces in North America, southern Africa, and Australia.
What is the Abitibi belt and what age type of rocks are exposed there?
The Abitibi greenstone belt is a 2,800-to-2,600-million-year-old greenstone belt that spans across the Ontario–Quebec border in Canada. It is mostly made of volcanic rocks, but also includes ultramafic rocks, mafic intrusions, granitoid rocks, and early and middle Precambrian sediments.
Is greenstone igneous metamorphic or sedimentary?
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.
How old are greenstone belts?
Greenstone-granite belts developed at many different times throughout the long Archean Eon. The Isua greenstone belt in West Greenland is about 3.85 billion years old.
How much is Isle Royale greenstone worth?
The gem-setter estimates the value of Isle Royale Greenstone at about $40,000 a pound. That puts this Lake Superior gem well ahead of the better known agate, with a current value of about $200 a pound.
How is greenstone changed into granitic continental rock?
How is greenstone changed into granitic continental rock? Magmas erupting.
Why are greenstone belts important in Ontario?
Greenstone belts host economic deposits of many minerals, including silver, copper and zinc, but they are best known for holding gold. Archaean-age greenstone belts in particular tend to host rich gold deposits. One example is Canada’s Abitibi greenstone belt, which is home to a slew of gold mines.
How did Isua greenstone belt form?
There are several lithologies that make up the Isua Greenstone Belt and the main rock types have been located and mapped. These rocks were most likely formed from the underplate melting of oceanic crust. The protoliths of these rocks were most likely a basalt, komatiite, and chert assemblage, or tonalite.