Greenstone belt

Greenstone belt

Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies.

The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks. Chlorite, actinolite and other green amphiboles are the typical green minerals.

A greenstone belt is typically several dozens to several thousand kilometres long and although composed of a great variety of individual rock units, is considered a 'stratigraphic grouping' in its own right, at least on continental scales.

Typically, a greenstone belt within the greater volume of otherwise homogeneous granite-gneiss within a craton contains a significantly larger degree of heterogeneity and complications and forms a tectonic marker far more distinct than the much more voluminous and homogeneous granites. Additionally, a greenstone belt contains far more information on tectonic and metamorphic events, deformations and palaeogeologic conditions than the granite and gneiss events, because the vast majority of greenstones are interpreted or provably basalts and other volcanic or sedimentary rocks. As such, understanding the nature and origin of greenstone belts is the most fruitful way of studying Archaean geological history. Greenstone belts are basically metamorphosed volcanic belts.

Nature and formation

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. Through time, the degree of sediment contained within greenstone belts has risen, and the amount of ultramafic rock (either as intrusive ultramafic to mafic layered intrusions or as volcanic komatiite) has decreased.

There is also a change in the structure and relationship of greenstone belts to their basements between the Archaean where there is little clear relationship, if any, between basalt-peridotite sheets of a greenstone belt and the granites they abut, and the Proterozoic where greenstone belts sit upon granite-gneiss basements and/or other greenstone belts, and the Phanerozoic where clear examples of island arc volcanism, arc sedimentation and ophiolite sequences become more dominant.

This change in nature is interpreted as a response to the maturity of the plate tectonics processes throughout the Earth's geological history. Archaean plate tectonics, if it occurred at all (as is debated), did not take place on mature crust and as such the presence of thrust-in allochthonous greenstone belts is expected. By the Proterozoic, magmatism was occurring around cratons and with established sedimentary sources, with little recycling of the crust, allowing preservation of more sediments. 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.

Greenstones, aside from containing basalts, also give rise to several types of metamorphic rocks which are used synonymously with 'metabasalt' etcetera; greenschist, whiteschist and blueschist are all terms spawned from study of greenstone belts.


"Greenstone belts" are distributed throughout geological history from the Phanerozoic Franciscan Belts of California where blueschist, whiteschist and greenschist facies are recognised, through to the Palaeozoic greenstone belts of the Lachlan Fold Belt, Eastern Australia, and a multitude of Proterozoic and Archaean examples.

Archaean greenstones are found in the Slave craton, northern Canada, Pilbara craton and Yilgarn Craton, Western Australia, Gawler Craton in South Australia. Examples are found in South and Eastern Africa, namely the Kaapvaal craton and also in the cratonic core of Madagascar, as well as West Africa and Brazil, northern Scandinavia and the Kola Peninsula (see Baltic Shield).

Proterozoic greenstones occur sandwiched between the Pilbara and Yilgarn cratons in Australia, and adjoining the Gawler Craton and within the extensive Proterozoic mobile belts of Australia, within West Africa, throughout the metamorphic complexes surrounding the Archaean core of Madagascar; the eastern United States, northern Canada and northern Scandinavia. The Abitibi greenstone belt in Ontario and Quebec is one of the largest Archean greenstone belts in the world.

Phanerozoic ophiolite belts and greenstone belts occur in the Franciscan Complex of south-western North America, within the Lachlan Fold Belt, the Gympie Terrane of Eastern Australia, the ophiolite belts of Oman and around the Guiana Shield.

The belts often contain ore deposits of gold, silver, copper, zinc and lead.

One of the best known greenstone belts in the world is the South African Barberton Greenstone belt, where gold was first discovered in South Africa. The Barberton Greenstone belt was first uniquely identified by Prof Annhauser at the University of the Witwatersrand, Johannesburg. His work in mapping and detailing the characteristics of the Barberton 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.

List of greenstone belts

*Abitibi greenstone belt (Quebec/Ontario, Canada)
*Barberton greenstone belt (South Africa)
*Bird River greenstone belt (Manitoba, Canada)
*Flin Flon greenstone belt (Manitoba/Saskatchewan, Canada)
*Isua greenstone belt (Southwestern Greenland)
*Pietersberg greenstone belt (South Africa)
*Taishan greenstone belt (Southeast Asia)
*Temagami greenstone belt (Ontario, Canada)

See also

* Greenschist
* Whiteschist
* Blueschist
* Komatiite
* Craton
* Metamorphism
* Tectonics


*Maarten J de Wit and Lewis D Ashwal (1997) "Greenstone Belts", Clarendon Press ISBN 0-19-854056-6 [ Excerpts and maps]
*Lowe, D. R. (1994) "Accretionary history of the Archean Barberton Greenstone Belt (3.55-3.22 Ga), southern Africa" Geology. 1994 Dec;22(12):1099-102. [ Abstract]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Isua greenstone belt — The Isua greenstone belt is an Archean greenstone belt in southwestern Greenland dated at 3.8 3.7 Ga and contains the oldest known, well preserved, metavolcanic (metamorphosed mafic volcanic), metasedimentary and sedimentary rocks on Earth. It… …   Wikipedia

  • Temagami greenstone belt — The Temagami greenstone belt is an Archean greenstone belt in Temagami, Ontario, located Unit km|100|0 northeast of Sudbury, Canada. It is characterized by felsic mafic volcanic rocks and averages about Unit km|13|0 wide and Unit km|29|0 long… …   Wikipedia

  • Flin Flon greenstone belt — The Flin Flon greenstone belt, also referred to as the Flin Flon Snow Lake greenstone belt, is a Precambrian greenstone belt located in the central area of Manitoba and east central Saskatchewan, Canada. It lies in the central portion of the… …   Wikipedia

  • Abitibi greenstone belt — The Abitibi greenstone belt is a 2,800 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… …   Wikipedia

  • Nuvvuagittuq greenstone belt — An outcrop of metamorphosed volcanosedimentary rocks at Porpoise Cove. Nuvvuagittuq greenstone belt, also called the Porpoise Cove greenstone belt, is a greenstone belt on the eastern shore of Hudson Bay in northern Quebec, Canada. With an age of …   Wikipedia

  • Swayse greenstone belt — The Swayze greenstone belt is a late Archean greenstone belt in northern Ontario, Canada. It is the southwestern extension of the Abitibi greenstone belt. [ [ 25729.htm Deformation history of… …   Wikipedia

  • Central Lapland Greenstone Belt — The Central Lapland Greenstone Belt (CLGB) is a greenstone belt located in the northern part of the Fennoscandian Shield. The region belongs to Lapland, northern Finland. The CLGB is part of a much larger belt of Paleoproterozoic greenstones, a… …   Wikipedia

  • Bird River greenstone belt — The Bird River greenstone belt is an Archean greenstone belt in southeastern Manitoba, Canada. [ [ 18.pdf Structural geology of the Bernic Lake area, Bird River greenstone belt, southwestern… …   Wikipedia

  • Greenstone — is a name given to several different types of minerals.* Pounamu, a form of green nephrite jade found in New Zealand and Australia * Chlorastrolite * Greenschist * Greenstone (archaeology), a type of stone used by early cultures, particularly in… …   Wikipedia

  • Volcanic belt — [ Trans Mexican Volcanic Belt in Mexico ] A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature (700… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.