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 Paleoarchean, also spelled Palaeoarchaean, is a geologic era within the Archean Eon. The name derives from Greek "Palaios" ancient. It spans the period of time 3,600 to 3,200 million years ago. The era is defined chronometrically and is not referenced to a specific level of a rock section on Earth. The earliest confirmed evidence of life comes from this era, and Vaalbara, one of Earth's earliest supercontinents, may have formed during this era.
The Acasta Gneiss Complex, also called the Acasta Gneiss, is a body of felsic to ultramafic Archean basement rocks, gneisses, that form the northwestern edge of the Slave Craton in the Northwest Territories, Canada, about 300 km (190 mi) north of Yellowknife, Canada. This geologic complex consists largely of tonalitic and granodioritic gneisses and lesser amounts of mafic and ultramafic gneisses. It underlies and is largely concealed by thin, patchy cover of Quaternary glacial sediments over an area of about 13,000 km2 (5,000 sq mi). The Acasta Gneiss Complex contains fragments of the oldest known crust and record of more than a billion years of magmatism and metamorphism. The Acasta Gneiss Complex is exposed in a set of anticlinoriums within the foreland fold and thrust belt of the Paleoproterozoic Wopmay Orogen.
The Yilgarn Craton is a large craton that constitutes a major part of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.
The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland, aged between 3.7 and 3.8 billion years. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks, and is the largest exposure of Eoarchaean supracrustal rocks on Earth. Due to its age and low metamorphic grade relative to many Eoarchaean rocks, the Isua Greenstone Belt has become a focus for investigations on the emergence of life and the style of tectonics that operated on the early Earth.
Vaalbara is a hypothetical Archean supercontinent consisting of the Kaapvaal Craton and the Pilbara Craton. E. S. Cheney derived the name from the last four letters of each craton's name. The two cratons consist of continental crust dating from 2.7 to 3.6 Ga, which would make Vaalbara one of Earth's earliest supercontinents.
The Kaapvaal Craton, along with the Pilbara Craton of Western Australia, are the only remaining areas of pristine 3.6–2.5 Ga crust on Earth. Similarities of rock records from both these cratons, especially of the overlying late Archean sequences, suggest that they were once part of the Vaalbara supercontinent.
The Pilbara Craton is an old and stable part of the continental lithosphere located in the Pilbara region of Western Australia.
The Barberton Greenstone Belt is a geologic formation situated on the eastern edge of the 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. Some of the oldest exposed rocks on Earth are located in the Barberton Greenstone Belt of the Eswatini–Barberton areas and these contain some of the oldest traces of life on Earth, second only to the Isua Greenstone Belt of Western Greenland. The Makhonjwa Mountains make up 40% of the Baberton belt. It is named after the town Barberton, Mpumalanga.
The Labrador Trough or the New Quebec Orogen is a 1,600 km (994 mi) long and 160 km (99 mi) wide geologic belt in Canada, extending south-southeast from Ungava Bay through Quebec and Labrador.
The geology of Zimbabwe in southern Africa is centered on the Zimbabwe Craton, a core of Archean basement composed in the main of granitoids, schist and gneisses. It also incorporates greenstone belts comprising mafic, ultramafic and felsic volcanics which are associated with epiclastic sediments and iron formations. The craton is overlain in the north, northwest and east by Proterozoic and Phanerozoic sedimentary basins whilst to the northwest are the rocks of the Magondi Supergroup. Northwards is the Zambezi Belt and to the east the Mozambique Belt. South of the Zimbabwe Craton is the Kaapvaal Craton separated from it by the Limpopo Mobile Belt, a zone of deformation and metamorphism reflecting geological events from Archean to Mesoproterozoic times. The Zimbabwe Craton is intruded by an elongate ultramafic/mafic igneous complex known as the Great Dyke which runs for more than 500 km along a SSW/NNE oriented graben. It consists of peridotites, pyroxenites, norites and bands of chromitite.
The Barberton greenstone belt (BGB) is located in the Kapvaal craton of southeastern Africa. It characterizes one of the most well-preserved and oldest pieces of continental crust today by containing rocks in the Barberton Granite Greenstone Terrain (3.55–3.22 Ga). The BGB is a small, cusp-shaped succession of volcanic and sedimentary rocks, surrounded on all sides by granitoid plutons which range in age from >3547 to <3225 Ma. It is commonly known as the type locality of the ultramafic, extrusive volcanic rock, the komatiite. Greenstone belts are geologic regions generally composed of mafic to ultramafic volcanic sequences that have undergone metamorphism. These belts are associated with sedimentary rocks that occur within Archean and Proterozoic cratons between granitic bodies. Their name is derived from the green hue that comes from the metamorphic minerals associated with the mafic rocks. These regions are theorized to have formed at ancient oceanic spreading centers and island arcs. In simple terms, greenstone belts are described as metamorphosed volcanic belts. Being one of the few most well-preserved Archean portions of the crust, with Archean felsic volcanic rocks, the BGB is well studied. It provides present geologic evidence of Earth during the Archean (pre-3.0 Ga). Despite the BGB being a well studied area, its tectonic evolution has been the cause of much debate.
The Huangling Anticline or Complex represents a group of rock units that appear in the middle of the Yangtze Block in South China, distributed across Yixingshan, Zigui, Huangling, and Yichang counties. The group of rock involves nonconformity that sedimentary rocks overlie the metamorphic basement. It is a 73-km long, asymmetrical dome-shaped anticline with axial plane orientating in the north-south direction. It has a steeper west flank and a gentler east flank. Basically, there are three tectonic units from the anticline core to the rim, including Archean to Paleoproterozoic metamorphic basement, Neoproterozoic to Jurassic sedimentary rocks, and Cretaceous fluvial deposit sedimentary cover. The northern part of the core is mainly tonalite-trondhjemite-gneiss (TTG) and Cretaceous sedimentary rock called the Archean Kongling Complex. The middle of the core is mainly the Neoproterozoic granitoid. The southern part of the core is the Neoproterozoic potassium granite. Two basins are situated on the western and eastern flanks of the core, respectively, including the Zigui basin and Dangyang basin. Both basins are synforms while Zigui basin has a larger extent of folding. Yuanan Graben and Jingmen Graben are found within the Dangyang Basin area. The Huangling Anticline is an important area that helps unravel the tectonic history of the South China Craton because it has well-exposed layers of rock units from Archean basement rock to Cretaceous sedimentary rock cover due to the erosion of the anticline.
Eoarchean geology is the study of the oldest preserved crustal fragments of Earth during the Eoarchean era from 4.031 to 3.6 billion years ago. Major well-preserved rock units dated to this era are known from three localities, the Isua Greenstone Belt in Southwest Greenland, the Acasta Gneiss in the Slave Craton in Canada, and the Nuvvuagittuq Greenstone Belt in the eastern coast of Hudson Bay in Quebec. From the dating of rocks in these three regions, scientists suggest that the beginning of plate tectonics could have started as far back as early as the Eoarchean.
Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon. The term "felsic" means that the rocks have silica content of 62–78%. Given that the Earth formed at ~4.5 billion year ago, Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities on the Earth's surface started 500 million years after the Earth's formation.
The Eastern Block of the North China Craton is one of the Earth's oldest pieces of continent. It is separated from the Western Block by the Trans-North China Orogen. It is situated in northeastern China and North Korea. The Block contains rock exposures older than 2.5 billion years. It serves as an ideal place to study how the crust was formed in the past and the related tectonic settings.
The Western Block of the North China Craton is an ancient micro-continental block mainly composed of Neoarchean and Paleoproterozoic rock basement, with some parts overlain by Cambrian to Cenozoic volcanic and sedimentary rocks. It is one of two sub-blocks within the North China Craton, located in east-central China. The boundaries of the Western Block are slightly different among distinct models, but the shapes and areas are similar. There is a broad consensus that the Western Block covers a large part of the east-central China.
The Dresser Formation is a Paleoarchean geologic formation that outcrops as a generally circular ring of hills the North Pole Dome area of the East Pilbara Terrane of the Pilbara Craton of Western Australia. This formation is one of many formations that comprise the Warrawoona Group, which is the lowermost of four groups that comprise the Pilbara Supergroup. The Dresser Formation is part of the Panorama greenstone belt that surrounds and outcrops around the intrusive North Pole Monzogranite. Dresser Formation consists of metamorphosed, blue, black, and white bedded chert; pillow basalt; carbonate rocks; minor felsic volcaniclastic sandstone and conglomerate; hydrothermal barite; evaporites; and stromatolites. The lowermost of three stratigraphic units that comprise the Dresser Formation contains some of the Earth's earliest commonly accepted evidence of life such as morphologically diverse stromatolites, microbially induced sedimentary structures, putative organic microfossils, and biologically fractionated carbon and sulfur isotopic data.
The Dharwar Craton is an Archean continental crust craton formed between 3.6-2.5 billion years ago (Ga), which is located in southern India and considered the oldest part of the Indian peninsula.
The Giyani Greenstone Belt (GGB), also known as the Sutherland Range, is located in the Limpopo province of South Africa at the north-eastern boundary of the Kaapvaal Craton. It is not as economically relevant as the Barberton greenstone belt located further south.
