|
Akia Terrane
The Akia terrane is a tectonostratigraphic terrane located in the North Atlantic craton, North Atlantic Craton in southern West Greenland. The Akia terrane is bounded to the Southeast by the Eoarchean, Eo- to Neoarchean, Neo-archaean tectonostratigraphic terranes of the Nuuk region, and to the North by the recently recognised Alanngua Complex, which separates the Akia terrane from the Neoarchaean Tuno terrane. The crust in the Akia terrane formed in two major pulses. The first at ~3.2 Ga, predominantly comprises dioritic gneisses, whereas the second, at ~3.0 Ga comprises a more diverse mix of Tonalite-trondhjemite-granodiorite, TTG and Diorite, dioritic gneisses with enclaves of Supracrustal rock, supracrustal rocks and mafic-ultramafic Intrusive rock, intrusions. Supracrustal rocks are largely tholeiitic and calc-alkaline Amphibolite, amphibolites formed at ~3.07 Ga. The mafic-ultramafic intrusions include peridotite cumulates and a belt of noritic intrusions formed at the same time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectonostratigraphic Terrane
In geology, a terrane (; in full, a tectonostratigraphy, tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a plate tectonics, tectonic plate (or broken off from it) and accretion (geology), accreted or "suture (geology), sutured" to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from the surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault (geology), fault. A sedimentary rock, sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation. An igneous rock, igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a igneous intrusion, stitching pluton. There is also an older usage of the term ''terrane'', which described a series of related rock formations or an area with a preponderance of a p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Society, London, Special Publications
The Geological Society of London, known commonly as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe, with more than 12,000 Fellows. Fellows are entitled to the postnominal FGS (Fellow of the Geological Society), over 2,000 of whom are Chartered Geologists (CGeol). The Society is a registered charity, no. 210161. It is also a member of the Science Council, and is licensed to award Chartered Scientist to qualifying members. The mission of the society is: "Making geologists acquainted with each other, stimulating their zeal, inducing them to adopt one nomenclature, facilitating the communication of new facts and ascertaining what is known in their science and what remains to be discovered". History The Society was founded on 13 November 1807 at the Freemasons' Tavern, Great Queen Street, in the Covent Garden district of London. It was partly the outcome of a previous club ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dike (geology), dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF diagram, QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pegmatite
A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite. However, rarer intermediate composition and mafic pegmatites are known. Many of the world's largest crystals are found within pegmatites. These include crystals of microcline, quartz, mica, spodumene, beryl, and tourmaline. Some individual crystals are over long. Most pegmatites are thought to form from the last fluid fraction of a large crystallizing magma body. This residual fluid is highly enriched in volatiles and trace elements, and its very low viscosity allows components to migrate rapidly to join an existing crystal rather than coming together to form new crystals. This allows a few very large crystals to form. While most pegmatites have a simple composition of minerals common in ordinary igneous rock ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphism
Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chemically active fluids, but the rock remains mostly solid during the transformation. Metamorphism is distinct from weathering or diagenesis, which are changes that take place at or just beneath Earth's surface. Various forms of metamorphism exist, including Regional metamorphism, regional, Contact metamorphism, contact, Hydrothermal metamorphism, hydrothermal, Shock metamorphism, shock, and Dynamic metamorphism, dynamic metamorphism. These differ in the characteristic temperatures, pressures, and rate at which they take place and in the extent to which reactive fluids are involved. Metamorphism occurring at increasing pressure and temperature conditions is known as ''prograde metamorphism'', while decreasin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granulite
Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure.D.R. Bowes (1989), ''The Encyclopedia of Igneous and Metamorphic Petrology''; Van Nostrand Reinhold They are of particular interest to geologists because many granulites represent samples of the deep continental crust. Some granulites experienced decompression from deep in the Earth to shallower crustal levels at high temperature; others cooled while remaining at depth in the Earth. The minerals present in a granulite will vary depending on the parent rock of the granulite and the temperature and pressure conditions experienced during metamorphism. A common type of granulite found in high-grade metamorphic rocks of the conti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orogeny
Orogeny () is a mountain-mountain formation, building process that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is tectonic uplift, uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation (physics), deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere (crust (geology), crust and uppermost mantle (geology), mantle). A synorogenic (or synkinematic) process or event is one that occurs during an orogeny. The word ''orogeny'' comes . Although it was used before him, the American geologist Grove Karl Gilbert, G. K. Gilbert used the term in 1890 to me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stagnant Lid
Lid tectonics, commonly thought of as stagnant lid tectonics or single lid tectonics, is the type of tectonics that is believed to exist on several silicate planets and moons in the Solar System, and possibly existed on Earth during the very early part of its history. The lid is the equivalent of the lithosphere, formed of solid silicate minerals. The relative stability and immobility of the strong cooler lids leads to stagnant lid tectonics, which has greatly reduced amounts of horizontal tectonics compared with plate tectonics (which can also be described as mobile lid tectonics). The presence of a stagnant lid above a convecting mantle was recognised as a possible stable regime for convection on Earth, in contrast to the well-attested mobile plate tectonics of the current eon. Formation A lid tectonic regime arises when the cold upper lithosphere is too viscous to participate in the underlying flow of the mantle. The lid's yield strength is high enough where the lid cannot br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magmatism
Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism. Magmatism is one of the main processes responsible for mountain formation. The nature of magmatism depends on the tectonic setting. For example, andesitic magmatism is associated with the formation of island arcs at convergent plate boundaries while basaltic magmatism is found at mid-ocean ridges during sea-floor spreading at divergent plate boundaries. On Earth, magma forms by partial melting of silicate rocks either in the mantle, continental or oceanic crust. Evidence for magmatic activity is usually found in the form of igneous rocks formed from magma. Convergent boundaries Magmatism is associated with all stages of the development of convergent plate boundar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subduction
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plate, the heavier plate dives beneath the other and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year. Subduction is possible because the cold and rigid oceanic lithosphere is slightly denser than the underlying asthenosphere, the hot, ductile layer in the upper mantle. Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere. The down-going slab sinks into the mantle largely under its own ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frontiers In Earth Science
Frontiers Media SA is a publisher of peer-reviewed, open access, scientific journals currently active in science, technology, and medicine. It was founded in 2007 by Kamila and Henry Markram. Frontiers is based in Lausanne, Switzerland, with offices in the United Kingdom, Spain, and China. In 2022, Frontiers employed more than 1,400 people, across 14 countries. All Frontiers journals are published under a Creative Commons Attribution License. In 2015, Frontiers Media was classified as a possible predatory publisher by Jeffrey Beall, though Beall's list was taken offline two years later in a decision that remains controversial. History The first journal published was ''Frontiers in Neuroscience'', which opened for submission as a beta version in 2007. In 2010, Frontiers launched a series of another 11 journals in medicine and science. In February 2012, the Frontiers Research Network was launched, a social networking platform for researchers, intended to disseminate the open ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maniitsoq Norite Belt
The Maniitsoq Norite Belt is a ~75 km x 15 km J-shaped belt of igneous norite intrusions, located in the Akia Terrane of the North Atlantic Craton, Greenland, near the town of Maniitsoq.Ravenelle, J. F., Weiershauser, L., and Cole, G. (2017). Report No.: 3CN024.004. Updated Independent Technical Report for the Maniitsoq Nickel-Copper-Cobalt-PGM Project, Greenland. Available at: https://s1.q4cdn.com/725069486/files/doc_downloads/technical_reports/Technical_Report_2017.pdf The belt is found as enclaves ranging from meter-scale pods to 8 km2 large intrusive bodies within the ~3050 to 2990 Ma TTG and dioritic gneisses of the Akia terrane. and formed contemporaneously with the host gneisses between ~3013 and 3001 Ma The norites underwent high grade granulite facies metamorphism at temperatures of ~800 °C and pressures of ~9 kbar (approximately 30 km depth) from ~3010 to 2980 Ma, soon after they were intruded. The norites were metamorphosed twice more at ~2.7 Ga and ~2.5 Ga. A wide v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
