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Ultrahigh-pressure Metamorphism
Ultra-high-pressure metamorphism refers to metamorphic processes at pressures high enough to stabilize coesite, the high-pressure polymorph of SiO2. It is important because the processes that form and exhume ultra-high-pressure (UHP) metamorphic rocks may strongly affect plate tectonics, the composition and evolution of Earth's crust. The discovery of UHP metamorphic rocks in 1984 revolutionized our understanding of plate tectonics. Prior to 1984 there was little suspicion that continental rocks could reach such high pressures. The formation of many UHP terrains has been attributed to the subduction of microcontinents or continental margins and the exhumation of all UHP terrains has been ascribed principally to buoyancy caused by the low density of continental crust—even at UHP—relative to Earth's mantle. While the subduction proceeds at low thermal gradients of less than 10°C/km, the exhumation proceeds at elevated thermal gradients of 10-30°C/km. Definition Metamorphism of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphic
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causing profound physical or chemical changes. During this process, the rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an igneous, sedimentary, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by their protolith, their chemical and mineral makeup, and their texture. They may be formed simply by being deeply buried beneath the Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from tectonic processes such as continental collisions, which cause horizontal pressure, friction, and distorti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenolith
A xenolith ("foreign rock") is a rock fragment (country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in igneous rock entrained during magma ascent, emplacement and eruption. Xenoliths may be engulfed along the margins of a magma chamber, torn loose from the walls of an erupting lava conduit or explosive diatreme or picked up along the base of a flowing body of lava on the Earth's surface. A xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes. Xenoliths can be non-uniform within individual locations, even in areas which are spatially limited, e.g. rhyolite-dominated lava of Niijima volcano (Japan) contains two types of gabbroic xenoliths which are of different origin - they were formed in different temperature and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodlark Basin
The Woodlark Basin is a geologic structural basin located in the southwestern Pacific Ocean and can be found to the southwest of the island country of Papua New Guinea. The basin is an extensional basin that is actively spreading and has a seafloor spreading center. This basin lies between the Indo-Australian Plate and the Solomon microplate and is located at 09°S, 155°E. The Woodlark Basin has an interesting geologic history dating back twenty million years to the initial opening of the basin; the spreading of the basin, however, has occurred within the past three million years. Due to the relatively young age of the basin, many researchers are interested in learning how the basin will continue to develop over time and how the plates will subduct. The subduction of the plates in the Woodlark Basin will be unique because the new crust being formed will be young and warm unlike most crust that gets subducted due to its low temperature and high density. Geology The Indo-Australian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodlark Plate
The Woodlark Plate is a small tectonic plate located in the eastern half of the island of New Guinea. It subducts beneath the Caroline plate along its northern border while the Maoke Plate converges on the west, the Australian plate converges on the south, and on the east an undefined compressive zone which may be a transform fault marking the boundary with the adjoining Solomon Sea Plate. It also contacts the South Bismarck Plate The South Bismarck Plate is a small tectonic plate located in the southern Bismarck Sea. The eastern part of New Guinea and the island of New Britain are on this plate. Tectonics Convergent boundaries line the southern border including the subdu ... due northeast. See also * References * Tectonic plates Geology of the Pacific Ocean {{tectonics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-orogenic Collapse
In geology, orogenic collapse is the thinning and lateral spread of thickened crust. It is a broad term referring to processes which distribute material from regions of high gravitational potential energy to regions of low gravitational potential energy. Orogenic collapse can begin at any point during an orogeny due to overthickening of the crust. Post-orogenic collapse and post-orogenic extension refer to processes which take place once tectonic forces have been released, and represent a key phase of the Wilson Cycle, between continental collision and rifting. Orogens (also known as orogenic belts, or more simply mountain ranges) are sections of thickened crust which are built up as tectonic plates collide. The thickening of the crust marks the start of an orogeny, or "mountain building event." As the orogeny progresses, the orogen may start spreading apart and thinning. Collapse processes can begin either once the orogeny ends as the tectonic forces cease, or during the orogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Western Gneiss Region
The Western Gneiss Region ( no, Gneisregionen) is a large geological unit in Norway chiefly made of gneiss rock that formed through metamorphism during the Caledonian orogeny. It makes up a tectono-stratigraphic terrane of the Scandinavian Caledonides and is also part of the Baltic shield. The region extends across western Norway from Bergen to Trondheim as a Caledonian window, outliers of the Western Gneiss Region crop out as far north as the Lofoten archipelago. The rocks of the Western Gneiss Region are made up of variously deformed Precambrian basement, and cover rocks of autochthonous and para-autochthonous origin with evidence of medium to high grade metamorphism including ultra-high-pressure metamorphism. Rocks of the Western Gneiss Region formed 1700 to 1600 million years ago in the Late Paleoproterozoic. What was to become the Western Gneiss Region was intruded by migmatites and granites during the Sveconorwegian orogeny The Sveconorwegian orogeny was an orogenic sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rheology
Rheology (; ) is the study of the flow of matter, primarily in a fluid ( liquid or gas) state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. Rheology is a branch of physics, and it is the science that deals with the deformation and flow of materials, both solids and liquids.W. R. Schowalter (1978) Mechanics of Non-Newtonian Fluids Pergamon The term ''rheology'' was coined by Eugene C. Bingham, a professor at Lafayette College, in 1920, from a suggestion by a colleague, Markus Reiner.The Deborah Number The term was inspired by the of |
Slab Detachment
In plate tectonics, slab detachment or slab break-off may occur during continent-continent or arc-continent collisions. When the continental margin of the subducting plate reaches the oceanic trench of the subduction zone, the more buoyant continental crust will in normal circumstances experience only a limited amount of subduction into the asthenosphere. The slab pull forces will, however, still be present and this normally leads to the breaking off or detachment of the descending slab from the rest of the plate. The isostatic response to the detachment of the downgoing slab is rapid uplift. Slab detachment is also followed by the upwelling of relatively hot asthenosphere to fill the gap created, leading in many cases to magmatism. The uncritical use of the slab-detachment model to explain disparate observations of magmatism, uplift and exhumation in continental collision zones has been criticised. Slab tears Detachment initiates at a particular point on the slab and will then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pamir Mountains
The Pamir Mountains are a mountain range between Central Asia and Pakistan. It is located at a junction with other notable mountains, namely the Tian Shan, Karakoram, Kunlun, Hindu Kush and the Himalaya mountain ranges. They are among the world's highest mountains. Much of the Pamir Mountains lie in the Gorno-Badakhshan Province of Tajikistan. To the south, they border the Hindu Kush mountains along Afghanistan's Wakhan Corridor in Badakhshan Province, Chitral District, Chitral and Gilgit-Baltistan regions of Pakistan. To the north, they join the Tian Shan mountains along the Alay Valley of Kyrgyzstan. To the east, they extend to the range that includes China's Kongur Tagh, in the "Eastern Pamirs", separated by the Yarkand River, Yarkand valley from the Kunlun Mountains. Name and etymology Since Victorian times, they have been known as the "Roof of the World", presumably a translation from Persian language, Persian. Names In other languages they are called: ps, , ; k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc located further from the subducting plate than the trench. The oceanic plate is saturated with water, mostly in the form of hydrous minerals such as micas, amphiboles, and serpentine minerals. As the oceanic plate is subducted, it is subjected to increasing pressure and temperature with increasing depth. The heat and pressure break down the hydrous minerals in the plate, releasing water into the overlying mantle. Volatiles such as water drastically lower the melting point of the mantle, causing some of the mantle to melt and form magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone. Volcanic arcs are distinct from volcanic chains formed over hotspots in the middle of a te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Banda Arc
The Banda Arc (main arc, Inner, and Outer) is a set of island arcs in eastern Indonesia. It is the result of the collision of a continent and an intra-oceanic island arc. The presently active arc is located on what appears to be oceanic crust whereas the associated subduction trench is underlain by continental crust. The convergence of the Indo-Australian plates and Eurasia resulted in the formation of the Sunda and Banda island arcs. The transitional zone between the arcs is located south of Flores Island and is characterized by the change in the tectonic regime along the boundary. Terminology Some academic literature refers to the arcs by location – so that main arc can be referred to as the 'southern', the 'western' Situated at the centre of three converging and colliding major tectonic plates, Indo-Australia, Eurasia, Pacific, the Banda arc includes young oceanic crust enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian contine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Al Hajar Mountains
The Hajar Mountains ( ar, جِبَال ٱلْحَجَر, Jibāl al-Ḥajar, ''The Rocky Mountains'' or ''The Stone Mountains'') in northeastern Oman and also the eastern United Arab Emirates are the highest mountain range in the eastern Arabian peninsula. Also known as "Oman Mountains", they separate the low coastal plain of Oman from the high desert plateau, and lie inland from the Gulf of Oman. ''Al'' () means "the", and ''Ḥajar'' () means "stone" or "rock". So ''al-Ḥajar'' () is named as "the stone" or "the rock". Geology Orography and tectonic setting The Hajar Mountains extend for through the UAE and Oman. They are located on the north-east corner of the Arabian Plate, reaching from the Musandam Peninsula through to the east coast of Oman. The range is about wide, with Jabal Shams being the highest peak at 3,009 m (9,872 ft) in the central region of the mountains. Currently, the Arabian Plate is moving north relative to the Eurasian Plate at per ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
