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A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). 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.
The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.
Cerro Galán is a caldera in the Catamarca Province of Argentina. It is one of the largest exposed calderas in the world and forms part of the Central Volcanic Zone of the Andes, one of the three volcanic belts found in South America. One of several major caldera systems in the Central Volcanic Zone, the mountain is grouped into the Altiplano–Puna volcanic complex.
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.
In geology, an igneous intrusion is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California.
Pampa de Achala is a region that lies at the heart of the Sierras de Córdoba located within Sierras Pampeanas, and located in central-northwest of Argentina. It is a rugged area with little vegetation, lying over 1,500 m (4,900 ft) above sea level, and which has distinctive species, ecology, relief and hydrography. The region is a regional water reserve, and the source of the vast majority of streams that run through the Córdoba Province. Quebrada del Condorito National Park is in the region.
The Sierra de las Quijadas National Park is a national park located in the northwestern part of the Argentine province of San Luis. It was established on December 10, 1991, to protect the natural features, representative of the Semiarid Chaco and the High Monte ecoregions.
The Sierras Pampeanas is a geographical region of Argentina.
The Andean orogeny is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous and Oligocene were periods of re-arrangements in the orogeny. The details of the orogeny vary depending on the segment and the geological period considered.
The Cornubian batholith is a large mass of granite rock, formed about 280 million years ago, which lies beneath much of Cornwall and Devon in the south-western peninsula of Great Britain. The main exposed masses of granite are seen at Dartmoor, Bodmin Moor, St Austell, Carnmenellis, Land's End and the Isles of Scilly. The intrusion is associated with significant quantities of minerals particularly cassiterite, an ore of tin which has been mined since about 2000 BC. Other minerals include china clay and ores of copper, lead, zinc and tungsten.
The methods of pluton emplacement are the ways magma is accommodated in a host rock where the final result is a pluton. The methods of pluton emplacement are not yet fully understood, but there are many different proposed pluton emplacement mechanisms. Stoping, diapirism and ballooning are the widely accepted mechanisms. There is now evidence of incremental emplacement of plutons.
Córdoba is a province of Argentina, located in the center of the country. Its neighboring provinces are Santiago del Estero, Santa Fe, Buenos Aires, La Pampa, San Luis, La Rioja, and Catamarca. Together with Santa Fe and Entre Ríos, the province is part of the economic and political association known as the Center Region.
The Famatinian orogeny is an orogeny that predates the rise of the Andes and that took place in what is now western South America during the Paleozoic, leading to the formation of the Famatinian orogen also known as the Famatinian belt. The Famatinian orogeny lasted from the Late Cambrian to at least the Late Devonian and possibly the Early Carboniferous, with orogenic activity peaking about 490 to 460 million years ago. The orogeny involved metamorphism and deformation in the crust and the eruption and intrusion of magma along a Famatinian magmatic arc that formed a chain of volcanoes. The igneous rocks of the Famatinian magmatic arc are of calc-alkaline character and include gabbros, tonalites, granodiorites and trondhjemites. The youngest igneous rocks of the arc are granites.
Farallon Negro is a volcano in the Catamarca province of Argentina. Active between about 9-8 million years ago, it was formerly a stratovolcano or a multi vent volcano. Eventually, erosion removed most of the volcano and exposed the underlying structure including subvolcanic intrusions.
Kari-Kari is a Miocene caldera in the Potosi department, Bolivia. It is part of the El Fraile ignimbrite field of the Central Volcanic Zone of the Andes. Volcanic activity in the Central Volcanic Zone has generated 44 volcanic centres with postglacial activity and a number of calderas, including the Altiplano-Puna volcanic complex.
The Colangüil Batholith is a group of plutons in western Argentina between the latitudes of 29 and 31° S. The plutons of the batholith were emplaced and cooled in the Late Paleozoic and the Triassic. Runs in a north–south direction. The plutons of the batholith are intruded into volcanic rocks produced by the same plutons plus some earlier deformed basement. The most common rocks in the batholith are granodiorite, granite and leucogranite. The batholith contains also a dyke swarm of north–south trending dykes. Compared to other subduction-related batholiths around the Pacific Ocean Colangüil Batholith is more felsic.
The geology of the Isle of Man consists primarily of a thick pile of sedimentary rocks dating from the Ordovician period, together with smaller areas of later sedimentary and extrusive igneous strata. The older strata was folded and faulted during the Caledonian and Acadian orogenies The bedrock is overlain by a range of glacial and post-glacial deposits. Igneous intrusions in the form of dykes and plutons are common, some associated with mineralisation which spawned a minor metal mining industry.
The Achala Batholith is a group of plutons in the Sierras de Córdoba in central Argentina. With a mapped surface of over 2,500 square kilometres (970 sq mi) it constitutes the largest group of intrusions exposed in the Sierras Pampeanas. The oldest reference to the batholith dates to 1932.
Volcanic and igneous plumbing systems (VIPS) consist of interconnected magma channels and chambers through which magma flows and is stored within Earth's crust. Volcanic plumbing systems can be found in all active tectonic settings, such as mid-oceanic ridges, subduction zones, and mantle plumes, when magmas generated in continental lithosphere, oceanic lithosphere, and in the sub-lithospheric mantle are transported. Magma is first generated by partial melting, followed by segregation and extraction from the source rock to separate the melt from the solid. As magma propagates upwards, a self-organised network of magma channels develops, transporting the melt from lower crust to upper regions. Channelled ascent mechanisms include the formation of dykes and ductile fractures that transport the melt in conduits. For bulk transportation, diapirs carry a large volume of melt and ascent through the crust. When magma stops ascending, or when magma supply stops, magma emplacement occurs. Different mechanisms of emplacement result in different structures, including plutons, sills, laccoliths and lopoliths.
Córdoba Fault is a geological fault in central Argentina. The fault is dextral and makes up the boundary between the rocks of the Pampean Orogen and Río de la Plata Craton. It is considered by scientists an extension of the Trans Brazilian Lineament.
References
- 1 2 3 4 5 Pinotti, L.P.; Coniglio, J.E.; Esparza, A.M.; D'Eramo, F.J.; Llambías, E.J. (2002). "Nearly circular plutons emplaced by stoping at shallow crustal levels, Cerro Aspero batholith, Sierras Pampeanas de Córdoba, Argentina". Journal of South American Earth Sciences . 15 (2): 251–265. doi:10.1016/S0895-9811(02)00033-0.
- ↑ Coniglio, Jorge E.; D'eramo, Fernando J.; Pinotti, Lucio P.; Demartis, Manuel; Agulleiro Insúa, Leonardo A.; Petrelli, Hugo A. (2010). "Control estructural de las mineralizaciones de fluorita del batolito Cerro Áspero, Sierras Pampeanas de Córdoba". Revista de la Asociación Geológica Argentina (in Spanish). 67 (4).
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