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Overprinting (geology)
In this igneous rock texture has been overprinted by foliation (geology), foliation associated with metamorphism. Overprinting is a geology, geological process that superimposes a set of characteristics on rock that partially obscure earlier characteristics. Examples include metamorphic overprinting (superimposed metamorphism), in which new structure, texture, or mineral composition is imposed on existing rock. For example, the Tauern window of Alps contains beds that were originally metamorphosed to eclogite but have since been overprinted to the blueschist and then the greenschist facies. Likewise, deformation associated with the Mazatzal orogeny in Arizona and New Mexico, US, was subsequently overprinted by deformation associated with the Picuris orogeny. Geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry exte ...
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Orthogneiss Geopark
Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under pressures ranging from 2 to 15 kbar, sometimes even more, and temperatures over 300 °C (572 °F). Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which f ...
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Geology
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences, including hydrology. It is integrated with Earth system science and planetary science. Geology describes the structure of the Earth on and beneath its surface and the processes that have shaped that structure. Geologists study the mineralogical composition of rocks in order to get insight into their history of formation. Geology determines the relative ages of rocks found at a given location; geochemistry (a branch of geology) determines their absolute ages. By combining various petrological, crystallographic, and paleontological tools, geologists are able to chronicle the geological history of the Earth as a whole. One aspect is to demonstrate the age of the Earth. Geology provides evidence for plate tectonics, the ev ...
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Tauern Window
The Tauern Window is a geological structure in the Austrian Central Eastern Alps. It is a window (in German ''fenster'') in the Austroalpine nappes where high-grade metamorphic rocks of the underlying Penninic nappes crop out. The structure is caused by a large dome-like antiform in the nappe stacks of the Alps. The relatively hard rocks of the Tauern Window are more resistant to erosion, so the window has a high relief. The mountain chains thus formed are called the Hohe Tauern. Most of Austria's highest mountains are in the Hohe Tauern, among them the Großglockner (3798 m) and Großvenediger (3674 m). See also * References External links * * Geology of the Alps Structural geology Geology of Austria Geology of Italy Window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent ...
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Alps
The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia. The Alpine arch extends from Nice on the western Mediterranean Sea, Mediterranean to Trieste on the Adriatic Sea, Adriatic and Vienna at the beginning of the Pannonian Basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrust fault, thrusting and Fold (geology), folding into high mountain peaks such as Mont Blanc and the Matterhorn. Mont Blanc spans the French–Italian border, and at is the highest mountain in the Alps. The Alpine region area contains 82 peaks higher than List of Alpine four-thousanders, . The altitude and size of the range affect the climate in Europe; in the mountain ...
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Eclogite
Eclogite () is a metamorphic rock containing garnet ( almandine- pyrope) hosted in a matrix of sodium-rich pyroxene ( omphacite). Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, zoisite, dolomite, corundum and, rarely, diamond. The chemistry of primary and accessory minerals is used to classify three types of eclogite (A, B, and C). The broad range of eclogitic compositions has led to a longstanding debate on the origin of eclogite xenoliths as subducted, altered oceanic crust. The name ''eclogite'' is derived from the Ancient Greek word for 'choice' (, ), meaning 'chosen rock' on account of its perceived beauty. It was first named by René Just Haüy in 1822 in the second edition of his work ''Traité de minéralogie''. Origins Eclogites typically result from high to ultrahigh pressure metamorphism of mafic rock at low thermal gradients of < as it is subducted to the lower crust to

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Blueschist
Blueschist (), also called glaucophane schist, is a metavolcanic rock that forms by the metamorphism of basalt and similar rocks at relatively low temperatures () but very high overburden pressure, pressure corresponding to a depth of . The blue color of the rock comes from the presence of the predominant minerals glaucophane and lawsonite. This combination of low temperature occurring at significant depth can only be explained in the context of plate subduction, followed by exhumation (geology), exhumation, which accounts for the rarity of this rock. Blueschists are schists typically found within orogeny, orogenic belts as terranes of lithology in fault (geology), faulted contact with greenschist or rarely eclogite facies rocks. Petrology Blueschist, as a rock type, is defined by the presence of the minerals glaucophane + ( lawsonite or epidote ) +/- jadeite +/- albite or Chlorite group, chlorite +/- garnet +/- white mica, muscovite in a rock of roughly basaltic composition ...
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Greenschist
Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as Chlorite group, chlorite, Serpentine subgroup, serpentine, and epidote, and :wikt:platy, platy minerals such as muscovite and platy serpentine. The platiness gives the rock schistosity (a tendency to split into layers). Other common minerals include quartz, orthoclase, talc, carbonate minerals and amphibole (actinolite). Greenschist is a general field petrology, petrologic term for metamorphic rocks, metamorphic or altered mafic volcanic rock. In Europe, the term ''prasinite'' is sometimes used. A ''greenstone'' is sometimes a greenschist but can also be rock types without any schistosity, especially metabasalt (spilite). However, basalts may remain quite black if primary pyroxene does not revert to chlorite or actinolite. To qualify for the name, ...
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Metamorphic Facies
A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures.Essentials of Geology, 3rd Edition, Stephen Marshak The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and places in the geological history of the area. The boundaries between facies (and corresponding areas on the temperature v. pressure graph) are wide because they are gradational and approximate. The area on the graph corresponding to rock formation at the lowest values of temperature and pressure is the range of formation of sedimentary rocks, as opposed to metamorphic rocks, in a process called diagenesis. Historic definition The name ''facies'' was first used for specific sedimentary environments in sedimentary rocks by Swiss geologist Amanz Gre ...
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Mazatzal Orogeny
The Mazatzal orogeny was an orogenic event in what is now the Southwestern United States from 1650 to 1600 Mya in the Statherian Period of the Paleoproterozoic. Preserved in the rocks of New Mexico and Arizona, it is interpreted as the collision of the 1700-1600 Mya age Mazatzal island arc terrane with the proto-North American continent. This was the second in a series of orogenies within a long-lived convergent boundary along southern Laurentia that ended with the ca. 1200–1000 Mya Grenville orogeny during the final assembly of the supercontinent Rodinia, which ended an 800-million-year episode of convergent boundary tectonism. Description Age and isotope data show that southern North America is composed of a series of northeast-trending provinces representing island arc terranes accreted onto the 1800 Mya core of Laurentia. These are the Yavapai province (1800–1700 Mya), the Mazatzal province (1700–1650 Mya), the Granite-Rhyolite province (1500–1300 Mya), and t ...
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Arizona
Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the northwest and California to the west, and shares Mexico-United States border, an international border with the Mexican states of Sonora and Baja California to the south and southwest. Its Capital city, capital and List of largest cities, largest city is Phoenix, Arizona, Phoenix, which is the most populous state capital and list of United States cities by population, fifth most populous city in the United States. Arizona is divided into 15 List of counties in Arizona, counties. Arizona is the list of U.S. states and territories by area, 6th-largest state by area and the list of U.S. states and territories by population, 14th-most-populous of the 50 states. It is the 48th state and last of the contiguous United States, contiguous states to be a ...
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New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also borders the state of Texas to the east and southeast, Oklahoma to the northeast, and shares Mexico-United States border, an international border with the Mexican states of Chihuahua (state), Chihuahua and Sonora to the south. New Mexico's largest city is Albuquerque, and its List of capitals in the United States, state capital is Santa Fe, New Mexico, Santa Fe, the oldest state capital in the U.S., founded in 1610 as the government seat of Santa Fe de Nuevo México, Nuevo México in New Spain. It also has the highest elevation of any state capital, at . New Mexico is the List of U.S. states and territories by area, fifth-largest of the fifty states by area, but with just over 2.1 million residents, ranks List of U.S. states and terri ...
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Picuris Orogeny
The Picuris orogeny was an orogenic event in what is now the Southwestern United States from 1.43 to 1.3 billion years ago in the Calymmian Period of the Mesoproterozoic. The event is named for the Picuris Mountains in northern New Mexico and interpreted either as the suturing of the Granite-Rhyolite crustal province to the southern margin of the proto-North American continent Laurentia or as the final suturing of the Mazatzal crustal province onto Laurentia. According to the former hypothesis, this was the second in a series of orogenies within a long-lived convergent boundary along southern Laurentia that ended with the ca. 1200–1000 Mya Grenville orogeny during the final assembly of the supercontinent Rodinia, which ended an 800-million-year episode of convergent boundary tectonism. Description Age and isotope data show that southern North America is composed of a series of northeast-trending provinces representing island arc terranes accreted onto the 1800 Mya core of La ...
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