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Slave Craton
The Slave Craton is an Archaean craton in the north-western Canadian Shield, in Northwest Territories and Nunavut. The Slave Craton includes the 4.03 Ga-old Acasta Gneiss which is one of the oldest dated rocks on Earth. Covering about , it is a relatively small but well-exposed craton dominated by ~2.73–2.63 Ga (billion years-old) greenstones and turbidite sequences and ~2.72–2.58 Ga plutonic rocks, with large parts of the craton underlain by older gneiss and granitoid units. The Slave Craton is one of the blocks that compose the Precambrian core of North America, also known as the palaeocontinent Laurentia. The exposed portion of the craton, called the Slave Province, comprises and has an elliptical shape that stretches NNE from Gros Cap on the Great Slave Lake to Cape Barrow on the Coronation Gulf and EW along latitude 64°N. It covers about and is bounded by Palaeoproterozoic belts to the south, east, and west, while younger rocks cover it to the north. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northwestern Canadian Shield
Northwestern or North-western or North western may refer to: * Northwest, a direction * Northwestern University, a private research university in Evanston, Illinois ** The Northwestern Wildcats, this school's intercollegiate athletic program ** Northwestern Medicine, an academic medical system comprising: *** Northwestern University Feinberg School of Medicine *** Northwestern Memorial Hospital. Other colleges and universities * Northwestern College (Iowa), a small Christian college in Iowa * University of Northwestern – St. Paul (formerly Northwestern College), a small Christian college, located in Roseville, Minnesota * The former Northwestern College in Watertown, Wisconsin, which was incorporated into Martin Luther College in New Ulm, Minnesota in 1995 * Northwestern Michigan College, a small college located in Traverse City, Michigan * Northwestern Oklahoma State University in Alva, Oklahoma * Northwestern State University, in Natchitoches, Louisiana * Northwestern Calif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronation Gulf
Coronation Gulf lies between Victoria Island and mainland Nunavut in Canada. To the northwest it connects with Dolphin and Union Strait and thence the Beaufort Sea and Arctic Ocean; to the northeast it connects with Dease Strait and thence Queen Maud Gulf. The northwest point is Cape Krusenstern (not the Cape Krusenstern in Alaska). South of that is Richardson Bay and the mouths (from west to east) of the Rae River, Richardson River and the large Coppermine River, Napaaktoktok River, and the Asiak River. The Tree River enters at the south center. At the southeast end is the large Bathurst Inlet Bathurst Inlet, officially Kiluhiqtuq, is a deep inlet located along the northern coast of the Canadian mainland, at the east end of Coronation Gulf, into which the Burnside and Western rivers empty. The name, or its native equivalent ''Kingo .... At the northeast end is Cape Flinders on the Kent Peninsula. In the center of the gulf lies the Duke of York Archipelago. The gulf was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratovolcano
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as . Stratovolcanoes are sometimes called composite volcanoes because of their composite stratified structure, built up from sequential outpourings of erupted materials. They are among the most common types of volcanoes, in contrast to the less common shield volca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Back River Volcanic Complex
The Back River volcanic complex is an Archean stratovolcano spanning the Northwest Territories– Nunavut border in Northern Canada. It is located northwest of Yellowknife and to the northwest of the Back River from which it takes its name. The volcano constitutes the Back Group of the Yellowknife Supergroup and is somewhat anomalous in the Slave craton because it has undergone only a low degree of deformation and is subhorizontal. The southern half of the complex is exposed at the crest of a small dome. This is the eroded portion of the stratovolcano that has been preserved in an upright position. The complex comprises four volcanic sedimentary sequences (Innerring, Thlewyco, Boucher-Regan, Kelsh) that correspond to the phases of growth and destruction of this stratovolcano. Innerring The Innerring sequence, which constitutes the oldest rocks of the complex, represents the upper part of an eroded early phase of the volcano (U-Pb zircon igneous age of 2.708 Gigaannum (Ga)). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluton
In geology, an igneous intrusion (or intrusive body or simply 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. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequence (geology)
In geology, a sequence is a stratigraphic unit which is bounded by an unconformity at the top and at the bottom. Definition In a more rigorous and general way a sequence is defined as a "relatively conformable .. genetically related succession of strata bounded by unconformities or their correlative surfaces" Special cases and related concepts Special cases of sequences include type 1 sequences and type 2 sequence In sequence stratigraphy, a sub discipline of geology, type 1 sequences and type 2 sequences are special sequences In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set ...s. A related concept are parasequences. Contrary to their name they are not smaller sequences. See also * Catena (soil) References Sequence stratigraphy {{Geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supracrustal Rock
Supracrustal rocks (''supra'' (Latin for "above")) are Rock (geology), rocks that were Deposition (geology), deposited on the existing basement rocks of the crust (geology), crust, hence the name. They may be further Metamorphism, metamorphosed from both sedimentary (rock), sedimentary and volcanic rocks. The oldest minerals on Earth are Detritus (geology), detrital zircon grains from the Yilgarn Craton in the Mesoarchaean (3.2–2.8 Ga) Jack Hills, Western Australia dated to up to 4.4 Ga, meaning that granitic continental crust and probably supracrustal rocks formed during the Hadean, within 200 million years of Earth accretion. Most Hadean rocks were probably recycled into the mantle before the end of the eon, however, and such pre-4.0 Ga mineral inclusions, the only traces from the earliest rock formation on Earth, are rare. The Acasta Gneiss, Acasta orthogneisses of the Slave Craton, Canada, are regarded to be the oldest rocks on Earth, dated to 4.06 Ga, in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Detritus (geology)
Detritus (; adj. ''detrital'' ) is particles of rock derived from pre-existing rock through weathering and erosion.Essentials of Geology, 3rd Ed, Stephen Marshak, p G-7 A fragment of detritus is called a clast.Essentials of Geology, 3rd Ed, Stephen Marshak, p G-5 Detrital particles can consist of lithic fragments (particles of recognisable rock), or of monomineralic fragments (mineral grains). These particles are often transported through sedimentary processes into depositional systems such as riverbeds, lakes or the ocean, forming sedimentary successions. Diagenetic processes can transform these sediments into rock through cementation and lithification, forming sedimentary rocks such as sandstone. These rocks can then in turn again be weathered and eroded to form a second generation of sediment. Detrital grains commonly weather at different rates, according to the Goldich dissolution series The Goldich dissolution series is a method of predicting the relative stability or weatheri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabbro
Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt. Much of the Earth's oceanic crust is made of gabbro, formed at mid-ocean ridges. Gabbro is also found as plutons associated with continental volcanism. Due to its variant nature, the term ''gabbro'' may be applied loosely to a wide range of intrusive rocks, many of which are merely "gabbroic". By rough analogy, gabbro is to basalt as granite is to rhyolite. Etymology The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his descri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tonalite
Tonalite is an igneous, plutonic ( intrusive) rock, of felsic composition, with phaneritic (coarse-grained) texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with alkali feldspar making up less than 10% of the total feldspar content. Quartz (SiO2) is present as more than 20% of the total quartz-alkali feldspar-plagioclase-feldspathoid ( QAPF) content of the rock. Amphiboles and biotite are common accessory minerals. In older references tonalite is sometimes used as a synonym for quartz diorite. However the current IUGS classification defines tonalite as having greater than 20% quartz, while quartz diorite varies its quartz content from 5 to 20%. The name is derived from the type locality of tonalites, adjacent to the Tonale Line, a major structural lineament and mountain pass, Tonale Pass, in the Italian and Austrian Alps. The name was first applied by Gerhard vom Rath in 1864. The term ''adamellite'' was originally applied by A. Cathrein in 1890 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphic Rock
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] |
Protolith
A protolith () is the original, unmetamorphosed rock from which a given metamorphic rock is formed. For example, the protolith of a slate is a shale or mudstone. Metamorphic rocks can be derived from any other kind of non-metamorphic rock and thus there is a wide variety of protoliths. Identifying a protolith is a major aim of metamorphic geology. Protoliths are non-metamorphic rocks and have no protoliths themselves. The non-metamorphic rocks fall into two classes: sedimentary rocks, formed from sediment, and igneous rocks, formed from magma. The source of the sediment of a sedimentary rock is termed its provenance. Magmatic protoliths can be further divided into three categories: ultramafic rock, mafic rock, and quartzo-feldspathic rock. Similarly, sedimentary protoliths can be classified as quartzo-feldspathic, pelitic, carbonate rocks, or some mixture of the three. On a geological time scale, the first protoliths were first formed shortly after the formation of the Earth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
