She introduces cross-hatching as an internal element in wheeling and receding shapes that recall igneous rocks scored with veins of quartz. |
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The mineralogical and textural alteration in the country rocks resulting from this heating by igneous bodies is called contact metamorphism. |
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Large tuff-filled clastic dykes invade volcaniclastic deposits associated with the Ferrar large igneous province. |
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The occurrence of these felsic extrusive igneous rocks potentially provides key information on the complex interplay of magmatism and tectonics. |
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Major crustal rifting has also played a part in the evolution of large bodies of Proterozoic sedimentary and igneous rocks. |
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Volcanic rocks of enormous thickness and deep-seated igneous intrusions from this period have created much of the geology of the Peruvian Andes. |
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During the past 250 million years, there have been 29 massive lava outpourings around the world, called large igneous provinces. |
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This transition coincides with an upsection increase in megaturbidite beds and increasing abundance of trace amounts of mafic igneous detritus. |
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While still on the parent body, much of the achondritic material was formed by igneous processes similar to those occurring on Earth today. |
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The igneous complex is composed of four steep-walled plutons separated by country rock septa and surrounded by a zone of small stocks and veins. |
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It has also been found in silica-poor igneous rocks, such as syenite, nepheline syenite, serpentinite, and lamprophyre. |
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The lava flow managed to spill over the cooled igneous rock but what little did was diverted away from the town. |
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The layering in these ultramafic rocks, and their position above mantle tectonites, is attributed to lower crustal igneous processes. |
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The crest of the Blue Ridge is usually underlain with Precambrian or Cambrian igneous rocks. |
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Conversely, there is during this time interval a general scarcity of erupted igneous rocks that can be reliably tied into relative stratigraphy. |
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Detrital quartz from an igneous source is usually substantially brighter in luminescence than quartz of an authigenic origin. |
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The three mountainous areas consist of large cores of igneous rocks surrounded by larger areas of metamorphic rocks, mostly schists and gneiss. |
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They were primarily studying the igneous rocks in the region but still managed to bag a few good fossils. |
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A Maori warrior made his mere of greenstone, an igneous rock, and ground one side to a sharp edge. |
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Mafic dike suites within Mesozoic igneous provinces of New England and Atlantic Canada. |
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Most of these are on igneous and metamorphic rock to minimize groundwater losses. |
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The basement of the Precordillera and Chilenia terranes are Grenville-age igneous and metamorphic rocks. |
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Two facies of regionally metamorphosed rocks that may be of either original sedimentary or igneous derivation are characterized by epidote. |
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Major shear zones containing basic and ultrabasic igneous rocks are interpreted as suture zones. |
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Weathered igneous and metamorphic rocks generally result in stony, well-drained, and relatively unfertile soils. |
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As an added bonus, the lava would simultaneously pave roads and sidewalks when it hardens into a glassy smooth surface of igneous rock. |
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On the basis of their morphology, they are interpreted to be late-stage igneous grains. |
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Petrogenesis Igneous petrogenesis is the process or set of processes by which igneous rocks are formed. |
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The intrusion is cut by other igneous rocks of uncertain age which could be late Caledonian. |
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A swarm of mafic igneous dikes have intruded the Estes pegmatite and make a showy display in the quarry face. |
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They probably represent the time of igneous emplacement of the granitic source rocks. |
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However, enormous emphasis has been placed on them for understanding igneous processes and the evolution of Earth. |
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They contain kilometre-scale blocks of igneous basement rocks, plucked by the rising diapir from the footwall of the fault. |
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Rhyme, in particular, lay on a major NE-trending fault and local igneous activity may have provided the energy to sustain the hot springs. |
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Below the lowest sheet of largely coherent mafic igneous rocks is the Phyllite-Quartzite Group, a sequence of turbidites and black mudrocks. |
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It is an igneous or fiery aura, not indeed in the open act of combustion, but composed of the finest and most minute particles of a peculiar species of elementary fire. |
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The established idea that granitoid magmas ascend through the continental crust as diapirs is being increasingly questioned by igneous and structural geologists. |
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The ophiolite contains a complete igneous stratigraphy of serpentinized ultramafics, gabbro, sheeted dykes and pillow lavas, as described by Moores. |
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Other fragments of igneous rock occur rarely and include granite, volcanic acidintermediate clasts with aphanitic texture and rounded fragments of silicified ash. |
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Extrusive igneous activity dominates the northwestern flank of the trough. |
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In common with other work on the western UK basins system, igneous underplating is invoked as the principal mechanism driving the epeirogenic uplift. |
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Evidently, the wealth of minerals found at Brumado is related to the intrusion of igneous dikes and subsequent associated hydrothermal mineralization. |
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These igneous rocks record the extensive magmatism that resulted from northward subduction of Neotethyan oceanic lithosphere beneath the Lhasa terrane. |
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The northwestern parts of La Hague comprise a suite of igneous units ranging in composition from diorite to granite monzonite collectively termed the Northern Granites. |
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The U content of these metamorphic baddeleyites is towards the low end of the range seen in igneous baddeleyite, but not sufficiently different to be diagnostic. |
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The grain size of an igneous rock depends upon the rate of cooling. |
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In other areas, large igneous rock formations of the Middle Silurian arose, such as those in Central Europe, as well as light sedimentation throughout the Baltic region. |
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This model has many similarities to published models of igneous feeder systems, which have traditionally been syntheses of a number of separate field exposures. |
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Overthrusting, volcanism, and plutonic igneous intrusion were identified as originating above the subduction zone where one plate is forced beneath the edge of its neighbour. |
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Aligned igneous minerals of euhedral potassium feldspar, plagioclase, biotite and hornblende in an undeformed quartz matrix define a magmatic foliation. |
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Basement rocks crop out along the entire La Hague peninsula in a number of fault-bounded blocks and as thin layers separated by intrusive Cadomian igneous bodies. |
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Clayey gravel or gravel, and crushed igneous rocks are commonly used as pavement materials, and cementitious binders are the main stabilising agents. |
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The regional physiognomy is characterized by broad ridges and rugged dissected stream valleys cutting through sedimentary rocks and scattered igneous knobs. |
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Within the gaunt pinnacles, in colours that represent ores and igneous rock, Ancient Egyptians, Semites and Nabataeans have left evidence of passage. |
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Narrow vertical fluid and gas escape pipes are a feature of some igneous systems and have been linked to mud volcano evolution in other sedimentary basins. |
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All of these factors are likely to be important in the case of the Besdegirmen rocks, and hence igneous crystallization ages may be greater than measured radiometric ages. |
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Although closely associated with plutonic igneous rocks, porphyry mineralization commonly encompasses large volumes of the surrounding host rocks to the intrusion. |
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An exception may be its type locality in Colombia, where it occurs in veinlets and pockets in carbonaceous sedimentary units apparently distant from igneous rocks. |
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The only known igneous rocks in the area are Permian periodotite and lamprophyre dikes as well as diatremes of ultramafic composition associated with the Fluorite district. |
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In contrast, the mineralized zones, above the topography created by the pre-mineralization igneous rocks, were not affected by this catastrophic sedimentation. |
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A volcanic or igneous breccia forms during eruptive activities. |
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Paleoproterozoic igneous and metamorphic rocks along with Paleozoic sedimentary rocks make up the basement complex of the San Juan Mountains of southwestern Colorado. |
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These metamorphic and plutonic igneous rocks form the uplifted core of the broadly anticlinal Owl Creek Mountains, a mountain range that formed during the Late Cretaceous. |
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A volcanic eruption, or magma rising and cooling close to the Earth's surface, will cause the formation of a wide variety of igneous rock crystals. |
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At Fort Lewis, the habitat is montane shrubland superimposed on intrusive igneous rocks forming laccoliths. |
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Alteration consists of several highly silicified igneous breccia bodies surrounded by sericite and clay-altered intrusive rocks. |
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Of the high-silica, coarse-grained, quartz-rich igneous rocks, granodiorites are quantitatively the most important. |
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The special edition also comes with three exclusive metallic paint finishes, silver steel, igneous grey and eclipse black. |
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Hoskin P, Schaltegger U The composition of zircon and igneous and metamorphic petrogenesis. |
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Especially noteworthy in thin section is the scarcity of potassium feldspar in any of the igneous clast types in this section. |
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The intent is to illustrate differences between extrusive and intrusive igneous textures. |
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Mafic igneous rocks with microlithic to intergranular texture are ubiquitous but less abundant than more felsic compositions. |
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Later intrusions have formed individual outcrops of igneous rock in each of these groups. |
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Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. |
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In addition there are infrequent outcrops of igneous rocks including lavas, tuffs and volcanic vent agglomerates. |
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This created some of the large caledonian igneous provinces throughout the Scottish Highlands. |
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These are in turn intruded by igneous dykes arranged radially around the Cheviot pluton. |
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Luca is now usually placed deep underground, in a fissure in hot igneous rocks, where she fed on sulphur, iron, hydrogen and carbon. |
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The Rocky Mountains expose igneous and metamorphic rock both from the Precambrian and from the Phanerozoic eon. |
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Quartz is a defining constituent of granite and other felsic igneous rocks. |
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The central cores of major mountain ranges consist of intrusive igneous rocks, usually granite. |
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Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. |
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Basalt is a common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus. |
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Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body. |
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All other minerals present are regarded as nonessential in almost all igneous rocks and are called accessory minerals. |
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Types of igneous rocks with other essential minerals are very rare, and these rare rocks include those with essential carbonates. |
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The following table is a simple subdivision of igneous rocks according to both their composition and mode of occurrence. |
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These are the elements that combine to form the silicate minerals, which account for over ninety percent of all igneous rocks. |
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The chemistry of igneous rocks is expressed differently for major and minor elements and for trace elements. |
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The river valley largely comprises alluvium deposits and there are also igneous intrusions of olivine dolerite throughout the area. |
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All three types may melt again, and when this happens, new magma is formed, from which an igneous rock may once more crystallize. |
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Deformational events are often also associated with volcanism and igneous activity. |
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Volcanic ashes and lavas accumulate on the surface, and igneous intrusions enter from below. |
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Dikes, long, planar igneous intrusions, enter along cracks, and therefore often form in large numbers in areas that are being actively deformed. |
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This research can be extrapolated to the field to understand metamorphic processes and the conditions of crystallization of igneous rocks. |
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Magnetic stratigraphers look for signs of magnetic reversals in igneous rock units within the drill cores. |
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This technique is used to date sequences that generally lack fossils or interbedded igneous rocks. |
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Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. |
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Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, the plane of juncture is a nonconformity. |
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Among the igneous dykes cutting the granite are a small number composed of a unique orthophyre. |
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Instead, the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion. |
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These igneous rocks are intruded into the Leverburgh and Langevat supracrustals. |
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These two belts of metasediments flank the South Harris igneous complex, and form the largest outcrop of such rocks in the Outer Hebrides. |
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Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. |
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In contrast to igneous and metamorphic rocks, a sedimentary rock usually contains very few different major minerals. |
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However, the origin of the minerals in a sedimentary rock is often more complex than in an igneous rock. |
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Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants. |
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The continental crust consists of lower density material such as the igneous rocks granite and andesite. |
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Most of this salt was released from volcanic activity or extracted from cool igneous rocks. |
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It is composed of a metamorphic and igneous platform which is the basis of the continental shield. |
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The FTFZ is flanked by two negative gravity anomalies associated with the accretion of igneous crust. |
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Volcanic passive margins they also are marked by numerous dykes and igneous intrusions within the subsided continental crust. |
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In addition, mantle plumes may heat the lithosphere and cause prodigious igneous activity. |
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The transitional crust of volcanic margins is composed of basaltic igneous rocks, including lava flows, sills, dykes, and gabbro. |
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The resulting large igneous province is, in area covered, the most extensive on earth. |
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The hotspot pairs include a large igneous province with continental volcanism opposite an oceanic hotspot. |
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There are a number of well documented examples of large igneous provinces identified by geological research. |
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Volcanic rifted margins are found on the boundary of large igneous provinces. |
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The correlation between gigantic volcanic events expressed in the large igneous provinces and mass extinctions was shown for the last 260 Myr. |
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Such dike swarms may form a large igneous province and are the roots of a volcanic province. |
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It has become especially useful to metamorphic and igneous geologists where index fossils are seldom available. |
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Granite has a felsic composition and is more common in recent geologic time in contrast to Earth's ultramafic ancient igneous history. |
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Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. |
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These igneous rocks consists of serpentine, greenstone and basalt, typical of rocks in southeastern regions of the Arabian Peninsula. |
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Many igneous rocks also contain the sulfide minerals pyrrhotite and pentlandite. |
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They are usually studied in the context of igneous petrology, although they are sometimes described using sedimentological terms. |
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The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. |
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A body of intrusive igneous rock which crystallizes from magma cooling underneath the surface of the Earth is called a pluton. |
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The Whin Sill or Great Whin Sill is a tabular layer of the igneous rock dolerite in County Durham and Northumberland in the northeast of England. |
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Plutons include batholiths, stocks, dikes, sills, laccoliths, lopoliths, and other igneous formations. |
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In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption. |
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A xenocryst is an individual foreign crystal included within an igneous body. |
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Andesite is an aphanitic and extrusive igneous rock composed of the Na-rich plagioclase, pyroxene and amphibole. |
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Zircons are part of the Earth's crust, which is found in igneous, sedimentary and metamorphic rocks. |
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The general ecosystem of the area is montane shrubland superimposed on intrusive igneous rocks forming laccoliths. |
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Olivine occurs in an ultra-basic igneous rock called dunite. |
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They are pecked or abraded on heavily jointed and fractured gabbro and granophyre igneous rock surfaces that have weathered into massive linear piles. |
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The north-east is occupied by the Oman mountains, a complex of igneous and metamorphic rocks emplaced by south-westerly directed thrusting in late Cretaceous times. |
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Although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in sedimentary rock. |
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As the intrusive igneous origin of the Whin Sill was determined in the 19th century, the term 'sill' was adopted by geologists for concordant, tabular intrusive bodies. |
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Compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. |
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But other hard and tough stones were used, such as igneous rocks from Penmaenmawr in North Wales, and similar working areas to Langdale have been found there. |
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Tuff can be classified as either sedimentary or igneous rocks. |
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When it has stopped moving, lava solidifies to form igneous rock. |
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Usually the area around the igneous rocks occur terobosaan remineralization process containing a very economical value such as tin and copper ore deposits. |
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This includes sedimentary bedding, faults and fractures, cuestas, igneous dikes and sills, metamorphic foliation and any other planar feature in the Earth. |
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The extrusive igneous rock equivalent of granite is rhyolite. |
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Trenches distant from an influx of continental sediments lack an accretionary prism, and the inner slope of such trenches is commonly composed of igneous or metamorphic rocks. |
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Volcanic margins form part of large igneous provinces, which are characterised by massive emplacements of mafic extrusives and intrusive rocks over very short time periods. |
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Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. |
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This sediment uplift was accompanied by igneous intrusions and volcanism. |
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Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains. |
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Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when the mud volcano is actually a vent of an igneous volcano. |
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An intrusive dike is an igneous body with a very high aspect ratio, which means that its thickness is usually much smaller than the other two dimensions. |
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A similar situation with igneous rocks occurs when xenoliths are found. |
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In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock. |
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These sedimentary sequences have been cut by igneous dykes and sills. |
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Granite and rhyolite are types of igneous rock commonly interpreted as products of the melting of continental crust because of increases in temperature. |
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Two important variables used for the classification of igneous rocks are particle size, which largely depends on the cooling history, and the mineral composition of the rock. |
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The classification of the many types of different igneous rocks can provide us with important information about the conditions under which they formed. |
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Extrusive igneous rocks, also known as volcanic rocks, are formed at the crust's surface as a result of the partial melting of rocks within the mantle and crust. |
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These rocks are largely igneous in origin, mixed with metamorphosed marble, quartzite and mica schist and intruded by later basaltic dykes and granite magma. |
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The Hebrides have a diverse geology ranging in age from Precambrian strata that are amongst the oldest rocks in Europe to Paleogene igneous intrusions. |
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Geologically the region is divided into the largely igneous and metamorphic west and sedimentary east, the dividing line slightly to the west of the River Exe. |
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In the far west, around County Galway and County Donegal, is a medium to high grade metamorphic and igneous complex of Caledonide affinity, similar to the Scottish Highlands. |
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It is interspersed with igneous intrusions of a more recent age, remnants of which formed mountain massifs such as the Cairngorms and Skye Cuillins. |
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