What Term Describes The Sizes, Shapes, And Arrangements Of Mineral Grains In An Igneous Rock?

Rock formed through the cooling and solidification of magma or lava

Igneous stone (derived from the Latin word ignis meaning fire), or magmatic rock, is i of the three primary rock types, the others existence sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava.

The magma can be derived from partial melts of existing rocks in either a planet'due south mantle or crust. Typically, the melting is caused by one or more of iii processes: an increment in temperature, a decrease in pressure, or a change in composition. Solidification into stone occurs either beneath the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to course granular, crystalline rocks, or without crystallization to class natural glasses.

Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended chaff and oceanic crust.

Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)

Geological significance

Igneous and metamorphic rocks make up ninety–95% of the peak 16 kilometres (ix.9 mi) of the Earth's crust past volume.^[1] Igneous rocks grade virtually fifteen% of the Globe'south current land surface.^{[note 1]} Most of the World'south oceanic chaff is made of igneous stone.

Igneous rocks are also geologically important because:

their minerals and global chemistry requite information about the composition of the lower chaff or upper mantle from which their parent magma was extracted, and the temperature and pressure atmospheric condition that allowed this extraction;^[3]
their absolute ages tin be obtained from various forms of radiometric dating and can exist compared to next geological strata, thus permitting scale of the geological fourth dimension calibration;^[4]
their features are normally characteristic of a specific tectonic environs, assuasive tectonic reconstructions (see plate tectonics);
in some special circumstances they host important mineral deposits (ores): for example, tungsten, can,^[5] and uranium^[6] are commonly associated with granites and diorites, whereas ores of chromium and platinum are usually associated with gabbros.^[vii]

Geological setting

Germination of igneous rock

Igneous rocks can be either intrusive (plutonic and hypabyssal) or extrusive (volcanic).

Intrusive

Intrusive igneous rocks make up the majority of igneous rocks and are formed from magma that cools and solidifies within the crust of a planet. Bodies of intrusive stone are known as intrusions and are surrounded past pre-existing stone (chosen land rock). The country rock is an excellent thermal insulator, then the magma cools slowly, and intrusive rocks are coarse-grained (phaneritic). The mineral grains in such rocks can generally exist identified with the naked eye. Intrusions can exist classified co-ordinate to the shape and size of the intrusive body and its relation to the bedding of the country rock into which it intrudes. Typical intrusive bodies are batholiths, stocks, laccoliths, sills and dikes. Mutual intrusive rocks are granite, gabbro, or diorite.

The key cores of major mount ranges consist of intrusive igneous rocks. When exposed by erosion, these cores (chosen batholiths) may occupy huge areas of the Globe's surface.

Intrusive igneous rocks that form at depth within the crust are termed plutonic (or abyssal) rocks and are normally coarse-grained. Intrusive igneous rocks that form about the surface are termed subvolcanic or hypabyssal rocks and they are usually much effectively-grained, oftentimes resembling volcanic stone.^[8] Hypabyssal rocks are less mutual than plutonic or volcanic rocks and oftentimes form dikes, sills, laccoliths, lopoliths, or phacoliths.

Extrusive

Extrusive igneous rock is made from lava released by volcanoes

Sample of basalt (an extrusive igneous rock), found in Massachusetts

Extrusive igneous stone, too known as volcanic rock, is formed by the cooling of molten magma on the earth'south surface. The magma, which is brought to the surface through fissures or volcanic eruptions, quickly solidifies. Hence such rocks are fine-grained (aphanitic) or even burnished. Basalt is the most common extrusive igneous rock^[nine] and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to class long polygonal columns. The Giant'due south Causeway in Antrim, Northern Ireland is an instance.

The molten rock, which typically contains suspended crystals and dissolved gases, is chosen magma.^[10] It rises because it is less dense than the rock from which information technology was extracted.^[11] When magma reaches the surface, it is called lava.^[12] Eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of submarine volcanic activity.^[thirteen]

The volume of extrusive rock erupted annually by volcanoes varies with plate tectonic setting. Extrusive stone is produced in the following proportions:^[14]

divergent boundary: 73%
convergent boundary (subduction zone): 15%
hotspot: 12%.

The behaviour of lava depends upon its viscosity, which is adamant by temperature, composition, and crystal content. High-temperature magma, most of which is basaltic in composition, behaves in a fashion similar to thick oil and, every bit information technology cools, treacle. Long, sparse basalt flows with pahoehoe surfaces are common. Intermediate composition magma, such every bit andesite, tends to form cinder cones of intermingled ash, tuff and lava, and may have a viscosity similar to thick, cold molasses or fifty-fifty safety when erupted. Felsic magma, such as rhyolite, is usually erupted at depression temperature and is up to 10,000 times every bit viscous as basalt. Volcanoes with rhyolitic magma unremarkably erupt explosively, and rhyolitic lava flows are typically of limited extent and have steep margins considering the magma is so viscid.^[15]

Felsic and intermediate magmas that erupt often exercise so violently, with explosions driven by the release of dissolved gases—typically water vapour, just too carbon dioxide. Explosively erupted pyroclastic cloth is called tephra and includes tuff, agglomerate and ignimbrite. Fine volcanic ash is also erupted and forms ash tuff deposits, which tin can oft comprehend vast areas.^[16]

Considering volcanic rocks are mostly fine-grained or glassy, it is much more hard to distinguish betwixt the different types of extrusive igneous rocks than between different types of intrusive igneous rocks. Generally, the mineral constituents of fine-grained extrusive igneous rocks can only be adamant by examination of thin sections of the rock under a microscope, so only an approximate classification can usually be fabricated in the field. Although nomenclature by mineral makeup is preferred by the IUGS, this is often impractical, and chemical classification is done instead using the TAS nomenclature.^[17]

Nomenclature

Close-upward of granite (an intrusive igneous rock) exposed in Chennai, India

Igneous rocks are classified co-ordinate to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body.

The classification of the many types of igneous rocks can provide important information nigh the conditions under which they formed. Two important variables used for the nomenclature of igneous rocks are particle size, which largely depends on the cooling history, and the mineral composition of the rock. Feldspars, quartz or feldspathoids, olivines, pyroxenes, amphiboles, and micas are all important minerals in the formation of near all igneous rocks, and they are basic to the classification of these rocks. All other minerals nowadays are regarded as nonessential in almost all igneous rocks and are called accessory minerals. Types of igneous rocks with other essential minerals are very rare, but include carbonatites, which comprise essential carbonates.^[17]

In a simplified classification, igneous rock types are separated on the basis of the type of feldspar nowadays, the presence or absence of quartz, and in rocks with no feldspar or quartz, the blazon of iron or magnesium minerals nowadays. Rocks containing quartz (silica in limerick) are silica-oversaturated. Rocks with feldspathoids are silica-undersaturated, because feldspathoids cannot coexist in a stable association with quartz.^{[ citation needed ]}

Igneous rocks that have crystals big plenty to exist seen by the naked eye are called phaneritic; those with crystals too small-scale to be seen are called aphanitic. By and large speaking, phaneritic implies an intrusive origin; aphanitic an extrusive one.^{[ citation needed ]}

An igneous rock with larger, clearly discernible crystals embedded in a effectively-grained matrix is termed porphyry. Porphyritic texture develops when some of the crystals grow to considerable size before the main mass of the magma crystallizes as finer-grained, compatible material.^{[ citation needed ]}

Igneous rocks are classified on the basis of texture and limerick. Texture refers to the size, shape, and system of the mineral grains or crystals of which the rock is equanimous.^{[ commendation needed ]}

Texture

Texture is an of import criterion for the naming of volcanic rocks. The texture of volcanic rocks, including the size, shape, orientation, and distribution of mineral grains and the intergrain relationships, will determine whether the stone is termed a tuff, a pyroclastic lava or a simple lava. Even so, the texture is only a subordinate role of classifying volcanic rocks, as most oft at that place needs to exist chemic information gleaned from rocks with extremely fine-grained groundmass or from airfall tuffs, which may exist formed from volcanic ash.^{[ citation needed ]}

Textural criteria are less critical in classifying intrusive rocks where the majority of minerals will exist visible to the naked eye or at least using a hand lens, magnifying glass or microscope. Plutonic rocks also tend to exist less texturally varied and less prone to showing distinctive structural fabrics. Textural terms can be used to differentiate dissimilar intrusive phases of big plutons, for instance porphyritic margins to large intrusive bodies, porphyry stocks and subvolcanic dikes. Mineralogical classification is most often used to classify plutonic rocks. Chemical classifications are preferred to classify volcanic rocks, with phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite".^{[ citation needed ]}

Basic classification scheme for igneous rocks based on their mineral composition. If the approximate book fractions of minerals in the stone are known, the rock name and silica content tin can be read off the diagram. This is not an verbal method, because the classification of igneous rocks also depends on other components, yet in well-nigh cases information technology is a good first estimate.

Mineralogical classification

The IUGS recommends classifying igneous rocks by their mineral composition whenever possible. This is straightforward for fibroid-grained intrusive igneous rock, only may crave examination of thin sections nether a microscope for fine-grained volcanic stone, and may be impossible for glassy volcanic rock. The rock must then be classified chemically.^[18]

Mineralogical nomenclature of an intrusive rock begins past determining if the rock is ultramafic, a carbonatite, or a lamprophyre. An ultramafic rock contains more than than 90% of iron- and magnesium-rich minerals such as hornblende, pyroxene, or olivine, and such rocks have their own classification scheme. Likewise, rocks containing more than than l% carbonate minerals are classified as carbonatites, while lamprophyres are rare ultrapotassic rocks. Both are further classified based on detailed mineralogy.^[19]

In the great bulk of cases, the rock has a more typical mineral composition, with significant quartz, feldspars, or feldspathoids. Nomenclature is based on the percentages of quartz, alkali feldspar, plagioclase, and feldspathoid out of the total fraction of the rock composed of these minerals, ignoring all other minerals nowadays. These percentages identify the rock somewhere on the QAPF diagram, which often immediately determines the stone blazon. In a few cases, such as the diorite-gabbro-anorthite field, additional mineralogical criteria must be applied to make up one's mind the terminal nomenclature.^[19]

Where the mineralogy of an volcanic rock tin exist adamant, information technology is classified using the same procedure, only with a modified QAPF diagram whose fields correspond to volcanic rock types.^[19]

Chemical classification and petrology

Total alkali versus silica classification scheme (TAS) as proposed in Le Maitre's 2002 Igneous Rocks – A classification and glossary of terms^[20] Blue surface area is roughly where element of group i rocks plot; yellowish area is where subalkaline rocks plot.

When it is impractical to classify a volcanic stone by mineralogy, the rock must exist classified chemically.

There are relatively few minerals that are of import in the germination of mutual igneous rocks, because the magma from which the minerals crystallize is rich in simply certain elements: silicon, oxygen, aluminium, sodium, potassium, calcium, atomic number 26, and magnesium. These are the elements that combine to form the silicate minerals, which account for over ninety pct of all igneous rocks. The chemistry of igneous rocks is expressed differently for major and pocket-sized elements and for trace elements. Contents of major and pocket-size elements are conventionally expressed as weight percent oxides (east.chiliad., 51% SiO_two, and 1.50% TiO₂). Abundances of trace elements are conventionally expressed every bit parts per one thousand thousand by weight (e.g., 420 ppm Ni, and 5.1 ppm Sm). The term "trace element" is typically used for elements nowadays in most rocks at abundances less than 100 ppm or so, but some trace elements may be present in some rocks at abundances exceeding i,000 ppm. The multifariousness of rock compositions has been defined by a huge mass of analytical data—over 230,000 rock analyses can exist accessed on the web through a site sponsored by the U. S. National Science Foundation (see the External Link to EarthChem).^{[ commendation needed ]}

The single well-nigh of import component is silica, SiO_two, whether occurring equally quartz or combined with other oxides as feldspars or other minerals. Both intrusive and volcanic rocks are grouped chemically past total silica content into broad categories.

Felsic rocks accept the highest content of silica, and are predominantly composed of the felsic minerals quartz and feldspar. These rocks (granite, rhyolite) are commonly light coloured, and have a relatively low density.
Intermediate rocks have a moderate content of silica, and are predominantly composed of feldspars. These rocks (diorite, andesite) are typically darker in colour than felsic rocks and somewhat more than dense.
Mafic rocks have a relatively depression silica content and are composed more often than not of pyroxenes, olivines and calcic plagioclase. These rocks (basalt, gabbro) are usually dark coloured, and have a higher density than felsic rocks.
Ultramafic stone is very low in silica, with more than ninety% of mafic minerals (komatiite, dunite).

This classification is summarized in the following table:

	Composition
Mode of occurrence	Felsic (>63% SiO_two)	Intermediate (52% to 63% SiO₂)	Mafic (45% to 52% SiO₂)	Ultramafic (<45% SiO₂)
Intrusive	Granite	Diorite	Gabbro	Peridotite
Extrusive	Rhyolite	Andesite	Basalt	Komatiite

The percentage of alkali metal oxides (Na₂O plus K₂O) is second only to silica in its importance for chemically classifying volcanic rock. The silica and alkaline oxide percentages are used to identify volcanic rock on the TAS diagram, which is sufficient to immediately classify virtually volcanic rocks. Rocks in some fields, such as the trachyandesite field, are farther classified by the ratio of potassium to sodium (so that potassic trachyandesites are latites and sodic trachyandesites are benmoreites). Some of the more mafic fields are farther subdivided or defined by normative mineralogy, in which an idealized mineral composition is calculated for the rock based on its chemical composition. For example, basanite is distinguished from tephrite by having a loftier normative olivine content.

Other refinements to the basic TAS classification include:

Ultrapotassic – rocks containing molar Grand₂O/Na_iiO >3.
Peralkaline – rocks containing tooth (G_twoO + Na_twoO)/Al_iiO_iii >1.^[21]
Peraluminous – rocks containing molar (K_iiO + Na_twoO + CaO)/Al₂O_three <1.^[21]

In older terminology, silica oversaturated rocks were called silicic or acidic where the SiO₂ was greater than 66% and the family term quartzolite was applied to the almost silicic. A normative feldspathoid classifies a rock every bit silica-undersaturated; an example is nephelinite.

AFM ternary diagram showing the relative proportions of Na_iiO + K₂O (A for Alkali earth metals), FeO + Fe₂O₃ (F), and MgO (M) with arrows showing the path of chemical variation in tholeiitic and calc-alkaline series magmas

Magmas are further divided into three serial:

The tholeiitic series – basaltic andesites and andesites.
The calc-alkaline serial – andesites.
The alkaline series – subgroups of alkaline basalts and the rare, very high potassium-bearing (i.e. shoshonitic) lavas.

The element of group i serial is distinguishable from the other two on the TAS diagram, beingness higher in total alkali oxides for a given silica content, only the tholeiitic and calc-alkaline serial occupy approximately the same part of the TAS diagram. They are distinguished past comparing full alkali with atomic number 26 and magnesium content.^[22]

These iii magma series occur in a range of plate tectonic settings. Tholeiitic magma series rocks are plant, for case, at mid-sea ridges, back-arc basins, oceanic islands formed by hotspots, island arcs and continental big igneous provinces.^[23]

All three series are found in relatively close proximity to each other at subduction zones where their distribution is related to depth and the age of the subduction zone. The tholeiitic magma series is well represented above immature subduction zones formed past magma from relatively shallow depth. The calc-element of group i and element of group i series are seen in mature subduction zones, and are related to magma of greater depths. Andesite and basaltic andesite are the most abundant volcanic rock in island arc which is indicative of the calc-alkaline magmas. Some isle arcs have distributed volcanic series every bit can be seen in the Japanese isle arc system where the volcanic rocks change from tholeiite—calc-alkaline metal—alkaline with increasing distance from the trench.^[24] ^[25]

History of classification

Some igneous rock names engagement to before the modernistic era of geology. For example, basalt equally a clarification of a particular composition of lava-derived stone dates to Georgius Agricola in 1546 in his work De Natura Fossilium.^[26] The word granite goes back at least to the 1640s and is derived either from French granit or Italian granito, significant simply "granulate stone".^[27] The term rhyolite was introduced in 1860 by the German traveler and geologist Ferdinand von Richthofen^[28] ^[29] ^[thirty] The naming of new stone types accelerated in the 19th century and peaked in the early 20th century.^[31]

Much of the early nomenclature of igneous rocks was based on the geological age and occurrence of the rocks. Nevertheless, in 1902, the American petrologists Charles Whitman Cross, Joseph P. Iddings, Louis V. Pirsson, and Henry Stephens Washington proposed that all existing classifications of igneous rocks should be discarded and replaced by a "quantitative" classification based on chemic analysis. They showed how vague, and frequently unscientific, much of the existing terminology was and argued that equally the chemical limerick of an igneous rock was its well-nigh fundamental feature, it should be elevated to prime number position.^[32] ^[33]

Geological occurrence, construction, mineralogical constitution—the hitherto accepted criteria for the discrimination of rock species—were relegated to the background. The completed rock analysis is first to be interpreted in terms of the stone-forming minerals which might exist expected to be formed when the magma crystallizes, due east.g., quartz feldspars, olivine, akermannite, Feldspathoids, magnetite, corundum, and so on, and the rocks are divided into groups strictly according to the relative proportion of these minerals to one another.^[32] This new classification scheme created a sensation, but was criticized for its lack of utility in fieldwork, and the classification scheme was abandoned by the 1960s. Withal, the concept of normative mineralogy has endured, and the work of Cross and his coinvestigators inspired a flurry of new classification schemes.^[34]

Among these was the classification scheme of M.A. Peacock, which divided igneous rocks into four series: the alkalic, the alkali-calcic, the calc-alkali, and the calcic series.^[35] His definition of the alkali serial, and the term calc-alkali, keep in use as office of the widely used^[36] Irvine-Barager classification,^[37] forth with Westward.Q. Kennedy's tholeiitic series.^[38]

By 1958, there were some 12 separate nomenclature schemes and at to the lowest degree 1637 rock type names in use. In that twelvemonth, Albert Streckeisen wrote a review article on igneous stone nomenclature that ultimately led to the formation of the IUGG Subcommission of the Systematics of Igneous Rocks. By 1989 a unmarried system of classification had been agreed upon, which was further revised in 2005. The number of recommended rock names was reduced to 316. These included a number of new names promulgated by the Subcommission.^[31]

Origin of magmas

The Earth's chaff averages about 35 kilometres (22 mi) thick under the continents, but averages only some 7–x kilometres (four.3–6.ii mi) below the oceans. The continental crust is composed primarily of sedimentary rocks resting on a crystalline basement formed of a slap-up diverseness of metamorphic and igneous rocks, including granulite and granite. Oceanic crust is composed primarily of basalt and gabbro. Both continental and oceanic chaff rest on peridotite of the drapery.^{[ citation needed ]}

Rocks may cook in response to a decrease in pressure, to a change in composition (such every bit an addition of water), to an increase in temperature, or to a combination of these processes.^{[ commendation needed ]}

Other mechanisms, such as melting from a meteorite impact, are less important today, but impacts during the accession of the Earth led to all-encompassing melting, and the outer several hundred kilometers of our early Earth was probably an ocean of magma. Impacts of large meteorites in the last few hundred million years have been proposed as 1 mechanism responsible for the extensive basalt magmatism of several large igneous provinces.^{[ citation needed ]}

Decompression

Decompression melting occurs considering of a decrease in pressure level.^[39]

The solidus temperatures of most rocks (the temperatures below which they are completely solid) increment with increasing pressure level in the absence of h2o. Peridotite at depth in the Earth's mantle may be hotter than its solidus temperature at some shallower level. If such stone rises during the convection of solid pall, information technology will absurd slightly equally it expands in an adiabatic process, but the cooling is only almost 0.3 °C per kilometer. Experimental studies of appropriate peridotite samples document that the solidus temperatures increment by 3 °C to 4 °C per kilometer. If the rock rises far enough, it will begin to melt. Melt droplets can coalesce into larger volumes and be intruded upwards. This process of melting from the upward move of solid mantle is critical in the development of the Globe.^{[ citation needed ]}

Decompression melting creates the sea chaff at mid-ocean ridges. Information technology also causes volcanism in intraplate regions, such as Europe, Africa and the Pacific sea floor. There, information technology is variously attributed either to the rise of mantle plumes (the "Plume hypothesis") or to intraplate extension (the "Plate hypothesis").^[40]

Effects of h2o and carbon dioxide

The change of rock composition most responsible for the creation of magma is the improver of water. Water lowers the solidus temperature of rocks at a given pressure. For case, at a depth of nigh 100 kilometers, peridotite begins to melt near 800 °C in the presence of excess water, but almost or higher up about 1,500 °C in the absence of water.^[41] Water is driven out of the oceanic lithosphere in subduction zones, and information technology causes melting in the overlying curtain. Hydrous magmas composed of basalt and andesite are produced direct and indirectly as results of aridity during the subduction process. Such magmas, and those derived from them, build up island arcs such every bit those in the Pacific Ring of Burn down. These magmas form rocks of the calc-alkaline series, an of import part of the continental crust.^{[ citation needed ]}

The addition of carbon dioxide is relatively a much less important crusade of magma germination than the addition of water, just genesis of some silica-undersaturated magmas has been attributed to the potency of carbon dioxide over water in their drapery source regions. In the presence of carbon dioxide, experiments document that the peridotite solidus temperature decreases by near 200 °C in a narrow pressure level interval at pressures corresponding to a depth of most 70 km. At greater depths, carbon dioxide can take more effect: at depths to about 200 km, the temperatures of initial melting of a carbonated peridotite composition were adamant to exist 450 °C to 600 °C lower than for the aforementioned composition with no carbon dioxide.^[42] Magmas of rock types such as nephelinite, carbonatite, and kimberlite are among those that may exist generated following an influx of carbon dioxide into mantle at depths greater than about 70 km.^{[ commendation needed ]}

Temperature increase

Increase in temperature is the almost typical mechanism for formation of magma within continental chaff. Such temperature increases can occur because of the upward intrusion of magma from the drapery. Temperatures can besides exceed the solidus of a crustal rock in continental chaff thickened by pinch at a plate boundary. The plate boundary between the Indian and Asian continental masses provides a well-studied instance, every bit the Tibetan Plateau just north of the boundary has crust about lxxx kilometers thick, roughly twice the thickness of normal continental crust. Studies of electrical resistivity deduced from magnetotelluric data take detected a layer that appears to comprise silicate melt and that stretches for at least one,000 kilometers within the middle crust along the southern margin of the Tibetan Plateau.^[43] Granite and rhyolite are types of igneous rock commonly interpreted as products of the melting of continental crust because of increases in temperature. Temperature increases also may contribute to the melting of lithosphere dragged downward in a subduction zone.^{[ commendation needed ]}

Magma evolution

Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition considering different minerals crystallize from the cook. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.

Nearly magmas are fully melted only for small parts of their histories. More than typically, they are mixes of cook and crystals, and sometimes also of gas bubbles. Cook, crystals, and bubbles usually have different densities, and then they can divide as magmas evolve.

As magma cools, minerals typically crystallize from the melt at different temperatures (partial crystallization). Every bit minerals crystallize, the composition of the residual melt typically changes. If crystals split up from the melt, and so the balance melt will differ in composition from the parent magma. For instance, a magma of gabbroic composition can produce a residue melt of granitic composition if early on formed crystals are separated from the magma. Gabbro may have a liquidus temperature nigh ane,200 °C, and the derivative granite-composition melt may take a liquidus temperature as low as about 700 °C. Incompatible elements are concentrated in the last residues of magma during partial crystallization and in the first melts produced during partial melting: either process can form the magma that crystallizes to pegmatite, a stone blazon commonly enriched in incompatible elements. Bowen's reaction series is of import for understanding the idealised sequence of partial crystallisation of a magma. Clinopyroxene thermobarometry is used to make up one's mind temperature and pressure level atmospheric condition at which magma differentiation occurred for specific igneous rocks.^{[ citation needed ]}

Magma composition tin can be determined by processes other than partial melting and fractional crystallization. For case, magmas normally interact with rocks they intrude, both by melting those rocks and past reacting with them. Magmas of dissimilar compositions can mix with one another. In rare cases, melts can dissever into ii immiscible melts of contrasting compositions.^{[ citation needed ]}

Etymology

The word igneous is derived from the Latin ignis, meaning "of fire". Volcanic rocks are named after Vulcan, the Roman name for the god of burn. Intrusive rocks are too called "plutonic" rocks, named after Pluto, the Roman god of the underworld.^{[ citation needed ]}

Gallery

A "skylight" pigsty, nigh 6 k (xx ft) across, in a solidified lava crust reveals molten lava below (flowing towards the tiptop right) in an eruption of Kīlauea in Hawaii
Devils Tower, an eroded laccolith in the Black Hills of Wyoming
A pour of molten lava flowing into Aloi Crater during the 1969-1971 Mauna Ulu eruption of Kilauea volcano
A laccolith of granite (light-coloured) that was intruded into older sedimentary rocks (dark-coloured) at Cuernos del Paine, Torres del Paine National Park, Chile
An igneous intrusion cutting by a pegmatite dike, which in plough is cut by a dolerite dike

Come across besides

List of rock types – List of rock types recognized by geologists
Metamorphic stone – Rock that was subjected to rut and force per unit area
Migmatite – Mixture of metamorphic rock and igneous rock
Petrology – Branch of geology that studies the origin, composition, distribution and structure of rocks
Sedimentary stone – Rock formed past the deposition and subsequent cementation of cloth

Notes

^ 15% is the arithmetic sum of the area for intrusive plutonic stone (7%) plus the expanse for extrusive volcanic stone (8%).^[ii]

References

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^ Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Printing. pp. 356–361. ISBN978-0-521-88006-0.
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^ Philpotts & Ague 2009, p. 96, 387-388.
^ Philpotts & Ague 2009, p. 139.
^ Philpotts & Ague 2009, pp. 52–59.
^ Philpotts & Ague 2009, pp. nineteen–26.
^ Philpotts & Ague 2009, pp. 28–35.
^ Schmincke, Hans-Ulrich (2003). Volcanism. Berlin: Springer. p. 295. doi:10.1007/978-iii-642-18952-4. ISBN978-three-540-43650-eight. S2CID 220886233.
^ Philpotts & Ague 2009, pp. 365–374.
^ Fisher, Richard Five.; Schmincke, H.-U. (1984). Pyroclastic rocks. Berlin: Springer-Verlag. p. v. ISBN3-540-12756-9.
^ Philpotts & Ague 2009, pp. 23–26, 59–73.
^ Philpotts & Ague 2009, pp. 73–77.
^ ^a ^b Philpotts & Ague 2009, pp. 139–143.
^ Le Bas, Yard. J.; Streckeisen, A. Fifty. (1991). "The IUGS systematics of igneous rocks". Journal of the Geological Society. 148 (5): 825–833. Bibcode:1991JGSoc.148..825L. CiteSeerX10.ane.1.692.4446. doi:ten.1144/gsjgs.148.5.0825. S2CID 28548230.
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External links

USGS Igneous Rocks Archived 21 February 2013 at the Wayback Auto
Igneous stone classification flowchart
Igneous Rocks Tour, an introduction to Igneous Rocks
The IUGS systematics of igneous rocks