Volcanoes/Volcanic rocks

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The diagram shows a classification and flow characteristics of volcanic rocks. Credit: J. Johnson (USGS).

"The behavior of a lava flow depends primarily on its viscosity (resistance to flow), slope of the ground over which it travels, and the rate of lava eruption. Because basalt contains the least amount of silica and erupts at the highest temperature compared to the other types of lava, it has the lowest viscosity (the least resistance to flow). Thus, basalt lava moves over the ground easily, even down gentle slopes. Dacite and rhyolite lava, however, tend to pile up around a vent to form short, stubby flows or mound-shaped domes."[1]

Igneous rocks[edit]

Samples of various igneous rocks from the Arequipa region of Peru are shown. Credit: Rojinegro81.

"An igneous rock is formed by the cooling and crystallization of molten rock."[1]

Igneous "rocks [are divided] into two broad categories based on where the molten rock solidified."[1]

The image on the right shows a collection of various igneous rocks: from top left to bottom right these are: granodiorite, andesite, syenite, gabbro, rhyolite, basalt, granite and an ignimbrite (a collective term for a special type of volcaniclastic sediment).

Andesites[edit]

Close view is of andesite lava flow from Brokeoff Volcano, California. Credit: United States of America Geological Survey.

Def. a "class of fine-grained intermediate [..] rock [...] containing mostly plagioclase feldspar"[2] is called an andesite.

"Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende. At the lower end of the silica range, andesite lava may also contain olivine. Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several km in length. Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100° C."[3]

Anorthosites[edit]

This is a piece of anorthosite from Tamil Nadu, India. Credit: Thamizhpparithi Maari.

Def. a "phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar"[4] is called an anorthite.

Aplites[edit]

This is an aplite sample from the NASA Rocklibrary. Credit: NASA.

Def. a "fine-grained granitic rock composed mostly of quartz and feldspars"[5] is called an aplite.

Basalts[edit]

This is an example of a basalt. Credit: USGS.

Def. a "hard mafic [...] rock of varied mineral content"[6] is called a basalt.

"Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt's low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move > 20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns. Basaltic lava fountains and fissure eruptions, however, still form explosive fountains hundreds of meters tall. Common minerals in basalt include olivine, pyroxene, and plagioclase. Basalt is erupted at temperatures between 1100 to 1250° C."[7]

"Basalt is the most common rock type in the Earth's crust (the outer 10 to 50 km). In fact, most of the ocean floor is made of basalt."[7]

"Huge outpourings of lava called "flood basalts" are found on many continents. The Columbia River basalts, erupted 15 to 17 million years ago, cover most of southeastern Washington and regions of adjacent Oregon and Idaho."[7]

"Basaltic magma is commonly produced by direct melting of the Earth's mantle, the region of the Earth below the outer crust. On continents, the mantle begins at depths of 30 to 50 km."[7]

"Shield volcanoes, such as those that make up the Islands of Hawai`i, are composed almost entirely of basalt."[7]

Benmoreites[edit]

Streckeisen's QAPF diagram is for a modal classification of volcanic rocks. Credit: -xfi-.

A "classification of volcanic rocks when modal analyses are lacking [...] is on a non-genetic basis using the total alkali-silica (TAS) diagram, and is as nearly consistent as possible with the [Quartz, Alkali feldspar, Plagioclase, Feldspathoid] QAPF modal classification. The diagram is divided into 15 fields, two of which contain two root names which are separated according to other chemical criteria, giving the following 17 root names: basalt, basaltic andesite, andesite, dacite, rhyolite, trachybasalt, basaltic trachyandesite, trachyandesite, trachyte, trachydacite, picrobasalt, basanite, tephrite, phonotephrite, tephriphonolite, phonolite and foidite. Using Na-K criteria, trachybasalt may be further divided into the sub-root names hawaiite and potassic trachybasalt, basaltic trachyandesite into the sub-root names mugearite and shoshonite, and trachyandesite into the sub-root names benmoreite and latite."[8]

Bostonites[edit]

A composite dyke cuts through the hard jointed blocks. Credit: Colin Smith.

Def. a "fine-grained, pale-colored, grey or pinkish intrusive rock, which consists essentially of alkali-feldspar"[9] is called a bostonite.

In the image on the right, a composite dyke cuts through the hard jointed blocks. It has a camptonite centre and bostonite borders.

"Magmatic zircon in the syenite (bostonite) part of a composite NE–SW-trending cogenetic bostonite–camptonite dyke in Orkney, Scotland, yields a laser ablation inductively coupled plasma mass spectrometry age of 313 ± 4 Ma and εHf(313 Ma) values of +6 to +11."[10]

Carbonatites[edit]

This carbonatite is from Jacupiranga Estado de São Paulo, Brazil. Credit: Eurico Zimbres.

Def. any "intrusive igneous rock having a majority of carbonate minerals"[11] is called a carbonatite.

The specimen in the image on the right is 20 cm X 14 cm. Its mineralogical composition by color is the black minerals are magnetite, the white are calcite and the green ones are olivine.

Cinerites[edit]

The bank of yellow rock lower center is cinerite. Credit: Arlette1.

Def. a "rock composed mostly of [...] ash"[12] is called a cinerite.

In the image on the right, the bank of yellow rock is a very fine ash deposit.

Clinopyroxenites[edit]

Pyroxenite banding exists at the boundary of a peridotite intrusion in the Western Gneiss Region, Otrøy, Møre og Romsdal, Norway. Credit: Woudloper.

In the image on the right a peridotite is seen above (mocca-colouring from weathered olivine; some purple garnets), followed by a clinopyroxenite band (greenish Cr-diopsite) and an orthopyroxenite (dark olive). The red minerals are garnets.

Dacites[edit]

Close view is of dacite lava from the May 1915 eruption of Lassen Peak, California. Credit: USGS.

Def. a "rock with a high iron content"[13] is called a dacite.

"Dacite lava is most often light gray, but can be dark gray to black. Dacite lava consists of about 63 to 68 percent silica (SiO2). Common minerals include plagioclase feldspar, pyroxene, and amphibole. Dacite generally erupts at temperatures between 800 and 1000°C. It is one of the most common rock types associated with enormous Plinian-style eruptions. When relatively gas-poor dacite erupts onto a volcano's surface, it typically forms thick rounded lava flow in the shape of a dome."[14]

"Even though it contains less silica than rhyolite, dacite can be even more viscous (resistant to flow) and just as dangerous as rhyolites. These characteristics are a result of the high crystal content of many dacites, within a relatively high-silica melt matrix. Dacite was erupted from Mount St. Helens 1980-86, Mount Pinatubo in 1991, and Mount Unzen 1991-1996."[14]

Diabases[edit]

This is an image of a rock, a diabase with an aphanitic groundmass and plagioclase phenocrysts. Credit: Siim Sepp.

Def. a "fine-grained [...] rock composed mostly of pyroxene and feldspar"[15] is called a diabase.

On the right is an image of a rock, a diabase with an aphanitic groundmass and plagioclase phenocrysts.

Diorites[edit]

This is a piece of diorite from Massachusetts, USA. Credit: Amcyrus2012.

Def. a speckled, coarse-grained rock consisting essentially of plagioclase, feldspar, and hornblende or other mafic minerals is called a diorite.

Def. a "grey [...] rock composed mostly of plagioclase feldspar, biotite, hornblende and/or pyroxene"[16] is called a diorite.

Dolerites[edit]

Exposed after long erosion, we now see regular, steeply inclined layers of dolerite which rest at a high angle to the smooth dip-slope of the schistose rocks. Credit: Jonathan Wilkins.

Def. a "fine-grained basaltic rock"[17] is called a dolerite.

Dunites[edit]

This is a dunite rock sample from Pilbara, Australia. Credit: Ebuhyo1.

Def. a "type of igneous rock with a coarse-grained or phaneritic texture"[18] with 90 % or more by volume of olivine is called a dunite.

On the right is an image of a dunite rock sample from Pilbara, Australia. The green to dark green color indicates a high magnesium content and distinguishes it from the granitic rocks in the region.

Feldspathoidolites[edit]

Gabbronorites[edit]

This is the Impala Black Granite - an attractive, 2 billion year old gabbronorite from South Africa. Credit: James St. John.

The image on the right shows a 2 x 109 b2k gabbronorite from South Africa.

Gabbros[edit]

Gabbro specimen is from Rock Creek Canyon, eastern Sierra Nevada, California. Credit: Mark A. Wilson, Department of Geology, The College of Wooster.

Def. a dark, coarse-grained plutonic rock of crystalline texture, consisting mainly of pyroxene, plagioclase feldspar, and often olivine is called a gabbro.

Def. "a coarsely crystalline, igneous rock consisting of lamellar pyroxene and labradorite"[19] is called a gabbro.

As with diamictites, rock definitions should be without regard to origin.

Granites[edit]

This is a highly modified IUGS classification of phaneritic igneous rocks. Credit: NASA/CSU Pomona.
View is of polished granite. Credit: Dake.
The color of a granite usually comes from the color of the feldspar. Credit: Luis Fernández García.
This is a polished native red granite from China. Credit: Rola Wang.

Def. a very hard, granular, crystalline, rock consisting mainly of quartz, mica, and feldspar is called a granite.

On the right is a mineral phase diagram for classifying phaneritic igneous rocks. The minerals represented are

  1. Q - quartz
  2. A - alkali feldspar such as microcline (KAlSi3O8), and
  3. P - plagioclase.

Granitoids[edit]

The image shows a weathered granitoid above and the resulting grus sand below. Credit: Qfl247.

On the right is a granitoid, albeit weathered, with the grus sand below that resulted from the weathering.

Granodiorites[edit]

Here's a photo of a granodiorite. Credit: Zerohuman.

Def. a "rock similar to granite, but containing more plagioclase than potassium feldspar"[20] is called a granodiorite.

Harzburgites[edit]

This is an IUGS igneous rock classification diagram for ultramafic rocks. Credit: Richard Harwood.

Def. an "ultramafic igneous rock, a variety of peridotite consisting mostly of olivine and low-calcium pyroxene"[21] is called a harzburgite.

Hawaiites[edit]

Geological sample is on display at the House of the Volcano, Reunion Island. Credit: David Monniaux.

Def. an "olivine basalt intermediate between alkali olivine and mugearite"[22] is called a hawaiite.

Hornblendites[edit]

This is a hornblendite. Credit: Khruner.

This hornblendite on the right has a cumulitic structure, ipidiomorphic texture composed of hornblende (darkish) and interstitial plagioclase (bright).

Hyaloclastites[edit]

This is a hyaloclastite sample on display at the House of the Volcano, Reunion Island. Credit: David Monniaux.

Def. a "rock containing glassy fragments"[23] is called a hyaloclastite.

A hyaloclastite sample on the right is on display at the House of the Volcano, Reunion Island.

Ijolites[edit]

This is an ijolite sample. Credit: NASA.

Def. a "rare igneous rock consisting essentially of nepheline and augite"[24] is called an ijolite.

Such an ijolite is shown in the image on the right.

Kimberlites[edit]

Picture is of a diamond-bearing kimberlite rock, from a mine somewhere in the US. Credit: Woudloper.

Def. a "variety of peridotite containing a high proportion of carbon dioxide; often contains diamonds"[25] is called a kimberlite.

Lamproites[edit]

This is a photograph of a sample of Lamproite with ruler for scale. Credit: JPL/NASA.

Def. any "of several volcanic rocks having a high potassium content"[26] is called a lamproite.

Lamprophyres[edit]

This lamprophyre has an ophitic fabric. Credit: Lysippos.

Def. an "uncommon, small-volume ultrapotassic igneous rock primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions"[27] is called a lamprophyre.

Latites[edit]

International Union of Geological Sciences (IUGS) classification of volcanic rocks is diagrammed. Credit: NASA/CSU Pomona.

"Igneous rocks are classified on the basis of mineralogy, chemistry, and texture."[28]

A latite has between 35 % and 65 % plagioclase by volume, and up to 5 % by volume of quartz.

Leucodiorites[edit]

Lherzolites[edit]

This lherzolite is from Dreiser Weiher, Eifel, Germany. Credit: Woudloper.

Def. a "dark-green igneous rock consisting largely of chrysolite, with pyroxene and picotite"[29] is called a lherzolite.

Monzodiorites[edit]

Monzogabbros[edit]

Monzogranites[edit]

Core sample is of Rochovce granite, coarse-grained biotite monzogranite (75.6 ± 1.1 Ma - Cretacous). Credit: Pelex.

Rochovce granite, composing the coring on the right, is a coarse-grained biotite monzogranite.

Monzonites[edit]

This is a monzonite sample. Credit: Khruner.

Def. an "intrusive igneous rock composed mostly of plagioclase and orthoclase"[30] is called a monzonite.

Monzosyenites[edit]

Mugearites[edit]

The rocks on the right here are mugearite of the middle flow. Credit: Anne Burgess.

Def. a "kind of orthoclase-bearing basalt that is made up of olivine, apatite, and opaque oxides"[31] is called a mugearite.

Nephelinites[edit]

A nephelinite lava flow is in Kaiserstuhl, SW Germany. Credit: Derhammer.

Def. "a dark, finely crystalline rock of volcanic origin, being a mixture of nepheline and pyroxene"[32] is called a nephelinite.

Norites[edit]

Sulfidic norite (field of view ~4.5 cm across) is from the Johns-Manville Reef, Lower Banded Series, Stillwater Complex. Credit: James St. John.

Def. a "granular crystalline rock consisting essentially of a triclinic feldspar (such as labradorite) and hypersthene"[33] is called a norite.

Obsidian[edit]

A specimen of obsidian is from Lake County, Oregon. Credit: Locutus Borg.

Def. "a type of black glass produced by volcanoes"[34] is called an obsidian.

Orthopyroxenites[edit]

ALH 84001 is an orthopyroxenite achondrite meteorite from Mars. Credit: Jstuby.

Def. "an ultramafic and ultrabasic rock that is almost exclusively made from the mineral orthopyroxene"[35] is called an orthopyroxenite.

Peridotites[edit]

Peridotite specimen is displayed. Credit: USGS.

Def. a "rock consisting of small crystals of olivine, pyroxene and hornblende"[36] is called a peridotite.

Phonolites[edit]

Rock name is tinguaite (variety of phonolite) and it is from Sweden. Credit: Siim Sepp.

Def. "a light-coloured rock of volcanic origin composed mostly of alkali feldspars"[37] is called a phonolite.

The dark needle-like minerals are aegirine phenocrysts.

Picrites[edit]

This is an IUGS Igneous Rock Classification Diagram using a Le Maitre plot. Credit: Richard Harwood.

Def. a "variety of high-magnesium olivine basalt"[38] is called a picrite.

Pumices[edit]

This piece of pumice is from the Teide volcano. Credit: MPF.

Def. a "light, porous type of pyroclastic igneous rock, formed during explosive volcanic eruptions when liquid lava is ejected into the air as a froth containing masses of gas bubbles"[39] is called a pumice.

Pyroxenites[edit]

This is an IUGS Igneous Rock Classification Diagram for Ultramafic Rocks with Hornblende. Credit: Richard Harwood.

Def. a "heavy, dark igneous rock consisting mostly of pyroxene minerals with smaller amounts of olivine and hornblende"[40] is called a pyroxenite.

Rhyolites[edit]

A rhyolite boulder near Carn Alw shows the characteristic pattern of swirling or parallel layers called flow banding caused by the molten magma meeting a hard surface before cooling and setting. Credit: ceridwen.
Flow banding is in rhyolite lava from Mono-Inyo Craters volcanic chain, California (black bands composed of obsidian). Credit: USGS.

Def. a rock "of felsic composition, with aphanitic to porphyritic texture"[41] is called a rhyolite.

"Rhyolite is a light-colored rock with silica (SiO2) content greater than about 68 weight percent. Sodium and potassium oxides both can reach about 5 weight percent. Common mineral types include quartz, feldspar and biotite and are often found in a glassy matrix. Rhyolite is erupted at temperatures of 700 to 850° C."[42]

"Rhyolite can look very different, depending on how it erupts. Explosive eruptions of rhyolite create pumice, which is white and full of bubbles. Effusive eruptions of rhyolite often produce obsidian, which is bubble-free and black."[42]

"Some of the United States' largest and most active calderas formed during eruption of rhyolitic magmas (for example, Yellowstone in Wyoming, Long Valley in California and Valles in New Mexico)."[42]

"Rhyolite often erupts explosively because its high silica content results in extremely high viscosity (resistance to flow), which hinders degassing. When bubbles form, they can cause the magma to explode, fragmenting the rock into pumice and tiny particles of volcanic ash."[42]

Scorias[edit]

This is a piece of scoria from the Golan Heights. Credit: Daniel Ventura.

Def. rough "masses of rock formed by solidified lava, and which can be found around a volcano's crater"[43] is called a scoria.

The piece of scoria in the image on the right is from the Golan Heights.

Silexites[edit]

This is an IUGS Igneous Rock Classification Diagram for plutonic rocks. Credit: Richard Harwood and IUGS.
These are large pieces of silexite at the motorway service station, La Lozère. Credit: Clem Rutter, Rochester, Kent, England.

On the left is a classification phase diagram of rocks showing the composition range for silexite.

On the right are large pieces of silexite at the motorway service station at La Lozère.

Syenites[edit]

This is a piece of syenite. Credit: USGS.
Rock name is särnaite (leucocratic variety of nepheline syenite) and it is from Sweden. Credit: Siim Sepp.

Def. an "igneous rock composed of feldspar and hornblende"[44] is called a syenite.

On the left is a leucocratic variety of nepheline syenite from Sweden called särnaite.

Tephrites[edit]

This is an image of a leucite tephrite lava used as a building facade. Credit: Roll-Stone.

Def. an "igneous rock consisting essentially of plagioclase and either leucite or nephelite, or both"[45] is called a tephrite.

Tonalites[edit]

A piece of tonalite on red granite gneiss from Tjörn in Sweden. Credit: Ingwik.

Def. an "igneous, plutonic rock composed mainly of plagioclase"[46] is called a tonalite.

Trachyandesites[edit]

A cut block of trachyandesite lava, used as a type of building stone. Credit: zarmel.

Def. roche "volcanique intermédiaire entre les trachytes et les andésites"[47] is called a trachyandesite.

Trachytes[edit]

This is an IUGS Igneous Rock Classification Diagram for volcanic rocks. Credit: Richard Harwood.

Def. a "pale igneous rock consisting mostly of potassium feldspar and plagioclase"[48] is called a trachyte.

Troctolites[edit]

Troctolite sample was brought back from the Moon by Apollo flight 17. Credit: NASA/Johnson Space Center photograph S73-19456.

Def. a "rare type of ultramafic intrusive rock, consisting primarily of olivine and calcic plagioclase"[49] is called a troctolite.

Trondhjemites[edit]

The profiles consist of tonalite, trondhjemite, and gneiss. Credit: Bjoertvedt.

On the right, is a rock cut displaying tonalite, trondhjemite and gneiss.

Websterites[edit]

Extremely coarse-grained, ultrahigh pressure garnet websterite is found near Selje, Norway. Credit: Simon Cuthbert.

Def. an "ultramafic and ultrabasic rock that consists of roughly equal proportions of orthopyroxene and clinopyroxene"[50] is called a websterite.

Wehrlites[edit]

The boundary of wehrlite and gabbro xenolith is ambiguous, suggesting both wehrlite and gabbro were still ductile. Credit: Niigata University.

Def. an "ultramafic and ultrabasic rock that is a mixture of olivine and clinopyroxene"[51] is called a wehrlite.

Extrusives[edit]

Extrusive igneous rock lying on the slope of Mount Etna. Credit: Ekočlen.

"Volcanic rocks (also called extrusive igneous rocks) include all the products resulting from eruptions of lava (flows and fragmented debris called pyroclasts)."[1]

On the right are extrusive igneous rocks lying on the slope of Mount Etna.

Intrusives[edit]

The image shows hardened intrusive igneous rocks. Credit: Adityamadhav83.

"Plutonic rocks (also called intrusive igneous rocks) are those that have solidified below ground; plutonic comes from Pluto, the Greek god of the underworld."[1]

Hardened intrusive igneous rocks at Tenneti park in Visakhapatnam, Vizag, are shown in the image on the right.

Petrography[edit]

Specimens of kimberlitic rocks from the Buffalo Head Hills in Alberta. Credit: Georgialh of Display by Alberta Geological Survey.

"The initial distinction between volcanic and plutonic rocks is made on the basis of texture (fine-grained volcanic vs. coarse-grained plutonic)."[1]

The image on the right shows a display of kimberlitic rocks from the Buffalo Head Hills in Alberta, Canada.

Geochemistry[edit]

The bar graph shows the major chemical elements forming igneous rocks. Credit: J. Johnson (USGS).

"Volcanic and plutonic rocks are divided further on the basis of chemistry and mineral composition. The classification scheme [above] is based on chemistry, and is perhaps the simplest method; there are many other classification methods for igneous rocks."[1]

"These rock types all have different characteristics, including temperature when fluid, viscosity (resistance to flow), composition, explosiveness, and types, amounts, and sizes of minerals."[1]

"Volcanic rocks are typically divided into four basic types according to the amount of silica (SiO2) in the rock (see [the bar graph above] at bottom").[1]

"Components of Igneous Rocks":[1]

  1. "rhyolite consists of more than 68% silica"[1]
  2. "dacite consists of about 63-68% silica"[1]
  3. "andesite consists of about 52-63% silica"[1]
  4. "basalt consists of about 48-52% silica".[1]

"Other major elements in varying proportion include titanium (TiO2), aluminum (Al2O3), iron (FeO or Fe2O3), manganese (MnO), magnesium (MgO), calcium (CaO), sodium (Na2O), potassium (K2O, and phosphorous (P2O5). The bar graph [above] shows the average concentration of each major element for the four basic types of volcanic rock."[1]

Mineralogy[edit]

The diagram correlates mineral composition with volcanic rock type. Credit: J. Johnson (USGS).

"When molten rock erupts onto the Earth's surface, it cools quickly, freezing the growth of existing minerals and preventing the development of new minerals. Such rapid cooling will typically produce lava rocks with a few small minerals suspended in a groundmass of volcanic glass. Molten rock that remains below the ground, however, cools very slowly so that existing minerals continue to grow and many new minerals develop. A slow rate of cooling will produce a coarse-grained plutonic rock that consists entirely of large crystals. Different names are given to such slow-cooling plutonic rocks on the basis of chemical composition and mineral proportions (for example, plutonic rocks of basaltic composition are called gabbro)."[1]

"This graph [on the right] shows the volume percent of minerals present in a plutonic rock that consists entirely of crystals. For example, a granite with 70% SiO2 might have 22% quartz, 38% alkali feldspar, 28% plagioclase feldspar, and 12% biotite."[1]

"The volume percent of minerals present in volcanic rocks typically varies 0-50%. To calculate the relative amounts of the crystals likely to be present, multiply the volume percent in the graph by the actual volume percent in the rock. For example, a rhyolite volcanic rock with 10% crystals, is likely to 2.2% quartz, 3.8% alkali feldspar, 2.8% plagioclase, and 1.2% biotite."[1]

Hypotheses[edit]

  1. The temperatures necessary to melt rocks and produce volcanic rocks can come from high resistance locally to electrical flow.

See also[edit]

References[edit]

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 J. Johnson (29 December 2009). "VHP Photo Glossary: Volcanic rocks". Menlo Park, California USA: USGS. Retrieved 2015-03-15.
  2. "andesite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 26 April 2014. Retrieved 2015-02-09.
  3. USGSAndesite (17 July 2008). "VHP Photo Glossary: Andesite". Menlo Park, California USA: USGS. Retrieved 2015-03-11.
  4. SemperBlotto (24 January 2007). "anorthosite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-03-19.
  5. SemperBlotto (28 January 2007). "aplite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-03-19.
  6. "basalt, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 21 January 2015. Retrieved 2015-02-09.
  7. 7.0 7.1 7.2 7.3 7.4 Volcano Hazards Program (30 March 2014). "VHP Photo Glossary: Basalt". U.S. Geological Survey. Retrieved 2015-02-19.
  8. M. J. Le Bas, R. W. Le Maitre, A. Streckeisen, B. Zanettin, and IUGS Subcommission on the Systematics of Igneous Rocks (1986). "A Chemical Classification of Volcanic Rocks Based on the Total Alkali-Silica Diagram". Journal of Petrology 27 (3): 745-50. doi:10.1093/petrology/27.3.745. http://petrology.oxfordjournals.org/content/27/3/745.short. Retrieved 2015-03-17. 
  9. Ruakh (19 June 2008). "Bostonite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-03-19.
  10. A.Mattias Lundmark, Roy H. Gabrielsen and John Flett Brown (December 2011). "Zircon U–Pb age for the Orkney lamprophyre dyke swarm, Scotland, and relations to Permo-Carboniferous magmatism in northwestern Europe". Journal of the Geological Society 168 (6): 1233-6. doi:10.1144/0016-76492011-017. http://jgs.lyellcollection.org/content/168/6/1233.abstract. Retrieved 2016-03-07. 
  11. "carbonatite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 9 November 2013. Retrieved 2015-03-19.
  12. "cinerite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 9 November 2013. Retrieved 2015-02-09.
  13. "dacite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 24 May 2014. Retrieved 2015-02-09.
  14. 14.0 14.1 DaciteUSGS (17 July 2008). "VHP Photo Glossary: Dacite". Menlo Park, California USA: USGS. Retrieved 2015-03-11.
  15. "diabase, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 16 December 2014. Retrieved 2015-02-09.
  16. "diorite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 7 June 2014. Retrieved 2015-02-09.
  17. "dolerite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. 23 April 2014. Retrieved 2015-02-09.
  18. Jackofclubs (27 September 2008). "dunite, In: Wiktionary". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-03-19.
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External links[edit]

{{Geology resources}}