Trachyandesite

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A cut block of trachyandesite lava from a volcano in Auvergne, France, used as building stone, forming part of the walls of Clermont-Ferrand Cathedral, France Trachyandesite at Clermont-Ferrand in France.jpg
A cut block of trachyandesite lava from a volcano in Auvergne, France, used as building stone, forming part of the walls of Clermont-Ferrand Cathedral, France
Trachyandesite is field S3 in the TAS diagram TAS-Diagramm-trachyandesite.png
Trachyandesite is field S3 in the TAS diagram

Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched in alkali metals and with an intermediate content of silica. [1] [2]

Contents

The term trachyandesite had begun to fall into disfavor by 1985 [1] but was revived to describe extrusive igneous rocks falling into the S3 field of the TAS classification. These are divided into sodium-rich benmoreite and potassium-rich latite. [3]

Trachyandesitic magma can produce explosive Plinian eruptions, such as happened at Tambora in 1815. [4] The Eyjafjallajökull 2010 eruption (VEI-4 [5] ), which disrupted European and transatlantic air travel from 15-20 April 2010, [6] for some time was dominated by trachyandesite. [7]

Petrology

Trachyandesite is characterized by a silica content near 58% and a total alkali oxide content near 9%. This places trachyandesite in the S3 field of the TAS diagram. [8] [3] When it is possible to identify the minerals present, trachyandesite is characterized by a high content of sodic plagioclase, typically andesine, and contains at least 10% alkali feldspar. [1] Common mafic accessory minerals are amphibole, biotite or pyroxene. Small amounts of nepheline may be present and apatite is a common accessory mineral. [2] Trachyandesite is not a recognized rock type in the QAPF classification, which is based on the actual mineral content. However, latite is recognized in this classification, while benmoreite would likely fall into either the latite or the andesite fields. [8]

Trachyandesite magmas can have a relatively high sulfur content, and their eruption can inject great quantities of sulfur into the stratosphere. [9] The sulfur may take the form of anhydrite phenocrysts in the magma. [10] The 1982 El Chichón eruption produced trachyandesite pumice rich in anhydrite, and released 2.2 × 107 metric tons of sulfur. [11]

Varieties

Sodium-rich trachyandesite (with %Na2O > %K2O + 2) is called benmoreite, while the more potassic form is called latite. Feldspathoid-bearing latite is sometimes referred to as tristanite. [12] Basaltic trachyandesite is transitional to basalt and likewise comes in two varieties, mugearite (sodium-rich) and shoshonite (potassium-rich). [8]

Occurrence

Trachyandesite is a member of the alkaline magma series, in which alkaline basaltic magma experiences fractional crystallization while still underground. This process removes calcium, magnesium, and iron from the magma. [13] [14] [15] As a result, trachyandesite is common wherever alkali magma is erupted, including late eruptions of oceanic islands [16] [14] and in continental rift valleys and mantle plumes. [17]

Trachyandesite is found in the Yellowstone area as part of the Absaroka Volcanic Supergroup, [18] and has been erupted in arc volcanism in Mesoamerica [11] and at Mount Tambora. [19]

Related Research Articles

<span class="mw-page-title-main">Gabbro</span> Coarse-grained mafic intrusive rock

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.

<span class="mw-page-title-main">Mafic</span> Silicate mineral or igneous rock that is rich in magnesium and iron

A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar. Mafic materials can also be described as ferromagnesian.

<span class="mw-page-title-main">Basalt</span> Magnesium- and iron-rich extrusive igneous rock

Basalt is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars.

<span class="mw-page-title-main">Rhyolite</span> Igneous, volcanic rock, of felsic (silica-rich) composition

Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite.

<span class="mw-page-title-main">Trachyte</span> Extrusive igneous rock

Trachyte is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alkali metals. It is the volcanic equivalent of syenite.

<span class="mw-page-title-main">Latite</span> Type of volcanic rock

Latite is an igneous, volcanic rock, with aphanitic-aphyric to aphyric-porphyritic texture. Its mineral assemblage is usually alkali feldspar and plagioclase in approximately equal amounts. Quartz is less than five percent and is absent in a feldspathoid-bearing latite, and olivine is absent in a quartz-bearing latite. When quartz content is greater than five percent the rock is classified as quartz latite. Biotite, hornblende, pyroxene and scarce olivine or quartz are common accessory minerals. Feldspathoid-bearing latite is sometimes referred to as tristanite.

<span class="mw-page-title-main">Andesite</span> Type of volcanic rock

Andesite is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.

<span class="mw-page-title-main">Basanite</span> Type of volcanic rock

Basanite is an igneous, volcanic (extrusive) rock with aphanitic to porphyritic texture. It is composed mostly of feldspathoids, pyroxenes, olivine, and plagioclase and forms from magma low in silica and enriched in alkali metal oxides that solidifies rapidly close to the Earth's surface.

<span class="mw-page-title-main">Volcanic rock</span> Rock formed from lava erupted from a volcano

Volcanic rocks are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "pyroclastics," and these are also technically sedimentary rocks.

<span class="mw-page-title-main">Flood basalt</span> Very large volume eruption of basalt lava

A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the Earth via a mantle plume. Flood basalt provinces such as the Deccan Traps of India are often called traps, after the Swedish word trappa, due to the characteristic stairstep geomorphology of many associated landscapes.

<span class="mw-page-title-main">Intrusive rock</span> Magmatic rock formed below the surface

Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.

<span class="mw-page-title-main">Rhyodacite</span> Volcanic rock rich in silica and low in alkali metal oxides

Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid cooling of lava relatively rich in silica and low in alkali metal oxides.

<span class="mw-page-title-main">Quartz latite</span> Rock composed mostly of alkali feldspar and plagioclase

A quartz latite is a volcanic rock or fine grained extrusive rock composed mostly of alkali feldspar and plagioclase with some quartz. It forms from the rapid cooling of magma of intermediate composition but moderately enriched in alkali metal oxides.

The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite. The variety of basalt in the series was originally called tholeiite but the International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to that term.

<span class="mw-page-title-main">Igneous intrusion</span> Body of intrusive igneous rocks

In geology, an igneous 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.

Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii.

<span class="mw-page-title-main">Benmoreite</span> Volcanic rock type

Benmoreite is a volcanic rock of intermediate composition. It is a silica-undersaturated sodium-rich variety of trachyandesite and belongs to the alkaline suite of igneous rocks.

<span class="mw-page-title-main">Igneous rock</span> Rock formed through the cooling and solidification of magma or lava

Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.

<span class="mw-page-title-main">Trachybasalt</span> Volcanic rock

Trachybasalt is a volcanic rock with a composition between trachyte and basalt. It resembles basalt but has a high content of alkali metal oxides. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and likely very small amounts of leucite or analcime.

The alkaline magma series is a chemically distinct range of magma compositions that describes the evolution of an alkaline mafic magma into a more evolved, silica-rich end member.

References

  1. 1 2 3 McBirney, Alexander R. (1984). Igneous petrology. San Francisco, Calif.: Freeman, Cooper. p. 503. ISBN   0198578105.
  2. 1 2 Neuendorf, Klaus K.E.; Mehl, James P. Jr.; Jackson, Julia A. (2011). Glossary of geology (Fifth revised ed.). American Geological Institute. ISBN   9781680151787.
  3. 1 2 Le Bas, M. J.; Streckeisen, A. L. (September 1991). "The IUGS systematics of igneous rocks". Journal of the Geological Society. 148 (5): 825–833. Bibcode:1991JGSoc.148..825L. doi:10.1144/gsjgs.148.5.0825. S2CID   28548230.
  4. Self, S.; Gertisser, R.; Thordarson, T.; Rampino, M. R.; Wolff, J. A. (2004). "Magma volume, volatile emissions, and stratospheric aerosols from the 1815 eruption of Tambora" (PDF). Geophysical Research Letters. 31 (20): L20608. Bibcode:2004GeoRL..3120608S. doi:10.1029/2004GL020925. hdl: 20.500.11820/6925218f-d09e-4f9d-9f2e-3ab8419b223f . S2CID   56290102.
  5. Eyjafjallajokull. Eruptive history. Global Volcanism Program. Retrieved 26 August 2020.
  6. Woodhouse, M. J.; Hogg, A. J.; Phillips, J. C.; Sparks, R. S. J. (January 2013). "Interaction between volcanic plumes and wind during the 2010 Eyjafjallajökull eruption, Iceland: VOLCANIC PLUMES AND WIND" (PDF). Journal of Geophysical Research: Solid Earth. 118 (1): 92–109. doi: 10.1029/2012JB009592 .
  7. Donovan, Amy R; Oppenheimer, Clive (March 2011). "The 2010 Eyjafjallajökull eruption and the reconstruction of geography: Commentary". The Geographical Journal. 177 (1): 4–11. doi:10.1111/j.1475-4959.2010.00379.x.
  8. 1 2 3 Philpotts and Ague 2009
  9. Schmincke, Hans-Ulrich (2004). Volcanism. Berlin, Heidelberg: Springer Berlin Heidelberg. p. 262. ISBN   9783642189524.
  10. Carroll, M. R.; Rutherford, Malcolm. J. (1 October 1987). "The Stability of Igneous Anhydrite: Experimental Results and Implications for Sulfur Behavior in the 1982 El Chichon Trachyandesite and Other Evolved Magmas". Journal of Petrology. 28 (5): 781–801. doi:10.1093/petrology/28.5.781.
  11. 1 2 Luhr, James F.; Logan, M.Amelia V. (September 2002). "Sulfur isotope systematics of the 1982 El Chichón trachyandesite: an ion microprobe study". Geochimica et Cosmochimica Acta. 66 (18): 3303–3316. Bibcode:2002GeCoA..66.3303L. doi:10.1016/S0016-7037(02)00931-6.
  12. Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge University Press. pp. 140–141. ISBN   9780521880060.
  13. Macdonald, Gordon A. (1983). Volcanoes in the sea : the geology of Hawaii (2nd ed.). Honolulu: University of Hawaii Press. pp. 51–52. ISBN   0824808320.
  14. 1 2 Philpotts and Ague 2009, pp. 369-370
  15. Rondet, Morgane; Martel, Caroline; Bourdier, Jean-Louis (December 2019). "The intermediate step in fractionation trends of mildly alkaline volcanic suites: An experimental insight from the Pavin trachyandesite (Massif Central, France)". Comptes Rendus Geoscience. 351 (8): 525–539. Bibcode:2019CRGeo.351..525R. doi: 10.1016/j.crte.2019.07.003 .
  16. MacDonald 1983, pp. 51-52
  17. Philpotts and Ague 2009, pp. 390–394
  18. Nelson, Willis H.; Pierce, William Gamewell (1968). "Wapiti formation and Trout Peak Trachyandesite, northwestern Wyoming". U.S. Geological Survey Bulletin. 1254-H. doi: 10.3133/b1254H .
  19. Self, S.; Rampino, M. R.; Newton, M. S.; Wolff, J. A. (1 November 1984). "Volcanological study of the great Tambora eruption of 1815". Geology. 12 (11): 659–663. Bibcode:1984Geo....12..659S. doi:10.1130/0091-7613(1984)12<659:VSOTGT>2.0.CO;2.