QAPF diagram with the approximate location of rhyodacite highlighted
TAS diagram with the approximate location of rhyodacite highlighted
Under IUGS guidelines, rhyodacites are not formally defined in either the QAPF classification, used to classify igneous rocks by their mineral content, or the TAS classification, used to classify volcanic rocks chemically. However, the IUGS allows the use of the term to describe rocks close to the boundary between the rhyolite and dacite fields in each classification scheme. Rhyodacite then describes a fine-grained igneous rock containing between 20% and 60% quartz and in which plagioclase makes up about two-thirds of the total feldspar content.[1][2] Such a rock will contain between 69% and 72% silica by weight.[3]
The U.S. Geological Survey defines rhyodacite as volcanic rock containing 20% to 60% quartz and with plagioclase making up 35% to 65% of the total feldspar content. This makes rhyodacite the extrusive equivalent of monzogranite.[4]
In addition to its quartz and feldspar content, rhyodacite commonly contains phenocrysts of andesine, biotite, hornblende, and pyroxene. Quartz and sanidine phenocrysts are less common than in rhyolite, and rhyolite has only scant mafic phenocrysts.[5]
Wikimedia Commons has media related to Rhyodacite.
^"Rock Classification Scheme - Vol 1 - Igneous" (PDF). British Geological Survey: Rock Classification Scheme. 1: 1–52. 1999.
^Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. pp. 139–143. ISBN9780521880060.
^Goff, Fraser; Gardner, Jamie N.; Reneau, Steven L.; Kelley, Shari A.; Kempter, Kirt A.; Lawrence, John R. (2011). "Geologic map of the Valles caldera, Jemez Mountains, New Mexico". New Mexico Bureau of Geology and Mineral Resources Map Series. 79: V13C–2606. Bibcode:2011AGUFM.V13C2606G. Retrieved 18 May 2020.
^ ab"Geologic units containing rhyodacite". usgs.gov.
^ abFisher, Richard V. (1984). Pyroclastic rocks. Berlin: Springer-Verlag. p. 22. ISBN3540127569.
^Troll, Valentin R.; Donaldson, Colin H.; Emeleus, C. Henry. (2004-08-01). "Pre-eruptive magma mixing in ash-flow deposits of the Tertiary Rum Igneous Centre, Scotland". Contributions to Mineralogy and Petrology. 147 (6): 722–739. Bibcode:2004CoMP..147..722T. doi:10.1007/s00410-004-0584-0. ISSN 1432-0967. S2CID 128532728.
^Emeleus, C.H. and Bell, B.R. (2005) British Regional Geology: The Palaeogene Volcanic Districts of Scotland, 4th edition, Nottingham, British Geological Survey, page 77
This volcanology article is a stub. You can help Wikipedia by expanding it.
rhyodacite, volcanic, rock, intermediate, composition, between, dacite, rhyolite, extrusive, equivalent, those, plutonic, rocks, that, intermediate, composition, between, monzogranite, granodiorite, form, from, rapid, cooling, lava, relatively, rich, silica, a. 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 A sample of rhyodacite from SlovakiaDescription Edit QAPF diagram with the approximate location of rhyodacite highlighted TAS diagram with the approximate location of rhyodacite highlighted Under IUGS guidelines rhyodacites are not formally defined in either the QAPF classification used to classify igneous rocks by their mineral content or the TAS classification used to classify volcanic rocks chemically However the IUGS allows the use of the term to describe rocks close to the boundary between the rhyolite and dacite fields in each classification scheme Rhyodacite then describes a fine grained igneous rock containing between 20 and 60 quartz and in which plagioclase makes up about two thirds of the total feldspar content 1 2 Such a rock will contain between 69 and 72 silica by weight 3 The U S Geological Survey defines rhyodacite as volcanic rock containing 20 to 60 quartz and with plagioclase making up 35 to 65 of the total feldspar content This makes rhyodacite the extrusive equivalent of monzogranite 4 In addition to its quartz and feldspar content rhyodacite commonly contains phenocrysts of andesine biotite hornblende and pyroxene Quartz and sanidine phenocrysts are less common than in rhyolite and rhyolite has only scant mafic phenocrysts 5 Occurrence EditLike other silica rich compositions rhyodacites are more abundant as pyroclastic rock than as lava flows 6 These include extensive ash flows and fallout sheets that are important stratigraphic markers 5 Rhyodacite lava flows occur in northwestern Ferry County Washington 4 and at An Sgurr on the island of Eigg in Scotland 7 References Edit Wikimedia Commons has media related to Rhyodacite Rock Classification Scheme Vol 1 Igneous PDF British Geological Survey Rock Classification Scheme 1 1 52 1999 Philpotts Anthony R Ague Jay J 2009 Principles of igneous and metamorphic petrology 2nd ed Cambridge UK Cambridge University Press pp 139 143 ISBN 9780521880060 Goff Fraser Gardner Jamie N Reneau Steven L Kelley Shari A Kempter Kirt A Lawrence John R 2011 Geologic map of the Valles caldera Jemez Mountains New Mexico New Mexico Bureau of Geology and Mineral Resources Map Series 79 V13C 2606 Bibcode 2011AGUFM V13C2606G Retrieved 18 May 2020 a b Geologic units containing rhyodacite usgs gov a b Fisher Richard V 1984 Pyroclastic rocks Berlin Springer Verlag p 22 ISBN 3540127569 Troll Valentin R Donaldson Colin H Emeleus C Henry 2004 08 01 Pre eruptive magma mixing in ash flow deposits of the Tertiary Rum Igneous Centre Scotland Contributions to Mineralogy and Petrology 147 6 722 739 Bibcode 2004CoMP 147 722T doi 10 1007 s00410 004 0584 0 ISSN 1432 0967 S2CID 128532728 Emeleus C H and Bell B R 2005 British Regional Geology The Palaeogene Volcanic Districts of Scotland 4th edition Nottingham British Geological Survey page 77 This volcanology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Rhyodacite amp oldid 1036997765, wikipedia, wiki, book, books, library,
