| 词条 | Phonolite |
| 释义 |
|name= Phonolite |alternative_name= |type= Extrusive igneous |type_link= Igneous |image= Aegirine-phonolite2-2005.jpg |image_size= |alt= A greenish-grey rock with fine dark linear features embedded |caption= Aegirine phonolite. Dark prismatic minerals are aegirine phenocrysts. |coordinates= |composition= nepheline, sodalite, hauyne, leucite, analcite, sanidine, anorthoclase |composition_secondary= biotite, amphibole, pyroxene, olivine }} Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grain) to porphyritic (mixed fine- and coarse-grain). Its intrusive equivalent is nepheline syenite. The name phonolite comes from the Ancient Greek meaning "sounding stone" because of the metallic sound it produces if an unfractured plate is hit; hence the English name clinkstone. Formation{{unreferenced section|date=July 2013}}Unusually, phonolite forms from magma with a relatively low silica content, generated by low degrees of partial melting (less than 10%) of highly aluminous rocks of the lower crust such as tonalite, monzonite and metamorphic rocks. Melting of such rocks to a very low degree promotes the liberation of aluminium, potassium, sodium and calcium by melting of feldspar, with some involvement of mafic minerals. Because the rock is silica-undersaturated, it has no quartz or other silica crystals, and is dominated by low-silica feldspathoid minerals more than feldspar minerals. A few geological processes and tectonic events can melt the necessary precursor rocks to form phonolite. These include intracontinental hotspot volcanism, such as may form above mantle plumes covered by thick continental crust. A-type granites and alkaline igneous provinces usually occur alongside phonolites. Low-degree partial melting of underplates of granitic material in collisional orogenic belts may also produce phonolites. Mineralogy and petrologyPhonolite is a fine-grained equivalent of nepheline syenite. They are products of partial melting, are silica-undersaturated, and have feldspathoids in their normative mineralogy. Mineral assemblages in phonolite occurrences are usually abundant feldspathoids (nepheline, sodalite, hauyne, leucite and analcite) and alkali feldspar (sanidine, anorthoclase or orthoclase), and rare sodic plagioclase. Biotite, sodium-rich amphiboles and pyroxenes along with iron-rich olivine are common minor minerals. Accessory phases include titanite, apatite, corundum, zircon, magnetite and ilmenite.[2] Blairmorite is an analcite-rich variety of phonolite.[3][4]OccurrenceNepheline syenites and phonolites occur widely distributed throughout the world[5] in Canada, Norway, Greenland, Sweden, the United Kingdom, the Ural Mountains, the Pyrenees, Italy, Eifel and Kaiserstuhl in Germany, Brazil, the Transvaal region, the Magnet Cove igneous complex of Arkansas, the Beemerville Complex of New Jersey,[6] as well as on oceanic islands such as the Canary Islands.[7] Nepheline-normative rocks occur in close association with the Bushveld Igneous Complex, possibly formed from partial melting of the wall rocks adjacent to that large ultramafic layered intrusion. Phonolite occurs in the related Pilanesberg Complex and Pienaars River Complex.[8] Examples
Economic importancePhonolites can be of interest as dimension stone or as aggregate for gravels. Rarely, economically mineralised phonolite-nepheline syenite alkaline complexes can be associated with rare-earth mineralisation, uranium mineralisation and phosphates, such as at Phalaborwa, South Africa. Phonolite tuff was used as a source of flint for adze heads and such by prehistoric people from Hohentwiel and Hegau, Germany.[15] Phonolites can be separated into slabs of appropriate dimensions to be used as roofing tiles in place of roofing slate. One such occurrence is in the French Massif Central region such as the Haute Loire département.{{citation needed|date=July 2013}} References1. ^Ridley, W. I., 2012, Petrology of Igneous Rocks, Volcanogenic Massive Sulfide Occurrence Model, USGS Scientific Report 2010-5070-C, Chapter 15. 2. ^Blatt, Harvey and Robert J. Tracy, Petrology, Freeman, 2nd ed. 1996, p. 52, {{ISBN|0-7167-2438-3}}. 3. ^{{cite book | url=http://publications.gc.ca/collections/collection_2017/rncan-nrcan/M44-93-1B.pdf | title=Analcite-bearing igneous rocks from the Crowsnest Formation, southwestern Alberta (Current Research report 93-B1) | publisher=Geological Survey of Canada | first=T.D. | last=Peterson | first2=K.L. |last2=Currie | year=1993 | pages=51–56}} 4. ^{{cite book | title=An Introduction to the Rock-Forming Minerals (3rd edition) | publisher=Mineralogical Society | first=W.A. | last=Deer | first2=R.A. | last2=Howie | first3=J. | last3=Zussman | year=2013 | location=London | isbn=9780903056274}} 5. ^Woolley, A.R., 1995. Alkaline rocks and carbonatites of the world., Geological Society of London. 6. ^Eby, G. N., 2012, The Beemerville alkaline complex, northern New Jersey, in Harper, J. A., ed., Journey along the Taconic unconformity, northeastern Pennsylvania, New Jersey, and southeastern New York: Guidebook, 77th Annual Field Conference of Pennsylvania Geologists, Shawnee on Delaware, PA, p. 85-91. 7. ^{{cite journal|last1=Bryan|first1=S. E|last2=Cas|first2=R. A. F.|last3=Martı́|first3=J|title=Lithic breccias in intermediate volume phonolitic ignimbrites, Tenerife (Canary Islands): constraints on pyroclastic flow depositional processes|journal=Journal of Volcanology and Geothermal Research|date=May 1998|volume=81|issue=3–4|pages=269–296|doi=10.1016/S0377-0273(98)00004-3|bibcode=1998JVGR...81..269B}} 8. ^{{cite book | title=Hydrothermal Mineral Deposits: Principles and Fundamental Concepts for the Exploration Geologist | publisher=Sringer-Verlag | author=Pirajno, Franco | year=1992 | location=Berlin | pages=267–269 | isbn=978-3-642-75673-3}} 9. ^{{Cite journal| doi = 10.1126/science.134.3487.1373| issn = 0036-8075| volume = 134| issue = 3487| pages = 1373 | last = Bassett| first = W. A.| title = Potassium-Argon Age of Devils Tower, Wyoming| journal = Science| date = October 1961| bibcode = 1961Sci...134.1373B| pmid=17807346}} 10. ^Marshall, Patrick, 'The occurrence of a mineral hitherto unknown in the phonolites of Dunedin, New Zealand', 1929. 11. ^{{cite journal|last1=Bausch|first1=W. M.|title=The central part of the Jebel Nefusa volcano (Libya) survey map, age relationship and preliminary results|journal=Geologische Rundschau|date=June 1978|volume=67|issue=2|pages=389–400|doi=10.1007/BF01802796|bibcode=1978GeoRu..67..389B}} 12. ^{{cite journal|last1=Ablay|first1=G. J.|last2=Carroll|first2=M. R.|last3=Palmer|first3=M. R.|last4=Marti|first4=J.|last5=Sparks|first5=R. S. J.|title=Basanite-Phonolite Lineages of the Teide-Pico Viejo Volcanic Complex, Tenerife, Canary Islands|journal=Journal of Petrology|date=May 1998|volume=39|issue=5|pages=905–936|doi=10.1093/petroj/39.5.905|bibcode=1998JPet...39..905A}} 13. ^{{cite web | url=http://www.geopark-monts-ardeche.fr/decouvrir-le-geopark/decouvrir-les-geosites-geopark/volcans-des-sucs-geopark/gerbier-de-jonc-et-sources-de-la-loire-2324.html | title=Gerbier de Jonc et sources de la Loire | publisher=Geopark - Parc Naturel Régional des Monts d'Ardèche | work=Volcans des sucs | accessdate=15 January 2017 | language=French}} 14. ^BGS map viewer http://mapapps.bgs.ac.uk/geologyofbritain/home.html 15. ^Affolter, J., 2002, Provenance des silex préhistoriques du Jura et des régions limitrophes, Archéologie neuchâteloise, 28. External links
3 : Igneous petrology|Volcanic rocks|Intermediate rocks |
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