Image Nephelinit.JPG thumb Nephelinite lava grey containing a xenolith of peridotite yellow , Kaiserstuhl , Germany. Nephelinite is a fine grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene variety augite . If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene augite and calcic plagioclase . Basalt, alkali basalt, basanite, tephritic nephelinite, and nephelinite differ partly in the relative proportions of plagioclase and nepheline. Alkali basalt may contain minor nepheline and does contain nepheline in its CIPW normative mineralogy . A critical ratio in the classification of these rocks is the ratio nepheline nepheline plus plagioclase . Basanite has a value of this ratio between 0.1 and 0.6 and also contains more than 10 olivine. Tephritic nephelinite has a value between 0.6 and 0.9. Nephelinite has a value ... of igneous rocks. Nephelinite is an example of a silica undersaturated igneous rock. The degree of silica .... Genesis of the less common mafic rocks such as nephelinite is usually ascribed to more than one ... rocks relatively rich in carbon dioxide. Nephelinite is found on ocean islands such as Oahu ... settings. An example is the Hamada nephelinite lava flow in southwest Japan which occurred in the late Miocene age. Nephelinite is also associated with the highly alkalic volcanism of the Ol Doinyo ... lava lake activity, erupts lava made of melilite nephelinite. The unusual chemical makeup of this igneous ... jointing in melilite olivine nephelinite from the Southern Balcones volcanic and intrusive rocks, Uvalde County, Texas. Olivine nephelinite flows also occur in the Wells Gray Clearwater volcanic ... Yukon Territory . Melilite olivine nephelinite intrusives of Cretaceous age are found in the area around ... 2003 Gold2003 abstracts A005.pdf Hamada nephelinite, SW Japan http it.stlawu.edu cnya lenweb1b.htm ... more details
Ijolite derived from the first syllable of the Finnish words Ii vaara, Iijoki, &c., common as geographical names in Finland , and the Gr. Xiflos, a stone , is an igneous rock consisting essentially of nepheline and augite . Ijolite is a rare rock type of considerable importance from a mineralogy mineralogical and petrology petrological standpoint. It occurs in various parts of the Kainuu region, northeast Finland and in the Kola Peninsula in northwest Russia on the shores of the White Sea . The pyroxene is morphic, yellow or green, and is surrounded by formless areas of nepheline. The accessory minerals are apatite , cancrinite , calcite , titanite and iivaarite , a dark brown titaniferous variety of melanite garnet . This rock is the plutonic and holo crystalline analogue of the nephelinite s and nepheline dolerites it bears the same relation to them as the nepheline syenite s have to the phonolite s. It is worth mentioning that a leucite augite rock, resembling ijolite except in containing leucite in place of nepheline, is known to occur at Shonkin Creek , near Fort Benton, Montana , and has been called missourite . References 1911 Category Igneous rocks Category White Sea nl Ijoliet uk ... more details
This article is about the igneous rock, basanite is also a variety of jasper File Basanite&Dunite bomb.JPG thumb Volcanic bomb of black basanite enclosing a xenolith of green dunite from R union File Montemartini Agrippina minore 1030446.JPG thumb Basanite statue of Agrippina Minor Basanite IPAc en icon b s n a t is an igneous rock igneous , volcanic extrusive rock geology rock with aphanitic to porphyritic texture. The mineral assembly is usually abundant feldspathoid s nepheline or leucite , plagioclase , and augite , together with olivine and lesser iron titanium oxides such as ilmenite and magnetite ulvospinel minor alkali feldspar may be present, as illustrated by the position of the field for basanite in the QAPF diagram . Clinopyroxene augite and olivine are common as phenocryst s and in the matrix geology matrix . The augite contains significantly greater titanium , aluminium and sodium than that in typical Tholeiite tholeiitic basalt . Quartz is absent, as are orthopyroxene and pigeonite . Chemically, basanites are low in silica 42 to 45 SiO sub 2 sub and high in alkali s 3 to 5.5 Na sub 2 sub O and K sub 2 sub O compared to basalt , which typically contains more SiO sub 2 sub , as evident on the diagram used for TAS classification . Nephelinite is yet richer in Na sub 2 sub O plus K sub 2 sub O compared to SiO sub 2 sub . Basanites occur both on continents and on ocean islands. For example, together with basalts, they are produced by Hotspot geology hotspot volcanism in the Hawaiian Islands Hawaiian and the Comoros Islands . ref http gsa.confex.com gsa 2003AM finalprogram abstract 65599.htm Geochemistry and petrology of a miocene trachyte basanite ref References references Commonscat Basanite Blatt, Harvey and Robert J. Tracy 1996 Petrology , 2nd ed., W. H. Freeman ISBN 0 7167 2438 3 http gsa.confex.com gsa 2003AM finalprogram abstract 65599.htm Buchwaldt, Robert 2003 Geochemistry and Petrology of a Miocene Trachyte Basanite Suite from Mt. Tsaratana ... more details
Infobox mountain name Volcano Mountain photo Volcano Mountain.jpg photo caption elevation m 1,239 elevation ref prominence location Yukon Yukon, Canada range Yukon Ranges coordinates coord 62.93 N 137.38 W type mountain region CA topo National Topographic System NTS 115.I 14 type Cinder cone age Holocene ? volcanic arc belt Northern Cordilleran Volcanic Province last eruption first ascent easiest route Volcano Mountain is an active volcano active cinder cone in central Yukon Yukon Territory , Canada , located a short distance north of Fort Selkirk , near the confluence of the Pelly River Pelly and Yukon River s. Volcano Mountain is called Nelr na in the Northern Tutchone language. Geology Volcano Mountain is the youngest volcano in the Fort Selkirk Volcanic Field and one of the youngest in the northern section of the Northern Cordilleran Volcanic Province . The lava at Volcano Mountain is called olivine nephelinite , which is a very uncommon type of lava. This type of lava is believed to have come from much deeper inside the Earth than the basalt ic lava. The last eruption from Volcano Mountain produced young nephelinitic lava flows that remain unvegetated and appear to be only a few hundred years old. However, dating of sediments in lake impounded by the lava flows indicated that the youngest flows could not be younger than mid Holocene and could be early Holocene or older. Volcanic hazards Future eruptions from Volcano Mountain would probably be lava flows, since there is a lack of pyroclastic material. The main hazards from Volcano Mountain are forest fire s started by the lava flows. Older volcanic deposits south of Volcano Mountain indicate that lava flows may have once partly blocked or at least altered the course of the Yukon River Yukon and Pelly River s. Any future activity in this area could disrupt the course of both of these major rivers and could have a serious impact on people living or working downstream. See also Portal Volcanism of Canada List of No ... more details
Infobox mineral name Gregoryite boxwidth boxbgcolor image imagesize alt caption category Carbonate mineral formula Na sub 2 sub ,K sub 2 sub ,Ca CO sub 3 sub strunz 05.AA.10 symmetry unit cell a 5.21 , c 6.58 molweight color colour habit system Hexagonal twinning cleavage fracture tenacity mohs luster streak diaphaneity gravity density polish opticalprop refractive birefringence pleochroism 2V dispersion extinction length fast slow fluorescence absorption melt fusibility diagnostic solubility impurities alteration other prop1 prop1text references ref name mindat http www.mindat.org min 6979.html Mindat.org ref ref http www.webmineral.com data Gregoryite.shtml Webmineral.com ref ref http www.handbookofmineralogy.com pdfs gregoryite.pdf Handbook of Mineralogy ref Gregoryite is an anhydrous carbonate that is rich in potasium and sodium ref name GeologyDictionary cite web url http www.theodora.com geology glossaryg.html gregoryite title Gregoryite definition work Dictionary of Geology accessdate 2011 05 21 ref examples of geochemical composition Na sub 2 sub ,K sub 2 sub ,Ca CO sub 3 sub , ref name mindat ref Cite journal last Mitchell first Roger H. coauthors Bruce A. Kjarsgaard title Experimental Studies of the System Na sub 2 sub CO sub 3 sub CaCO sub 3 sub MgF sub 2 sub at 0 1 GPa Implications for the Differentiation and Low temperature Crystallization of Natrocarbonatite journal Journal of Petrology publisher Oxford Journals year 2010 url http petrology.oxfordjournals.org content early 2010 12 02 petrology.egq069.abstract accessdate 2011 05 21 doi 10.1093 petrology egq069 volume 52 issue 7 8 pages 1265 1280 ref Na sub 0.78 sub K sub 0.05 sub Ca sub 0.17 sub CO sub 3 sub ref Cite journal last Hay first Richard L title Holocene carbonatite nephelinite tephra deposits of Oldoinyo Lengai, Tanzania journal Journal of Volcanology and Geothermal Research volume 37 issue 1 pages 77 91 publisher Elsevier Netherlands year 1989 url http www.sciencedirect.com science? ob Arti ... more details
widespread in the Northern Cordilleran Volcanic Province. These include nephelinite , basanite ... flows are composed of olivine nephelinite, a type of lava not commonly found on Earth. ref name KW Nephelinite lavas are usually interpreted to have originated much deeper in the Earth s mantle unlike ... KW The nephelinite lava flows at Volcano Mountain remain clear from vegetation and seem to be only a few ... However, dating of sediments in a lake dammed by the nephelinite lavas suggest the lava flows could ... more details
in the Northern Cordilleran Volcanic Province. ref name CH These include nephelinite , basanite and peralkaline ... consist of olivine nephelinite and basanite magmas. ref name CH Minor plugs made of gabbro ic and granite ... more details
. A normative feldspathoid classifies a rock as silica undersaturated an example is nephelinite ... peridotite. American Mineralogist, v. 92, p. 370 379 ref Magmas of rock types such as nephelinite , carbonatite ... more details
, alkaline basalt, and olivine nephelinite . Lava flows in the north east flowed down valleys to the sea ... part of the Central Plateau, there are olivine melilite nephelinite, olivine nephelinite, quartz tholeiite ... side of the Central Pateau an olivine nephelinite is from Ma 24.9 , and a flow of nepheline hawaiite ... more details
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