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 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
File Basanite&Dunite bomb.JPG thumb right 250px Basanite black File Montemartini Agrippina minore 1030446.JPG thumb right 250px 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 and the Comores Islands. ref http gsa.confex.com gsa 2003AM finalprogram abstract 65599.htm Geochemistry and petrology of a miocene trachyte basanite ref The term basanite has occasionally been used to refer to the mineral jasper , for example a black flint y or chert cherty jasper found in several New England states of the USA. Such varieties of jasper are also informally known as Lydian stone, lydite and have been used as Touchstone assaying tool touchstone s in testing the purity of precious metal alloy s. References references Commonscat Basanite Blatt, Harvey and Robert J. Tracy 1996 ... 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
widespread in the Northern Cordilleran Volcanic Province. These include nephelinite , basanite ... abbr on from the volcano. ref name KW These lava 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 ... Cordilleran Volcanic Province. ref name KW The nephelinite lava flows at Volcano Mountain remain ... 01 title Fort Selkirk accessdate 2009 03 30 ref However, dating of sediments in a lake dammed by the nephelinite ... more details
in the Northern Cordilleran Volcanic Province. ref name CH These include nephelinite , basanite ... areas consist of olivine nephelinite and basanite magmas. ref name CH Minor plugs made of gabbro ... more details
an example is nephelinite . History of classification In 1902 a group of American petrographers ... types such as nephelinite , carbonatite , and kimberlite are among those that may be generated following ... more details
four types alkali olivine basalt, quartz tholeiite Ma 30.7 , alkaline basalt, and olivine nephelinite ... melilite nephelinite, olivine nephelinite, quartz tholeiite lava flows. These ran south down ... nephelinite is from Ma 24.9 , and a flow of nepheline hawaiite is from Ma 24.2 . In the western Midlands ... more details
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