komatiite spinifex texture

A striking characteristic feature of such lavas is `spinifex' texture-plate-like crystals of olivine ((Mg,Fe) 2 SiO 4), millimetres to decimetres long, in a fine-grained matrix of spherulitic clinopyroxene (Ca(Mg,Fe,Al)(Si,Al) 2 O 6), dendritic chromite ((Mg,Fe)(Cr,Al,Fe) 2 O 4) and altered glass. Large sheaves of subparallel olivine crystals broaden towards the base of the ow. Fig.3: Three stages during the solidification of a spinifex-textured komatiite flow. Komatiite lava had a very low viscosity - it could flow like an ultradense gas. geol./fife ky 16957/gbr source Abstract. Kerr and Arndt (2001) have also emphasized that komatiites should display characteristic textural features such as spinifex (bladed and acicular olivine, and/or pyroxene crystals in fine-grained matrix). Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. Basaltic lavasnormally have eruption temperatures of about 1100 °C to 1250°C. For Permissions, please e-mail: journals.permissions@oxfordjournals.org, Mineralogy constraints on magmatic processes controlling adakitic features of early permian high-magnesium diorites in the Western tianshan orogenic belt, From explosive vent opening to effusive outpouring: mineral constraints on magma dynamics and timescales at paricutin monogenetic volcano, Corrigendum to ‘Parental Magma Composition of the Main Zone of the Bushveld Complex: Evidence from in situ LA-ICP-MS Trace Element Analysis of Silicate Minerals in the Cumulate Rocks’, The role of lithospheric thickness in the formation of ocean islands and seamounts: contrasts between the Louisville and Emperor-Hawaiian hotspot trails, EXPERIMENTS WITH PYROXENE AT THE LIQUIDUS, Receive exclusive offers and updates from Oxford Academic. From Large igneous provinces. Komatiites were named for their type locality along the Komati River in South Africa. Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. The plate-like olivine crystals in the central sheaf have their largest faces parallel to the outcrop surface. DIFFERENTIATION OF KOMATIITE FLOWS 283 (c) Random olivine spinifex texture makes up the upper 2 m of the spinifex layer. ---------------------- Komatiites are very rare, magnesium-rich, extrusive, ultramafic igneous rocks. Specimen is 9 cm wide. Part of the evidence that komatiites are not magnesium-rich simply because of cumulate olivine is textural: some contain spinifex, a texture attributable to rapid crystallization of the olivine from a magnesium-rich melt. Crystal growth is retarded due to the superfluid nature of the komatiite, and proceeds in a 'flash freeze' to form the spinifex texture. 3 are part of the same pillowed flow. Komatiites are rare and predominantly found in rocks of Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. st. andrews, dep. All rights reserved. 2), the outcrop is less massive, but the sill is also ∼6 m thick and contains onl… [1] [2] [3] La erupción de komatitas fue particularmente común en el Precámbrico, cuando el flujo de calor en la Tierra era mayor. In this part of the flow, fine (2 mm), randomly-oriented equant and tabular skeletal olivine grains lie in a matrix of fine-grained skeletal pyroxene, skeletal and solid equant chromite, and devitrified glass (Fig. Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. Komatiit je vyvretá ultrabázická hornina, vyznačuje sa vysokým obsahom horčíka, najmä v MgO a väčšinou aj typickou spiniflex štruktúrou. In the part of the outcrop immediately east of this area (see Fig. Specimen is 9 cm wide. Specimen is 9 cm wide. [Del río Komati (Transvaal, Suráfrica)]. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. Swirling spinifex texture in metakomatiite in the Precambrian of Ontario, Canada. Spinifex-textured komatiites in the Selva greenstone belt are the first unequivocal examples of komatiites in the Transition Subdomain of the Carajás Mineral Province. Specimen is 9 cm wide. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. Spinifex komatiite sills in cumulate komatiite lava flow (Upper Komatiitic Unit). Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. The "spinifex" texture is named after an Australian grass that grows in clumps with similar shapes. Sampling location The source material for OKUM was collected at Serpentine Mountain in McArthur Township, 25 km south of Timmins, NE Ontario, Canada. This material is typical of a Mg-poor komatiite or komatiitic basalt. Abstract. The classic texture of komatiites is spinifex texture, named after clumps of long, spiky (& painful!) 1. Descargar esta imagen: Komatiite un tipo de rocas ultramáficas manto de roca volcánica, derivada del río Komati Sudáfrica, mostrando textura pinifex - E03GC8 de la biblioteca de Alamy de millones de fotografías, ilustraciones y vectores de alta resolución. Las komatitas tienen por lo general una textura compuesta de olivinos en forma de cuchillos que pueden tener de varios milímetros a varios decímetros de largo rodeados de una matriz de clinopiroxeno esferulítico, cromita dendrítica y vidrio alterado. OKUM represents a 1.5 m wide spinifex zone at the top of a 14 m wide flow that showed good differentiation into various units. 49 Ga Komati Formation, Barberton Greenstone Belt, South Africa, Archean ultramafic flows in Munro Township, Cooling and crystallization of komatiite flows from Zimbabwe, Komatiite flows from the Reliance formation, Belingwe Belt, Zimbabwe: 1. Zdrojová magma komatiitov pochádza zo zemského plášťa. ---------------------- Komatiites are very rare, magnesium-rich, extrusive, ultramafic igneous rocks. This sample displays a characteristic 'spinifex texture' of large, elongate olivine crystals, an indication of rapid crystallisation from under cooled magma. OKUM represents a 1.5 m wide spinifex zone at the top of a 14 m wide flow that showed good differentiation into various units. Komatiite /Spinifex Texture. This is a rare volcanic rock of ultramafic origin. Spinifex-textured komatiite flows are generally subdivided into three major units, as illustrated in Fig. Komatiite was named for its type locality along the Komati River in South Africa, and frequently displays spinifex texture composed of large dendritic plates of olivine and pyroxene. Compared to the b… Compared to the basaltic lava of the Hawaiian plum… Komatiite is relatively common in Archean greenstone belts, rare in Proterozoic belts, and virtually absent in younger regions. geol./fife ky 16957/gbr source komatiita (komatiite) Geol. Spinifex komatiite sills in cumulate komatiite lava flow (Upper Komatiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711-2.717 Ga; Pyke Hill, near the Potter Mine, east of Timmins, Ontario, Canada) 13 (33964996718).jpg 4,000 × 3,000; 11.58 MB The type area is the 3.5 Ga Barberton greenstone belt of South Africa where the rock type was first discovered. Spinifex-textured olivine plates hosted in sulfides are usually named “interspinifex ore” in komatiite-hosted sulfide deposits. The pillows shown in Fig. A thin (1… Here we report the results of a petrological and geochemical investigation of a ~5m thick komatiite sill in Dundonald Township, Ontario. Roca volcánica ultramáfica, formada a partir de magmas de alta temperatura y elevado contenido en MgO (del 18 al 32%) y caracterizada por la presencia en ella de unas texturas esqueléticas llamadas spinifex.V. 3). Figure 2 Well-developed spinifex texture in a komatiite ow at Pyke hill. Picritic rocks (fine grained, usually basalt-like volcanic, ultramafic rocks) defined chemically as having < 53wt % SiO^2, ≥ 18 wt% MgO, <1% (Na 2 O+K 2 O) and or a field term for similar-appearing rocks exhibiting spinifex textures from coarse, platey, skeletal olivine and/or pyroxenes. st. andrews, dep. Descargar esta imagen: Komatiite un tipo de rocas ultramáficas manto de roca volcánica, derivada del río Komati Sudáfrica, mostrando textura pinifex - E03GC8 de la biblioteca de Alamy de millones de fotografías, ilustraciones y vectores de alta resolución. Komatiite lava from the type locality in the Komati Valley, Barberton Mountainland, South Africa, showing the distinctive "spinifex texture" formed by dendritic plates of olivine (scale shown by a hammer on the right edge of photo) The spinifex texture is the result of rapid crystallization of a supercooled liquid. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Sampling location The source material for OKUM was collected at Serpentine Mountain in McArthur Township, 25 km south of Timmins, NE Ontario, Canada. spinifex-textured komatiites: a review of textures, mineral compositions and layering other title les komatiites a texture spinifex: revue des textures, des compositions et des stratifications (fr) author donaldson ch univ. Specimen is 9 cm wide. Komatiite igneous rock. grasses. Many komatiite flows were erupted above their liquidus temperature and may have had temperatures in excess of 1600°C. Recognized in well preserved Archaean greenstone belts. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. Kidd-Munro Assemblage, Timmins, Ontario, Canada. komatiite An extrusive igneous rock of peridotite composition, dominated by essential magnesium olivine accompanied by lesser amounts of aluminous clinopyroxene and chromite, and found as lava flows and shallow sills within Archaean and Proterozoic rock successions. Komatiite ( /koʊˈmɑːti.aɪt/) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava with ≥ 18 wt% MgO. The type area is the 3.5 Ga Barberton greenstone belt of South Africa where the rock type was first discovered. Komatiites with spinifex texture have short to long blades or plates of olivine mixed with smaller-scale blades of pyroxene. Komatiite sample collected from the Abitibi greenstone belt near Englehart, Ontario, Canada. Komatiite sample collected from the Abitibi greenstone belt near Englehart, Ontario, Canada. Komati River Valley, South Africa. International audienceAlthough komatiite has been defined as an ultramafic volcanic rock characterized by spinifex texture, there is a growing recognition that similar textures can also form in high-level dykes and sills. komatiite An extrusive igneous rock of peridotite composition, dominated by essential magnesium olivine accompanied by lesser amounts of aluminous clinopyroxene and chromite, and found as lava flows and shallow sills within Archaean and Proterozoic rock successions. The higher melting temperatures required to produce komatiite have been attributed to the presumed higher geothermal gradients in the Archean Earth. 2 This property permitted the solidification of some individual lava flows that are only 1 cm thick. Spinifex is one of the most spectacular magmatic textures. Komatiite sample collected near Engelhart, Ontario, Canada. These striking textures provide valuable information | Collectables, Rocks, Fossils, Minerals, Fossils | eBay! 5 m thick lower olivine cumulate zone (Fig. Komatiite sample collected from the Abitibi greenstone belt near Englehart, Ontario, Canada. Nesbitt was first to recognize what has come to be known as the spinifex paradox: Spinifex texture is commonly found in the interior of komatiite flows, well below the upper chilled crust. The morphology of these large, preferentially oriented crystals has not previously been reproduced experimentally (Donaldson, 1982; Ginibre et al., 1997). La komatita es una roca volcánica formada a partir de magma extremadamente caliente, fluida y rica en magnesio que deriva de un manto terrestre caliente. ---------------------- (Click on the photo to zoom in on the gray rock surface at center-top and upper left to see the swirling geometry of the spinifex crystals.) Spinifex komatiite. The higher melting temperatures required to produce komatiite have been attributed to the presumed higher geothermal gradientsin the Archean Earth. Magmas of komatiitic compositions have a very high melting point, with calculated eruption temperatures in excess of 1600 °C. Spinifex texture-typical of Komatiites The name Spinifex refer to a spiky grass in Australian. A workable definition of komatiite should include the phrase “komatiite is an ultramafic volcanic rock containing spinifex or related to lavas containing this texture”. This restriction in age is thought to be due to cooling of the mantle, which may have been 100 – 250°C hotter during the Archean (4.0 to 2.5 billion years ago). A striking characteristic feature of such lavas is ‘ Spinifex-textured komatiite flows are generally sub- divided into three major units, as illustrated in Fig. The origin of spinifex texture in komatiites. The lower contact of vesicular to pillowed komatiite is approximately 30-40° steeper with respect to the regional stratigraphy and the upper contact with a 1.5 m thick random spinifex-textured komatiite, is approximately 20° steeper. Komatiites are usually distinguished from other magnesium-rich volcanic rocks, such as picrites and meimechites, by having spinifex texture, such that Brooks and Hart (1974) and Kerr and Arndt (2001) suggested that komatiites should be defined as ultramafic rocks that either contain spinifex texture or are spatially associated with spinifex-textured rocks. Komatiite ( /koʊˈmɑːti.aɪt/) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava with ≥ 18 wt% MgO. Many komatiite flows were erupted above their liquidus temperature and may have had temperatures in excess of 1600°C. Formation of Spinifex Texture in Komatiites: an Experimental Study A major problem is that the dendritic morphology of the olivine resembles that of crystals grown in laboratory experiments at high cooling rates (>50°C/h), but at the position where these textures form, up to several meters below the komatiite flow top, the cooling rate cannot have been greater than 1–5°C/h. Komati River Valley, South Africa. Komatiite is relatively common in Archean greenstone belts, rare in Proterozoic belts, and virtually absent in younger regions. Spinifex-textured komatiites in the Selva greenstone belt are the first unequivocal examples of komatiites in the Transition Subdomain of the Carajás Mineral Province. Primary (magmatic) mineral species also encountered in komatiites include olivine, the pyroxenes augite, pigeonite and bronzite, plagioclase, chromite, ilmenite and rarely pargasitic amphibole. The olivine grains are less closely packed, randomly distributed and poorly sorted. Komatiitic lava would have behaved as a superfluid when erupted; it would have behaved as fluidly as water. The classic texture of komatiites is spinifex texture, named after clumps of long, spiky (& painful!) The "spinifex" texture is named after an Australian grass that grows in clumps with similar shapes. 3D). Schematic representation of Kambalda reentrant embayment with associated komatiite and sulfide (2004). Outcrops of spinifex-textured komatiites, located ∼1.5 km to the south of the Carajás ridge, were discovered during regional exploration for Ni-Cu-(PGE) sulfide deposits by VALE. The pillow lava horizons overlie spinifex-textured or vesicular komatiite. Spinifex, a texture characterized by the presence of large skeletal or dendritic crystals of olivine or pyroxene, is present in many, but not all komatiite flows (Nesbitt 1971). spinifex-textured komatiites: a review of textures, mineral compositions and layering other title les komatiites a texture spinifex: revue des textures, des compositions et des stratifications (fr) author donaldson ch univ. Restricted in komatiite and most distinctive feature in the field . Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. Komatiite / koʊˈmɑːti.aɪt / is a type of ultramafic mantle-derived volcanic rock. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Kambalda type komatiitic nickel ore deposits are a class of magmatic iron-nickel-copper-platinum-group element ore deposit in which the physical processes of komatiite volcanology serve to deposit, concentrate and enrich a Fe-Ni-Cu-(PGE) sulfide melt within the lava flow environment of an erupting komatiite volcano Komatiites were named for their type locality along the Komati River in South Africa. The most striking examples comprise large olivine plates that form parts of giant, decimeter-sized dendritic crystals that are oriented perpendicular to the roof of the komatiitic unit (Fig. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. A workable definition of komatiite should include the phrase “komatiite is an ultramafic volcanic rock containing spinifex or related to lavas containing this texture”. Komatiite is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava with magnesium oxide content higher than 18% by weight. Basaltic lavas normally have eruption temperatures of about 1100 to 1250 °C. Formed due to rapid cooling of rich magnesium lavas. From James St. John. Fig.2: Diagram of percentage liquid vs temperature illustrating the large difference in the liquidus-solidus gap between komatiite and basalt. Modified from Arndt, N., & Fowler, A. International audienceAlthough komatiite has been defined as an ultramafic volcanic rock characterized by spinifex texture, there is a growing recognition that similar textures can also form in high-level dykes and sills. This material is typical of a Mg-poor komatiite or komatiitic basalt. Pyroxene shows zoning. Petrography and mineralogy, Growth forms and composition of chromian spinel in MORB magma: diffusion-controlled crystallization of chromian spinel, Morphology and composition of spinel in Pu'u ‘O’o lava (1996–1998), Kilauea volcano, Hawaii, Journal of Volcanology and Geothermal Research, The origin of spinifex texture in komatiites, Komatiites II: experimental and theoretical investigations of post-emplacement cooling and crystallization, © The Author 2006. (2004). Komatiite is relatively common in Archean greenstone belts, rare in Proterozoic belts, and virtually absent in younger regions. ---------------------- (Click on the photo to zoom in on the gray rock surface from the center to the upper left to see the swirling geometry of the spinifex crystals.) - "The origin of spinifex texture in komatiites" Outcrops of spinifex-textured komatiites, located ∼1.5 km to the south of the Carajás ridge, were discovered during regional exploration for Ni-Cu-(PGE) sulfide deposits by VALE. Komatiite lava from the type locality in the Komati Valley, Barberton Mountainland, South Africa, showing the distinctive "spinifex texture" formed by dendritic plates of olivine (scale shown by a hammer on the right edge of photo) Large, downward-radiating spinifex textures in komatiitic. [1] [2] [3] La erupción de komatitas fue particularmente común en el Precámbrico, cuando el flujo de calor en la Tierra era mayor. Geothermal gradients in the Transition Subdomain of the ow texture in komatiites the. This sample displays a characteristic 'spinifex texture ' of large, elongate olivine are... | eBay of South Africa higher melting temperatures required to produce komatiite have been attributed to outcrop. Gap between komatiite and most distinctive feature in the Selva greenstone belt near Englehart, Ontario,.... 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