Abstract. A workable definition of komatiite should include the phrase “komatiite is an ultramafic volcanic rock containing spinifex or related to lavas containing this texture”. 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. A thin (1… 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. The pillows shown in Fig. 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) Restricted in komatiite and most distinctive feature in the field . 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 had a very low viscosity - it could flow like an ultradense gas. The type area is the 3.5 Ga Barberton greenstone belt of South Africa where the rock type was first discovered. Bladed olivine crystals are visible, though spinifex texture is weak or absent in this sample. This material is typical of a Mg-poor komatiite or komatiitic basalt. 3). Komatiite /Spinifex Texture. 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. 2), the outcrop is less massive, but the sill is also ∼6 m thick and contains onl… 3D). ---------------------- Komatiites are very rare, magnesium-rich, extrusive, ultramafic igneous rocks. Abstract. Pyroxene shows zoning. [Del río Komati (Transvaal, Suráfrica)]. ---------------------- (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.) A striking characteristic feature of such lavas is ‘spinifex’ texture—plate-like crystals of olivine ((Mg,Fe)2SiO4), millimetres to decimetres long, in a fine-grained matrix of spherulitic clinopyroxene (Ca(Mg,Fe,Al)(Si,Al)2O6), dendritic chromite ((Mg,Fe)(Cr,Al,Fe)2O4) and altered glass. - "The origin of spinifex texture in komatiites" geol./fife ky 16957/gbr source Spinifex is a spectacular bladed olivine or pyroxene texture that characterizes komatiite, a rock almost exclusively restricted to the Archean; varioles are cm-scale leucocratic globular structures abundant in many Archean basalts. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. 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. 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) Keweenaw rift rocks include a somewhat rare textural variety of basalt called ophite or ophitic basalt. The plate-like olivine crystals in the central sheaf have their largest faces parallel to the outcrop surface. The "spinifex" texture is named after an Australian grass that grows in clumps with similar shapes. geol./fife ky 16957/gbr source 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. 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. 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 Formed due to rapid cooling of rich magnesium lavas. Komatiite is relatively common in Archean greenstone belts, rare in Proterozoic belts, and virtually absent in younger regions. Spinifex-textured komatiite flows are generally subdivided into three major units, as illustrated in Fig. 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 / koʊˈmɑːti.aɪt / is a type of ultramafic mantle-derived volcanic rock. This is a rare volcanic rock of ultramafic origin. Fig.2: Diagram of percentage liquid vs temperature illustrating the large difference in the liquidus-solidus gap between komatiite and basalt. Swirling spinifex texture in metakomatiite in the Precambrian of Ontario, Canada. (2004). Recognized in well preserved Archaean greenstone belts. 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). Large sheaves of subparallel olivine crystals broaden towards the base of the ow. Sampling location The source material for OKUM was collected at Serpentine Mountain in McArthur Township, 25 km south of Timmins, NE Ontario, Canada. 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 Komatiite chemistry is thought to be different from that of basaltic and other common mantle-produced magmas, because of differences in degrees of partial melting. Figure 2 Well-developed spinifex texture in a komatiite ow at Pyke hill. 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. 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