komatiite spinifex texture

I i l Spinifex texture komatiite blllbl Platy-spinifex komatiite • Cumulate texture komatiite I Basalt •l Pillow Basalt • • Massive sulfides Matrix sulfides Interflow sediment "Silicate domes" Basalt Flow Top Ocelli Localities Figure 1. Large, downward-radiating spinifex textures in komatiitic. 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. ---------------------- (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.) Komatiit je vyvretá ultrabázická hornina, vyznačuje sa vysokým obsahom horčíka, najmä v MgO a väčšinou aj typickou spiniflex štruktúrou. This property permitted the solidification of some individual lava flows that are only 1 cm thick. Many komatiite flows were erupted above their liquidus temperature and may have had temperatures in excess of 1600°C. Modified from Arndt, N., & Fowler, A. ---------------------- Komatiites are very rare, magnesium-rich, extrusive, ultramafic igneous rocks. 1). The classic texture of komatiites is spinifex texture, named after clumps of long, spiky (& painful!) Komatiite is relatively common in Archean greenstone belts, rare in Proterozoic belts, and virtually absent in younger regions. The classic texture of komatiites is spinifex texture, named after clumps of long, spiky (& painful!) Komatiite ( /koʊˈmɑːti.aɪt/) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava with ≥ 18 wt% MgO. Komatiitic lava would have behaved as a superfluid when erupted; it would have behaved as fluidly as water. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. 3 are part of the same pillowed flow. textura spinifex. DIFFERENTIATION OF KOMATIITE FLOWS 283 (c) Random olivine spinifex texture makes up the upper 2 m of the spinifex layer. The type area is the 3.5 Ga Barberton greenstone belt of South Africa where the rock type was first discovered. Komatiitic lava was extremely fluid when it erupted (possessing the viscosity close to that of water but with the density of rock). The morphology of these large, preferentially oriented crystals has not previously been reproduced experimentally (Donaldson, 1982; Ginibre et al., 1997). The distinctive spinifex texture is formed by skeletal, platy, or acicular crystals of olivine, orthopyroxene, or clinopyroxene, or their pseudomorphs in ultramafic and mafic lavas or silicate-rich furnace slag. st. andrews, dep. Komatiites are high-temperature, fluid, magnesium-rich lavas typically of Archaean age. 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. 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. 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. 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 Spinifex-textured olivine plates hosted in sulfides are usually named “interspinifex ore” in komatiite-hosted sulfide deposits. Komatiite sample collected near Engelhart, Ontario, Canada. Komatiite sample collected from the Abitibi greenstone belt near Englehart, Ontario, Canada. 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