Prior, Aziz Rahimi-Chakdel*, Alan P. Boyle**. Although exsolution lamellae may occur in meta-morphic rocks, small recrystallized pyrox- It has been argued that the origin of the peculiar texture and chemistry may be intimately linked to melt/rock reactions at successively decreasing liquid vol-umes in a porous melt flow system. Source for information on poikilitic: A Dictionary of Earth Sciences dictionary. 2) are uniquely indicative of igneous origin. Poikilitic texture - smaller grains of one mineral are completely enclosed in large, optically continuous grains of another mineral. a "poikilitic texture" is said for a crystal that contains many inclusions of other minerals (like the vesuvianite in photo 46197, that contains garnet crystals) 9th Dec 2020 17:15 UTC Uwe Kolitsch Manager Ophitic texture is defined inconsistently, but it is an important variety of basalt texture where pyroxene (or occasionally olivine) forms larger crystals and typically contains numerous crystals of plagioclase (right). The texture of a rock is a result of various processes that controlled the rockâs genesis and, along with mineralogy and chemical composition, provides information that we may use to interpret the rockâs origin and history Table 3.1 at end of Chapter 3 provides a glossary of common igneous rock textures Pyroxenes may vary from < 1 to 10 cm and may include as many as hundreds of plagioclases. Garnet chemistry The larger crystals have more widely separated nuclei than the enclosed crystals, and may grow faster, thus enclosing surrounding grains. c) Backscattered electron image of an olivine hosted melt inclusion. Intergranular texture - a texture in which the angular interstices between plagioclase grains are occupied by grains of ferromagnesium minerals such as olivine, pyroxene, or ⦠Compositional characteristics of minerals in certain fragments, such as highlyâunequilibrated clinopyroxene (CaO, 14.5 to 17.3 wt %; Al 2 O 3, 6.7%) and relatively high CaO (0.70 to 2.5 wt %) in orthopyroxene in a Ngawi fragment, seem to indicate a melt origin. Department of Earth & Ocean Sciences, University of Liverpool, Liverpool, L69 3GP, U.K. *now at ** email: apboyle@liverpool.ac.uk Department of Geology, Faculty of Science, University of Agricultural Science, GORGAN â IRAN. The following terms are commonly used to describe the texture of igneous rocks: i. Phaneritic Texture: The texture of a rock provides a clue whether the magma cooled fast or slowly and where the rock was formed. Neither exsolution lamellae nor poikilitic textures (fig. It is most probably a localised product of side-wall contamination. poikilitic Applied to the texture produced when several orientated or unorientated crystals are enclosed within a larger crystal in an igneous rock. a) Backscattered electron image showing the texture in the rock. This disequilibrium texture points to a xenocrystic origin for the anhedral orthopyroxene. In general igneous rocks formed underground have mineral of larger size than the igneous rocks formed above the ground. (c, e). relatively abundant, poikilitic xenoliths attest to a more complex evolution. The xenocrysts are up to 750 μm and contain magnetite inclusions. 4. 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