While poikilitic textures commonly develop in igneous rocks, both metamorphic and metasomatic rocks may be poikilitic (i.e., poikiloblastic). It is most probably a localised product of side-wall contamination. (c, e). 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. d) Photomicrograph taken by crossed polarizers, showing poikilitic texture. The following terms are commonly used to describe the texture of igneous rocks: i. Phaneritic Texture: Garnet chemistry b) Photomicrograph taken by crossed polarizers, showing textures and melt inclusions within the plagioclase. Prior, Aziz Rahimi-Chakdel*, Alan P. Boyle**. Poikilitic texture - smaller grains of one mineral are completely enclosed in large, optically continuous grains of another mineral. a) Backscattered electron image showing the texture in the rock. The larger crystals have more widely separated nuclei than the enclosed crystals, and may grow faster, thus enclosing surrounding grains. 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 provides a clue whether the magma cooled fast or slowly and where the rock was formed. Origin of poikilitic garnet in a leucogranite dike Dave J. relatively abundant, poikilitic xenoliths attest to a more complex evolution. Source for information on poikilitic: A Dictionary of Earth Sciences dictionary. 2) are uniquely indicative of igneous origin. Intergranular texture - a texture in which the angular interstices between plagioclase grains are occupied by grains of ferromagnesium minerals such as olivine, pyroxene, or … This disequilibrium texture points to a xenocrystic origin for the anhedral orthopyroxene. Neither exsolution lamellae nor poikilitic textures (fig. 4. c) Backscattered electron image of an olivine hosted melt inclusion. poikilitic Applied to the texture produced when several orientated or unorientated crystals are enclosed within a larger crystal in an igneous rock. 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 In general igneous rocks formed underground have mineral of larger size than the igneous rocks formed above the ground. The xenocrysts are up to 750 μm and contain magnetite inclusions. Compositional characteristics of minerals in certain fragments, such as highly‐unequilibrated 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. Although exsolution lamellae may occur in meta-morphic rocks, small recrystallized pyrox- Pyroxenes may vary from < 1 to 10 cm and may include as many as hundreds of plagioclases. 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 – IRAN. The texture of a rock is a result of various processes that controlled the rock’s genesis and, along with mineralogy and chemical composition, provides information that we may use to interpret the rock’s origin and history Table 3.1 at end of Chapter 3 provides a glossary of common igneous rock textures