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A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.
These igneous intrusive rocks consist of granitic and pegmatitic dike swarms, i.e. the Cottonwood, Cremation, Sapphire, and Garnet pegmatite complexes, that cut the Granite Gorge Metamorphic Suite from east to west. They formed as granite magma, and related pegmatite fluids, filled crack-systems as magma migrated through the crust. The chemical ...
Magma that is extruded as lava is extremely dry, but magma at depth and under great pressure can contain a dissolved water content in excess of 10%. Water is somewhat less soluble in low-silica magma than high-silica magma, so that at 1,100 °C and 0.5 GPa , a basaltic magma can dissolve 8% H 2 O while a granite pegmatite magma can dissolve 11% ...
Greisen is formed by self-generated alteration of a granite and is a class of moderate- to high-temperature magmatic-hydrothermal alteration related to the late-stage release of volatiles dissolved in a magma during the solidification of that magma. Greisens are usually variably altered rocks, grading from coarse, crystalline granite, commonly ...
Granite (/ ˈ ɡ r æ n ɪ t / GRAN-it) is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase.It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Migmatite on the coast of Saaremaa, Estonia. Intricately-folded migmatite from near Geirangerfjord, Norway. Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock ...
Porphyritic rocks are a product of igneous differentiation, and are generally formed when a column of rising magma is cooled in two stages: In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains, with a diameter of 2mm or more. In the final stage, the magma is cooled rapidly at relatively shallow ...
The pegmatite is centrally located in the Lone Grove pluton, a 1.6 Ga old rapakivi granite, intruded into Valley Spring Gneiss. Geologic evidence suggests the pluton's emplacement as a rather shallow intrusion of magma, possibly in a sub-caldera type situation. An original depth of five to seven kilometers may be assumed for the present level ...