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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. It is common in the continental crust of Earth, where it is found in igneous ...
The average density of basalt is 2.9 g/cm 3, compared, for example, to granite’s typical density of 2.7 g/cm 3. [16] The viscosity of basaltic magma is relatively low—around 10 4 to 10 5 cP—similar to the viscosity of ketchup, but that is still several orders of magnitude higher than the viscosity of water, which is about 1 cP). [17]
Exfoliating slabs of granite, on Half Dome in Yosemite National Park, USA. Exfoliating granite is a granite undergoing exfoliation, or onion skin weathering (desquamation).The external delaminated layers of granite are gradually produced by the cyclic variations of temperature at the surface of the rock in a process also called spalling.
An example of such texture, related to fractioned crystallization, is intergranular (also known as intercumulus) textures that develop wherever a mineral crystallizes later than the surrounding matrix, hence filling the left-over interstitial space. Various oxides of chromium, iron and titanium show such textures, such as intergranular chromite ...
Oceanic: 5 – 10 km (3 – 6 mi) thick [4] and composed primarily of denser, more mafic rocks, such as basalt, diabase, and gabbro. The average thickness of the crust is about 15 – 20 km (9 – 12 mi). [5] Because both the continental and oceanic crust are less dense than the mantle below, both types of crust "float" on the mantle.
Hornblende and biotite were stable under the pressures and other conditions below the surface, but unstable at higher levels. In the ground-mass of these rocks, augite is almost universally present. But the plutonic representatives of the same magma, granite, and syenite contain biotite and hornblende far more commonly than augite. [36]
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
These accumulations typically occur on the floor of the magma chamber, although they are possible on the roofs if anorthite plagioclase is able to float free of a denser mafic melt. [ 1 ] Cumulates are typically found in ultramafic intrusions , in the base of large ultramafic lava tubes in komatiite and magnesium rich basalt flows and also in ...