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Felsic. In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. [1] It is contrasted with mafic rocks, which are relatively richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen ...
Mafic. A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium -rich varieties of ...
In a simplified compositional classification, igneous rock types are categorized into felsic or mafic based on the abundance of silicate minerals in the Bowen's Series. Rocks dominated by quartz, plagioclase, alkali feldspar and muscovite are felsic. Mafic rocks are primarily composed of biotite, hornblende, pyroxene and olivine.
Rhyolite (/ ˈraɪ.əlaɪt / RY-ə-lyte) [1][2][3][4] is the most silica -rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase.
Igneous differentiation. In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is ...
The oceanic arc crust is more mafic (basaltic/gabbroic) while the continental arc crust is prone to intermediate or felsic composition (andesitic/dioritic). [ 12 ] In some cases, both a continental arc and oceanic arc can form along the strike of a single subduction zone (e.g. Aleutian Islands and Alaska Peninsula ).
The magma forming this lava is often felsic, having high to intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less viscous mafic magma. [2] Extensive felsic lava flows are uncommon, but have traveled as far as 15 km (9 mi). [3]
Diorite. Diorite (/ ˈdaɪ.əraɪt / DY-ə-ryte) [1][2] is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is intermediate in composition between low-silica (mafic) gabbro and high-silica (felsic) granite.