Search results
Results from the WOW.Com Content Network
Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Molten felsic magma and lava is more viscous than molten mafic magma and lava. Felsic magmas and lavas have lower temperatures of melting and solidification than mafic magmas and lavas.
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
When the rare earth element-enriched felsic magma cools down to become rock, intense weathering of the rock further concentrates the rare earth element deposit. [65] Therefore, the property of magma and the weathering intensity is the key to concentrate the rare earth element deposits.
Eruptions of felsic magma were predominantly viscous during this stage of activity, resulting in the magma piling up around volcanic vents to create a series of lava domes. Individual domes grew up to 0.094 cubic kilometres (0.023 cubic miles) in the glacially eroded core of the bimodal stratovolcano.
Felsic peralkaline rocks [c] such as trachyte, comendite and pantellerite were also produced by volcanism of the MEVC and represent about 40% of the total eruptive volume, resulting from prolonged fractional crystallization [d] of mantle-derived basaltic magma in magma chambers.
The oldest felsic rocks that are currently exposed intruded pre-existing, even older, mafic crustal rock and crystallized well beneath the Earth's surface. Later, these rocks were thermally metamorphosed, intruded by additional felsic magma, and partially melted during Eoarchean thermal events occurred about 3.85 to 3.72 Ga and 3.66 to 3.59 Ga.
Intermediate or andesitic magmas contain 52% to 63% silica, and are lower in aluminium and usually somewhat richer in magnesium and iron than felsic magmas. Intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes , such as in the Andes . [ 26 ]
Some mafic magmas escape sideward after stalling in the melt containing zone; these generate more mafic volcanic systems at the edge of the felsic volcanism, [19] such as Cerro Bitiche. [10] The magmas are mixtures of crust derived and mafic mantle-derived melts with a consistent petrological and chemical signature. [ 21 ]