What is the meaning of andesitic?
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What is the meaning of andesitic?
andesite. / (ˈændɪˌzaɪt) / noun. a fine-grained tan or grey volcanic rock consisting of plagioclase feldspar, esp andesine, amphibole, and pyroxene.
How do you determine if an igneous rock is andesitic in composition?
Mineral Composition Andesite is rich in plagioclase feldspar and amphibole minerals. Quartz and pyroxene minerals may be absent or present in small quantities. Small amounts of mica will be present as biotite or muscovite. Andesite usually does not contain olivine.
How is andesitic formed?
Andesite is a volcanic rock. It is fine-grained because it forms by the rapid cooling of magmas usually when it erupts onto the Earth’s surface and forms lava flows. Andesite forms from magma that contains less quartz (silica) than rhyolite but more than basalt.
Where is andesite formed?
Andes Mountains
Andesite is an extrusive rock intermediate in composition between rhyolite and basalt. Andesite lava is of moderate viscosity and forms thick lava flows and domes. The word andesite is derived from the Andes Mountains in South America, where andesite is common.
What kind of rock is andesite?
volcanic rock
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
Where are andesitic rocks found?
Not only the Andes, where the name was first applied to a series of lavas, but most of the cordillera (parallel mountain chains) of Central and North America consist largely of andesites. The same rock type occurs in abundance in volcanoes along practically the entire margin of the Pacific Basin.
How does magma become andesitic?
Andesitic magma is formed through wet partial melting of the mantle. The mantle under the ocean has contact with water. When subduction, or continental plates pulling away from one another, occurs, the mantle will heat up and water is pushed into it.
What texture is andesite?
porphyritic
It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
What is the importance of andesite?
Andesite may be used as aggregate or fill, but it is not ideal for concrete applications because it is high in silica, and causes alkali-silica reactivity in the concrete. Andesitic volcanism is associated closely with porphyry copper deposits and it is a host rock for much of the world’s copper ore.
What is importance of andesite rock?
Why is andesite gray?
Andesite is usually light to dark gray in colour, due to its content of hornblende or pyroxene minerals.
Where is andesitic magma found?
Granitic, or rhyolitic, magmas and andesitic magmas are generated at convergent plate boundaries where the oceanic lithosphere (the outer layer of Earth composed of the crust and upper mantle) is subducted so that its edge is positioned below the edge of the continental plate or another oceanic plate.
What does andesitic magma mean?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
What type of volcano is andesitic?
stratovolcanoes
Andesite commonly erupts from stratovolcanoes, where they form small-volume flows that typically advance only short distances down the flanks of a volcano. The two examples shown here are short andesite flows advancing down the slope of the Lascar volcano in Chile, and the Colima volcano in Mexico.
Is andesite a rock or mineral?
Andesite is a volcanic rock similar to basalt only lighter in color and containing less iron and magnesium than basalt. Often containing phenocrysts (large conspicuous crystals), Andesite is a host rock for Andesine, a precious gemstone. A majority of the Earth’s continental crust is composed of andesitic rocks.
What does andesitic magma produce?
ANDESITIC LAVA Whereas basalt forms a’a and pahoehoe surface forms, andesite generally produces blocky lava. Here, the surface contains smooth-sided, angular fragments (blocks) that are not as splintery or vesicular as a’a lava fragments.
