A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm.
Composition
Primary
Intermediate: plagioclase (often andesine) and pyroxene or hornblende
Secondary
Magnetites, biotite, sphene, and quartz
Andesite (/ˈændəzaɪt/)[1] is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.[2]
Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic.[3] Along with basalts, andesites are a component of the Martian crust.
The name andesite is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826.[4]
^"andesite". Merriam-Webster.com Dictionary.
^Macdonald, Gordon A.; Abbott, Agatin T.; Peterson, frank L. (1983). Volcanoes in the sea : the geology of Hawaii (2nd ed.). Honolulu: University of Hawaii Press. p. 127. ISBN 0824808320.
^Rudnick, Roberta L.; Fountain, David M. (1995). "Nature and composition of the continental crust: A lower crustal perspective". Reviews of Geophysics. 33 (3): 267–309. Bibcode:1995RvGeo..33..267R. doi:10.1029/95RG01302.
^Jackson, Julia A., ed. (1997). "andesite". Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN 0922152349.
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(aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and...
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metamorphic rock, and sedimentary rock. Adakite – Volcanic rock type Andesite – Type of volcanic rock Alkali feldspar granite – Type of igneous rock...
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three series: The tholeiitic series – basaltic andesites and andesites. The calc-alkaline series – andesites. The alkaline series – subgroups of alkaline...
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having high to intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less viscous mafic magma. Extensive felsic lava...
high in potassium, is rare but sometimes is found in volcanic arcs. The andesite member of each series is typically most abundant, and the transition from...
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