Earth:Los Gemelos-El Saladillo
Los Gemelos-El Saladillo are monogenetic volcanoes in Argentina .
Geologic context
The Nazca Plate subducts beneath the South America Plate, giving rise to the volcanism in the Andean Central Volcanic Zone, including mafic back-arc volcanism which is often associated with tectonic lineaments.[1]
Los Gemelos ( [ ⚑ ] 24°45′S 66°10′W / 24.75°S 66.167°W) and El Saladillo ( [ ⚑ ] 24°33′23″S 66°12′10″W / 24.55639°S 66.20278°W) lie in the Calchaqui Valley, close to the towns of La Poma and El Saladillo.[2] The valley is bordered by two thrust faults, at least one (the Calchaqui fault) of which has had historical earthquakes;[3] the Los Gemelos volcanic cones were constructed along the fault.[4]
Geology
Los Gemelos consists of three individual vents, the northern two have generated scoria cones the southern features a fissure. The vents have produced about 0.45 cubic kilometres (0.11 cu mi) of lava,[5] three from the northern and two from the central vent; lava flows reach the bed of the Calchaqui River and have flowed along its bed,[6] damming the river and forming a lake.[7] El Saladillo consists of two partially eroded cones which have generated lava flows and several smaller cones generated by explosive eruptions.[6]
The two volcanoes have erupted shoshonitic rocks,[2] consisting of trachybasalt andesite.[8] They contain phenocrysts of clinopyroxene, mica, olivine and plagioclase but also xenoliths.[6]
Eruption history
The volcanoes were constructed during the Pleistocene.[4] The activity at Los Gemelos appears to be associated with an episode of tectonic activity, and on the basis of sediments in the lava-dammed lake the eruption occurred about 35,000 years ago.[9]
References
- ↑ Guzmán, Petrinovic & Brod 2006, p. 51,52.
- ↑ 2.0 2.1 Guzmán, Petrinovic & Brod 2006, p. 52.
- ↑ Guzmán, Petrinovic & Brod 2006, p. 53.
- ↑ 4.0 4.1 "Gemelos-Saladillo". Smithsonian Institution. https://volcano.si.edu/volcano.cfm?vn=355866.
- ↑ Guzmán, Petrinovic & Brod 2006, p. 54.
- ↑ 6.0 6.1 6.2 Guzmán, Petrinovic & Brod 2006, p. 55.
- ↑ Guzmán, Petrinovic & Brod 2006, p. 65.
- ↑ Guzmán, Petrinovic & Brod 2006, p. 61.
- ↑ Guzmán, Petrinovic & Brod 2006, p. 66.
Sources
- Guzmán, S.R.; Petrinovic, I.A.; Brod, J.A. (November 2006). "Pleistocene mafic volcanoes in the Puna–Cordillera Oriental boundary, NW-Argentina" (in en). Journal of Volcanology and Geothermal Research 158 (1–2): 51–69. doi:10.1016/j.jvolgeores.2006.04.014. ISSN 0377-0273.
Bibliography
- Von Wolff, F (1929) (in de). Der Volcanismus II Band: Spezieller Teil 1 Teil Die Neue Welt (Pazifische Erdhalfte) der Pazifische Ozean und Seine Randgebiete. Stuttgart: Ferdinand Enke. p. 354. "El Volcan" may refer to this volcano.
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