Negro de Chorrillos

Negro de Chorrillos lies on the Puna. Cerro Tuzgle and the major Calama-Olacapato-El Toro fault lie nearby, as do active and inactive hot springs.[2] This major fault zone is accompanied by a chain of volcanic systems.[3] The basement in the region is formed by Precambrian-Cambrian units with Cretaceous-Oligocene sediments[4] and ignimbrites from the Aguas Calientes caldera.[5]

Negro de Chorrillos is a volcano in the Andes.

Negro de Chorrillos covers a surface of about 5.88 square kilometres (2.27 sq mi).[6] It has erupted lava flows of the aa lava and block lava type, which flowed 4 kilometres (2.5 mi) down a valley. Ash fall, lava bombs and scoria are also found.[7] Both Negro de Chorrillos and neighbouring San Jerónimo centres have heights of 300–450 metres (980–1,480 ft) and widths of 750–950 metres (2,460–3,120 ft).[5] The volume of both centres is less than 0.1 cubic kilometres (0.024 cu mi).[8] Negro de Chorrillos may be the source of local pyroclastic flows, and material eroded from such flows.[9]

The Negro de Chorrillos monogenetic volcano formed during the Pleistocene. Together with neighbouring San Geronimo volcano it lies on a left-trending strike-slip fault,[10] the El Toro fault.[11] Nearby faults include the Incachule fault to the south and the Chorrillos fault to the north, which actually crosses the Negro de Chorrillos centre.[12] Both faults are part of the Calama-Olacapato-El Toro fault.[7] An onset of crustal tension probably facilitated the ascent of magma.[5]

Negro de Chorrillos like San Geronimo has erupted basaltic trachyandesite to trachyandesite,[13] both shoshonite magmas.[11] They formed over the volcanic back-arc of the Peru-Chile Trench; low percentage melts that were contaminated with lithospheric material formed these two centres.[14]

Eruption dates from the volcano are contradictory; radiometric dates range from 200,000 ± 150,000 years ago,[9] 450,000 years ago,[10] or 200,000 ± 80,000 years ago according to potassium-argon dating.[7] Lava flows from Negro de Chorrillos were later cut by fault offset.[15]

References
  1. Coira, B.; Kay, S. Mahlburg; Viramonte, J. (1993-08-01). "Upper Cenozoic Magmatic Evolution of the Argentine Puna—a Model for Changing Subduction Geometry". International Geology Review. 35 (8): 707. doi:10.1080/00206819309465552. ISSN 0020-6814.
  2. Giordano et al. 2013, p. 77.
  3. Petrinovic et al. 2006, p. 241.
  4. Giordano et al. 2013, p. 79.
  5. Petrinovic et al. 2006, p. 244.
  6. Giordano et al. 2013, p. 83.
  7. Kay, Coira & Mpodozis 2008, p. 138.
  8. Schreiber, U.; Schwab, K. (1991). "Geochemistry of quaternary shoshonitic lavas related to the Calama-Olacapato-El Toro Lineament, NW Argentina". Journal of South American Earth Sciences. 4 (1–2): 74. doi:10.1016/0895-9811(91)90019-h.
  9. Seggiaro, Raúl Eudocio; Guzman, Silvina; Pereyra, Ricardo; Coppolecchia, Mariana; Cegarra, Marcelo (2016-12-30). "NEOTECTÓNICA Y VOLCANISMO MONOGENÉTICO CUATERNARIO SOBRE EL SEGMENTO CENTRAL DEL LINEAMIENTO CALAMA OLACAPATO TORO (COT)". Revista de la Asociación Geológica Argentina (in Spanish). 73 (4): 475. ISSN 1851-8249.
  10. Giordano et al. 2013, p. 78.
  11. Kay, Coira & Mpodozis 2008, p. 433.
  12. Kay, Coira & Mpodozis 2008, p. 137.
  13. Petrinovic et al. 2006, p. 245.
  14. Kay, Coira & Mpodozis 2008, p. 135.
  15. Lanza, F.; Tibaldi, A.; Bonali, F. L.; Corazzato, C. (2013-05-08). "Space–time variations of stresses in the Miocene–Quaternary along the Calama–Olacapato–El Toro Fault Zone, Central Andes". Tectonophysics. 593: 33–56. doi:10.1016/j.tecto.2013.02.029.

Sources
  • Giordano, Guido; Pinton, Annamaria; Cianfarra, Paola; Baez, Walter; Chiodi, Agostina; Viramonte, José; Norini, Gianluca; Groppelli, Gianluca (2013-01-01). "Structural control on geothermal circulation in the Cerro Tuzgle–Tocomar geothermal volcanic area (Puna plateau, Argentina)". Journal of Volcanology and Geothermal Research. 249: 77–94. doi:10.1016/j.jvolgeores.2012.09.009.CS1 maint: ref=harv (link)
  • Kay, Suzanne Mahlburg; Coira, Beatriz; Mpodozis, Constantino (2008-01-01). Field trip guide: Neogene evolution of the central Andean Puna plateau and southern Central Volcanic Zone. Field Guides. 13. pp. 117–181. doi:10.1130/2008.0013(05). ISBN 978-0-8137-0013-7. ISSN 2333-0937.CS1 maint: ref=harv (link)
  • Petrinovic, I. A.; Riller, U.; Brod, J. A.; Alvarado, G.; Arnosio, M. (2006-04-15). "Bimodal volcanism in a tectonic transfer zone: Evidence for tectonically controlled magmatism in the southern Central Andes, NW Argentina". Journal of Volcanology and Geothermal Research. 152 (3–4): 240–252. doi:10.1016/j.jvolgeores.2005.10.008.CS1 maint: ref=harv (link)
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