La Hoyada volcanic complex

La Hoyada is a volcanic complex in the Andes, directly southwest of Cerro Blanco.[2]

The volcanic complex reaches an altitude of approximately 3,800 metres (12,500 ft).[3] Breccia, ignimbrites, lava domes and lava flows have been described at La Hoyada.[2] The ignimbrites cover a surface area of 5 square kilometres (1.9 sq mi).[1] The volcanic complex has been affected by faulting.[4]

Ignimbrites erupted at La Hoyada have been described as moderately welded andesites,[1] of green-grey colour.[5] The intermediate composition of dykes at La Hoyada contrasts with that of other volcanic rocks associated with extensional tectonics in the Puna, which tend to be of mafic composition.[6] Some of the rocks underwent supergene mineralization later.[4] The La Hoyada mine has yielded Cu and Pt.[7]

Paleozoic rocks form the basement beneath Cerro Blanco, which also partly covers La Hoyada.[8] Neoproterozoic and Ordovician sequences are also found at La Hoyada.[9] Sometimes both volcanic centres are considered to be the same volcano.[3] La Hoyada is usually considered a back-arc volcanic centre,[10] and has been associated with extensional tectonics.[6]

The volcanic complex was active in the Miocene and Pliocene.[2] An age of 7.04 ± 0.03 million years ago has been determined for the ignimbrites.[5] Another date for the complex is 9.8 ± 0.6 million years ago.[11] Two distinct volcanic events have been dated 7.4-2.42 million years ago.[12]

References

1. Guzmán et al. 2014, p. 175.
2. Brunori et al. 2013, p. 280.
3. de Silva, S. L.; Spagnuolo, M. G.; Bridges, N. T.; Zimbelman, J. R. (31 October 2013). "Gravel-mantled megaripples of the Argentinean Puna: A model for their origin and growth with implications for Mars". Geological Society of America Bulletin. 125 (11–12): 1913. doi:10.1130/B30916.1.
4. Montero Lopez et al. 2010, p. 55.
5. Guzmán et al. 2014, p. 185.
6. Montero Lopez et al. 2010, p. 48.
7. Beder, Roberto (April 1927). "Los yacimientos minerales de la Republica Argentina relacionados con las rocas igneas de las diferentes epocas geologicas". Revistas de la Universidad Nacional de Cordoba (in Spanish). Retrieved 25 August 2016.
8. Brunori et al. 2013, p. 281.
9. Montero Lopez et al. 2010, p. 51.
10. Álvarez, Orlando; Gimenez, Mario; Folguera, Andres; Spagnotto, Silvana; Bustos, Emilce; Baez, Walter; Braitenberg, Carla (November 2015). "New evidence about the subduction of the Copiapó ridge beneath South America, and its connection with the Chilean-Pampean flat slab, tracked by satellite GOCE and EGM2008 models". Journal of Geodynamics. 91: 78. doi:10.1016/j.jog.2015.08.002.
11. Schoenbohm, Lindsay M.; Strecker, Manfred R. (October 2009). "Normal faulting along the southern margin of the Puna Plateau, northwest Argentina". Tectonics. 28 (5): 5. doi:10.1029/2008TC002341.
12. Montero Lopez et al. 2010, p. 71.

Sources

• Montero Lopez, M.C.; Hongn, Fernando D.; Strecker, Manfred R.; Marrett, Randall; Seggiaro, Raúl; Sudo, Masafumi (October 2010). "Late Miocene–early Pliocene onset of N–S extension along the southern margin of the Central Andean Puna Plateau: Evidence from magmatic, geochronological and structural observations". Tectonophysics. 494 (1–2): 48–63. doi:10.1016/j.tecto.2010.08.010.CS1 maint: ref=harv (link)
• Guzmán, Silvina; Grosse, Pablo; Montero-López, Carolina; Hongn, Fernando; Pilger, Rex; Petrinovic, Ivan; Seggiaro, Raúl; Aramayo, Alejandro (December 2014). "Spatial–temporal distribution of explosive volcanism in the 25–28°S segment of the Andean Central Volcanic Zone". Tectonophysics. 636: 170–189. doi:10.1016/j.tecto.2014.08.013.CS1 maint: ref=harv (link)
• Brunori, C.A.; Bignami, C.; Stramondo, S.; Bustos, E. (August 2013). "20 years of active deformation on volcano caldera: Joint analysis of InSAR and AInSAR techniques". International Journal of Applied Earth Observation and Geoinformation. 23: 279–287. doi:10.1016/j.jag.2012.10.003.CS1 maint: ref=harv (link)