Cerro Guacha

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Coordinates: 22°45′S 67°28′W / 22.750°S 67.467°W / -22.750; -67.467
Source: Wikipedia, the free encyclopedia.
Cerro Guacha
Cerro Guacha is located in Bolivia
Cerro Guacha
Cerro Guacha
Highest point
Coordinates22°45′S 67°28′W / 22.750°S 67.467°W / -22.750; -67.467
Naming
Language of nameSpanish

Cerro Guacha is a

Altiplano-Puna volcanic complex
(APVC). A number of volcanic calderas occur within the latter.

Cerro Guacha and the other volcanoes of that region are formed from the

Nazca plate beneath the South America plate
. Above the subduction zone, the crust is chemically modified and generates large volumes of melts that form the local caldera systems of the APVC. Guacha is constructed over a basement of sediments.

Two major ignimbrites, the 5.6-5.8

mya
Guacha ignimbrite with a volume of 1,300 cubic kilometres (310 cu mi) and the 3.5-3.6 mya Tara ignimbrite with a volume of 800 cubic kilometres (190 cu mi) were erupted from Cerro Guacha. More recent activity occurred 1.7 mya and formed a smaller ignimbrite with a volume of 10 cubic kilometres (2.4 cu mi).

The larger caldera has dimensions of 60 by 40 kilometres (37 mi × 25 mi) with a rim altitude of 5,250 metres (17,220 ft). Extended volcanic activity has generated two nested calderas, a number of lava domes and lava flows and a central resurgent dome.

Geography and structure

The caldera was discovered in 1978 thanks to

Landsat imagery. It lies in Bolivia next to the Chilean frontier. The terrain is difficult to access being located at altitudes between 3,000–4,000 metres (9,800–13,100 ft). The caldera is named after Cerro Guacha, a feature named as such by local topographic maps.[1] Later research by the Geological Service of Bolivia indicated the presence of three welded tuffs.[2] Paleogene red beds and Ordovician sediments form the basement of the caldera.[3]

Cerro Guacha is part of the

Sol de Manana and Guacha,[4] with recent activity encompassing the extrusion of Quaternary lava domes and flows. Deformation in the area occurs beneath Uturuncu volcano north of the Guacha centre.[5]

A westward-facing semicircular scarp (60 by 40 kilometres (37 mi × 25 mi)) contains subvertically banded Guacha ignimbrite layers rich in

lacustrine deposits and welded ignimbrites. Another eastern collapse was generated by the Tara Ignimbrite eruption, with dimensions of 30 by 15 kilometres (18.6 mi × 9.3 mi).[2][6] The margins of the caldera-graben structure are about 5,250 metres (17,220 ft) high while the caldera floors are about 1,000 metres (3,300 ft) lower. Probably dacitic lava domes are found on the northern caldera rim, with the caldera floor possibly containing lava flows.[1]

The caldera contains a

dacitic. The Puripica Chico lavas on the western side of the caldera are not associated with a collapse.[6] Dark coloured lava flows are found to the southwest of the caldera.[8]

Some geothermal activity occurs within the caldera.[9] Laudrum et al. suggested that the heat from Guacha and Pastos Grandes may be transferred to the El Tatio geothermal system to the west.[10]

Geology

Guacha is part of a volcanic complex in the

mya. Previously, the area was formed from a Paleozoic marine basin with some early volcanics.[2]

Since the

Nazca plate. Recently a change in volcanic activity away from ignimbritic towards cone-forming volcanism has been observed.[5]

Local

Guacha caldera is part of the

Gravitic research indicates the presence of a low density area centered beneath Guacha.[12] The magmatic body underpinning the APVC is centered beneath Guacha.[13] Guacha caldera is also closely linked to the neighbouring La Pacana caldera.[14]

The Guacha caldera forms a structure with the neighbouring

mya ago and dramatically increased more than a million years later. Volcanic activity is linked to this fault zone and to the thermal maturation of the underlying crust.[15] After 4 million years ago activity waned again in the Altiplano-Puna volcanic complex.[16]

Geologic record

The Guacha system was constructed over a timespan of 2 million years with a total volume of 3,400 cubic kilometres (820 cu mi).[17] Eruptive activity occurred at regular intervals. Calculations indicate that the Guacha system was supplied by magmas at a rate of 0.007–0.018 cubic kilometres per year (5.3×10−5–0.000137 cu mi/Ms).[12]

Located at a high altitude in an area of long term arid climate has preserved old volcanic deposits over time.[4] Thus, unlike in other areas of the world such as the Himalayas where water erosion governs the landscape the morphology of the Altiplano-Puna volcanic complex is mostly tectonic in origin.[18]

Composition and magma properties

The Guacha Ignimbrite is

andesitic-rhyolithic.[2] The Guacha Ignimbrite contains 62-65% SiO2, Puripicar 67-68% and the Tara Ignimbrite 63%. Plagioclase and quartz are found in all ignimbrites.[17]

Geological considerations indicate that the Guacha ignimbrite was stored at a depth of 5–9.2 kilometres (3.1–5.7 mi) and the Tara ignimbrite at a depth of 5.3–6.4 kilometres (3.3–4.0 mi). Zircon temperatures are 716 °C (1,321 °F), 784 °C (1,443 °F) and 705 °C (1,301 °F) for Guacha, Tara and Chajnantor respectively.[7]

Climate

The climate of the Central Andes is characterized by extreme aridity. The eastern mountain chain of the Andes prevents moisture from the Amazon from reaching the Altiplano area. The area is also too far north for the precipitation associated with the Westerlies to reach Guacha. This arid climate may go back to the Mesozoic and was enhanced by geographical and orogenic changes during the Cenozoic.[19]

Sol de Manana fields.[20]

Eruptive history

Guacha has been the source of eruptions with volumes of more than 450 cubic kilometres (110 cu mi)

plutons feeding such eruptions are assembled over millions of years.[6]

The Guacha ignimbrite (including the Lowe Tara Ignimbrite, Chajnantor Tuff, Pampa Guayaques Tuff and possibly the Bonanza Ignimbrite)

Uturunku volcano along the Quetena valley[6] until Suni K'ira.[2] Some ash deposits in the northern Chilean Coast Range are linked to the Guacha eruption.[21] The Guacha ignimbrite was also known as Lower Tara at first.[2]

The later Tara ignimbrite (including the Upper Tara Ignimbrite, the Filo Delgado Ignimbrite and the Pampa Tortoral Tuff)

andesitic magma.[7]

The Puripica Chico ignimbrite is known for having formed the Piedras de Dali

mya, making it the youngest Guacha caldera volcanite.[6]

The Puripicar ignimbrite has a volume of 1,500 cubic kilometres (360 cu mi) and is 4.2

mya old.[17] After research indicated that it was different from another ignimbrite named Atana,[23] it was originally linked to the Guacha caldera but Salisbury et al. in 2011 linked the Tara ignimbrite to Guacha instead.[2] Another ignimbrite associated with Guacha is the Guataquina Ignimbrite named after Paso de Guataquina. It covers an area of 2,300 square kilometres (890 sq mi) and has an approximate volume of 70 cubic kilometres (17 cu mi).[1] It was later interpreted to be a combination of the Guacha, Tara and non-Guacha Atana ignimbrites.[2]

See also

References

  1. ^
    doi:10.1016/0377-0273(78)90029-X
    .
  2. ^ a b c d e f g h i j Iriarte, Rodrigo (2012). "The Cerro Guacha caldera complex : an upper Miocene-Pliocene polycyclic volcano-tectonic structure in the Altiplano Puna Volcanic Complex of the Central Andes of Bolivia". OSU Libraries. Oregon State University. Retrieved 27 September 2015.
  3. ^ Mobarec, Roberto C.; Heuschmidt, B. (1994). "Evolucion Tectonica Y Differenciacion Magmatica De La Caldera De Guacha, Sudoeste De Bolivia" (PDF). biblioserver.sernageomin.cl (in Spanish). Concepcion: 7o Congreso Geologico Chileno. Archived from the original (PDF) on 27 November 2015. Retrieved 26 November 2015.
  4. ^
    doi:10.1130/0091-7613(1989)017<1102:APVCOT>2.3.CO;2
    .
  5. ^
    S2CID 129924955
    . Retrieved 27 November 2015.
  6. ^
    doi:10.1130/B30280.1
    . Retrieved 26 September 2015.
  7. ^ a b c d Grocke, Stephanie (2014). "Magma dynamics and evolution in continental arcs : insights from the Central Andes". OSU Libraries. Oregon State University. Retrieved 28 September 2015.
  8. doi:10.1016/0377-0273(81)90028-7
    .
  9. doi:10.1016/j.jvolgeores.2006.04.019
    .
  10. hdl:10533/142624
    .
  11. ISSN 1851-8249
    . Retrieved 26 September 2015.
  12. ^
    doi:10.1016/j.jvolgeores.2007.07.015
    .
  13. ISBN 9781862392113
    . Retrieved 26 November 2015.
  14. S2CID 129924955
    . Retrieved 26 September 2015.
  15. doi:10.1016/j.jsames.2007.10.004
    .
  16. S2CID 129724498
    .
  17. ^
    doi:10.1016/j.jvolgeores.2010.08.013
    .
  18. doi:10.1146/annurev.earth.25.1.139
    .
  19. doi:10.1146/annurev.earth.35.031306.140158
    .
  20. doi:10.1016/j.jvolgeores.2013.05.014
    .
  21. doi:10.1016/j.jvolgeores.2013.11.001
    .
  22. doi:10.1029/2012GC004276
    .
  23. doi:10.1016/0377-0273(89)90066-8
    .

External links
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