Irruputuncu

Coordinates: 20°43′55″S 68°33′08″W / 20.73194°S 68.55222°W / -20.73194; -68.55222
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For the mountain on the border of Chile and Bolivia in the Potosí Department, Daniel Campos Province, see
Iru Phutunqu (Chile-Daniel Campos)
.
Irruputuncu
Iru Phutunqu, Iruputuncu, Irruputunco
Irruputuncu is located in Bolivia
Irruputuncu
Irruputuncu
Location in Bolivia, on the border with Chile
Highest point
Cordillera Occidental
Geology
Age of rockPleistocene-Holocene
Mountain typeStratovolcano
Last eruption1995[1]

Irruputuncu is a

Central Volcanic Zone
(CVZ).

The volcano has been active during the

Seismic activity is also observed on Irruputuncu, and ongoing fumarolic activity releasing 21–50 t/d (0.24–0.57 long ton/ks) of sulfur dioxide
has left sulfur deposits in the active crater.

The Central Volcanic Zone is thinly inhabited and most volcanoes are not under reconnaissance, but Irruputuncu is watched by the Chilean

SERNAGEOMIN geologic service. The possibility of geothermal energy
production from the volcano has been examined.

Etymology and alternative names

The name Irruputuncu derives from

Peruvian feather grass and phutunqu a small vessel or a hole, pit, crater.[4] Alternative names are Irruputunco and Iruputuncu.[1]

Geography and geology

Regional setting

The

Austral Volcanic Zone (AVZ). The "Volcanoes of the World" catalogue counts about 575 eruptions in the entire volcanic belt.[5]

Volcanic activity in the belt is usually linked to the dehydration of the subducting slabs, which causes water and other subducted components to be added to the overlying mantle. In the case of the CVZ, this addition generates magmas that are further modified by the thick crust in the area, forming andesites, dacites and rhyolites.[5]

Local setting

Volcanism in the CVZ is linked to the subduction of the Nazca plate beneath the

Alitar, Lastarria and Tacora. Irruputuncu and other volcanoes including Guallatiri, Isluga, Lascar and San Pedro have displayed phreatic or magmatic-phreatic activity.[7] The arid climate of the area has led to good preservation of volcanic structures.[8]

A small gap about 100 km (62 mi) wide, which is known as the "Pica gap" but includes the

Alto Toroni volcano that features vigorous seismic activity,[9] separates Irruputuncu from Isluga in the north.[5] Irruputuncu is part of an elliptical alignment of volcanoes that extends to the east, which may be linked to a cup-shaped intrusion in the crust.[10] Older Pliocene volcanoes around Irruputuncu are Laguna volcano to the northeast and Bofedal to the southeast.[6] Irruputuncu lies at the end of a chain of volcanoes that trends northeastward away from it.[1] It may be part of a larger volcano system in the area.[11]

The volcanic complex sits on top of

diatomites. Further volcanic rocks beneath Irruputuncu are hydrothermally altered dacites that may be part of an older now deeply eroded edifice.[6]

Irruputuncu is a relatively small, 5,163 m (16,939 ft) high volcano,

rhyolitic ignimbrite is found southwest of the volcano.[13] The oldest lava flows on the northern and eastern side of the volcano were erupted from a northeastern crater named Crater I and are 35–113 m (115–371 ft) thick with erosional features and preserved ogives. They have a volume of around 0.097 km3 (0.023 cu mi).[6]

The younger flows are known as Queñoas lava flows; they form six distinct flows on the western sides of the volcano. They have different appearances depending on the side; the northwestern flows form lateral lava levees and ogives and reach thicknesses of 117–180 metres (384–591 ft) while the other flows have lobate structures with thicknesses of 23–95 m (75–312 ft). These thicknesses may be the result of high-viscosity magma and/or low eruption rates. A major block and ash deposit with the volume of 0.023 km3 (0.0055 cu mi) covers a surface area of 11.333 km2 (4.376 sq mi); it was highly mobile considering the distances it reached from the volcano on all three sides of the younger crater. It contains large blocks and has long flow ridges. A second block and ash flow formed by the collapse of lava domes covers 0.801 km2 (0.309 sq mi). Its blocks are somewhat smaller and its ridges are poorly developed.[6] Fissure eruptions have generated large lava flows from the flanks.[8] The El Pozo ignimbrite covers a surface area of 0.02 km2 (0.0077 sq mi) northwest of the volcano with a thickness of 50 m (160 ft), an approximate volume of 0.001 km3 (0.00024 cu mi) and is probably linked to Irruputuncu, in which case it would be the volcano's oldest unit.[6]

Irruputuncu underwent a flank collapse that subdivides the volcano into two edifices, the older Irruputuncu I and the younger Irruputuncu II, about 140 ± 40 ka ago. This flank collapse extends 6.3 km (3.9 mi) southwest from the older crater I and is about 10 m (33 ft) thick. It was formed by the collapse of the southwestern flank and forms three distinct units formed by hummock-forming lava blocks and flow ridges up to 1 km (0.62 mi) long. Each stage is associated with an individual crater named Crater I and Crater II. The flank collapse was probably produced by oversteepening of the volcano or by asymmetric growth.[6] Subsequent activity of the volcano has completely filled the scarp.[1] The lack of ground deformation during eruptive activity suggests the magma chamber of Irruputuncu may be more than 7–15 km (4.3–9.3 mi) deep, which may be linked to the thickness of the crust beneath the Central Andes, ranging 50–70 km (31–43 mi).[14]

Irruputuncu displays vigorous fumarolic activity that occupies about half the summit crater and is visible within several 10 km (6.2 mi).

pahoehoe-type morphology. Deposits are generally yellow but close to the fumaroles they display different colours depending on their temperatures.[6] Upon exposure to the air they can burn.[19] Gravel and eolian deposits form sedimentary units around the volcano.[6]

Composition

Irruputuncu's rocks consist of andesite- and dacite-containing

clinopyroxene crystallization with some mixing.[6] Irruputuncu's rocks show minor evidence of crustal contamination, similar to other CVZ volcanoes located within transition zones.[20]

Water is the most important component in the volcano's fumarolic gases, comprising 96.05% to 97.95% by volume.[12] Examinations of deuterium and oxygen-18 content of the water have determined that like the water of fumaroles in other Andean volcanic centres, Irruputuncu water is a mixture of weather-related water and water contained in andesite. The helium isotope ratios indicate the magmatic component dominates the gasses at Irruputuncu,[21][16] Much of the carbon dioxide comes from subducted and crustal carbonates.[21] The gases escape from oxidizing magma at 491–781 °C (916–1,438 °F) and pass through a weakly developed hydrothermal system with temperatures of c. 340 °C (644 °F).[12] Argon isotope ratios appear to be radiogenic.[16]

Eruptive history

The oldest rocks at Irruputuncu are lavas that have been dated by

potassium-argon dating to 10.8 ± 0.6 mya.[22] The oldest component clearly belonging to the volcano is the El Pozo ignimbrite that was erupted 258.2 ± 48.8 ka, forming a multi-layered ignimbrite that was probably generated by the injection of new, hot magma into older, cooler magma. A lava dome on the upper flank on the western side of the volcano is 0.14 ± 0.04 mya old. The block and ash flow between 55.9 ka and 140 ka old, but has not been precisely dated. The Crater lavas are 55.9 ± 26.8 ka old. The block and ash flow on the southwestern flank was formed 1570 ± 900 years BP.[6] Tephra layers found in the Salar Grande area of the Atacama Desert may originate at Irruputuncu.[23]

Historical activity of Irruputuncu is unclear. An unconfirmed eruption was reported in Bolivia in December 1989 and fumarolic activity in the crater was reported on 25 March 1990.

phreatomagmatic activity, were seen on 26 November 1995.[6] The plume's colour changed between black and white repeatedly.[1] Another plume was observed on 1 September 2003; neither of these incidents were accompanied with noticeable ground deformation.[14] Like some other volcanoes in the area, activity at Irruputuncu has not been preceded by ground inflation during historical times. Several theories, including aliasing of the imagery, have been proposed to explain the lack of ground inflation.[25] [26]

Ongoing seismic activity at a rate of about 5–6 earthquakes per 10 days recorded in two separate phases, November 2005-March 2006 and April 2010-February 2011 respectively and including one seismic swarm during the first measurement period, has been recorded at Irruputuncu. Some of this activity may be caused by mine blasts from nearby mining projects. Geothermal anomalies of about 9 K (16 °F) have been noted,[9] including hot springs west and northwest of the volcano.[6]

Threats and geothermal prospecting

With the exception of Peruvian volcanoes such as Misti, most of the volcanoes of the CVZ are in remote areas and are not closely watched.[5] Irruputuncu is a remote volcano; a road between Iquique and the Collahuasi mine[27] and mining infrastructure west of the volcano are the major sites that could be affected by future activity.[24]

The 1995 eruption drew attention to volcanic hazards in the

SERNAGEOMIN, which produces regular status reports[2] and which in 2020 classified it as a "type III" volcano, owing to its proximity to Collahuasi mine.[29] There are also hazard maps available.[30] Future eruptions could involve both the emission of lava domes and lava flows or explosive eruptions; the western and northwestern flanks would be the most affected.[24]

Irruputuncu has been examined as a potential location for a geothermal energy project involving a company named Minera Doña Inés de Collahuasi.[31] A geothermal prospect made at the base of Irruputuncu indicated the presence of water at temperatures of up to 220 °C (428 °F) in a deep reservoir.[32]

Climate and vegetation

El Niño-Southern Oscillation variability.[34]

See also

References

  1. ^ a b c d e f g "Irruputuncu". Global Volcanism Program. Smithsonian Institution.
  2. ^
    SERNAGEOMIN. Archived from the original
    on 22 October 2016. Retrieved 6 June 2016.
  3. ^ "San Pedro de Quemes" (in Spanish). Instituto Nacional de Estadística. Archived from the original on 14 August 2014. Retrieved 6 June 2016.
  4. ^ Ludovico Bertonio, Kastilla-Aymara simi qullqa: Iru. - Ichu espinoso. Phutunqu. - Un vasito de barro o redoma. Phutunqu vel Phujru. - Hoyo de la tierra sin agua, no muy hondo.
  5. ^
    doi:10.4067/S0716-02082004000200001
    .
  6. ^
    doi:10.1016/j.jsames.2015.08.012
    .
  7. doi:10.1016/j.jvolgeores.2010.02.006
    .
  8. ^
    S2CID 128979648
    .
  9. ^
    doi:10.1016/j.jvolgeores.2014.05.004
    .
  10. doi:10.1016/j.epsl.2008.02.020
    .
  11. S2CID 134049891
    .
  12. ^
    SERNAGEOMIN. Archived from the original
    (PDF) on 25 November 2015. Retrieved 5 June 2016.
  13. ISSN 0716-0208
    . Retrieved 1 October 2015.
  14. ^
    S2CID 18453316
    .
  15. ^
    S2CID 129450763
    .
  16. ^
    doi:10.4401/ag-5173
    .
  17. SERNAGEOMIN (in Spanish). Antofagasta: 11th Chilean Geologic Congress. pp. 443–446. Archived from the original
    (PDF) on 5 June 2016. Retrieved 5 June 2016.
  18. ISSN 0072-1077
    .
  19. ^ Ahlfeld, F; Branisa, L (1960). Geologia de Bolivia. Boliviano Petróleo. p. 195.
  20. doi:10.1130/B26538.1
    .
  21. ^
    S2CID 53062425
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  22. doi:10.1016/0012-8252(82)90042-3
    .
  23. S2CID 214198721
    .
  24. ^
    ISSN 0717-7305. Archived from the original
    (PDF) on 30 August 2021. Retrieved 20 August 2021.
  25. doi:10.1002/jgrb.50288
    .
  26. S2CID 129058847
    .
  27. ISBN 978-1-86239-220-5
    .
  28. S2CID 246752706
    .
  29. ^ "Sernageomin da a conocer nuevo ranking de volcanes" (in Spanish). SERNAGEOMIN. 20 February 2020. Retrieved 5 December 2021.
  30. ^ "Ministro entrega mapas de peligro volcánico en Tarapacá". 24horas.cl (in Spanish). 17 October 2013. Retrieved 9 June 2018.
  31. doi:10.1016/j.rser.2015.07.001
    .
  32. S2CID 55363214
    .
  33. S2CID 244554572
    .
  34. S2CID 246068513
    .

External links
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