Английская Википедия:Antofalla

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Шаблон:Short description Шаблон:Good article Шаблон:Infobox mountain Antofalla is a Miocene-Pliocene volcano in Argentina's Catamarca Province. It is part of the volcanic segment of the Andes in Argentina, and it is considered to be part of the Central Volcanic Zone, one of the volcanic zones of the Andes. Antofalla forms a group of volcanoes that are aligned on and behind the main volcanic arc. Antofalla itself is a remote volcano.

Antofalla and other Andean volcanoes form because the Nazca Plate is subducting beneath the South American Plate. Antofalla volcano is located in a region with a "basins and ranges" topography, where during the Miocene ranges were uplifted and basins formed through tectonic movement. It sits on a basement formed by Eocene-Miocene sedimentary units over a much older crystalline basement.

Antofalla is formed by a principal volcano, the Шаблон:Convert high Antofalla volcano proper, and a surrounding complex of smaller volcanic systems that are formed by lava flows and pyroclastic material. The whole complex was active between 10.89–1.59 million years ago; whether activity occurred in historical time is unclear.

Name

The mountain is first attested in a map of 1900 as Antofaya, although an earlier map in 1632 uses the name Antiofac for the whole region.[1] The name may be derived from Шаблон:Lang, Шаблон:Lang, Шаблон:Lang, which means "metal" (especially "copper") in the indigenous language Quechua.[2] Pedro Armengol Valenzuela hypothesized that the second part of the name is Шаблон:Lang, "collect"; thus the name Antofalla would mean "collection of copper".[3] Another theory is that Antofalla is derived from the Diaguita language.[4]

Geography and structure

Antofalla lies in the Antofagasta de la Sierra department of theШаблон:SfnШаблон:Sfn northernШаблон:Sfn Catamarca Province, in northwestern Argentina.Шаблон:SfnШаблон:Sfn The towns of Antofalla, Puesto Cuevas, Botijuela and Potrero Grande are east, southeast, south and southwest of the volcano, respectively.[5]Шаблон:Sfn Gravel roads run along the northern, northeastern and east-southeast-southern sides of the volcanic complex,Шаблон:Sfn but the volcano is difficult to access.Шаблон:Sfn Precolumbian constructions, including a platform on the summit of Antofalla, have been found.[6]

Antofalla is part of the Central Volcanic Zone of the Andes, which runs along the border between Argentina and ChileШаблон:Sfn and whose main expression occurs in the Western Cordillera.Шаблон:Sfn The volcanoes of the Central Volcanic Zone lie at high altitudes, and the volcanic zone spans the countries of Argentina, Bolivia, Chile and Peru.[7] Present-day activity in the Central Volcanic Zone occurs at Lascar and Lastarria,Шаблон:Sfn and about 44 centres have been active in the Holocene.Шаблон:Sfn Aside from stratovolcanoes, calderas with large ignimbrites are also part of the Central Volcanic Zone; the Altiplano–Puna volcanic complex is a complex of such large calderas.[8]

Antofalla is a cluster of stratovolcanoes,Шаблон:Sfn with the Шаблон:Convert high Antofalla volcano at its centre.[9]Шаблон:Sfn An altar with a stone pyramid lies on its summit,[10] and the mountains Llullaillaco, Pajonales and Pular can be seen from the top of the mountain.[11]

A number of other centres developed around the main Antofalla volcano, forming a Шаблон:Convert wide volcanic area;[9]Шаблон:Sfn counterclockwise from the north these are:[5]Шаблон:Sfn

These volcanic centres overlap with each other,Шаблон:Sfn are all much smaller than the main Antofalla volcano and have experienced little erosion. All these volcanoes are formed by lava domes, lava flows and pyroclastic units.Шаблон:Sfn Ignimbrites are also found and one of these forms Cerro Onas,Шаблон:Sfn while a more recent one occurs in the Quebrada de las Cuevas area.Шаблон:Sfn Between Cerro de la Aguada and Cerro Cajeros lies the Cerro la Botijuela obsidian dome.Шаблон:Sfn On the western and southwestern side of the complex, some cinder cones can be found,Шаблон:Sfn and fissure vents linked to faults cut through the volcanic complex.Шаблон:Sfn Finally, a sector collapse deposit and collapse amphitheatre can be observed at Quebrada de las Minas and Quebrada el Volcán.Шаблон:Sfn A large scale topographic anomaly surrounds the entire volcanic complex,[13] and seismic tomography has shown the presence of low-velocity anomalies linked to the volcanic group.[14]

The Salar de Antofalla, one of the largest salt pans in the world,[10] lies southeast of the Antofalla complex.Шаблон:Sfn It is one of many salt pans that developed within closed basins of the region and its surface lies at an elevation of Шаблон:Convert;[15] other such salt pans include Salar Archibarca north-northwest of Antofalla,Шаблон:Sfn Salina del Fraile south-southwest and Salar del Rio Grande northwest.Шаблон:Sfn There also are several lakes such as Laguna Las Lagunitas on the northeastern foot of Antofalla, Laguna Patos west of Cerro Lila – Cerro Ojo de Antofalla and Laguna Cajeros southwest of Cerro Lila – Cerro Cajeros. Most of the northwestern flank of the main Antofalla volcano drains into the Salar de Archibarca, while the southeastern flank has drainages connecting it to the Salar de Antofalla through the (from northeast to southwest) Quebrada de las Cuevas, Quebrada del Volcan and Quebrada de las Minas; the latter two join before entering the salt panШаблон:Sfn in a large fan, the Campo del Volcán.[5] Northeast of the Conito de Antofalla, the Rio Antofalla originates and flows southeastward into the Salar de AntofallaШаблон:Sfn in a large alluvial fan, similar to other drainages that enter the Salar de Antofalla.Шаблон:Sfn Finally, south of Antofalla lies Vega Botijuela,[5] a hot spring that discharges Шаблон:Convert warm water at a rate of Шаблон:Convert,[16] and which has emplaced a Шаблон:Convert wide travertine.Шаблон:Sfn There is a conspicuous travertine cone at Botijuela,Шаблон:SfnШаблон:Sfn an extinct geyser. Other warm springs in the area are Vega Antofalla, El Hervidero and Te bén Grande; they may be nourished by thermal waters that ascent on faults.[17]

Geology

Off the western coast of South America, the Nazca Plate subducts beneath the South American PlateШаблон:Sfn at a rate of about Шаблон:Convert;Шаблон:Sfn this subduction is responsible for volcanic activity in the Central Volcanic Zone[8] and elsewhere in the Andes.Шаблон:Sfn Volcanism does not occur along the entire length of the subduction zone; north of 15° and south of 28° the subducting plate moves downward at a shallower angle and this is associated with the absence of volcanic activity.Шаблон:Sfn Other volcanic zones exist in the Andes, including the Northern Volcanic Zone in Colombia and EcuadorШаблон:Sfn and the Southern Volcanic Zone also in Chile.Шаблон:Sfn A furtherourth volcanic zone, the Austral Volcanic Zone, is caused by the subduction of the Antarctic Plate beneath the South American Plate and lies south of the Southern Volcanic Zone.[7]

A fault runs in north–south direction in the western part of the Antofalla complex.Шаблон:Sfn Many geologic lineaments control tectonics across the whole region, they direct the ascent of magma and the location of basins; some of these lineaments exist since the Precambrian. One of these lineaments in the region trends north-northeast and separates the Arequipa-Antofalla terrane from the Pampia terrane.Шаблон:Sfn

Geologic record

The regional geography developed during the Middle and Late Miocene, when basins and ranges were formed by thrusting and subsidence; the basins were filled with evaporites above older molasse-like material, while the ranges are mainly formed by Paleozoic rocks. Precambrian and Late Cretaceous rocks crop out in the Eastern Cordillera on the eastern margin of the Puna.Шаблон:Sfn The tectonic activity decreased about 9 million years ago, with the exception of a brief reactivation less than 4 million years ago. The present-day southern Puna is tectonically quiescent,Шаблон:Sfn although fault scarps indicate recent ground movements.Шаблон:Sfn

The oldest volcanic activity occurred during the Permian and early Jurassic, and the present-day manifestations consist mainly of lava and pyroclastic material. During the Cenozoic, a number of now inactive volcanoes and ignimbrites, the latter of which typically have volumes of less than Шаблон:Convert, erupted in the region.Шаблон:Sfn Only less than Шаблон:Convert thick ignimbrites were deposited during the Eocene-early Miocene, probably from vents in the Coastal Cordillera.Шаблон:Sfn During the Eocene, the subduction became shallower, moving volcanism eastward into the main Andes.Шаблон:Sfn Volcanic activity dramatically increased during the Miocene, during which large stratovolcanoes and ignimbrites were emplaced; it is often not clear from which centre a given ignimbrite is sourced from.Шаблон:Sfn Later volcanic activity was characterized by the emplacement of ignimbrites and of monogenetic volcanoes, which consist of cinder cones and lava flows with small volumes. Some of these cones are partially eroded,Шаблон:Sfn other ones have a fresh appearance and these are as little as 200,000 ± 90,000 years old,Шаблон:Sfn with even more recent (Holocene) activity possible.[18] While the Miocene phase of high activity was linked to a fast subduction regime, the monogenetic activity may be linked to delamination of the crust beneath the Puna insteadШаблон:Sfn as well as with a change in tectonic regime that favoured crustal extension.Шаблон:Sfn The transition between the two volcanic phases was characterized by a decrease in volcanic activity.[15]

The Juan Fernández Ridge was subducted in the region between 11–8 million years ago according to Kraemer et al. 1999. This may have generated a flat subduction profile and thus allowed volcanic arc-like volcanism to occur in the region behind the actual volcanic arc.Шаблон:Sfn

Local

Antofalla lies in the Salar de Antofalla areaШаблон:Sfn of the Argentine Puna, a high plateau located over a thick crust of the Andes. It is a basin and range-like region with volcanoes.Шаблон:Sfn Before the Neogene the region was not part of the Andes proper, being located behind the mountain chain, and was integrated into the mountain chain by tectonic movements.Шаблон:Sfn

Antofalla together with neighbouring Cerro Archibarca, Cerro Beltrán and Tebenquicho is part of a group of long lived volcanic complexes that developed in the Argentine Puna;Шаблон:SfnШаблон:Sfn the first and the last of these lie due north and northeast of Antofalla, respectively.Шаблон:Sfn All of them appear to be associated with a lineament known as the Archibarca lineament, which crosses the Andes in northwest-southeast direction,Шаблон:Sfn and which additionally includes the Escondida ore occurrenceШаблон:Sfn and the volcanoes Llullaillaco, Corrida de Cori and Galán.Шаблон:Sfn This lineament may be an area where the crust is unusually weak.Шаблон:Sfn Other such lineaments in the Andes are the Calama-Olacapato-El Toro lineament and the Culampajá one.Шаблон:Sfn Seismic tomography has found a low-velocity zone under Antofalla, which may be an active magma body.[19]

The terrain beneath the volcano is formed in part by the crystalline basement of Precambrian-Paleozoic ("Antofalla Metamorphites"Шаблон:Sfn) age mainly north of the volcano and often interpreted as ophiolite, and by sedimentary units of Eocene-Miocene age that crop out on its southern side and by a conglomerate unit known as the Potrero Grande Formation.Шаблон:Sfn Parts of the basement crop out where it have been exposed by erosion, such as in the Rio Antofalla and the Quebrada de las Minas,Шаблон:Sfn and more generally in two sectors north and south of the volcano.Шаблон:Sfn

Composition

Antofalla has erupted andesite and dacite,Шаблон:Sfn with dacite dominantШаблон:Sfn and rhyolite a less common rock type;Шаблон:Sfn the entire spectrum from basaltic andesite to rhyolite has been found. Thin lava flows form most of the basalt-like rocks, which are subordinate at Antofalla.Шаблон:Sfn The rocks have a porphyric textureШаблон:Sfn and contain phenocrysts including biotite, clinopyroxene, hornblende, ilmenite, magnetite, olivine, orthopyroxene, plagioclase, quartz and sanidine; not all of these occur in every rock.Шаблон:Sfn

Magma genesis appears to involve extensive interactions with the lower crust, a process which at first gave rise to rhyolitic material; later the now heavily altered crust interacted less with newer magmas and thus a more basaltic andesite-andesite-dacite unit developed.Шаблон:Sfn

Hydrothermal alteration has occurred on the southeastern flanks of the complex at Quebrada de las Minas and on Antofalla's western flank.Шаблон:Sfn Volcanic systems like Antofalla and volcano-plutonic complexes often develop mineral deposits through hydrothermal and epithermal processes; such has also happened at Antofalla, yielding occurrences of gold, lead, silver and zinc. These became targets of mining operations:

  • The latter three extracted on the eastern side of Antofalla in the old Los Jesuitas mine.Шаблон:Sfn
  • There are ruins of a gold mining settlement close to the town of Antofalla.[10]
  • A map of 1900 mentions the existence of an Antofaya silver mine on the southeastern side of the complex.[1]
  • A more recent map showing the existence of a mining site on Quebrada de las Minas.Шаблон:Sfn

Mining at Antofalla goes back to 1700 at least,[20] and infrastructure includes mills.[21] Significant ore deposits may exist at the volcano,Шаблон:Sfn but their deep burial in the poorly eroded volcanic complex hampers their exploitation.Шаблон:Sfn

Climate, vegetation and fauna

Antofalla lies in a region of arid climate, with about Шаблон:Convert precipitation, much of it in the form of snow at high elevations. Temperatures change drastically from day to night and vice versa,Шаблон:Sfn ranging from Шаблон:Convert in the wider region; the climate has been characterized as continental.Шаблон:Sfn The region lies between two major climatic regimes, a northerly regime dominated by easterly moisture flows which occur during summer, and a southerly regime where westerlies transport moisture from the west mainly in winter.Шаблон:Sfn

Vegetation is scarce in the region. Where water is available, marsh vegetation and the so-called pajonales and tolares form; Deyeuxia, Festuca and Stipa grasses make up the former and Adesmia, Acantholippia, Baccharis, Fabiana, Senecio and Parastrephia thorn-bearing bushes the latter.Шаблон:Sfn

Animals in the region include llamas, various rodents and vicuñas, as well as carnivores such as Darwin's rhea, pumas and South American foxes. Human hunters were also active in the region and have left a number of archeological traces, including projectilesШаблон:Sfn and trenches where hunters hid from prey.Шаблон:Sfn The extreme climate and scarcity of water restrict human habitation to small areas, however.Шаблон:Sfn

Climatological implications

During winter snow covers the peaks; meltwater formed during spring has cut gullies into the mountains.Шаблон:Sfn There are not many creeks on Antofalla that carry water year round, although deep ravines with evidence of flash flood activity can be discerned.Шаблон:Sfn

The main Antofalla volcano may have been glaciated during the Pleistocene,Шаблон:Sfn but this is disputed especially for the lower mountains of the complex.Шаблон:Sfn It is likely that in the past, more water was available and led to the deposition of alluvial fans at the margins of basinsШаблон:Sfn although there is no evidence that a lake ever formed in the Salar de Antofalla, unlike in other salars farther north.Шаблон:Sfn Indeed, the early Holocene was colder and wetter than present-day, and precipitation may have reached Шаблон:Convert.Шаблон:Sfn

Eruptive history

The Antofalla complex has been active from the Miocene 11 million years ago into the Quaternary and has generated a large variety of volcanic rocks;Шаблон:Sfn it is thus considered to be a very long-lived volcano.Шаблон:Sfn The subsidiary peaks around Antofalla were all considered to be extinct by Ferdinand von Wolff.[12]

The first phase of volcanic activity occurred between 10.89–10.1 million years ago. At that time, eruptions covered the terrain beneath the volcano with ignimbrites of rhyolitic composition.Шаблон:Sfn Subsequently, lava flows of maficШаблон:Efn to trachydacitic composition were emplaced, in part on top of the earlier ignimbrites.Шаблон:Sfn Between 9.09–1.59 million years ago activity was continuous and dominated by lava flows of andesitic to dacitic composition, which constructed the main Antofalla volcano and the surrounding vents. Small felsicШаблон:Efn eruptions generating lava domes and ignimbrites concluded this activity, with the ignimbrite in Quebrada de las Cuevas dated to 1.59 ± 0.08 million years ago.Шаблон:Sfn Other volcanic units attributed to this volcanic complex are the Aguas Calientes basalt,Шаблон:Sfn the Los Patos ignimbriteШаблон:Sfn of lower Pliocene ageШаблон:Sfn and the Tambería Ignimbrite.Шаблон:Sfn

Even later, several mafic centres grew southwest and west of the Antofalla complex.Шаблон:Sfn Fumarolic activity continues to this day,[22] the existence of geysers was reported in 1962[23] and traces of an extinct geyser such as sinter structures have been found at Botijuelas.[12] There are reports that the main volcano "smoked" occasionally[12] such as in 1901 and 1911[9] and Antofalla is sometimes incorrectly considered the highest active volcano in the world,[24] but the Global Volcanism Program considers the complex as Pleistocene in age,[9] and no clear evidence of Holocene activity is found.[18]

Climbing

Antofalla is a technically simple climb and there are guides in the region. The main Antofalla volcano can be ascended in three days, although the paths are not always easy to reach by vehicle. Low temperatures and high wind are common issues.[10]

Notes

Шаблон:Notelist

References

Шаблон:Portal Шаблон:Reflist

Sources

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Шаблон:Refend

External links

Шаблон:Andean volcanoes

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  1. ↑ 1,0 1,1 Ошибка цитирования Неверный тег <ref>; для сносок Quesada2009 не указан текст
  2. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Holmer2013 не указан текст
  3. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Valenzuela1918 не указан текст
  4. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Latorre1997 не указан текст
  5. ↑ 5,0 5,1 5,2 5,3 Ошибка цитирования Неверный тег <ref>; для сносок KayCoira2008 не указан текст
  6. ↑ Ошибка цитирования Неверный тег <ref>; для сносок LeibowiczMoyano2018 не указан текст
  7. ↑ 7,0 7,1 Ошибка цитирования Неверный тег <ref>; для сносок Stern2004 не указан текст
  8. ↑ 8,0 8,1 Ошибка цитирования Неверный тег <ref>; для сносок SiebelSchnurr2001 не указан текст
  9. ↑ 9,0 9,1 9,2 9,3 Ошибка цитирования Неверный тег <ref>; для сносок GVP не указан текст
  10. ↑ 10,0 10,1 10,2 10,3 Ошибка цитирования Неверный тег <ref>; для сносок PoloPuna не указан текст
  11. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Vitry2017 не указан текст
  12. ↑ 12,0 12,1 12,2 12,3 Ошибка цитирования Неверный тег <ref>; для сносок VonWolff1929 не указан текст
  13. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Perkins2016 не указан текст
  14. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Bianchi2013 не указан текст
  15. ↑ 15,0 15,1 Ошибка цитирования Неверный тег <ref>; для сносок Voss2002 не указан текст
  16. ↑ Ошибка цитирования Неверный тег <ref>; для сносок PesceMiranda2003 не указан текст
  17. ↑ Ошибка цитирования Неверный тег <ref>; для сносок PaoliBianchi2002 не указан текст
  18. ↑ 18,0 18,1 Ошибка цитирования Неверный тег <ref>; для сносок PeruccaMoreiras2009 не указан текст
  19. ↑ Ошибка цитирования Неверный тег <ref>; для сносок ChenKufner2020 не указан текст
  20. ↑ Ошибка цитирования Неверный тег <ref>; для сносок LavandaioCatalano2004 не указан текст
  21. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Cienfuegos1899 не указан текст
  22. ↑ Ошибка цитирования Неверный тег <ref>; для сносок JayWelch2013 не указан текст
  23. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Colqui1962 не указан текст
  24. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MolinaLittle1981 не указан текст
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