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'''Vicuña Pampa''' is a volcano in [[Argentina]]. It is part of the [[Central Volcanic Zone]] of the Andes and is located on the southeastern margin of the [[Altiplano|Puna plateau]]. It consists out of a {{convert|30|km}} wide volcanic complex that is constructed by outwards-propagating [[lava flows]]. The centre of the complex is carved out by a {{convert|18|km}} wide depression, which was originally interpreted as a [[caldera]] but appears to be [[Erosion caldera|erosional]] in origin. It is drained southward by the [[Rio Vicuña Pampa]].

The volcano was constructed in two phases. In the first phase about 12 million years ago, the main volcanic edifice was constructed out of lava flows and probably formed a steep cone. After this stage, a phase of erosion, probably aided by higher [[orographic precipitation]] carved the present-day central depression. The second stage took place within the central depression and consists of [[lava dome]]s.

== Geography and geomorphology ==

Vicuña Pampa is in the [[Catamarca Province]] of Argentina, {{convert|100|km}} north of the town of [[Belén, Catamarca|Belen]].<ref name="Rossello1980" /> The volcano lies in the Central Andes, more specifically on the southeastern margin of the [[Altiplano|Puna]] plateau where a steep topographic step forms the edge of the plateau.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=750}}{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=225}}

The volcano is part of the [[Central Volcanic Zone]] of the Andes, which extends itself across southern [[Peru]] and [[Bolivia]] and northern [[Chile]] and Argentina. The Central Volcanic Zone since the [[Miocene]] has been volcanically active with large [[ignimbrite]] eruptions, especially in the more northerly [[Altiplano-Puna volcanic complex]]{{sfn|Guzmán|Grosse|Montero-López|Hongn|2014|p=170}} and in the southerly [[Galán]] and [[Luingo|Luingo caldera]] systems.{{sfn|Guzmán|Grosse|Montero-López|Hongn|2014|p=172}}

Vicuña Pampa is a volcanic complex with a diameter of about {{convert|30|km}},{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=750}} with flanks that gently slope outward.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=754}} [[Lava flow]]s make up the bulk of the edifice and are intercalated with [[conglomerate (geology)|conglomerate]]s and [[breccia]]s.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=756}} These lava flows propagated outward away from the centre of the volcanic complex,{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=753}} reaching lengths of about {{convert|17|km}} or even {{convert|19|km}}.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=758}} Some short lava flows were fed by a large [[Dike (geology)|dyke]] swarm that is intruded into the edifice,{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=758}} and which crops out within the central depression of the volcano.{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=226}} Several different types of dykes have been observed there.{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=231}}

A {{convert|1200|m}} deep {{convert|18|km}} wide central depression is open towards the southeast.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=750}} Originally it was interpreted as a collapse [[caldera]], but no evidence of [[ignimbrite]]s or other features of such calderas were identified; it is thus today considered an erosional landform.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=752}}{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=225}} The [[basement (geology)|basement]] beneath the volcano and some volcanic units are exposed within the central depression.{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=225}} The depression has a flat floor with landforms such as [[alluvial fan]]s, and it drains southward{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=754}} as the {{ill|Rio Vicuña Pampa|WD=Q21832355}} stream;{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=763}} the volcano is named after the river.<ref name="Rossello1980" /> The Rio Vicuña Pampa is one of the few rivers that have succeeded in invading the Puna-Altiplano high plateau; among the others are the [[San Juan del Oro River]], the [[Choqueyapu River]] and the {{ill|Rio Consata|WD=Q21798831}} the latter two both in Bolivia.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=765}}

Within the central depression, lava flows and breccia crop out in part in the form of [[lava neck]]s and [[lava plug]]s,{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=756}} as well as several breccia outcrops called the Cerro Morado Epiclastic Succession and the Cerro Bayo, La Cumbre and Nacimientos Breccias.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|pp=756-758}} The Cerro Bayo unit is formed by [[lava dome]]s and associated block-and-ash flows in the southwestern segment of the depression.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=762}}

== Geology ==

Off the western coast of South America, the [[Nazca Plate]] [[Subduction|subducts]] beneath the [[South America Plate]] at a rate of {{convert|7|-|8|cm/year|in/year}}, but was faster in the past.{{sfn|Roy|Cassard|Cobbold|Rossello|2006|p=262}}

The Puna is the site of many volcanoes, including large [[caldera]] volcanoes such as [[Cerro Blanco (volcano)|Cerro Blanco]] and [[Galán]]. Such calderas form when volcanic edifices collapse and leave elliptical or circular depressions; not all depressions within volcanic edifices form in such a process, however.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=750}}

Vicuña Pampa is constructed on top of a [[basement (geology)|basement]] formed by [[granitic]] and [[metamorphic]] rocks that date back to [[Precambrian]] to [[Cretaceous]] times;{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=752}} together with some other regional volcanic centres the Vicuña Pampa volcano seems to coincide with the demarcation between the basement and [[Ordovician]] metamorphic sediments.{{sfn|Guzmán|Grosse|Montero-López|Hongn|2014|p=183}} A number of sediment-filled basins are found south of the volcanic complex and are in part filled by volcanic sediments. Several [[fault (geology)|fault]]s occur in the area, including the Vicuña Pampa fault which has offset part of the volcanic complex and crosses its eastern sector.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=752}} The volcano is part of a lineament with the Filo Colorado centre farther southeast.{{sfn|Roy|Cassard|Cobbold|Rossello|2006|p=265}}

=== Composition ===

Volcanic rocks at Vicuña Pampa consist of [[basalt]], [[basaltic andesite]], [[andesite]], [[trachyandesite]] to [[trachydacite]]. The rocks contain [[phenocryst]]s of [[amphibole]], [[biotite]], [[clinopyroxene]], [[olivine]], [[orthopyroxene]], [[plagioclase]] and [[quartz]].{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=757}} The volcanic complex has been investigated for [[mining]] opportunities.{{sfn|Roy|Cassard|Cobbold|Rossello|2006|p=278}}

== Eruption history ==

Vicuña Pampa was constructed in two separate stages. The first stage occurred about 12 million years ago,{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=758}} it generated the various necks and lower lava flows which crop out in the central depression. Most likely, this phase of volcanism took the form of a rapid pulse and was then subject to intense erosion, giving rise to the large volume breccia deposits. This erosion phase was followed by another more steady phase of volcanism that constructed most of the volcanic complex, including the lava flows on its outer flanks.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=762}} The stratigraphic relationships have been interpreted as reflecting the development of a steep volcanic cone, followed by lateral eruptions that enlarged the edifice.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=763}} Dates obtained on the older complex shows ages of 12.19 and 12.41 million years ago for the first stage.{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=225}}

Between the two stages, intense erosion generated the central depression and cut deeply into the first stage volcanic edifice.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=762}} This depression was created by complex erosion, not by large scale explosive eruptions, as there is no evidence of the latter. The climate was wetter in the region at that time, probably because at that time [[orographic precipitation]] was focused on the eastern margin of the Puna and thus allowed much more rapid erosion than the present-day arid climate. Material eroded during that time was transported by the Rio Vicuña Pampa into the foreland.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=763}} Activity of local [[fault (geology)|fault]] systems{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=764}} and the ability of the central depression to centralize runoff may have further aided in the erosion process.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=765}}

In the second stage of activity, lava domes and dykes were emplaced within the depression,{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=762}} which contained waterbodies at that time; traces of these waterbodies have been identified in the second stage volcanics.{{sfn|Guzmán|Strecker|Martí|Petrinovic|2017|p=764}} This late stage may have occurred during the late [[Miocene]].{{sfn|Guzmán|Neri|Carniel|Martí|2017|p=225}}

== References ==
{{Reflist|refs=
<ref name="Rossello1980">{{cite book|last1=Rossello|first1=EA|title=Revista de la Asociación Geológica Argentina|date=1980|publisher=Asociación Geológica Argentina|page=436|chapter-url=https://books.google.com/books?id=xMjrEhQKMMsC&q=Vicuna+Pampa%2C+Departamento+Belen%2C+Provincia+de+Catamarca&pg=PA436|accessdate=19 December 2017|language=es|chapter=Nuevo complejo volcanico Vicuna Pampa, Departamento Belen, Provincia de Catamarca}}</ref>
}}

=== Sources ===
{{refbegin}}
* {{cite journal|last1=Guzmán|first1=Silvina|last2=Grosse|first2=Pablo|last3=Montero-López|first3=Carolina|last4=Hongn|first4=Fernando|last5=Pilger|first5=Rex|last6=Petrinovic|first6=Ivan|last7=Seggiaro|first7=Raúl|last8=Aramayo|first8=Alejandro|title=Spatial–temporal distribution of explosive volcanism in the 25–28°S segment of the Andean Central Volcanic Zone|journal=Tectonophysics|date=December 2014|volume=636|pages=170–189|doi=10.1016/j.tecto.2014.08.013|bibcode=2014Tectp.636..170G|issn=0040-1951|hdl=11336/32061|hdl-access=free}}
* {{cite journal|last1=Guzmán|first1=Silvina|last2=Neri|first2=Marco|last3=Carniel|first3=Roberto|last4=Martí|first4=Joan|last5=Grosse|first5=Pablo|last6=Montero‐López|first6=Carolina|last7=Geyer|first7=Adelina|title=Remarkable variability in dyke features at the Vicuña Pampa Volcanic Complex, Southern Central Andes|journal=Terra Nova|date=1 August 2017|volume=29|issue=4|pages=224–232|doi=10.1111/ter.12268|bibcode=2017TeNov..29..224G|language=en|issn=1365-3121|url=https://hal-insu.archives-ouvertes.fr/insu-01522829/file/Guzm-n_et_al-2017-Terra_Nova.pdf}}
* {{cite journal|last1=Guzmán|first1=Silvina|last2=Strecker|first2=Manfred R.|last3=Martí|first3=Joan|last4=Petrinovic|first4=Ivan A.|last5=Schildgen|first5=Taylor F.|last6=Grosse|first6=Pablo|last7=Montero-López|first7=Carolina|last8=Neri|first8=Marco|last9=Carniel|first9=Roberto|last10=Hongn|first10=Fernando D.|last11=Muruaga|first11=Claudia|last12=Sudo|first12=Masafumi|title=Construction and degradation of a broad volcanic massif: The Vicuña Pampa volcanic complex, southern Central Andes, NW Argentina|journal=GSA Bulletin|date=1 May 2017|volume=129|issue=5–6|pages=750–766|doi=10.1130/B31631.1|bibcode=2017GSAB..129..750G|language=en|issn=0016-7606|hdl=10261/152221|hdl-access=free}}
* {{cite journal|last1=Roy|first1=R.|last2=Cassard|first2=D.|last3=Cobbold|first3=P.R.|last4=Rossello|first4=E.A.|last5=Billa|first5=M.|last6=Bailly|first6=L.|last7=Lips|first7=A.L.W.|title=Predictive mapping for copper–gold magmatic-hydrothermal systems in NW Argentina: Use of a regional-scale GIS, application of an expert-guided data-driven approach, and comparison with results from a continental-scale GIS|journal=Ore Geology Reviews|date=November 2006|volume=29|issue=3–4|pages=260–286|doi=10.1016/j.oregeorev.2005.10.002|issn=0169-1368|hdl=11336/16669|hdl-access=free}}
{{refend}}

== External links ==
{{cite thesis|last=Rossello|first=Eduardo Antonio|title=Geología del complejo volcánico Vicuña pampa, Departamento Belén, Provincia de Catamarca|language=es|publisher=Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales|year=1983|url=https://hdl.handle.net/20.500.12110/tesis_n1806_Rossello|ref=none}}

[[Category:Volcanoes of Catamarca Province]]
[[Category:Miocene volcanoes]]