Iru Phutunqu (Chile-Nor Lípez)
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Irruputuncu is a volcano in the commune of Pica,
Tamarugal Province Tamarugal Province ( es, Provincia de Tamarugal) is one of two provinces in the northern Chilean region of Tarapacá. The capital is the city of Pozo Almonte. Name The province is named after Pampa del Tamarugal. Spanish name: * Provincia de Tam ...
, Tarapacá Region, Chile, as well as San Pedro de Quemes Municipality, Nor Lípez Province, Potosí Department,
Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...
. The mountain's summit is high and has two summit craters—the southernmost -wide one has active fumaroles. The volcano also features
lava flows Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
,
block and ash flow A block and ash flow or block-and-ash flow is a flowing mixture of volcanic ash and large (>26 cm) angular blocks commonly formed as a result of a gravitational collapse of a lava dome or lava flow. Block and ash flows are a type of pyroclastic fl ...
s and several
lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...
s. The volcano is part of the Andean
Central Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...
(CVZ). The volcano has been active during the Pleistocene and Holocene, with major eruptions occurring 258.2 ± 48.8 ka ago, between 55.9 ka and 140 ka ago and 1570 ± 900 BP (380 ± 900 AD), which were accompanied by the formation of ignimbrites. Historical volcanic activity is less clear; an eruption in 1989 is considered unconfirmed. Plumes linked to
phreatomagmatic Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...
eruptive activity were observed on 26 November 1995 and 1 September 2003. Seismic activity is also observed on Irruputuncu, and ongoing fumarolic activity releasing of 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 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service ( es, Servicio Nacional de Geología y Minería; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and adv ...
geologic service. The possibility of
geothermal energy Geothermal energy is the thermal energy in the Earth's crust which originates from the formation of the planet and from radioactive decay of materials in currently uncertain but possibly roughly equal proportions. The high temperature and pres ...
production from the volcano has been examined.


Etymology and alternative names

The name Irruputuncu derives from Aymara ''iru'' spiny
Peruvian feather grass ''Jarava ichu'', commonly known as Peruvian feathergrass, ''ichhu'', ''paja brava'', ''paja ichu'', or simply ''ichu'' (Quechua for straw), is a grass species in the family Poaceae native to the Americas. It is found growing in a vast area: Mex ...
and ''phutunqu'' a small vessel or a hole, pit, crater. Alternative names are ''Irruputunco'' and ''Iruputuncu''.


Geography and geology


Regional setting

The
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
of the
Nazca plate The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Na ...
and the Antarctic plate beneath the western side of South America has generated a belt of volcanic activity named the Andean Volcanic Belt. The belt is separated in a number of volcanic zones by segments lacking recent volcanic activity; in these segments, shallow subduction of the plates presumably displaces the
asthenosphere The asthenosphere () is the mechanically weak and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between ~ below the surface, and extends as deep as . However, the lower boundary of the asthenosphere is not ...
away from these segments. The segments with active volcanism are the
Northern Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Ame ...
(NVZ), the
Central Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...
(CVZ), the
Southern Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American ...
(SVZ) and the
Austral Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andes, Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Am ...
(AVZ). The "Volcanoes of the World" catalogue counts about 575 eruptions in the entire volcanic belt. 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 A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...
. 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
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
s.


Local setting

Volcanism in the CVZ is linked to the subduction of the Nazca plate beneath the South America plate. This subduction within the past 27.5
mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...
has triggered a thickening of the crust and
orogeny Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...
. Approximately 44 volcanic centres that are either active or potentially active are found in the CVZ. Some centres are fumarolically active; these include Alitar,
Lastarria Lastarria is a high stratovolcano that lies on the border between Chile and Argentina. It is remote and the surroundings are uninhabited but can be reached through an unpaved road. The volcano is part of the Central Volcanic Zone, one of the fou ...
and
Tacora Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Near the border with Peru, it is one of the northernmost volcanoes of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic b ...
. Irruputuncu and other volcanoes including
Guallatiri Guallatiri is a high volcano in Chile. It is located southwest of the Nevados de Quimsachata volcanic group and is sometimes considered to be part of that group. It is a stratovolcano with numerous fumaroles around the summit. The summit may b ...
,
Isluga Isluga () is a stratovolcano located in Colchane, west of the Chile- Bolivia border and at the west end of a group of volcanoes lined up in an east-west direction, which also includes the volcanoes Cabaray and Tata Sabaya. Isluga has an elon ...
, Lascar and San Pedro have displayed phreatic or magmatic-phreatic activity. The arid climate of the area has led to good preservation of volcanic structures. A small gap about wide, which is known as the "Pica gap" but includes the Pliocene-Pleistocene Alto Toroni volcano that features vigorous seismic activity, separates Irruputuncu from Isluga in the north. 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. Older Pliocene volcanoes around Irruputuncu are Laguna volcano to the northeast and Bofedal to the southeast. Irruputuncu lies at the end of a chain of volcanoes that trends northeastward away from it. It may be part of a larger volcano system in the area. The volcanic complex sits on top of ignimbrite layers, the Miocene Ujina and Pleistocene Pastillos Ignimbrites. These ignimbrites are and thick, the former is a welded ignimbrite that was erupted 9.3 ± 0.4 mya and the latter in two stages 0.79 ± 0.2 - 0.73 ± 0.16 mya and 0.32 ± 0.25 mya. In terms of composition, the Ujina is pink-grey crystals and pumice and the Pastillos a gray-white pumice forming the lower member and the upper member of the Pastillos contains cinerites with accessory
claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...
s,
siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...
s and diatomites. Further volcanic rocks beneath Irruputuncu are hydrothermally altered dacites that may be part of an older now deeply eroded edifice. Irruputuncu is a relatively small, high volcano, which covers a surface area of with a volume of and has two summit craters, of which the -wide southwestern one is fumarolically active. Crater II, the youngest crater, is surrounded by the Crater lava flows that form lava domes and seven short lava flows long, thick and with a total volume of emitted from it. They have weakly developed
ogives The ''Ogives'' are four pieces for piano composed by Erik Satie in the late 1880s. They were published in 1889, and were the first compositions by Satie he did not publish in his father's music publishing house. Satie was said to have been insp ...
and there is no evidence of glacial activity anywhere on the volcano. The current edifice is constructed within a collapsed amphitheater of an older edifice. Overall, the volcano has a pristine morphology. Block and ash flows and thick lava flows of high viscosity form the stratocone. A
rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
ignimbrite is found southwest of the volcano. The oldest lava flows on the northern and eastern side of the volcano were erupted from a northeastern crater named Crater I and are thick with erosional features and preserved ogives. They have a volume of around . 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 while the other flows have lobate structures with thicknesses of . 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 covers a surface area of ; 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 . Its blocks are somewhat smaller and its ridges are poorly developed. Fissure eruptions have generated large lava flows from the flanks. The El Pozo ignimbrite covers a surface area of northwest of the volcano with a thickness of , an approximate volume of and is probably linked to Irruputuncu, in which case it would be the volcano's oldest unit. 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 southwest from the older crater I and is about 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 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. Subsequent activity of the volcano has completely filled the scarp. The lack of
ground deformation Ground may refer to: Geology * Land, the surface of the Earth not covered by water * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical ...
during eruptive activity suggests the magma chamber of Irruputuncu may be more than deep, which may be linked to the thickness of the crust beneath the Central Andes, ranging . Irruputuncu displays vigorous fumarolic activity that occupies about half the summit crater and is visible within several . The high fumaroles have temperatures of and are composed mainly by sulfur dioxide, followed by minor amounts of
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
, hydrogen chloride,
hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...
, methane, nitrogen and oxygen. In addition, argon, carbon monoxide, helium, hydrogen and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
are found. The temperatures of the fumaroles are comparable with or exceed the
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...
at such altitudes.
ASTER Aster or ASTER may refer to: Biology * ''Aster'' (genus), a genus of flowering plants ** List of ''Aster'' synonyms, other genera formerly included in ''Aster'' and still called asters in English * Aster (cell biology), a cellular structure shap ...
imagery indicates Irruputuncu's fumarole field has a small surface area with high temperatures. Total sulfur dioxide flux from the volcano is between . The fumarolic activity has left sulfur deposits on the volcano. Sulfur deposits are found in the youngest crater in an area of about , and also form small sulfur flows with pahoehoe-type morphology. Deposits are generally yellow but close to the fumaroles they display different colours depending on their temperatures. Upon exposure to the air they can burn. Gravel and eolian deposits form sedimentary units around the volcano.


Composition

Irruputuncu's rocks consist of andesite- and dacite-containing hornblende and
pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...
. The El Pozo ignimbrite is pumice-rich and has a composition between trachyandesite and trachydacite. Minerals
amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...
,
biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...
, hornblende, quartz and plagioclase comprise the rocks. The Irruputuncu I lava flows are composed of trachyandesitic with biotite and plagioclase, while the Queñoas are composed of andesite and trachyandesite. The block and ash flows and Crater lavas consist of solely trachyandesitic rocks. Overall, these rocks belong to the potassium-rich calc-alkaline series typical of CVZ volcanoes. The magmas are formed by plagioclase and clinopyroxene crystallization with some mixing. Irruputuncu's rocks show minor evidence of crustal contamination, similar to other CVZ volcanoes located within transition zones. Water is the most important component in the volcano's fumarolic gases, comprising 96.05% to 97.95% by volume. 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, Much of the carbon dioxide comes from subducted and crustal carbonates. The gases escape from oxidizing magma at and pass through a weakly developed hydrothermal system with temperatures of . Argon isotope ratios appear to be radiogenic.


Eruptive history

The oldest rocks at Irruputuncu are lavas that have been dated by potassium-argon dating to 10.8 ± 0.6 mya. 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. Tephra layers found in the Salar Grande area of the Atacama Desert may originate at Irruputuncu. 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. Another report indicates activity in December 1960. Eruption plumes on Irruputuncu, which reached an altitude of and dispersed to the east, probably triggered by
phreatomagmatic Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...
activity, were seen on 26 November 1995. The plume's colour changed between black and white repeatedly. Another plume was observed on 1 September 2003; neither of these incidents were accompanied with noticeable
ground deformation Ground may refer to: Geology * Land, the surface of the Earth not covered by water * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical ...
. 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. Ongoing seismic activity at a rate of about 56 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 have been noted, including hot springs west and northwest of the volcano.


Threats and geothermal prospecting

With the exception of Peruvian volcanoes such as
Misti Misti, also known as Putina or Guagua Putina, is a stratovolcano of andesite, dacite, and rhyolite located in southern Peru near the city of Arequipa. With its seasonally snow-capped, symmetrical cone, Misti stands at above sea level and lies betw ...
, most of the volcanoes of the CVZ are in remote areas and are not closely watched. Irruputuncu is a remote volcano; a road between Iquique and the Collahuasi mine and mining infrastructure west of the volcano are the major sites that could be affected by future activity. The 1995 eruption drew attention to volcanic hazards in the Western Cordillera. In Chile, Irruputuncu is surveilled by
SERNAGEOMIN 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service ( es, Servicio Nacional de Geología y Minería; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and adv ...
, which produces regular status reports and which in 2020 classified it as a "type III" volcano, owing to its proximity to Collahuasi mine. There are also hazard maps available. Future eruptions could involve both the emission of lava domes and lava flows or
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such ...
s; the western and northwestern flanks would be the most affected. Irruputuncu has been examined as a potential location for a geothermal energy project involving a company named . A geothermal prospect made at the base of Irruputuncu indicated the presence of water at temperatures of up to in a deep reservoir.


Climate and vegetation

''
Polylepis tarapacana ''Polylepis tomentella'', known in its native habitat by the Spanish common name ''queñoa de altura'' (polylepis or quenoa of ighaltitude), is a short tree or shrub which is found in small, scattered groupings along the mountainous borders of ...
'' trees on Irruputuncu have been used (through
tree rings Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
) to reconstruct atmospheric radiocarbon concentrations and regional climatic variability, including El Niño-Southern Oscillation variability.


See also

* Geology of Bolivia * Geology of Chile * List of volcanoes in Bolivia * List of volcanoes in Chile


References


External links


AVA Images
{{DEFAULTSORT:Iru Phutunqu (Chile-Nor Lipez) Volcanoes of Potosí Department Volcanoes of Tarapacá Region Stratovolcanoes of Chile Andean Volcanic Belt Active volcanoes Subduction volcanoes Bolivia–Chile border International mountains of South America Mountains of Bolivia Mountains of Chile Polygenetic volcanoes Holocene stratovolcanoes Quaternary South America