Product Code Database
Irruputuncu is a volcano in the commune of Pica, Tamarugal Province, Tarapacá Region, Chile, as well as San Pedro de Quemes Municipality, Nor Lípez Province, Potosí Department, Bolivia. The mountain's summit is high and has two summit craters—the southernmost -wide one has active . The volcano also features lava flows, block and ash flows and several . The volcano is part of the Andes Central Volcanic Zone (CVZ).
The volcano has been active during the Pleistocene and Holocene, with major eruptions occurring 258.2 ± 48.8 Kiloannum ago, between 55.9 ka and 140 ka ago and 1570 ± 900 Before Present (380 ± 900 AD), which were accompanied by the formation of ignimbrites. Historical volcanic activity is less clear; an eruption in 1989 is considered unconfirmed. Eruption column linked to phreatomagmatic 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 geologic service. The possibility of geothermal energy production from the volcano has been examined.
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 wedge. In the case of the CVZ, this addition generates magmas that are further modified by the thick crust in the area, forming , and .
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 with accessory , and . 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 and there is no evidence of Glacier 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 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 Levee 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 vent 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 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 chloride, hydrogen fluoride, methane, nitrogen and oxygen. In addition, argon, carbon monoxide, helium, hydrogen and sulfur are found. The temperatures of the fumaroles are comparable with or exceed the boiling point at such altitudes. ASTER 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.
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 Carbonate rock. 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.
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 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. 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 west and northwest of the volcano.
The 1995 eruption drew attention to volcanic hazards in the Western Cordillera. In Chile, Irruputuncu is surveilled by SERNAGEOMIN, 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 eruptions; the western and northwestern flanks would be the most affected.
Olca and Irruputuncu have been examined as a potential location for a geothermal energy project involving a company named Minera Doña Inés de Collahuasi. A geothermal prospect made at the base of Irruputuncu indicated the presence of water at temperatures of up to in a deep reservoir; the volcano was thus classified as "highly favourable area".
|
|
