Infiernillo is a

volcanic field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

in Argentina. The field is located northwest of Malargue, at the Rio Salado. The volcanic field, part of 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 ...

, has formed three individual vents with associated lava flows.

Formation

Volcanic activity in the Andes and the region between the Andes and the Atlantic Ocean is caused by 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 ...

beneath the South America plate. While the main

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

is formed by the dehydration of the descending slab of oceanic lithosphere, the origin of volcanism beneath the main volcanic arc is unclear. One of these volcanic structures is the Payenia volcanic field between 34°30′–38°S southern latitude; it was probably formed by magmas generated by

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 ...

overriding a steepening subducting Nazca plate. This province, with a surface area of , includes

Payún Matrú Payún Matrú is a shield volcano in the Reserva Provincial La Payunia of the Malargüe Department, south of the Mendoza Province in Argentina. It lies in the back-arc region of the Andean Volcanic Belt, and was formed by the subduction of the ...

and Llancanelo volcanic field. The basement in the area is formed from

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

sedimentary rocks and

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

volcanic rocks. Activity is controlled by tectonic extension west of the Andes and has sent lava flows which reach the Rio Salado. The Infiernillo is part of a transitory region of the Southern Volcanic Zone between the northern and central segment thereof. There are three vents named Hoyo Colorado, La Hoyada and Loma Negra. The first vent erupted 6890 ± 40 BCE as found by

radiocarbon Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...

dating, while ages of 69,000 ± 50,000 and 34,000 ± 70,000 have been obtained on the other two centres, respectively. The oldest age in the field is 0.83 ± 0.11

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 ...

; other dates found are less than 100,000-200,000 years old. These other volcanoes are located around Niña Encantada lake and include Mesillas and Lagunita. Hoyada volcano is a crater with a diameter of . It is surrounded by

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...

falls and forms a long lava flow which after splits into two branches. The presence of levees in the flow indicates that the flow rate diminished during the eruption. Lagunitas volcano conversely is a high

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...

-like cone that generated a blocky lava flow long. This lava flow also dammed an ephemeral stream, creating a lake. The Loma Negra cone is older than the Lagunitas one considering that the Lagunitas lava flow is deflected by the Loma Negra cone and lava. The Loma Negra cone formed a lava flow long. A

phreatic ''Phreatic'' is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption. Hydrology The term phreatic (the word originates from the Greek , meaning "well" ...

explosion at its margins formed the Nina Encantada lake. Hoyo Colorado is a cone which generated a complex lava field damming the Salado river. Hoyo Colorado has erupted approximately twice as much rock as the other three centres. The first three cones all erupted

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...

containing hornblende and

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

and

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

. Hoyo Colorado is much more olivine-rich and contains

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 ...

. Major element analyses indicate similarity to the Planchon-Peteroa volcanic centre at the same latitude. The rare-earth element contents are transitional between Planchon-Peteroa and Patagonia alkali basalt signatures.

References

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