Doña Ines is a

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

. It is a

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

age

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 ...

which is formed from

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 that form its summit area and

nuee ardente A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...

deposits which form the flanks of the volcano. Located north of the Salar de Pedernales, Doña Ines is a high cone with a diameter of .

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 form the top of the volcano and

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...

deposits are found on its flanks, generating a noticeable slope contrast between the steeper upper parts of the edifice and the more gentle lower slopes. The nuee ardente deposits contain blocks with sizes of up to . Overall the volcano covers a surface area of about . Additional lava domes can be found on the eastern slopes of the volcano. A subsidiary vent, active at the same time as the main volcano, has formed the Loma Dona Ines rocks south of the main volcano. The Gemelas-Fortuna volcanic centres lie nearby. The basement beneath the volcano on its northern side is formed by

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

sedimentary and volcanic rocks. Doña Ines is part of the Maricunga Belt, a

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 ...

at the western edge of the Puna plateau. Doña Ines together with Cerros Bravos, La Coipa and the Maricunga volcanoes lies in the northern part of the belt, west of 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 ...

. Volcanic activity within this belt has generated a number of mineral deposits. Doña Ines lies in the northern part of the belt. It is considered part of a volcanic chain with the Pastillito and Volcan de la Sal cones, probably dependent on tectonic fractures, which lies in a long north-south valley. The volcano is the source of the Inez Chica

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

, 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 erupted 16.2 million years ago which covers a surface area of . The volcano has erupted

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...

and

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

, both containing

hornblende Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks ...

. The rocks of the summit lava domes contain hornblende,

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 ...

and smaller amounts of orthopyroxene. The rocks of Doña Ines have a content between 56 and 64%. Based on the composition of

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 ...

, the amphibole crystals formed in magmas with temperatures spanning , with the central vent magmas having higher temperatures at amphibole crystallization and also showing evidence of a more complex magma system. The

was active approximately 15 million years ago, during the

. A date of 15.0 ± 0.3 million years ago has been obtained on one lava flow.

References

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The geochemical evolution of volcan Donna Ines in the central volcanic zone of Chile
{{DEFAULTSORT:Dona Ines Miocene stratovolcanoes Stratovolcanoes of Chile Volcanoes of Atacama Region

See also

References

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External links