Lauca (volcano)

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Lauca
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Lauca
Location of Lauca in Chile
Highest point
Elevation 5,140 m (16,860 ft) [1]
Coordinates 18°20′S69°23′W / 18.333°S 69.383°W / -18.333; -69.383 Coordinates: 18°20′S69°23′W / 18.333°S 69.383°W / -18.333; -69.383 [2]
Naming
English translationAquatic grass
Language of name Aymara
Geography
Location Putre, Arica y Parinacota Region
Flag of Chile.svg  Chile
Parent range Altiplano, Andes
Geology
Age of rock Miocene-Pliocene
Mountain type Stratovolcano
Volcanic belt Central Volcanic Zone
Last eruption Pliocene

Lauca is a 5,140 metres (16,860 ft) [1] high andesitic stratovolcano in the Central Volcanic Zone of the Andes on the Altiplano in northern Chile. Administratively it is located in Putre, Arica y Parinacota Region. The volcano was active during the Late Miocene from 10.5 million years ago onwards. A major ignimbrite collapsed the volcano in the Late Pliocene.

Stratovolcano Tall, conical volcano built up by many layers of hardened lava and other ejecta

A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).

Altiplano Plateau in west-central South America

The Altiplano, Collao, Andean Plateau or Bolivian Plateau, in west-central South America, is the area where the Andes are the widest. It is the most extensive area of high plateau on Earth outside Tibet. The bulk of the Altiplano lies in Bolivia, but its northern parts lie in Peru, and its southern parts lie in Chile and Argentina.

Chile Republic in South America

Chile, officially the Republic of Chile, is a South American country occupying a long, narrow strip of land between the Andes to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far south. Chilean territory includes the Pacific islands of Juan Fernández, Salas y Gómez, Desventuradas, and Easter Island in Oceania. Chile also claims about 1,250,000 square kilometres (480,000 sq mi) of Antarctica, although all claims are suspended under the Antarctic Treaty.

Contents

Geology

Andesites from the Lauca volcano, active in the Late Miocene as of 10.5 million years ago, [3] exist in two groups, plagioclase rich ones which underwent alteration and fine grained silicic ones that are fresher. [1] The territory is underpinned with a crust formed from rocks of Precambrian to Cretaceous age, with thicknesses up to 70 kilometres (43 mi). [2] Amphibole rich lava flows formed a uniform volcanic cone. A later major ignimbrite eruption caused the collapse of the centre and formed the Lauca ignimbrite. [1] A caldera is present, with a lava dome at the northeastern rim. [1]

Andesite An intermediate volcanic rock

Andesite ( or ) is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and rhyolite, and ranges from 57 to 63% silicon dioxide (SiO2) as illustrated in TAS diagrams. The mineral assemblage is typically dominated by plagioclase plus pyroxene or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other volcanic rocks are illustrated in QAPF diagrams.

Plagioclase feldspars, albite - anorthite solid solution series

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 properly known as the plagioclase feldspar series (from the Ancient Greek for "oblique fracture", in reference to its two cleavage angles). This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796–1872) in 1826. The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium and calcium atoms can substitute for each other in the mineral's crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or 'record-groove' effect.

The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.

The Lauca ignimbrite has a thickness up to 150 metres (490 ft), covering the El Diablo Formation in parts and filling the Lluta Canyon. Ar-Ar ages for this rhyolitic ignimbrite have been determined at 2.73 ± 0.02 Ma based on sanidine analysis and 2.87 ± 0.05 Ma from biotite. [4] The Lauca ignimbrite has been correlated to the Pérez ignimbrite in Bolivia and the Pachía ignimbrite in southern Peru. [5] Along the Copaquilla-Tignámar Fault, uplifting the eastern side over the western side, [6] the Lauca ignimbrite has been displaced over 100 to 150 metres (330 to 490 ft), indicative of tectonic activity after deposition in the Late Pliocene. [7] In parts, the Lauca ignimbrite is covered by conglomeratic terrace deposits. [8]

Lluta River river in Chile

The Lluta River is a river located in the northern portion of the Arica y Parinacota Region of Chile. Its headwaters are on the western flanks of the Andes of the Parinacota Province, just a few kilometers south of the border with Peru, and empties into the Pacific Ocean about 4 km north of the city of Arica.

Rhyolite An igneous, volcanic rock, of felsic (silica-rich) composition

Rhyolite is an igneous, volcanic rock, of felsic (silica-rich) composition (typically > 69% SiO2 – see the TAS classification). It may have any texture from glassy to aphanitic to porphyritic. The mineral assemblage is usually quartz, sanidine and plagioclase (in a ratio > 2:1 – see the QAPF diagram). Biotite and hornblende are common accessory minerals. It is the extrusive equivalent to granite.

Sanidine feldspar, tectosilicate mineral

Sanidine is the high temperature form of potassium feldspar with a general formula K(AlSi3O8). Sanidine is found most typically in felsic volcanic rocks such as obsidian, rhyolite and trachyte. Sanidine crystallizes in the monoclinic crystal system. Orthoclase is a monoclinic polymorph stable at lower temperatures. At yet lower temperatures, microcline, a triclinic polymorph of potassium feldspar, is stable.

See also

The Caldera Lauca is a caldera in the Arica y Parinacota Region of Chile. It is located in the Cordillera Occidental, in the valley of the Lauca River. The elliptic caldera has an east-west extension of 23 kilometres (14 mi) and 50 kilometres (31 mi) in north-south direction, buried beneath the late Miocene Vilañuñumani-Tejene volcanic complex in the north and ending at Chucal in the south. The 21 mya Oxaya Ignimbrite originates in the caldera. The eastern border of the caldera is buried beneath younger ignimbrites and deposits but is located east of the Guallatiri volcano. An Oligocene fault marks the western edge of the caldera.

Lauca National Park national park

Lauca National Park is located in Chile's far north, in the Andean range. It encompasses an area of 1,379 km2 of altiplano and mountains, the latter consisting mainly of enormous volcanoes. Las Vicuñas National Reserve is its neighbour to the south. Both protected areas, along with Salar de Surire Natural Monument, form Lauca Biosphere Reserve. The park borders Sajama National Park in Bolivia.

Lauca River river

The Lauca River is a binational river. It originates in the Chilean Altiplano of the Arica and Parinacota Region, crosses the Andes and empties into Coipasa Lake in Bolivia.

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Andean Volcanic Belt Volcanic belt in South America

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Taapaca Volcano in Chile

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La Pacana mountain in Chile

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Kunturiri (Bolivia-Chile) mountain on the border of Bolivia and Chile

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Cerro Guacha

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Chusmiza complex is a Miocene volcano in Chile. It is the largest stratovolcano of the Miocene in the western Andean escarpment, with a volume of 400 cubic kilometres (96 cu mi). It is constructed from andesite. Potassium-argon dating has established an age of 11.3±0.3 mya.

El Rojo Norte is a cinder cone in the Andes, constructed on top of volcano debris in the Lauca basin.

Guallatiri mountain in Parinacota Province Chile

Guallatiri is a 6,071-metre (19,918 ft) 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 be composed of either a lava dome or a pyroclastic cone, while the lower flanks of the volcano are covered by lava flows and lava domes. The volcano's eruptions have produced mostly dacite along with andesite and rhyolite.

Oxaya Formation is a geological formation in northern Chile made up of ignimbrite sheets. The formation formed about 25 to 19 million years ago in the Late Oligocene and Early Miocene. Oxaya Formation is deformed by the Oxaya anticline.

Azapa Formation is a geological formation in northern Chile made up of gravels of fluvial origin. It is conformably overlain by Oxaya Formation. Azapa Formation is deformed by the Oxaya anticline.

Guaichane-Mamuta is a volcano in Chile. It is formed by a caldera and lava flows which form two separate systems. The volcano is of Miocene age.

Pica gap is a segment in the Central Volcanic Zone of Chile where volcanic activity is absent. It is named after the Altos de Pica region.

Tatajachura is a stratovolcano in Chile, in the Isluga National Park.

Wheelwright caldera is a caldera in Chile. It is variously described as being between 11 kilometres (6.8 mi) and 22 kilometres (14 mi) wide and lies in the Central Volcanic Zone of the Andes. A lake lies within the caldera, which is among the largest of the Central Andes. The caldera lies in the region of Ojos del Salado, the world's tallest volcano.

Vilama (caldera) mountain

Vilama is a Miocene caldera in Bolivia and Argentina. Straddling the border between the two countries, it is part of the Central Volcanic Zone, one of the four volcanic belts in the Andes. Vilama is remote and forms part of the Altiplano-Puna volcanic complex, a province of large calderas and associated ignimbrites that were active since about 8 million years ago, sometimes in the form of supervolcanoes.

References

  1. 1 2 3 4 5 Wigger et al., 2012, p.81
  2. 1 2 Wörner et al., 1992
  3. Kött et al., 1995
  4. García et al., 2011, p.1053
  5. Charrier et al., 2013, p.245
  6. Charrier et al., 2013, p.255
  7. Charrier et al., 2013, p.247
  8. Schlunegger et al., 2010, p.S132

Bibliography

Reynaldo Charrier is a Chilean geologist who has contributed to the tectonostratigraphy of Chile. In 2000 he received the award "Premio Juan Brüggen".

<i>International Journal of Earth Sciences</i> journal

International Journal of Earth Sciences is a peer-reviewed scientific journal published monthly by Springer Science+Business Media. It covers original and review papers on the history of earth and is an international Geoscience journal. Subject areas covered in the journal include: dynamics of the lithosphere, tectonics and volcanology, sedimentology, evolution of life, marine and continental ecosystems, global dynamics of physicochemical cycles, mineral deposits and hydrocarbons, and surface processes.

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