Altiplano–Puna volcanic complex
The Altiplano–Puna volcanic complex (Spanish: Complejo volcánico Altiplano-Puna), also known as APVC, is a
In the
Geography
The
Geology
The APVC is generated by the
Ignimbrites deposited during eruptions of APVC volcanoes are formed by "boiling over" eruptions, where magma chambers containing viscous crystal-rich volatile-poor magmas partially empty in tranquil, non-explosive fashion. As a result, the deposits are massive and homogeneous and show few size segregation or fluidization features. Such eruptions have been argued to require external triggers to occur.[6] There is a volume-dependent relationship between homogeneity of the eruption products and their volume; large volume ignimbrites have uniform mineralogical and compositional heterogeneity. Small volume ignimbrites often show gradation in composition. This pattern has been observed in other volcanic centres such as the Fish Canyon Tuff in the United States and the Toba ignimbrites in Indonesia.[11]
Petrologically, ignimbrites are derived from
Since the Miocene, less silicic magmas containing
Eruptions are affected by the local conditions, resulting in high altitude eruption columns that are sorted by westerly stratospheric winds. Coarse deposits are deposited close to the vents, while fine ash is carried to the Chaco and eastern cordillera. The highest volcanoes in the world are located here, including 6,887 metres (22,595 ft) high Ojos del Salado and 6,723 metres (22,057 ft) high Llullaillaco. Some volcanoes have undergone flank collapses covering as much as 200 square kilometres (77 sq mi).[8] Most calderas are associated with fault systems that may play a role in caldera formation.[14]
Scientific investigation
The area's calderas are poorly understood and some may yet be undiscovered. Some calderas were subject to comprehensive research.
The dry climate and high altitude of the Atacama Desert has protected the deposits of APVC volcanism from erosion,[7][16] but limited erosion also reduces the exposure of buried layers and structures.[3] Evidence of volcanic activity and cyclic variation has been obtained from remote fallout deposits as well.[18]
Geologic history
The APVC area before the upper Miocene was largely formed from
Ignimbrites range in age from 25
Activity waned after 2
The APVC is still active, with recent unrest and ground inflation detected by
Extent
The APVC erupted over an area of 70,000 square kilometres (27,000 sq mi)[25] from ten major systems, some active over millions of years and comparable to Yellowstone Caldera and Long Valley Caldera in the United States.[4] The APVC is the largest ignimbrite province of the Neogene[21] with a volume of at least 15,000 cubic kilometres (3,600 cu mi),[25] and the underlying magmatic body is considered to be the largest continental melt zone,[21] forming a batholith.[7] Alternatively, the body revealed by seismic studies is the remnant mush of the magma accumulation zone.[9] Deposits from the volcanoes cover a surface area of more than 500,000 square kilometres (190,000 sq mi).[8] La Pacana is the largest single complex in the APVC with dimensions 100 by 70 square kilometres (39 sq mi × 27 sq mi), including the 65 by 35 kilometres (40 mi × 22 mi) caldera.[7]
Magma generation rates during the pulses are about 0.001 cubic kilometres per year (0.032 m3/s), based on the assumption that for each 50–100 cubic kilometres (12–24 cu mi) of arc there is one caldera. These rates are substantially higher than the average for the Central Volcanic Zone, 0.00015–0.0003 cubic kilometres per year (0.0048–0.0095 m3/s). During the three strong pulses, extrusion was even higher at 0.004–0.012 cubic kilometres per year (0.13–0.38 m3/s). Intrusion rates range from 0.003–0.005 cubic kilometres per year (0.095–0.158 m3/s) and resulted in
Source of magmas
Modelling indicates a system where
Another model requires the intrusion of
Between 18 and 12
Magma generation in the APVC is periodical, with pulses recognized 10, 8, 6, and 4 mya. The first stage included the Artola, Granada, Lower Rio San Pedro and Mucar ignimbrites. The second pulse involved the Panizos, Sifon and Vilama ignimbrites and the third was the largest, with a number of ignimbrites. The fourth pulse was weaker than the preceding ones and involved the Patao and Talabre ignimbrites among others.[9]
The magmas beneath the APVC are noticeably rich in
Tomographic studies
Subsystems
- Aguas Calientes caldera[34] (24°15′S 66°30′W / 24.250°S 66.500°W)[6]
- Alto de los Colorados (26°05′S 68°15′W / 26.083°S 68.250°W)[6]
- Cerro Bitiche[10]
- Cerro Blanco caldera (26°41′S 67°46′W / 26.683°S 67.767°W)[6]
- Cerro Chanka (21°48′S 68°15′W / 21.800°S 68.250°W)[23]
- Cerro Chao (22°07′S 68°09′W / 22.117°S 68.150°W)[23]
- Cerro Chascon (21°53′S 67°54′W / 21.883°S 67.900°W)[23]
- Cerro Chillahuita (22°10′S 68°02′W / 22.167°S 68.033°W)[23]
- Cerro Galán (26°00′S 66°50′W / 26.000°S 66.833°W)[6]
- Cerro Morado[6] (22°51′S 66°43′W / 22.850°S 66.717°W)[35]
- Cerro Panizos (22°15′S 67°45′W / 22.250°S 67.750°W)[6]
- Chipas caldera[6]
- Coranzulí caldera (23°0′S 66°15′W / 23.000°S 66.250°W)[6]
- Delmedio (24°10′S 67°03′W / 24.167°S 67.050°W)[36]
- El Morro-Organullo[6]
- Granada complex (22°57′S 66°58′W / 22.950°S 66.967°W)[6]
- Guacha caldera (22°45′S 67°28′W / 22.750°S 67.467°W)[6]
- Huayra Huasi volcanic complex (23°30′S 66°37′W / 23.500°S 66.617°W)[37]
- Kapina caldera (21°50′S 67°35′W / 21.833°S 67.583°W)[6]
- Laguna Amarga caldera (26°42′S 68°30′W / 26.7°S 68.5°W)[6]
- La Torta (22°26′S 67°58′W / 22.433°S 67.967°W)[23]
- La Pacana (23°10′S 67°25′W / 23.167°S 67.417°W)[6]
- Lascar[4]
- Negra Muerta volcanic complex (24°28′S 66°12′W / 24.467°S 66.200°W)[6]
- Pairique volcanic complex (22°54′S 66°48′W / 22.900°S 66.800°W)[6]
- Pastos Grandes[7]
- Pocitos (24°10′S 67°03′W / 24.167°S 67.050°W)[36]
- Purico Complex (22°57′S 67°45′W / 22.950°S 67.750°W)[6]
- Quevar (24°19′S 66°43′W / 24.317°S 66.717°W)[36]
- Rachaite complex (23°0′S 66°5′W / 23.000°S 66.083°W)[6]
- Ramadas volcanic complex (24°10′S 66°20′W / 24.167°S 66.333°W)[38]
- Rincon volcanic complex (24°05′S 67°20′W / 24.083°S 67.333°W)[36]
- Tastil volcano (24°45′S 65°53′W / 24.750°S 65.883°W)[36]
- El Tatio[4]
- TulTul (24°10′S 67°03′W / 24.167°S 67.050°W)[36]
- Uturuncu[22] (22°16′12″S 67°10′48″W / 22.27000°S 67.18000°W)[25]
- Vallecito caldera (26°30′S 68°30′W / 26.500°S 68.500°W)[6]
- Vilama (22°36′S 66°51′W / 22.600°S 66.850°W)[6]
Ignimbrites
- Abra Grande Ignimbrite, 6.8 mya.[6]
- Acay Ignimbrite, 25 cubic kilometres (6.0 cu mi) 9.5–9.9 mya.[6]
- Antofalla Ignimbrite, 11.4–9.6 mya.[6]
- Arco Jara Ignimbrite, 2 cubic kilometres (0.48 cu mi) 11.3 mya.[6]
- Artola/Mucar Ignimbrite, 100 cubic kilometres (24 cu mi) 9.4–10.6 mya.[6]
- Atana Ignimbrite, 1,600 cubic kilometres (380 cu mi)[6] 4.11 mya.[39]
- Blanco Ignimbrite, 7 cubic kilometres (1.7 cu mi).[6]
- Caspana Ignimbrite, 8 cubic kilometres (1.9 cu mi) 4.59–4.18 mya.[11]
- Cerro Blanco Ignimbrite, 150 cubic kilometres (36 cu mi) 0.5–0.2 mya.[6]
- Cerro Colorado, 9.5–9.8 mya.[6]
- Cerro Lucho lavas, 1 cubic kilometre (0.24 cu mi) 10.6 mya.[6]
- Cerro Panizos Ignimbrite, 650 cubic kilometres (160 cu mi) 6.7–6.8 mya.[6]
- Chuhuilla Ignimbrite, 1,200 cubic kilometres (290 cu mi) 5.45 mya.[3]
- Cienago Ignimbrite, 7.9 mya.[6]
- Cueva Negra/Leon Muerto Ignimbrites, 35 cubic kilometres (8.4 cu mi) 3.8–4.25 mya.[6]
- Cusi Cusi Ignimbrite, >10 mya.[6]
- Galan Ignimbrite, 550 cubic kilometres (130 cu mi) 2.1 mya.[6]
- Granada/Orosmayo/Pampa Barreno Ignimbrite, 60 cubic kilometres (14 cu mi) 10-10.5 mya.[6]
- Grenada Ignimbrite, 9.8 mya.[15]
- Guacha Ignimbrite, 1,200 cubic kilometres (290 cu mi) 5.6–5.7 mya.[6]
- Guaitiquina Ignimbrite, 5.07 mya.[6]
- Laguna Amarga Ignimbrite, 3.7–4.0, 5.0 mya.[6]
- Laguna Colorada Ignimbrite, 60 cubic kilometres (14 cu mi) 1.98 mya.[3]
- Laguna Verde Ignimbrite, 70 cubic kilometres (17 cu mi) 3.7–4.0 mya.[6]
- Las Termas Ignimbrite 1 and 2, 650 cubic kilometres (160 cu mi) 6.45 mya.[6]
- Los Colorados Ignimbrite, 7.5–7.9 mya.[6]
- Merihuaca Ignimbrites, 50 cubic kilometres (12 cu mi) 5.49–6.39 mya.[6]
- Morro I Ignimbrite, 12 mya.[6]
- Morro II Ignimbrite, 6 mya.[6]
- Pairique Chico block and ash, 6 cubic kilometres (1.4 cu mi) 10.4 mya.[6]
- Pampa Chamaca, 100 cubic kilometres (24 cu mi) 2.52 mya.[6]
- Pitas/Vega Real Grande Ignimbrites, 600 cubic kilometres (140 cu mi) 4.51–4.84 mya.[6]
- Potrero Grande Ignimbrite, 9.8–9 mya.[6]
- Potreros Ignimbrite, 6.6 mya.[6]
- Purico Ignimbrite, 100 cubic kilometres (24 cu mi) 1.3 mya.[6]
- Puripicar Ignimbrite, 1,500 cubic kilometres (360 cu mi) 4.2 mya.[6]
- Rachaite volcanic complex, 7.2–8.4 mya.[6]
- Rosada Ignimbrite, 30 cubic kilometres (7.2 cu mi) 6.3–8.1 mya.[6]
- Sifon Ignimbrite, 8.3 mya.[6]
- Tajamar/Chorrillos Ignimbrite, 350 cubic kilometres (84 cu mi) 10.5–10.1 mya.[6]
- Tamberia Ignimbrite, 10.7–9.5 mya.[6]
- Tara Ignimbrite, 100 cubic kilometres (24 cu mi) 3.6 mya.[6]
- Tatio Ignimbrite, 40 cubic kilometres (9.6 cu mi) 0.703 mya.[3]
- Toba 1 Ignimbrite, 6 cubic kilometres (1.4 cu mi) 7.6 mya.[6]
- Toconao pumice, 100 cubic kilometres (24 cu mi)[6] 4.65 mya.[39]
- Vallecito Ignimbrite, 40 cubic kilometres (9.6 cu mi) 3.6 mya.[6]
- Verde Ignimbrite, 140–300 cubic kilometres (34–72 cu mi) 17.2 mya.[6]
- Vilama Ignimbrite, 8.4–8.5 mya.[6]
- Vizcayayoc Ignimbrite, 13 mya.[6]
References
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Bibliography
- del Potro, Rodrigo; Díez, Mikel; Blundy, Jon; Camacho, Antonio G.; Gottsmann, Joachim (2013). "Diapiric ascent of silicic magma beneath the Bolivian Altiplano". Geophysical Research Letters. 40 (10): 2044–2048. S2CID 31771758.
- Salisbury, M. J.; Jicha, B. R.; de Silva, S. L.; Singer, B. S.; Jimenez, N. C.; Ort, M. H. (2010). "40Ar/39Ar chronostratigraphy of Altiplano-Puna volcanic complex ignimbrites reveals the development of a major magmatic province". Geological Society of America Bulletin. 123 (5–6): 821–840. doi:10.1130/B30280.1.
- Chmielowski, Josef; Zandt, George; Haberland, Christian (1999). "The Central Andean Altiplano-Puna magma body". Geophysical Research Letters. 26 (6): 783–786. S2CID 129812369.
- De Silva, S.; Zandt, G.; Trumbull, R.; Viramonte, J. G.; Salas, G.; Jimenez, N. (2006). "Large ignimbrite eruptions and volcano-tectonic depressions in the Central Andes: a thermomechanical perspective". Geological Society, London, Special Publications. 269 (1): 47–63. S2CID 129924955.