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Apacheta-Aguilucho (5,581 metres (18,310 ft) and 5,283 metres (17,333 ft), respectively) is a group of volcanoes located in the northern Altiplano-Puna volcanic complex which has produced lava flows in the Plio-Pleistocene. The volcanoes were constructed in five stages over local ignimbrites from andesites and dacites, as well as a basement made from Tertiary epiclastic material. A geothermal system is located in the local Incaliri graben. The graben is filled with breccias, tuffs and lavas, and is buried by 100 metres (330 ft) thick ashfalls. Hydrothermal alteration has occurred on many flanks of the volcanoes and on the eastern flank a debris avalanche deposit has been identified, likely formed by the collapse of hydrothermally altered and destabilized material.
Contents
Apacheta's western side and the northeastern parts of the Chac-Inca dome have moraines from to the last glacial stage. The complex is located 55 kilometres (34 mi) northwest of El Tatio and 105 kilometres (65 mi) northeast of Calama, Chile.
Geologic history
In the first three stages, the andesitic-dactitic Apacheta volcano formed. Apacheta is moderately eroded and presents a crater covered with pyroclastic flows. It is sealed with a 2.5 kilometres (1.6 mi) long porphyritic dacite flow with flow structures.
In the second two stages, two dacitic lava domes Chac-Inca and Pabellón were erupted north and east of Aguilucho. The volcano was also constructed by lava flows but the domes are the youngest structures in the area, being dated 50 ka or 80–130 ka by potassium-argon dating.
Fumarolic activity
The volcanic complex is still fumarolically active, including on the eastern flank of Apacheta. The chemistry of the gases is mixed but includes a strong magmatic component (temperature 250–330 °C (482–626 °F)) which indicates that the volcanic complex has still a magmatic system.
Debris avalanche
The eastern flank of the complex contains a debris avalanche deposit 4.27 kilometres (2.65 mi) long that covered a surface area of 3 square kilometres (1.2 sq mi). Andesite-dacite lavas, breccias and hydrothermally altered material form the landslide mass that is confined by older lava flows. Hummocks are found along the entire flow; their size decreases from 4–20 metres (13–66 ft) to 0.1–2 metres (3.9 in–6 ft 6.7 in) high. Based on the topography and the slide structures, the flow first ran east-west, then encountered older lava flows and deflected southeastward. Distally the flow continued WNW-ESE.
Geothermal projects
In 1998, a drill by the Chilean National Mining Company accidentally showed the existence of steam heated to 88 °C (190 °F) while drilling a water well. Four wells were drilled 1,300–2,000 metres (4,300–6,600 ft) deep between 2009–2010, indicating the existence of a deep system with temperatures of 260 °C (500 °F). Urzua et al. evaluated an electrical power potential of 400 megawatts (540,000 hp). Enel Green Power has planned to create a 50 megawatts (67,000 hp) power plant from 13 wells, Chile's first commercial scale geothermal plant.