Chiqllarasu

Chiqllarasu (Quechua, chiqlla green, Ancash Quechua rasu snow, ice, mountain with snow, Hispanicized spelling Chicllarazo) Portugueza or Portuguesa is a mountain in the Andes of Peru, about 5167 m high. It is situated in the Ayacucho Region, Cangallo Province, Paras District. Chiqllarasu lies north-east of the mountain Saywa Q'asa, between the villages Patawasi (Patahuasi) in the northwest and Kichkawasi (Quichcahuasi) in the southeast.

Chiqllarasu lies on the top of the crest of the Western Cordillera. It features a 7 x wide caldera, known as the Cerro Sagollan caldera. Within the 800 m thick deposits gold and silver have been found. These are epithermal deposits with low sulfide content. The caldera was formed on a central volcano which erupted andesite and dacite. This edifice originally reached a diameter of 30 km or more, and contained lava domes and short lava flows, which are most recognizable on the eastern side of the volcano. The Rio Apacheta and the Rio Quichcahuasi drain the edifice.

The Atunsulla tuff is formed by many flows of rhyolite which contain clasts and pumice. It advanced as much as 40 km along the Rio Cachi, reaching the Ayacucho basin. The river has eroded deep into the tuff, which has been removed in many places by erosion.. Initially its volume may have been about 50 km3. This volcano may be underpinned by a large batholith..

Samples from the pre-Atunsulla tuff volcano have been dated at 4–3.5 million years ago. The Atunsulla tuff was erupted from Chiqllarasu around 2.4 million years ago. A long break in volcanic activity, during which the edifice was deeply eroded, may have occurred before this eruption. A resurgent dome formed 1.9 million years ago. Hydrothermal activity occurred both before and after the eruption of the Atunsulla tuff, and the mineralization occurred 1.9 million years ago, This volcano is among the youngest in a Central Peru volcanic chain ; hot water indicate that the geothermal system may be still active.