Evolution of Parinacota volcano, Central Andes, Northern Chile

Abstract

Parinacota is an active composite stratovolcano located in the Central Andes of Northern Chile (18°S). During its earlier stage (Parinacota 1 unit, Late Pleistocene, 300-70? ka) rhyolitic to andesitic magmas were erupted, forming a voluminous lava-dome complex with its associated pyroclastic fans (mainly block-and-ash flow deposits), essentially deposited towards the Upper Lauca basin (West). It later evolved to a steep-sided composite stratocone (Parinacota 2 unit, Late Pleistocene-Holocene, 70?-8 ka), mainly formed by andesitic lava flows and scoria tephra fallout deposits.Around 8 ka ago the ancestral Parinacota volcano, built during Parinacota 1 and 2, partially collapsed towards the west, in a single and catastrophic event generating the outstanding Parinacota Debris Avalanche deposit.Soon after the collapse a new stratocone started to build with the emission of andesitic lava flows and pyroclastic flows, and their associated fallout deposits (Parinacota 3 unit, Holocene, <8 ka). Some lahars mainly directed towards the south, west and east have also been generated during Parinacota 3. Contemporaneously with the formation of the central cone, a series of flank cones and their associated basaltic andesite to andesitic lava flows were formed (Ajata centres, 6-1.4 ka). These centres erupted through two fractures, NNE and NS oriented, in the south-western flank of the volcano. The new cone (Parinacota 3 unit) has an estimated minimum volume of 18 km 3 , giving a minimum eruption rate of 2.25 km 3 ka -1 for the last 8,000 years, which means that Parinacota volcano must be considered one of the most active volcanoes in the Central Andes of Northern Chile during the Holocene.