Pleistocene to recent magmatic evolution of the Planchon-Peteroa Volcanic Complex, Chile
Abstract
The active Planchon-Peteroa volcanic complex in the Andean Southern Volcanic Zone (35°S) comprises several vents that have erupted effusively and explosively with deposits ranging from basaltic andesite to rhyolite. Extensive 40Ar/39Ar dating underway , paired with field observations and geochemical data refine the geologic map and Pleistocene-recent eruptive history. Multiple pulses of elevated volcanic activity constructed the different parts of the complex (Azufre, Planchon I, Planchon II, and Peteroa). To the south, Azufre (~300 - 150 ka) is the oldest, most voluminous, and most compositionally variable edifice. The Planchon I (<50 ka) phase built the northern flank of the complex and is characterized predominantly by basaltic andesite magmatism. Planchon II lavas erupted to build the northwest part of the complex following the collapse of the NW-flank of the volcano and coeval 10 km3 debris avalanche at ~11 ka. Today, interaction of magmatic activity from Peteroa (a cluster of four active vents) with the ice on the glaciated southern summit could trigger a similar collapse . Peteroa has been the source of recent volcanism and a number of explosive eruptions in the Holocene. Thus, knowledge of magmatic processes which trigger explosive eruptive activity is essential to hazard assessment. One such eruption formed the 0.05 km3 Pomez de los Baños deposit at about 1 ka comprising mingled basaltic andesite and trachyte. Sieve cores in plagioclase and normally zoned crystals with An-rich cores in the trachyte imply mixing of magmas prior to eruption. We hypothesize that intrusion of mafic magma into a more silicic reservoir may have triggered the eruption. Measurement of mineral and melt inclusion compositions are underway to decipher the physics and timescales of destabilization and shifts in melt chemistry as a result of mingling and mixing . This work, combined with investigation of the older ~7 ka andesitic Los Ciegos pyroclastic flow and a crystal-rich ash fall from the 2019 Planchon eruption aim to characterize drivers o f explosive volcanism spanning the Holocene.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMV021.0021K
- Keywords:
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- 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGY;
- 8419 Volcano monitoring;
- VOLCANOLOGY;
- 8434 Magma migration and fragmentation;
- VOLCANOLOGY;
- 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGY