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Monthly timescales of magma ascent and eruption triggering in two reservoirs beneath Hornopirén volcano, Southern Volcanic Zone

Eduardo Morgado1, Brandon Candia1, Sebastián Pérez1, Mauricio Mella2, Felix Boschetty3, Helen Thornhill3, Raimundo Brahm4

  • Affiliations: 1Escuela de Geología, Universidad Mayor, Santiago, Chile. 2Oficina Técnica Puerto Varas, SERNAGEOMIN, Puerto Varas, Chile. 3School of Earth and Environment, University of Leeds, Leeds, UK. 4School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington, New Zealand. 

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 70

  • Programme No: 1.2.15

  • Theme 1 > Session 2

Abstract

The Southern Volcanic Zone (SVZ), the most active volcanic region of the Andes, is characterised by the Liquiñe-Ofqui Fault Zone (LOFZ), a major NS trending structure, which extends ~1200 km long. Small eruptive centers are commonly built over the LOFZ, including Caburgua-Huelemolle, Fui Cones, Carrán-Los Venados, and Cayutué-La Viguería. An exception is the Hornopirén composite volcano (41°52′28″S, 72°25′53″W), located around 10 km north of the town of Hornopirén. The eruptive products of Hornopirén volcano across its three units exhibit basaltic to basaltic-andesitic compositions. The products of the most recent unit are representative of the eruptive history of the Hornopirén volcano, exhibiting fall deposits and lavas. Its mineralogy includes phenocrysts of plagioclase, olivine, spinel, clinopyroxene, and orthopyroxene. Thermometric, oxybarometric, and barometric calculations indicate temperatures of ~1090 °C, an oxygen fugacity buffer of ΔNNO+1, and the existence of two magma reservoirs beneath Hornopirén volcano at depths of approximately 7 and 23 km, respectively. Olivine phenocrysts display both normal and reverse zoning, reflecting interactions between magmas from the two reservoirs. The reverse zoning yields timescales of ~50 days, representing thermal re-equilibration recorded in crystals from the upper reservoir, while the normal zoning corresponds to magma transport from the lower to upper reservoir with timescales of ~110 days. These findings highlight the role of the Liquiñe-Ofqui Fault Zone facilitating ascent and eruption-triggering processes, with implications for volcanic hazard assessment in the region.