Preliminary Study of melt inclusions of the Copahue volcano of the phreatomagmatic eruptions of 2000, 2012, and 2016, Andean Southern Volcanic Zone, Argentina-Chile

PEREIRA DA SILVA, SARA MARIA; MONCADA, DANIEL; ROBIDOUX, PHILIPPE; CASELLI, ALBERTO TOMÁS

Reykjavik

Conferencia; European Current Research on Fluid and Melt Inclusions - ECROFI-2023; 2023

University of Iceland

The Copahue volcano is currently the most active volcanic system in Argentine and borders of Chile. Volatiles are the fundamental cause of the ascent, effervescence, expansion, and fragmentation of the magma and have been used to study a wide range of topics (Rose-Koga et al. 2021). To understand the content of pre-eruptive magmatic volatiles, the pyroclastic material was studied in the eruptive events of 2000, 2012 and 2016, which allowed identifying Melt Inclusion Assemblages (MIAs). The different MIAs identified by Cannatelli et al. (2016) are found in all mineral phases, mostly re-crystallized with one or more bubbles and daughter oxide minerals. This indicates a mixing of two types of magmas that evolve at different depths. The material was described in thin sections, by looking at 3 eruptive events that ejected bomb of basaltic-andesite composition with phenocrysts of plagioclase, pyroxene, and olivine. As a preliminary result, the host minerals (olivines and pyroxenes) were selected and the MIAs differentiated into 4 types (Tab. 1) were identified: MIA rich glass (MIAg), MIA rich crystal (MIAc), MIA rich bubble (MIAb), MIA rich crystal and bubble (MIAcb). The heterogeneity of these MIAs could indicate different processes in the trapping conditions of these volatiles in the magma. At least 3 MIAs were identified for each eruptive event, indicating different phases of volatile content during the magma ascent. Preliminary observations show the existence of MIAg zonation in pyroxenes, and also more incipiently in olivines. The next step will be working toward establishing a chronological scheme for the formation of these MIAs.