Stratigraphy and structure of Chachahuén volcanic complex, southern Mendoza province, Argentina

Journal article (2024)

Authors

J. Octavio Palma Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universitetet i Oslo
Steffi Burchardt Uppsala University
T. Schmiedel Uppsala University, Universitetet i Oslo
Dougal A. Jerram Universitetet i Oslo, DougalEARTH Ltd.
Karen Mair Universitetet i Oslo
Héctor A. Leanza Museo Argentino de Ciencias Naturales (MACN) – CONICET
Olivier Galland Universitetet i Oslo
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Published Date

2024

Language

English

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Abstract

The Chachahuén Volcanic Complex is an eroded Upper Miocene arc to back-arc volcanic system that was emplaced in the north-eastern edge of the Neuquén Basin, southern Mendoza province, Argentina. It was formed as the result of shallowing followed by steepening of the Nazca plate during Miocene-Pliocene, and is characterized by a volcanism which ranges from trachydacites to basalts. Thanks to erosion, the stratigraphy and the shallow plumbing systems of the volcano are well-exposed. A new evolution for the volcano stratigraphy is proposed, based on new field observations, satellite imagery, and incorporating the radiometric and petrological data of previous works. The stratigraphy is constrained around one main explosive event, recorded by a thick dacitic pyroclastic density current (PDC) deposit (the Corrales Ignimbrite) (>150m). The main units forming the Chachahuén Volcanic Complex are (1) the pre-dacite PDC deposits (trachydacitic to rhyolitic) Vizcachas Formation, (2) the thick Corrales Ignimbrite, (3) a post-dacite trachyandesitic PDC deposits (dominated by block and ash (BAF) deposits) and thick lava flows, and (4) thin mafic basaltic lava flows. The collapse of a large elliptical caldera occurred during the Trachyandesite phase. The main magma transport channels and feeders are sub-vertical dykes, which exhibit a radial distribution centred on the main caldera depression. Moreover, cryptodomes mainly preserved outside the rim of the caldera accommodated the transport and emplacement of the more silicic magma during the Trachyandesite phase.