New insights into the Permian-Triassic magmatism of southern Cerro Cacheuta, Argentina /Avances en el conocimiento del magmatismo Permo-Triasico del flanco sur del Cerro Cacheuta, Argentina

• Published in: Earth sciences research journal 2023-12, Vol.27 (4), p.343
• Main Authors: Ma, Gallardo, Adrian H, Mule, Melisa, Giaccardi, Aldo, Crespo, Esteban, Aguilera, David
• Format: Article
• Language: English
• Subjects: Analysis; Argentina; Breccia; Evolution; Geodes; Honduras; Iron oxides; Magmatism; Porphyry; Silica; South America; Tectonics (Geology); Volcanic ash, tuff, etc; Volcanoes
• ISSN: 1794-6190
• DOI: 10.15446/esrj.v27n4.107538

The igneous rocks of Cerro Cacheuta are considered a typical expression of the Permian-Triassic magmatism within the Andes Precordillera of Mendoza, Argentina. In particular, the southwestern margin of this hilltop is characterised by intermediate volcanic and felsic intrusives from the Choiyoi Group, one of the most extensive volcano-sedimentary suites of southern South America. The Choiyoi magmatism is widely associated with dramatic tectonic and environmental changes in the Gondwana supercontinent. Therefore, a better characterisation of the igneous facies of Cerro Cacheuta is critical to understand the evolution of Gondwana and recognise the multiple events that occurred towards the end of the Permian. This paper presents new data about the mineralogy, petrography, and geochemistry of the plutonic and volcanic units of Cerro Cacheuta, which enables authors to draw additional conclusions about the genesis and evolution of the magmatism in the region. Microscope observations indicate that the volcanic rocks are largely consistent with intermediate facies dominated by a porphyry texture with plagioclase and sanidine phenocrystals within a trachytic groundmass. Coetaneous breccias of possible hydrothermal origin and geodes with cryptocrystalline silica, limonite, and quartz are also recognised in outcrops. Geochemical analysis suggests that the lavas would likely correspond to andesites from a calc-alkaline magmatic arc. Furthermore, trace elements show enrichment in LREE/HREE, a slight negative anomaly in Eu, and concentration ratios compatible with crustal extension during the initial stages of the Choiyoi Group. Based on their chemical similarities, the monzonites of the Boca del Rio Pluton would correlate with the lower section of the Choiyoi Group, of Permian age. In contrast, granites of the Cacheuta Pluton show a signature typically recognised in units from the Triassic and, therefore, would be comparable to the upper member of the Choiyoi Group. Keywords: mineralogy; petrography; geochemistry; Cerro Cacheuta; Argentina Las rocas igneas del Cerro Cacheuta son consideradas una de las manifestaciones mas tipicas del magmatismo Permo-Triasico de la Precordillera de los Andes de Mendoza, Argentina. En especial, el flanco sudoeste del Cerro Cacheuta se caracteriza por la presencia de rocas volcanicas de composicion intermedia e intrusivos felsicos del Grupo Choiyoi, una de las secuencias volcano-sedimentarias de mayor distribution geografica en Sudameric