Hawaiian and Strombolian style monogenetic volcanism in the extra-Andean domain of central-west Argentina

GUSTAVO W. BERTOTTO, ERNESTO A. BJERG, CARLOS A. CINGOLANI

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

Elsevier

Lugar: Londres; Año: 2006 p. 430 - 444

0377-0273

Abstract: In the provinees of Mendoza and La Pampa (eentral-western Argentina), retroare volcanism was aetive from the Mioeene through historie times. There are approximately 40 basaltie eruptive eenters between 36°S and 3T30'S to the East of 68°40'W. These eenters were studied in order to define their volcanologieal evolution. The vents are eonstituted of seven lithofacies: Le., (A-l) weakly welded lapilli and bomb beds; (A-2) agglutinated spatter and bomb beds; (A-3) agglutinated spatter beds; (B) ash beds; (C) lava flows; (D) conduit fill; and (E) dikes. Three eruptive episodes (phases) were identified. The first one generated agglutinated spatter and bomb beds (lithofacies A-2), whieh eonstitute the interual part ofthe edifiees. These are followed by weakly welded lapilli and bomb beds (lithofaeies A-l) and agglutinated spatter beds (lithofaeies A-3). The final episode includes lava flows (lithofaeies C), minor agglutinated spatter deposits (lithofacies A-3) and isolated lapilli and bomb clasts. We postulate Hawaiian style fountaining activity as responsible for the generation of agglutinated spatter and bombs beds, and variations between Strombolian and Hawaiian aetivity for the formation of sueeessions of weakly welded lapilli and bomb beds and agglutinated spatter beds. The vent features and the homogeneity of the erupted magma suggest that the studied volcanoes were monogenetic.   Keywords: monogenetic volcanoes; basalts; Argentina; Hawaiian; Strombolian