Relationship between Neogene volcanic centers and the foreland advance of deformation: The Malargüe fold-and-thrust belt 35°-36°S, 69°50′W, Southern Central Andes, Argentina

Abstract

The presence of Neogene volcanic centers have been poorly studies between 35° and 36°S, 69°50′W in the Malargüe Fold-and-Thrust Belt, Argentina. This work used field observations, stratigraphic sections, whole-rock geochemistry, and ⁴⁰Ar/³⁹Ar geochronology to characterize three polygenetic volcanic successions: Butamallín, Fiero, and Picudo de la Ventana and their relationship with the synorogenic deposits. Their emplacement spans from the Early Miocene (16.7 ± 1.7 Ma), through the Late Miocene (9.8 ± 1.0 Ma), to the Pliocene (6.5 ± 0.5 Ma), with each center displaying distinctive geochemical signatures associated with retroarc magmatism, arc-related magmatism, and retroarc magmatism with depleted mantle affinities. The volcanic successions unconformably overlie synorogenic units, acting as sediment sources and influencing basin architecture. The relationship with synorogenic successions, together with paleoflow indicators and clast compositions, reveals four evolutionary stages: (1) a foreland basin in the Early Miocene, (2) the development of wedge-top basins during the Middle Miocene, (3) arc migration and volcanic expansion in the Late Miocene, and (4) the formation of piggyback basins associated with mantle-derived magmatism from the Late Miocene to the Pliocene. These results support a model of forelandward (eastward) propagation of the Malargüe Fold-and-Thrust Belt (MFTB) in the southern Central Andes of Argentina.