Structural inheritance and stress regimes as primary controls on the distribution and volume of volcanism in the Central Andes

Volcanism in the Central Andes has been active from the Late Oligocene to the presents, with volcanic centers distributed across the Western Cordillera and western Altiplano-Puna Plateau. Although previous studies have linked this distribution to inherited crustal structures and sublithospheric processes, the role of the crustal stress field in controlling both the volume and spatial patterns of volcanism remains poorly constrained. Here, we analyze the spatial distribution, inferred magma pathways, and erupted volumes of 140 Neogene both stratovolcanoes and monogenetic volcanoes between 24.5° and 26.5°S. Using volcano morphology and crater elongation directions, σHmax orientations and magma ascent directions are inferred. The total Neogene volcanic output in the study area is estimated at 1252 km3, with output rates increasing from ˜28 km3/Myr during the Early Miocene to a peak of ˜102 km3/Myr during the Early Pliocene. Volcanism is preferentially aligned along NW-SE trends associated with the Archibarca and Culampajá fault systems, and subordinately along NNE-SSW structures such as the Arizaro-Pedernales and Antofalla faults. Four main evolutionary stages are identified: (1) localized volcanism at fault intersections under a reverse-faulting stress regime during the Early Miocene; (2) widening along NE-SW trends, during the transition from reverse-faulting to strike-slip-faulting stress regime in the Middle Miocene; (3) peak volcanic volumes focused along NW-SE clusters, during a strike-slip-faulting stress regime in the Late Miocene-Early Pliocene; and, (4) spatial restricted activity in the Late Pliocene-Quaternary during a strike-slip/normal faulting stress regime. The results suggest that variations in the volume and distribution of volcanism are strongly influenced by local stress field conditions and the geometry of inherited crustal structures. This study highlights the importance of a strike-slip-faulting stress regime in controlling not only magma emplacement patterns, but also volcanic output volume in continental arcs.