Structures et mécanismes de déformation volcano-tectoniques le long de l'arc sud Chili
Université Pontificale du Chili, Santiago
The nature of the interplay between tectonics and volcanism has been explored for decades in different tectonic settings at a different spatial and temporal scales. Among them, the Andes are a superb natural laboratory to unravel the fundamental processes driving this interplay because of their along-strike differences in crustal thickness, geologic history and structural style.
The marked along-strike differences in the nature, kinematics and style of deformation coeval with active volcanism reflects the way by which oblique convergence between Nazca and South American plates is accommodated, which in turn is largely controlled by active and inherited basement faults. In northern Chile, stratovolcanoes (SV) and minor eruptive centers (MEC), lying on a thick crust, are spatially associated with margin-parallel folds and reverse faults or transverse structures within and overall compressional intra-arc setting. In the south, in turn, dextral transpressional deformation dominates, and SV are spatially associated with ENE and WNW-striking fault systems, some of which are inherited from pre-Andean tectonics. MEC lie either along margin-parallel strike-slip faults or on transverse structures, forming clusters of up to a hundred centers.
Recent studies, using local seismic networks (Sielfeld et al. 2019, Pearce 2019), show that Andean WNW and ENE-striking transverse faults in central and southern Chile are seismogenic and may be linked to fluid migration in the crust, which is consistent with longer-term geological observations.
Feedbacks among crustal deformation, magma storage and magma migration can be further assessed with the use of numerical models. These models can place key mechanical constraints on the interplay between tectonics and volcanism in continental margins in general.