Dynamic and kinematic characterization of the basement structures of the Mocho-Choshuenco Volcanic Complex, Southern Andes, Chile

Abstract Mocho-Choshuenco Volcanic Complex (MCVC) is one of the most hazardous volcanoes in Chile's Southern Volcanic Zone (SVZ). It is located at 40°S 72°W in Los Rios Region, Chile, where the SVZ coexists with the margin-parallel Liquine-Ofqui Fault System (LOFS) and with NW-striking Andean Transverse Faults (ATF). The LOFS is 1200 km-long intra-arc strike-slip fault system located between 38° and 46°S, and partially controls the occurrence, spatial distribution and geometry of major stratovolcanoes. The fault-fracture networks induced by crustal deformation plays an essential role in the generation of pathways, facilitating the transport and emplacement of magmas. Thus, the Chilean Andes provides one of the best natural laboratories in the world to assess the link between tectonics and volcanism. In this study, we provide new structural, kinematic and dynamic insights, which would condition the formation and evolution of the MCVC and laying foundations for future works. Structural field data was collected and analyzed from regional and local scales. The strain analysis shows heterogeneous deformation. The stress field analysis at a regional scale indicates a strike-slip dominated transpressional regime with N61°E-trending σ1 and N26°W-trending σ3, which is consistent with the actual oblique convergence. Deformation driven by this oblique convergence is partially partitioned, where the margin-parallel component originates the dextral strike-slip in LOFS. Results are consistent with reactivation of preexisting NW-striking faults under the regional stress field, facilitating hydrothermal fluid flow and magma migration, associated with volcanoes, dikes and minor eruptive centers present in the study area. As a final result, we propose a simplified, three-dimensional model for the MCVC's basement, contributing to the understanding of the system and the way in which the different factors interact.