TTE294

Caracterización estructural del valle de Reigolil, IX Región de …

ABSTRACT The Reigolil valley, located approximately at 39°S in the intra-arc of the southern volcanic zone (SVZ), has a N-S orientation extending for almost 40 kilometers, to the west is the main trace of the Liquiñe Ofqui fault system (LOFS), with dextral transpressional kinematics with more than 1,200 km long, responsible for accommodating the deformation caused by oblique subduction and control the magmatic and hydrothermal fluids pathways along the SVZ. This system includes the Reigolil Pirihueico fault (RPF), present in the Reigolil valley. In order to obtain more and new information on the structural characteristics of the area, several field trips were carried out to collect data on the structures present, and topographic surveys of specific areas were carried out to evaluate possible changes in the relief that would indicate current tectonic activity. With the data, a regional stress analysis was performed for the study area. The results obtained show evidence consistent with the major structural systems present in the area, the faults are preferentially oriented NE-SW, N-S and NW-SE, the first two orientations associated with the RPF, while the last orientation is evidence of Andean Transverse Faults (ATF). The observed dykes also follow similar trends, predominantly NW SE and N-S orientations, and to a lesser degree NE-SE orientations. Furthermore, faults were found in volcanic deposits of known age, which delimits the time in which the deformation of these deposits occurred. In relation to the stress analysis, three directions were obtained, the main one of direction σ 1 64/10 and σ 3 162/37, parallel to the current main stress caused by oblique subduction. The second stress direction σ 1 324/7 and σ 3 231/21, which is associated with the interaction with the ATFs, reactivated by the current subduction regime. Finally, the last stress obtained has a direction of σ 1 81/14 and σ 3 204/66, which would be associated with the Pliocene compressional event. It is concluded that the zone is dominated under the current stress regime induced by oblique subduction, the results are consistent with those found by other authors along the LOFS. The presence of a local NW-SE direction stress is also inferred, associated to a structure that would be part of the ATF, which could act under certain stages of the subduction seismic cycle, due to its uncoupled condition from the current main system. As for the evidence found in Quaternary deposits, it is possible to indicate that there is recent tectonic activity in the area, which is bounded between the present and ca. 2900 BP.

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