Polyorogenic structure of the San Rafael Block, Mendoza, Argentina: New data for the interpretation of the Chanic Orogen

The Paleozoic pre-Carboniferous rocks of the San Rafael Block, located to the east of the Los Reyunos Gondwanan Thrust, show Chanic structures (Late Devonian-early Carboniferous) with east vergence, which were generated in the absence of metamorphism. This Paleozoic succession is unconformably located on the basement of Cuyania. The rocks, located to the west of the Los Reyunos Thrust, were deformed by two fold episodes, the first and main (D1) west verging, developed under low to very low-grade metamorphic conditions, and the second (D2) east verging and mainly developed near Los Reyunos Reservoir. Therefore, the Los Reyunos Thrust must be considered a reactivation of a Chanic structure during the Gondwanan Orogeny (late Carboniferous-early Permian). The ancient Chanic thrust could be responsible for the overlay of the hinterland of the western branch of the Chanic Orogen on the foreland of its eastern branch, at the end of the collision between the Cuyania and Chilenia subplates. The results of this work have been related to those of nearby areas located to the north and west, which has allowed the elaboration of a model that explains the characteristics of the Chanic Orogen in this area. During the Carboniferous, the Los Reyunos Thrust was reactivated as a normal fault, facilitating the sedimentation of carboniferous rocks thousands of meters thick in its hanging wall and later, during the Gondwanan deformation, it underwent a tectonic inversion. During the Andean cycle, the Permian-Triassic beds of the Choiyoi Group were deposited in relation to NW-SE trending normal faults, giving rise to rollover structures. Finally, during the Cenozoic, Andean compression gave rise to the formation of an open antiform, in whose core is the Mesoproterozoic-Paleozoic basement of the San Rafael Block.

Automated summary

The Los Reyunos Thrust is a thrust fault formed during the Gondwanan Orogeny (Late Carboniferous-Early Permian) as a result of a collision between the Cuyania and Chilenia subplates. This thrust fault reactivated a pre-existing Chanic structure and played a role in the deposition of Carboniferous rocks in its hanging wall. The results of this study contribute to our understanding of the Chanic Orogen in the area and its relationship with nearby regions.