Structural setting of the Chanic orogen (Upper Devonian) at central-western Argentina from remote sensing and aeromagnetic data. Implications in the evolution of the proto-Pacific margin of Gondwana

ARIZA, JUAN P.; BOEDO, FLORENCIA L.; SÁNCHEZ, MARCOS A.; CHRISTIANSEN, RODOLFO; PÉREZ LUJAN, SOFÍA B.; VUJOVICH, GRACIELA I.; MARTÍNEZ, PATRICIA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2018 vol. 88 p. 352 - 366

0895-9811

The basement of the Central Andes located in central-western Argentina (31¨¬20¡ÇS - 69¨¬22¡ÇW) is composed by theCuyania and Chilenia terranes which were amalgamated to Gondwana in the Early-Mid Paleozoic. Between thePrecordillera (Cuyania) and Frontal Cordillera (Chilenia) there are exposures of marine metasedimentary rocksassociated with mafic rocks with an E-MORB chemical signature that represent the remnants of an extensionalbasin developed between both terranes. The stratigraphic features and the distribution of the Early-MidPaleozoic units along the Western Precordillera were constrained by remote sensing techniques. This allowed usto identify two stages in the evolution of the sedimentary in-fill of the marine basin: an initial stage (Mid-LateOrdovician) marked by widespread extensional tectonics and a finning-upwards sequence interbedded withvolcanic-plutonic mafic rocks; and a Late Ordovician?-Devonian where the sedimentation was characterized bythe development of coarsening-upwards sequences with low participation of mafic rocks. Flattened parallel foldsassociated with pre-Andean thrusts have locally a top-to-the SW vergence. These pre-Andean (Late Devonian)structures are the relics of the Chanic orogen whose double vergence is the result of the control exerted byprevious structures related to the ordovician rifting. This is constrained by the residual and regional magneticanomalies which reflect an important correlation between deep and surface structures. We propose the inceptionof a subduction zone with an eastward polarity on the proto-Pacific margin of Gondwana as the responsible forthe compressive geotectonic framework that led to the closure of the Western Precordillera basin during the LateDevonian and the development of the Chanic thick-skinned-dominated orogen.