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, J P; BOEDO, F; VUJOVICH GRACIELA; SANCHEZ, M.; MARTÍNEZ, P.; CHRISTIANSEN, RODOLFO; PEREZ LUJAN SOFIA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2018 p. 352 - 366

0895-9811

Located in the central-western Argentina (31º20´S - 69º22´W) the basement of Central Andes is composed by theCuyania and Chilenia terranes which were amalgamated to Gondwana in the Early-Mid Paleozoic. BetweenPrecordillera (Cuyania) and Frontal Cordillera (Chilenia) there are exposures of metasedimentary rocks of continentalslope and ocean floor associated with mafic rocks with E-MORB signature that represent remnants of the Cuyanoocean developed between both terranes. The stratigraphic features and the distribution of the Early-Mid Paleozoicunits along the Western Precordillera were constrained by remote sensing images (band ratios images). This allowedus to 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 an upward decreasing sequence interbedded withvolcanic-plutonic mafic rocks; and a Late Ordovician?-Devonian where the sedimentation was characterized by thedevelopment of upward coarsening sequences with low participation of mafic rocks. Flattened parallel folds associatedwith pre-Andean thrusts have locally a top-to-the SW vergence. These pre-Andean (Late Devonian) structures are therelicts of the Chanic orogen whose double vergence is the result of the control exercised by previous structures relatedto the Ordovician rifting. This is constrained by the residual and regional magnetic anomalies which reflect animportant relationship between deep and surface structures. We propose the inception of a subduction zone witheastward polarity on the proto-pacific margin of Gondwana as responsible of the compressive geotectonic frameworkthat led to the closure of the Cuyano ocean during the Late Devonian and the development of the Chanic thick-skindominatedorogen