Zircon and apatite fission track analyses: new insight about the exhumation of Cordillera del Viento, Neuquén basin, Argentina

PONS, MARÍA J.; ZATTIN, MASSIMILIANO; GIACOSA, RAÚL E.; GONZÁLEZ, SANTIAGO N.; GRECO, GERSON A.

Puerto Madryn

Congreso; XXI Congreso Geológico Argentino; 2022

Asociación Geológica Argentina

The Cordillera del Viento (CV) is the western sector of the inner Chos Malal fold and thrust belts (CMFTB) and exposes basement (Carboniferous and Permo-Triassic) and its cover rocks of the Neuquén basin (Late Triassic to the Neogene). Sánchez et al. (2020), based on thermochronology data performed in the different units of the Neuquén Basin, define that the faults of the CMFTB, shows a normal sequence of deformation toward the foreland from Late Cretaceous to Late Miocene. In this contribution we present the first zircon fission tracks (ZFT) and apatite fission tracks (AFT) analyses carried out in the basement rocks of the Neuquén basin in order to give a contribute to the understanding of the evolution of the inner thick-skinned zone of the CMFTB.The study area is located in the southwest zone of the CV Anticline eastward of the CV Fault (Giacosa et al. 2014) where Andacollo Group rocks, formed by Carboniferous volcanoclastic (Arroyo del Torreón For- mation; U-Pb 328-325 Ma, Suarez et al. 2012 and references there in) and marine rocks (Huaraco Formation; U-Pb, 304 Ma, Suarez et al. 2012), are intruded by the Huingancó granodiorite of Huinganco Volcanic Pluto- nic Complex (HVPC; U-Pb, 282.5±2 Ma, Hervé et al. 2013). Previous units are intruded by dacitic porphyry dykes. These three units have been sampled for a petrographic characterization in order to select the best samples for ZFT and AFT analyses, performed at the Padova, and Late Andes S. A., laboratories.The medium grained quarzitic sub-rounded well sorted sandstones of Huaraco Formation, with traces of micas, zircon, apatite, and tourmaline as accessories minerals, were selected to separate zircons for ZFT analysis. The ZFT analysis was carry out on 27 grains and gave a central cooling age of 140.8 ±6.2 Ma (with 2-test of 36.05%). A granodiorite sample of Huinganco volcanic-plutonic Complex shows a granophyric texture and consists of subhedral plagioclase crystals (40%), anhedral potassic feldspar (27%), quartz (8%), amphibole (5%), micas (15%), zircon and apatite as accessories (