Historia de exhumación de la granodiorita Huingancó, cordillera del viento, provincia de Neuquén

Abstract

This degree thesis aims to decipher the exhumation history of Permian granodiorites corresponding to the Huingancó Plutonic Complex in the southern sector of the Cordillera del Viento (37°6'6.8” – 37°18'30” S / 70°47'40” – 70°21'0.2” W), within the Chos Malal fold-thrust belt. In this regard, mineral chemistry studies were carried out on the granodiorites from electronic microprobe data to infer the P-T conditions of emplacement, resulting in 700 - 900°C and pressures ranging between 1 and 2.4 kbar. Using a geostatic gradient of 3.7 km/kbar, these values give an estimate of emplacement depths between 4 and 9 km. Then, on the western flank of the Cordillera del Viento anticline, along the Huaraco creek, five samples of the Huingancó Granodiorite were taken to perform apatite fission track (AFT) analysis. This analysis provided new ages of cooling for the study area that are between 50 and 80 Ma. Also, the inverse thermal modeling developed using the fission track data allowed the observation of two significant exhumation events during the Andean cycle. The first during the Late Cretaceous-Paleocene and the second at Miocene times, with an interval of gradual cooling or stability during Eocene-Oligocene times. These two important cooling events are associated with the main construction pulses of the Cordillera del Viento. Finally, to characterize its tectonic evolution a structural kinematic model is proposed based on a balanced structural section and its reconstruction to its non-deformed pre-Cretaceous state. The resulting model allows us to identify the structures and mechanisms of uplift rising the Cordillera del Viento, and their association with the main exhumation events depicted in the inverse thermal modeling. The main structure of the Cordillera del Viento corresponds to a fault bending fold that involves the basement in the deformation. Subsequently, its insertion as an intercutaneous wedge is related with development of the thin-skinned structures at the internal sector of the Chos Malal fold and thrust belt.