THE THERMO-MECHANICAL STATE OF THE ANDES IN THE ALTIPLANO-PUNA REGION: INSIGHTS FROM CURIE ISOTHERM AND EFFECTIVE ELASTIC THICKNESS DETERMINATION

We present new constraints on the temperature distribution beneath the Altiplano-Puna plateau region and a new model of effective elastic thickness for the Central Andes. The aim of this study is to better assess the thermal state of the plateau and surrounding regions and analyze its influence on the elastic thickness and strength of the lithosphere. We performed a statistical analysis of the magnetic anomaly in frequency domain in order to obtain the depth to the bottom of the magnetic layer, interpreted as the Curie isotherm. The effective elastic thickness was calculated from the flexure analysis in frequency domain of the deflection of the crust and the pseudo-topography (an artificial construction that allows accounting for the internal loads). We find that the Puna and the volcanic arc present the shallowest Curie isotherm and highest heat-flow in agreement with conductivity, velocity and attenuation anomalies suggesting the presence of partial melts within the crust. In addition, the Altiplano exhibits a deeper Curie isotherm in coincidence with other observations pointing to a stronger lithosphere than in the Puna. Our results show that the effective elastic thickness correlates only partially with the thermal state and that, consequently, other processes, such as inheritance of the elastic thickness, need to be considered to explain the observations and avoid misinterpretations in the variability of the thermal field.