A transpressive stress regime for the Laguna del Maule Volcanic Complex

Abstract

The Laguna del Maule Volcanic Complex is a post-glacial active magmatic system, located on the border between Argentina and Chile, at 36°S in the Andean Range. This complex is characterized by multiple silicic eruptive centers surrounding a 23 × 16 km lake. The eruptive products range from basalts to rhyolites, with a predominance of acidic rocks in more than 50 eruptions that took place in the last 25 ka. Previous models proposed a transtensional regime during its activity, linked to a bend in a major dextral fault, the Troncoso fault. We propose that those structural models were biased by the fact that seismicity was focused on the Troncoso fault preceding 2014. Here, we present an updated seismic catalog, which provides a broader understanding of the active structures in the area. Structural analysis based on remote sensing and outcrop-scale measurements of kinematic indicators allowed us to characterize the fault kinematics and the local stress field. Integrating the structural and seismological data, we propose that the actual volcanism took place in a transpressional stress regime, consistent with the regional tectonic setting and the silicic volcanism of the Laguna del Maule Volcanic Complex.