Three-dimensional resistivity image of the magmatic system beneath Lastarria volcano and evidence for magmatic intrusion in the back arc (northern Chile)

Abstract

Lazufre volcanic center, located in the central Andes, is recently undergoing an episode of uplift, conforming one of the most extensive deforming volcanic systems worldwide, but its magmatic system and its connection with the observed uplift are still poorly studied. Here we image the electrical resistivity structure using the magnetotelluric method in the surroundings of the Lastarria volcano, one of the most important features in the Lazufre area, to understand the nature of the magmatic plumbing, the associated fumarolic activity, and the large-scale surface deformation. Results from 3-D modeling show a conductive zone at 6km depth south of the Lastarria volcano interpreted as the magmatic heat source which is connected to a shallower conductor beneath the volcano, showing the pathways of volcanic gasses and heated fluid. A large-scale conductive area coinciding with the area of uplift points at a magma intrusion at midcrustal depth. Key Points Electrical resistivity images of the Lastrarria volcano The magmatic source is located to the south of Lastarria volcano Deep conductor in the back arc suggests magmatic intrusion.