Integrated geophysical and petrological constraints on crustal melt in the Central Andes at the so-called zombie volcano: the PLUTONS project
IPGP - Îlot Cuvier
Séminaires Tectonique et Mécanique de la Lithosphère
Cornell University, USA, now visiting professor at University of Bristol
The central Andes is a key global location to study the architecture of transcrustal magmatic systems as it currently hosts the world's largest zone of silicic partial melt in the form of the Altiplano-Puna Magma or Mush Body (APMB). Further, the APMB is dynamic, with a ground deformation pattern 150 km in diameter that lasted for several decades, centered on Uturuncu volcano, Bolivia. I will discuss results from the recently completed international PLUTONS project, which focused a suite of geophysical, petrological, and geomorphological techniques at Uturuncu with numerical modeling to infer the subsurface distribution, quantity, and movements of partial melts. We find geophysical anomalies extending from the base of the crust to the surface indicating multiple distinct reservoirs of magma and/or hydrothermal fluids with different physical properties. The characteristics of the geophysical anomalies differ somewhat depending on the technique used - reflecting the different sensitivity of each method to subsurface melt (or fluid) of different compositions, temperature, connectivity, and volatile content, and highlighting the need for integrated, multi-disciplinary studies. We offer a new interpretation of the cause of ground deformation related to reorganization of the magma mush that causes no net ground deformation over hundred to thousands of years that is consistent with the lack of tilted shorelines around Uturuncu. I will also describe recent changes to the deformation pattern from a broad uplift and subsidence (called a "sombrero" by some) to more localized subsidence and possible explanations for the change.