We will address the fundamental questions on the processes that form, modify and destroy continental lithosphere and control lithospheric dynamics along Andean-type continental margins through a collaborative international passive-source seismic experiment in the southern Puna of the central Andean plateau. The southern Puna (25 degrees S to 28 degrees S) is not only key to understanding Andean evolution, it is also the type locale for testing the delamination hypothesis for removal of thickened eclogitic continental crust along with continental mantle lithosphere. Such crustal removal provides an explanation for the near absence of a dense mafic root in many orogenic regions (including the central Andean plateau to the north) as well as the equally, if not more important, bulk andesitic composition of the continental crust. We here propose to acquire the detailed geophysical data needed to test whether current lithospheric structure is compatible with this process, as well as to fill in a critical gap in modern geophysical coverage along strike in a distinctive part of the central Andean plateau. This project will involve deploying a total of 25 broadband and 45 intermediate-period three component seismic stations and employing a number of new and well-established techniques to image the details of the lithospheric seismic velocity structure and local seismicity patterns. This is a truly international project in that it will benefit from the participation of scientists from the U.S., Germany, and South America. The images will be integrated with the regional geology and the geochemical signature of relevant volcanism to form a robust geodynamic model for the evolution of the central Andean mountain belt. We intend to study mantle dynamics and mantle flow associated with slab lithosphere using a combination of seismic tomographic methods (surface wave, body wave, and attenuation) as well as the large volume of prior geologic studies in this region to help constrain the extent, timing and amount of lithospheric removal within the southern Puna plateau. This work will train a number of American, German, and Argentine students in modern seismological data acquisition and processing. The study will contribute to improved understanding of the broader aspects of the earthquake and volcanic hazards in the Andes which have devastating potential, as well as the origin of natural resources in this classic mineral terrane. Lastly, this study serves as a forerunner and geodynamic reference for planned EARTHSCOPE investigations of older, comparable orogenic systems in the western U.S.
