  We present a local earthquake tomography to illuminate the crustal and
uppermost mantle structure beneath the southern Puna plateau and to test the
delamination hypothesis. Vp and Vp/Vs ratios were obtained using travel time
variations recorded by 75 temporary seismic stations between 2007 and 2009. In
the upper crust, prominent low Vp anomalies are found beneath the main volcanic
centers, indicating the presence of magma and melt beneath the southern Puna
plateau. In the lowlands to the southeast of the Puna plateau, below the
Sierras Pampeanas, a high Vp body is observed in the crust. Beneath the Moho at
around 90 km depth, a strong high Vp anomaly is detected just west of the giant
backarc Cerro Galan Ignimbrite caldera with the robustness of this feature
being confirmed by multiple synthetic tests. This high velocity body can be
interpreted as a delaminated block of lower crust and uppermost mantle
lithosphere under the southern Puna plateau. The low velocities in the crust
can be interpreted as having been induced by the delamination event that
triggered the rise of fluids and melts into the crust and induced the high
topography in this part of the plateau. The tomography also reveals low
velocity anomalies that link arc magnetism at the Ojos del Salado volcanic
center with slab seismicity clusters at depths of about 100 and 150 km and
support fluid fluxing in the mantle wedge due to dehydration reaction within
the subducted slab.
