Lithospheric delamination beneath the southern Puna plateau resolved by local earthquake tomography

TL;DR

This study uses local earthquake tomography to investigate the crustal and upper mantle structure beneath the southern Puna plateau, providing evidence for lithospheric delamination and its effects on regional magmatism and topography.

Contribution

It offers the first detailed seismic imaging supporting the delamination hypothesis beneath the southern Puna plateau, linking seismic anomalies to geological processes.

Findings

High Vp anomaly west of Cerro Galan indicates delaminated lower crust and uppermost mantle.

Low Vp anomalies in the crust suggest fluid and melt migration due to delamination.

Seismic links between arc magmatism and slab dehydration support mantle wedge fluid fluxing.

Abstract

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.