A High-Resolution Seismic Survey Across the Balmuccia Peridotite, Ivrea Zone, Italy – Project Dive

Abstract

The Ivrea Verbano Zone (IVZ) is one of the most complete crust–upper mantle geological references in the world, and the Drilling the Ivrea-Verbano zone project (DIVE) aims to resolve the uncertainties below this area. Geophysical anomalies detected across the IVZ indicate that dense, mantle-like rocks are located at depths as shallow as ca. 1–3 km. Thus, within DIVE several geological, geochemical and geophysical studies are planned, including the drilling of a 4 km deep borehole that will penetrate the Balmuccia Peridotite (Val Sesia, Italy), a peridotite body that outcrops in the IVZ. The objective of this borehole is to approach, and possibly cross, the crust–mantle transition zone, and provide for the first time geophysical in-situ measurements of the deepest rocks of the IVZ. One of the primary requirements before drilling is a seismic site characterization, to define with precision the correct positioning and orientation of the borehole, to assess potential drilling hazards and to allow for the spatial extrapolation of the borehole logs. For that goal, two joint geophysical surveys were performed in October 2020 in a collaboration between GFZ Potsdam, Université de Lausanne and Montanuniversität Leoben: (1) a deep seismic survey performed by GFZ Potsdam, entitled SEismic imaging of the Ivrea ZonE (SEIZE), consisting of two approximately orthogonal 15 km-long seismic lines, that aim to resolve the deeper structure of the IVZ in the area, and (2) a smaller seismic survey at the proposed drill site, entitled Highresolution SEismic imaging of the Ivrea ZonE (HiSEIZE), geared towards providing high-resolution seismic images of the uppermost few km. In this study,