Defense
Student: Ingrid Herzog
Program: Geophysics
Title: "Upper Crust of the Carajás Province: Seismic Structure from Travel-Time Tomography"
Advisor: Prof. Dr. Marcelo Belentani de Bianchi
Judging Comitee:
- Prof. Dr. Marcelo Belentani de Bianchi - Presidente e Orientador - IAG/USP
- Prof. Dr. Marcelo Peres Rocha - UnB (por videoconferência)
- Prof. Dr. Gilberto da Silva Leite Neto - ON/MCTI (por videoconferência)
Other Members:
- Prof. Dr. Giuliano Sant'Anna Marotta - UnB
- Prof. Dr. Aderson Farias Nascimento - UFRN
- Prof. Dr. Marcelo Sousa de Assumpção - IEE/USP
Abstract:
This study addresses the characterization of the crustal seismic structure in the Carajás Province, aiming to understand how the P- and S-wave velocities of the medium correlate with the regional geodynamic evolution through the integration of tomographic results and pre-existing geological knowledge. The local velocity model was obtained by seismic travel-time tomography inversion of seismic travel times associated with 190 local events recorded by temporary and permanent seismic stations in the region, allowing the reconstruction of the lateral distribution of seismic velocities down to a depth of 25 km and the inference of crustal compartmentalization at the regional scale. Together with the event locations, a 1D model for the region was obtained, showing a Conrad discontinuity at a depth of 21 km, a Moho at 39 km and, finally, a Vp/Vs ratio of 1.734 (3), also consistent with receiver function results for the region. In the final inverted model, we observed that domains associated with the preserved Archean basement, the exposure of the lower crust, lithologies derived from mantle-derived magmas, and intense metamorphism exhibit high seismic velocities. Areas associated with supracrustal sequences, metasedimentary sequences, and sedimentary cover exhibit significant reductions in seismic velocity, demonstrating that the different tectonic terranes possess distinct signatures regarding the physical properties of the medium, with well-defined seismic velocity contrasts. The obtained results demonstrate that the crust of the region is heterogeneous, complex, and compartmentalized, reflecting the superposition of different geological formation events. These results contribute to a more detailed characterization of part of the Amazonian Craton at the shallow crustal scale, also reinforcing the importance of seismological methods for the geodynamic interpretation of complex mineral provinces.
Keywords: Local seismic tomography; Crustal compartmentalization; Carajás Province; Amazonian Craton; Geodynamics.