Banca de DEFESA: RODRIGO MEDEIROS VIEIRA GARCIA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RODRIGO MEDEIROS VIEIRA GARCIA
DATE: 24/04/2026
TIME: 09:00
LOCAL: PPGMEG (via canal do Youtube)
TITLE:

Physical, petrogenetic, and geodynamic processes related to volcanism in the pre-salt sequence of the central Santos Basin.

KEY WORDS:
PAGES: 95
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SPECIALTY: Petrologia
SUMMARY:

The largest volumes of oil and gas reserves in Brazil occur in the Lower Cretaceous sedimentary sequence beneath a thick evaporitic layer in the Santos Basin. Mafic magmatic rocks are associated with this pre-salt sequence, being interbedded with the main source and reservoir intervals, and their genesis and role in the petroleum system are still not fully understood. Pre-salt magmatism is related to the tectonic evolution of the basin during the breakup of Gondwana and persisted until the Late Aptian, throughout the sag stage, being traditionally interpreted mainly on the basis of geophysical data, with limited use of petrological and geochemical information in petrogenetic and geodynamic models. This dissertation presents an integrated petrological study of sidewall core samples recovered from two boreholes located in the northern and southern portions of the central Santos Basin. The studied rocks correspond to high- and low-Ti tholeiitic basalts, whose eruptive episodes occurred synchronously with the sedimentary processes responsible for the formation of the main pre-salt reservoirs. The investigation involved petrographic analyses, whole-rock geochemistry of major, trace and rare earth elements, and petrogenetic modeling, aiming to reconstruct magmatic processes, volcanic styles, and associated geodynamic scenarios. The results indicate that the high-Ti tholeiitic basalts in the northern part of the study area correspond to a single thick basalt flow, approximately 48 m in thickness. In contrast, the low-Ti tholeiitic basalts in the southern portion record multiple volcanic episodes, including effusive and explosive events, fed by at least six distinct subvolcanic magmatic sources during three volcanic events separated by periods of sedimentary quiescence. Petrogenetic modeling suggests that both basalt groups were derived from different degrees of partial melting of a common mantle source. Geochemical data and modeling results are consistent with a geodynamic scenario involving interactions between a shallow, enriched asthenosphere and the subcontinental lithospheric mantle during the early stages of Gondwana rifting. There is no direct evidence for the contribution of melts derived from a mantle plume, although its possible presence at deeper levels may have provided the thermal input required to promote partial melting of the shallow mantle. This magmatic regime implies a high geothermal gradient during the formation of the pre-salt petroleum system in the Santos Basin.

COMMITTEE MEMBERS:
Externo à Instituição - GABRIEL MEDEIROS MARINS - PETROBRAS
Interno - ***.345.068-** - JULIO CESAR LOPES DA SILVA - UFRJ
Externo à Instituição - MARCOS DE MAGALHÃES MAY ROSSETTI - UFRJ
Presidente - 387109 - SERGIO DE CASTRO VALENTE