Banca de DEFESA: CYNTHIA VARGAS CASTRO DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : CYNTHIA VARGAS CASTRO DA SILVA
DATE: 21/01/2026
TIME: 14:00
LOCAL: PPGMEG (via canal do Youtube)
TITLE:

Magmatism of the Pre-Salt sequence in the central-southern portion of the Santos Basin: petrogenetic processes and mantle geodynamics

KEY WORDS:

Tholeite Magmatism; Pre-Albian Magmatism; Santos Basin; Petrogenesis; Mantle Heterogeneity.

PAGES: 60
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SPECIALTY: Petrologia
SUMMARY:

This dissertation investigates the Pre-Albian mafic magmatism of the Santos Basin Pre-Salt sequence, associated with the rifting of Gondwana and the opening of the South Atlantic. The study integrates petrographic, stratigraphic, and geochemical data from two igneous sections of wells 3-BRSA-1290-SPS and 3-BRSA-883-RJS. The results demonstrate that the magmas from both wells are predominantly tholeiitic, with the exception of an alkaline sample (4923) in well 3-BRSA-883-RJS. Petrogenetic modeling indicates melting in the spinel zone, with depths between 44 km and 68 km, varying between wells: 63 km - 68 km for 3-BRSA-1290-SPS and 44 km - 51 km for 3-BRSA-883-RJS. The compositional distinction between the wells, separated by only 120 km, demonstrates mantle heterogeneity on an intra-basin scale, with the Southern well (3-BRSA-1290-SPS) deriving from enriched sources (E-MORB/OIB) and the Central well (3-BRSA-883-RJS) from more depleted sources (N-MORB to E-MORB), acting as markers of local tectonic segmentation during the rifting of Gondwana. The differentiation processes were predominantly governed by fractional crystallization in closed systems or with limited recharge (RFC), as demonstrated by the models applied to the sample pairs 6200-6185 and 5066-4904. AFC modeling indicates that crustal assimilation processes were restricted to specific samples (such as those from pairs 5025-4916 and 5066-4904), where they occurred with low assimilation rates (r = 0.2). The compositional diversity observed between wells is primarily attributed to the fusion of heterogeneous mantle domains at different depths in the spinel zone, with differentiation acting as a secondary process of mantle signatures. Academically, the results quantitatively validate the importance of mantle heterogeneities and lithospheric segmentation during the rifting of Gondwana, demonstrating that enriched (EM1) and depleted (DMM) domains coexisted in different sectors of the basin. From an exploratory standpoint, the petrogenetic definition of the 'Parati' (Post-Rift, enriched sources) and 'Tupi' (Rift, depleted sources) members offers geochemical criteria for mapping petroleum systems in the pre-salt province, conditioning the distribution of source rocks and reservoir architecture. Beyond their importance as chronostratigraphic markers, these events perform complementary exploratory functions: the first as an intrusive element (generation of traps and thermal maturation), and the second as a unit with reservoir/seal potential.

COMMITTEE MEMBERS:
Presidente - 387109 - SERGIO DE CASTRO VALENTE
Interno - 1648928 - ARTUR CORVAL VIEIRA
Externo à Instituição - MARCOS DE MAGALHÃES MAY ROSSETTI - UFRJ
Externa à Instituição - MONICA DA COSTA PEREIRA LAVALLE HEILBRON - UERJ