Banca de QUALIFICAÇÃO: LEILANE SOUZA SCRIBELK

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : LEILANE SOUZA SCRIBELK
DATE: 28/11/2022
TIME: 10:00
LOCAL: Departamento de Petrologia e Geotectônica
TITLE:

Geodynamic and petrogenetic models for the post-rift magmatism in Santos Basin.

KEY WORDS:

Santos basin, post-rift magmatism, geodynamics

PAGES: 104
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SPECIALTY: Petrologia
SUMMARY:

Six magmatic sections interbedded with coquinas were sampled along well X drilled in Santos
Basin. Sidewall core samples from these magmatic sections were studied applying a
methodology divided in three main steps: analysis of well sections, petrography and
lithogeochemistry. The magmatic sections were taken as stacking miaskitic, alkaline basalt
flows, being time-related with the coquinas of the post-rift phase of Santos Basin. Geochimical
modelling showed that basalts from different magmatic sections are not cogenetic by
differentiation processes, except for the bottom section, indicating that the flows were erupted
from different vents. Modal batch partial melting models showed that the parental magmas can
derive from different amounts of partial melting from the same fertile source within the garnet
stability zone. However, this could only happen at extreme values within the wide range of
amounts of partial melting required to give rise to alkaline basalts. Therefore, derivation from
distinctive mantle sources should be kept in mind as a likely possibility for the petrogenesis of
these alkaline basalts. Binary mixing models showed that neither the subcontinental
lithospheric mantle nor the depleted mantle contributed to the petrogenesis of the alkaline
basalts. The lithogeochemica data indicate a role for the melting of the Tristan da Cunha plume
tail. Altogether, the petrogenesis of the alkaline basalts allow to propose a geodynamic model
for Santos Basin in which the Tristan plume tail melts beneath a strongly stretched continental
crust. This crust was not thick enough to support large magma chambers with long time of
residence so that crustal assimilation could take place. The petrogenetic and geodynamic
models imply in a shallow Moho and location of Santos Basin above a anomalous hot mantle
during the Aptian. The petrophysical data of the well profiles were qualitatively evaluated as a
means of test possible correlations with the petrographic data. Different values of gamma-ray,
resistivity, sonic, neutron porosity and bulk density may be related mainly with distinctive
structures of the basalts, such as brecciation, absence of amydales and amounts e sizes of the
amygadales.

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