Banca de DEFESA: JOSÉ ALEXANDRE PAIXÃO DA CUNHA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOSÉ ALEXANDRE PAIXÃO DA CUNHA
DATE: 19/01/2023
TIME: 09:00
LOCAL: videoconferência - https://www.youtube.com/@ppggufrn
TITLE:

Petrochemistry, petrophysics and geophysics of carbonatite complexes and associated
ultramafics of the São José do Campestre Archean Nucleous, NE Brazil

KEY WORDS:

Carbonatite; ultramafic; gravimetry; primary carbonatite; crustal carbonatite.

PAGES: 84
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

Carbonatites are exotic rocks with more than 50% carbonate of igneous origin and SiO2 <20% in their geochemical composition, which are commonly associated with several lithotypes. At the Nucleus São José do Campestre Archean (NASJC), State of Rio Grande do Norte (NE of Brazil), occurrences of carbonatites associated with ultramafic pyroxenitic rocks are reported. NASJC is formed by different generations of dioritic and granitic metagranitoids and metassupracrustals of Archean age (3.41-2.68 Ga). The pyroxenitic and carbonatites rocks within NASJC are recognized by circular / elliptical feature, as well as to truncate low angle structures from the basement and dark massapê soil. The pyroxenitic rock contains as essential minerals and accessories: diopside with or without escapolite, garnet, titanite, plagioclase and opaque minerals. Carbonatite consists of calcite and olivine with or without phlogopite, garnet and Mg-ferrite / magnetite. The lithochemistry data from carbonatites reveals that the SiO2 values are less than 20% and CaO values are around 40%. The trace elements (Ba, Sr, Nb, Zr) and ETR are low when compared to the average of carbonatites in the literature, although some studies have similar values. Petrophysical density data show an expressive contrast between the ultramafic / carbonatite rock and the gneiss country-rock, resulting in a gravimetric anomaly with a strong gradient. 2D modeling performed under the
gravimetric profile, suggests an ellipsoidal geometry, like other carbonatitic bodies worldwide. The exposed data in this contribution allow us to classify the investigated carbonate rocks as carbonatites from a primary mantle or crustal source.

COMMITTEE MEMBERS:
Externo à Instituição - ELTON LUIZ DANTAS - UnB
Externo à Instituição - FRANCISCO VALDIR SILVEIRA - SGB
Interno - 2042352 - FREDERICO CASTRO JOBIM VILALVA
Externo à Instituição - IGNEZ DE PINHO GUIMARÃES - UFPE
Presidente - 350630 - ZORANO SERGIO DE SOUZA