Banca de DEFESA: João Gabriel Cavalcante Vieira

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : João Gabriel Cavalcante Vieira
DATE: 20/03/2024
TIME: 14:00
LOCAL: Sala de Videoconferência do IGD
TITLE:

PETROGRAPHY AND GEOCHEMISTRY OF ALTO TAPAJÓS GROUP ROCKS IN THE EXTREME SOUTHEAST OF AMAZONAS STATE, BRAZIL

KEY WORDS:

Alto Tapajós Basin; Nd isotopes; Provenance.

PAGES: 83
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

This study provides petrographic, whole-rock element and Nd isotope geochemical data for sedimentary rocks from three drill core sections in the extreme northwestern region of the Alto Tapajós Basin, Mid-South Amazonia, Brazil. The investigated succession hosts a phosphate occurrence with regional economic significance. The sections comprise a basal muddy-dolomitic portion, associated with the Terra Preta Formation, and an upper sandy muddy portion, related to the São Benedito Formation. Facies associations suggest deposition in a shallow marine environment dominated by storm activity, from outer shelf to lower shoreface. Geochemical data support an intracratonic rift setting with some collisional signatures probably inherited from source rocks. Concentrations of Rb, Ba, Sr, Th, U, Zr, Hf, Y, Sc, V, Cr, Cu, Ni, and Zn indicate felsic sources. Early diagenetic REE redistributions related to authigenic fluorapatite occurred along the sections. Affected REE and isotopic compositions were not used for provenance considerations. Nd isotopic compositions, particularly of fine grained rocks, suggest upper continental crust and/or recycled provenance, with model ages ranging from 2.32 to 2.49 Ga. The main source areas for the succession are related to Rondônia Juruena, Tapajós-Parima, and Central Amazon Provinces. Notably, one marl sample exhibited a much older model age of 3.35 Ga, suggesting a possible contribution from more distal source areas, related to Carajás and Transamazon Provinces, or from unknown proximal units.

COMMITTEE MEMBERS:
Presidente - ***.642.020-** - ADRIANA MARIA COIMBRA HORBE - UFPA
Interna - ***.400.141-** - EDI MENDES GUIMARAES - UnB
Interna - 1658822 - LUCIETH CRUZ VIEIRA
Externa à Instituição - MARLY BABINSKI - USP