Banca de DEFESA: Gabriel Castro de Oliveira Domingues

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Gabriel Castro de Oliveira Domingues
DATE: 25/11/2022
TIME: 14:00
LOCAL: Sala de videoconferência do IGD
TITLE:

Manganese associated with the Araí a Paranoa Groups in the northeast portion of the state of Goiás

KEY WORDS:

Romanechita, litioforita, hausmannita, hydrothermal, supergenic origin

PAGES: 74
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

Small Mn deposits occur in the external zone of Brasilia fold belt, a Neoproterozoic orogen located in Central Brazil. The deposits are associated with the Arai Group (Monjolo) a Paleoproterozoic rift basin and Paranoa group (Minaçu, Raizama, Niquelandia, Pedra Preta, Fortaleza, Vãozinho, Corrente, Vereda, Formosa, Brazlândia, Formoso) a cratonic margin basin of Mesoproterozoic age. These small deposits occur as layers, plates, fillings in pockets and fractures and are considered of supergenic origin. Studies carried out by X-ray diffraction, SEM, EPMA and chemical analysis indicate the presence of pyrolusite, cryptomelane and, to a lesser extent, hausmannite together with higher concentrations of U, Tl and Sr, Co/Zn ratios and high ratios (La/Yb)N and Eu/Eu* in the one associated with the Arai Group. Romanechite, hollandite, lithiophorite, cryptomelane and pyrolusite and higher concentrations of Al2O3, Ba, Co, Cu, Ni, greater variation of REE, in addition to low ratios (La/Yb)N are the characteristic of those associated with the Paranoa Group. Statistical analysis of the data (Principal component) identified that the chemical variations in those from Paranoa Group are related to the intensity of the supergenic activity that forms romanechite and lithiophorite in the most advanced stages as it concentrates Al, Ba, Co, Cu, Ni and Zn. However, the presence of hausmannite and the geochemical characteristics (low Co/Zn ratios and high (La/Yb)N and Eu/Eu*) indicates a hydrothermal contribution to the Arai Group. The lower ratios (La/Yb)N may be associated with supergenic alteration and fractionation in Sm and Nd isotopes, in addition to the more radiogenic values of Sr isotopes.
The 208Pb/206Pb and 207Pb/206Pb ratios do not vary with the (La/Yb)N ratios and present high values of 206Pb/204Pb in samples MJ1 and RZ1. The εNd and TDM values indicate ancient continental source.

BANKING MEMBERS:
Externo à Instituição - MÁRCIO FERNANDO DOS SANTOS ALBUQUERQUE - UNESP
Presidente - 1210338 - ADRIANA MARIA COIMBRA HORBE
Interno - 1852544 - JEREMIE GARNIER
Interno - 418662 - ROBERTO VENTURA SANTOS