Banca de DEFESA: CAROLINE ARAUJO FREITAS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : CAROLINE ARAUJO FREITAS
DATE: 13/02/2023
TIME: 14:00
LOCAL: Sala de Videoconferência do IG e Plataforma Teams
TITLE:

BEHAVIOR OF RARE EARTH ELEMENTS AND Nd and Sr ISOTOPES IN LATERITIC PROFILES IN CENTRAL BRAZIL.

KEY WORDS:

Tropical weathering, Lateritic duricrust, Mineralogy, REE, Nd- Sr isotope

PAGES: 70
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SPECIALTY: Geoquímica
SUMMARY:

Studies on mineralogy and geochemistry in lateritic profiles provide information on the fluid/rock interaction and contribute to the understanding of weathering processes. In this sense, a mineral and geochemical study was carried out in two lateritic profiles in Goiás. Despite the chemical differences associated with the distinct mineral phases in each parent rock, weathering and lateritization of the phyllite in profile 1 and a sandstone in profile 2, originated two lateritic profiles structured in saprolite, mottled, ferruginous and dismantled lateritic crust. In profile 2, the reworking of the ferruginous crust from the

hydration of the hematite originated the superimposed latosol. Lateritization caused the decomposition of muscovite and illite in profile 1 and microcline and illite in profile 2, which resulted in leaching, especially of cations and traces associated with these phases to the detriment of the concentration of Fe2O3, P2O3, ETRL, LOI, As, Cu, Pb, V, Th and Zn in profile 1, and in addition to those of U, Sc and Cs in profile 2, which are also leached in crustal decomposition and soil formation. The heavy rare earth elements are controlled in profile 1 by muscovite and are depleted with the advance of weathering, while in profile 2 they are retained because they are associated with zircon, rutile and anatase, they are residual in weathering. The light rare earths are associated in both profiles with the secondary phases (fe, illite and kaolinite oxides) and are concentrated with the advance of weathering, however the soil formation in profile 2 results in its impoverishment due to the transformation of kaolinite into gibbsite. The ratios of Sm/Nd and εNd(0) preserve the signature of the rocks if they are not fractionated, while the ratios Rb/Sr and 87Sr/87Sr, higher in profile 1 due to its association with muscovite, of both profiles are decreasing for the top in a similar way, reflecting the weathering of the primary minerals

BANKING MEMBERS:
Presidente - 1210338 - ADRIANA MARIA COIMBRA HORBE
Externo à Instituição - CLAUDIO GERHEIM PORTO - UFRJ
Interno - 1303786 - ELTON LUIZ DANTAS
Interno - 1852544 - JEREMIE GARNIER