Voltar
Artigo Acesso aberto Produção Nacional Revisado por pares
BIBTEX RIS

Geochemical and isotopic constraints on the petrogenesis of the Cretaceous alkaline Morro Redondo intrusive complex, Rio de Janeiro, Brazil: implications for alkaline magma genesis

2024; Volume: 7; Issue: 2 Linguagem: Inglês

10.29396/jgsb.2024.v7.n2.1

ISSN

2595-1939

Autores

Carlos Eduardo Miranda Mota, Arthur Silva, Fred Jourdan, Mauro César Geraldes, Guilherme Loriato Potratz,

Tópico(s)

earthquake and tectonic studies

Resumo

The Morro Redondo Complex is composed of plutonic and volcanic alkaline rocks.This igneous complex is part of the Poços de Caldas -Cabo Frio Magmatic Alignment (PCCFA).This study aims to contribute to the understanding of the petrogenesis of the rocks in the Morro Redondo complex and, thereby, contribute to the debate on the genesis of the PCCFA.In this work, we conducted analyses of whole-rock geochemistry, 40 Ar/ 39 Ar thermochronology, U-Pb geochronology on zircon grains, and Rb-Sr, Sm-Nd, and Lu-Hf isotopic analyses.Four distinct lithotypes are present: nepheline syenites, alkali feldspar syenites, trachytes, and phonolites.The rocks of the Morro Redondo complex are miaskitic, have intermediate values of SiO2, and show significant crustal assimilation, mainly observed in the relationship between the SSI and (Na+K)/Al indices, together with the Hf isotopic signature.A hornblende crystal obtained from a sample of nepheline syenite provided a plateau age of 74.35 ± 0.50 Ma.The initial ratios of 87 Sr/ 86 Sr range from 0.70565 to 0.71042, and the initial ratios of 143 Nd/ 144 Nd range from 0.51234 to 0.5124.Hf data suggest a hybrid origin for the Morro Redondo complex, with sources from both crustal and mantle origins.The data obtained indicate that at least three magmatic pulses contributed to the formation of the Morro Redondo complex, with the participation of both crustal and mantle sources, generating magmas of miaskitic affinity.Geochemical and isotopic constraints on the petrogenesis of the Cretaceous alkaline Morro Redondo intrusive complex, Rio de Janeiro, Brazil: implications for alkaline magma genesis

Referência(s)