Evidence for ca. 2046 Ma high-grade metamorphism in Paleoproterozoic metasedimentary rocks of the northern Borborema Province, NE Brazil: constraints from U-Pb (LA-ICP-MS) zircon ages

Journal of the Geological Survey of Brazil

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ISSN: 2595-1939
Editor Chefe: Evandro Luiz Klein
Início Publicação: 15/05/2018
Periodicidade: Quadrimestral
Área de Estudo: Multidisciplinar, Área de Estudo: Multidisciplinar

Evidence for ca. 2046 Ma high-grade metamorphism in Paleoproterozoic metasedimentary rocks of the northern Borborema Province, NE Brazil: constraints from U-Pb (LA-ICP-MS) zircon ages

Ano: 2019 | Volume: 2 | Número: 3
Autores: Bruno de Oliveira Calado, Felipe Grandjean Costa, Iaponira Paiva Gomes, Joseneusa Brilhante Rodrigues
Autor Correspondente: Bruno Calado | [email protected]

Palavras-chave: Paleoproterozoic, detrital zircon, metamorphism, Borborema, geochronology

Resumos Cadastrados

Resumo Inglês:

This study presents LA-ICP-MS U-Pb detrital zircon ages on a migmatitic paragneiss of the
Jaguaretama Complex, northern Borborema Province, NE-Brazil. This metasedimentary rock
comprises a stromatic migmatite with alternating layers of metapelite, metapsammite and garnettourmaline-
bearing leucosome. The paleosome displays a well-developed schistosity, with fine to
medium-grained textures, and locally garnet porphyroblasts. Backscattered electron images show
that many of the zircon grains display metamorphic overgrowths (recrystallization) and cores with
igneous oscillatory zoning. The detrital zircon grains show 207Pb/206Pb ages clustering from 2.51
to 2.12 Ga (with 90% conc.), evidencing that the igneous sources were generated mostly during the
Transamazonian/Eburnean orogeny. The age of 2137±9 Ma of the youngest and most concordant
detrital zircon (core) is interpreted as the maximum depositional age of the protolith. The youngest
and most concordant (conc. 99%) 207Pb/206Pb apparent age obtained in a metamorphic zircon
overgrowth was 2046±6 Ma, which is interpreted as the age of high-grade metamorphism. This age
of metamorphism is similar to other records of Paleoproterozoic high-grade metamorphic events in
the Borborema Province and other cratonic domains (e.g. São Francisco and West Africa cratons).
This age also represents the minimum depositional age of the protolith. Therefore, the depositional
age of the studied supracrustal rock may be bracketed between ca. 2.14 and 2.05 Ga.