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
Article Sidebar
Main Article Content
Abstract
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 garnet-tourmaline-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.
Article Details
The papers are published in the open access format, being freely available to any user, under a CC-BY Creative Commons license.
By submitting this manuscript for evaluation, the authors are aware of the CC-BY Creative Commons license. In the case of manuscript approval, the author responsible for the manuscript (corresponding author), hereinafter referred to as CEDENTE (ASSIGNOR), hereby assigns and transfers to CPRM-Serviço Geológico do Brasil, holder of the JGSB, free of charge, on his behalf and on behalf from all co-authors, the right of the first publication. This includes the rights of editing, publication, translation into another language and reproduction by any process, worldwide, today and in the future.
After the first publication by the JGSB, authors hold the copyright without restrictions and are allowed to disclose and distribute their work through personal website pages and institutional repositories.
At the same time, the ASSIGNOR declares that the content of the manuscript is of sole responsibility of the authors and that this content does not infringe the copyrights and/or other property rights of third parties, that is, that any contents of the manuscript and its attachments, if taken from other publications, are duly referenced and, when necessary, the permissions for publications of such contents were requested by the authors from the copyright holders; that the disclosure of images (if any) has been authorized and that it assumes full moral and/or patrimonial responsibility, due to its content, before third parties.