A review of the main tectonic settings of Palaeo-and-Mesoarchean ore deposits in the northern São Francisco Craton, NE Brazil

ABSTRACT

This work is based on the unprecedented Tectonic-Geochronological Map of Bahia (TGMBA): metallogenic implications. In the TGMBA, sixteen tectonic domains were identified, and the main mineral occurrences and deposits in each were recorded. Of the Palaeo-Mesoarchean blocks, the Gavião (GB), Serrinha (SB) and Uauá (UB) blocks were highlighted. The southern GB was formed by plate tectonics, in two stages, at ca. 3403–3378 and 3259–3240 Ma. These rocks served as basement for the Umburanas Greenstone Belt, which comprises felsic metavolcanic rocks (3147 Ma) interspersed with ocean floor mafic metavolcanics and could have been the source of the recently found orogenic gold. This crust could also have formed the basal section of the Brumado metavolcanic-sedimentary sequence, which hosts one of the most important magnesite mines in the world. The northern part of the GB hosts TTGs with ages of ca. 3642–3520 Ma, the oldest known rocks in the whole São Francisco Craton. This region served as a passive margin for the Jacobina-Umburanas Sea, where quartzites and conglomerates (3305 Ma) with detrital gold were deposited and, in the deeper portions of this sea, Mesoarchean ocean floor or Island-arc basalts (3200 Ma) with pillow-lava structures were formed. On the platform of this basin, Mn deposits were formed in association with pelites and sandstones

KEYWORDS:

• Bahia
• são francisco craton
• paleoarchean
• mesoarchean
• tectonics
• metallogenesis

Acknowledgments

The authors thank Companhia Baiana de Pesquisa Mineral (CBPM) and Serviço Geológico do Brasil (CPRM) for their support in the development of the field activities, and geologist Maurício Haag for his support with the figures of this article. Barbosa, J.S.F. thanks Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for a Research Grant (grant number 303508/2019-1). The authors thank Prof. Sergio P. Neves and Prof. Reinhardt A. Fuck for their useful comments, which improved this manuscript, and Dr Robert J. Stern for the careful editorial handling.

Disclosure statement

No potential conflict of interest was reported by the author(s).

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Funding

This work was supported by the CNPQ Conselho Nacional de Desenvolvimento Científico e Tecnológico [303508/2019-1].