Petrogenesis, geochronology, and tectonic setting of the Calymmian 1.45–1.50 Ga basic magmatism in the Southern Ribeira Belt, Brazil: evidence of intracontinental rifting and Columbia break-up

ABSTRACT

We present new petrographic, whole-rock geochemistry, and SHRIMP U – Pb zircon geochronological data of metabasic rocks interlayered as sills in the metasedimentary units of the Perau and Betara formations, Votuverava Group, Southern Ribeira Belt, Brazil. These formations overlie ~ 1.8 Ga Paleoproterozoic metagranitoids that represent basement inliers from the Paranapanema Craton. Petrography and whole-rock geochemistry allow the recognition of four groups, ranging from primitive to evolved compositions: i) cumulatic metadolerites (G1), ii) isotropic metadolerites (G2), iii) ortho-amphibolites (G3); and iv) ferroan ortho-amphibolites (G4). They exhibit tholeiitic subalkali basaltic composition, near-flat REE patterns, and signatures between N- and E-MORB. Fractional crystallization under low fO2 conditions is the main petrogenetic process controlling the magmatic evolution, as observed by Ti/V and Cr/Y ratio and tholeiitic trends. Crustal contamination signatures are observed through negative Nb anomaly, Th/Nb-Ti/V proxies trends, LILE enrichment, and, also, assimilated xenocryst zircons aged ~ 2.2 Ga. REE and trace element systematics indicate that the basic magmas were generated by ~ 20–10% partial melting of a model asthenospheric mantle source within spinel facies. TiO2/Yb-Nb/Yb and Nb/Yb-Zr/Yb ratio proxies and P-MORB metabasic rocks, previously described in the literature within the Votuverava Group, suggest a plume-influenced melt. A new SHRIMP U – Pb zircon age of 1448 ± 11 Ma was determined for an ortho-amphibolite sample (G3 group). We propose an intracontinental tectonic setting for the genesis of the metadolerites whitin the Perau and Betara formations, suggesting that this extensional event is associated with the Paranapanema Craton rifting. Furthermore, the genesis of the studied metabasic rocks could be associated with a regional extensional event during Calymmian times (~1.5–1.45 Ga), which generated basic magmatism in several other cratons, such as the Congo, São Francisco, Siberian, Laurentian, and China cratons, linked to the break-up of the Columbia Supercontinent.

KEYWORDS:

• Sill-like emplacement
• fractional crystallization
• crustal contamination
• thinned lithosphere
• mantle plume

Acknowledgment

We would like to express our gratitude to Dr. Monica Heilbron, Dr. Sebastián Oriolo, and an anonymous third reviewer for their suggestions and reviews that greatly improved the quality of the manuscript. We also thank Dr. Robert J. Stern for his support during the editorial process.

Disclosure statement

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

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2358487

Additional information

Funding

This work was supported by the Diagenesis Project (a partnership between SHELL Brazil and Federal University of Paraná, under grant no. ANP 20257-2) and the project The Rio de La Plata Craton and the Western Gondwana Assembly (FAPESP - Fundação de Amparo à Pesquisa do Estado de São Paulo - under grant no.15/03737-0, 2017).