Late Neoproterozoic P-T-t paths of syn- and post-collisional metamorphism in the Paranaguá Terrane, Ribeira Belt (Brazil): implications for West Gondwana assembly

ABSTRACT

Phase diagram modelling and U-Pb monazite ages reveal a clockwise Pressure-Temperature-time metamorphic evolution in the Paranaguá Terrane (Ribeira Belt – SE Brazil) and characterized important tectonic events. Comparisons of our dataset with the Dom Feliciano and Kaoko belts indicate a contrasting metamorphic evolution of South American and African units during West Gondwana assembly. The Paranaguá Terrane is considered an arc-related unit formed during the western Gondwana accretion, comprising Paleoproterozoic basement inliers, metasedimentary rocks and late Neoproterozoic granites. Metapelites mineral assemblages and chemistry combined with isotopic data indicate three tectonometamorphic stages for the terrane. M1 (640–610 Ma) is associated with collisional processes that resulted in a greenschist to lower amphibolite facies regional metamorphism (540–580°C and ~6-8 kbar). The progression of the metamorphism followed a decompression path of c. 2–4 kbars and reached P-T conditions of ~725°C at ~5 kbars (M2 – 610-580 Ma). M2 is associated with post-collisional processes related to slab-break off and partial exhumation of deeply buried sequences. Metapelites low-temperature retrograde conditions define a late M3 (540–500 Ma) metamorphic event. Our results demonstrate the similarities and differences of the Paranaguá-Dom Feliciano-Kaoko orogenic system. The metamorphic evolution of the Paranaguá Terrane and Northern Dom Feliciano Belt exhibits a geothermal gradient controlled by broad magmatic activity and post-collisional processes. In contrast, their suggested African counterpart (Kaoko Belt) shows a Barrovian metamorphic trend. This dataset permitted a refined time-space evolution of these southwest Gondwana units.

KEYWORDS:

• Gondwana
• Pan-African orogeny
• Paranaguá Terrane
• P-T-t evolution
• metamorphism

Acknowledgments

The authors thank the financial support provided by the PETROBRAS/LAMIR/FUNPAR Microbial Project (n° 23075.120789/2016-11) and grant 2018/10012-0, São Paulo Research Foundation (FAPESP), the team from the Laboratory of Mineral and Rocks analysis (LAMIR-UFPR), and the support from Federal University of Paraná (UFPR) and Geology Department (DEGEOL-UFPR). FMF thanks the research productivity grant 307732/2019-3, National Council of Technological and Scientific Development (CNPq). We acknowledge Dra Tara Jonell and Dr Renjie Zhou suggestions for the manuscript improvement. We also appreciate the comments, suggestions and criticisms from Dra. Claudia Regina Passarelli, Dr. Sebastian Oriolo, one anonymous reviewer and the editor Dr Robert J. Stern.

Article highligits

• Metapelites mineral assemblages constrain three P-T metamorphic stages;

• Metamorphic conditions are strongly controlled by magmatism thermal influx;

• Paranaguá Terrane evolution is associated with the Dom Feliciano-Kaoko Belts;

• Tectonometamorphic features suggest contrasting evolution of the West Gondwana.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by PETROBRAS [23075.120789/2016-11]; the Conselho Nacional de Desenvolvimento Científico e Tecnológico [307732/2019-3]; Fundação de Amparo à Pesquisa do Estado de São Paulo [2018/10012-0].