Toward an integrated model of geological evolution for NE Brazil-NW Africa: The Borborema Province and its connections to the Trans-Saharan (Benino-Nigerian and Tuareg shields) and Central African orogens

Abstract

Both the Borborema Province of NE Brazil and the geological provinces of NW Africa (the Trans-Saharan Orogen consisted of the Tuareg and Benino-Nigerian shields and the Central African Orogen of Cameroon, Chad, and Central African Republic) are complex geological regions with superposition of distinct deformational, metamorphic and magmatic events and final structural configuration during the Brasiliano/Pan-African Orogeny (ca. 625-510 Ma). These provinces represent the site of major mountain building processes in the Ediacaran/Cambrian transition that culminated in the amalgamation of West Gondwana after the collision of the West African-São Luís, São Francisco-Congo, and Saharan paleocontinents. In the last years, discovery and characterization of key tectonic units such as ophiolites, eclogites, HP/UHP rocks, and both oceanic and continental magmatic arcs are helping to clarify these processes and propose tectonic models for the geological evolution of NE Brazil-NW Africa. Connections of the marginal belts that frame these provinces, bordering the eastern margin of the West African-São Luís Craton (Médio Coreaú-Dahomeyides-Gourma-West Tuareg Shield) and the northern margin of the São Francisco-Congo Craton (Rio Preto-Riacho do Pontal-Sergipano-Yaoundé-Central African) are progressively better constrained, while correlations within the interior, highly reworked and sectioned portions of both the Borborema Province, the Benino-Nigerian Shield, the Central and East Tuareg Shield, Western Cameroon, and Adamawa-Yadé domains are more complicated and demand further investigation. Some of the questions of prime importance in this context are the continuation or not of the 1000-920 Ma Cariris Velhos Belt of NE Brazil into NW Africa, and if the basement-dominated North Borborema/Benino-Nigerian (NOBO-BENI) and Alto Pajeú-Alto Moxotó-Rio Capibaribe-Pernambuco-Alagoas/Adamawa-Yade (APAMCAPAY) domains could represent major decratonized blocks (such as LATEA in the Central Tuareg Shield), perhaps developed due to hyperextension and detachment of a Greater São Francisco-Congo paleocontinent northern margin. In this case, the Goiás-Pharusian and Transnordestino-Central African oceanic realms along with restricted internal oceans such as the hypothetical Piancó-Alto Brígida/Western Cameroon (PAB-WECA) Seaway probably separated these ancient paleocontinental blocks during the Neoproterozoic. The development of subduction zones and the docking of Neoproterozoic juvenile terranes welded the hyperextended Archean/Paleoproterozoic lithospheric fragments together and they became squeezed and reworked in between the major cratonic landmasses during the Brasiliano/Pan-African Orogeny. The quest for the sites of ancient oceans and continents that once composed NE Brazil and NW Africa goes on and tentative scenarios will surely benefit from novel geological, isotopic, and geochronological data put forward in the near future.

Decratonization by Rifting followed by Orogeny and Transcurrent Dispersal of Old Terranes in NE Brazil: A Common Feature of Gondwana Amalgamation?

“…We suggest that Tonian extension, recorded by bimodal magmatism and rift-related sedimentation followed by passive margin sedimentation, would have opened a narrow ocean recorded by marginal ophiolites dated at ca. 0.82 Ga, breaking apart the greater São Francisco Craton/Benino-Nigerian Shield 18 ( Fig. 4A).…”

“…This craton is bound to the north by the late Neoproterozoic orogenic Borborema Province. In the province, pre-orogenic extension started as early as 1000-900 Ma and resulted in the development of intracontinental extensional basins 13 , passive margin basins anking the SFC [14][15][16] , and separation of the SFC from the African Benino-Nigerian Shield 17,18 . Remarkably, this orogenic province includes a number of reworked and deformed Archean-Paleoproterozoic terranes among the Neoproterozoic sedimentary basins and granitic intrusions 19 .…”

Accretionary models for the Neoproterozoic evolution of the Borborema Province: advances and open questions

“…Highpressure to ultrahigh-pressure metamorphism has also been documented on coeval eclogites from Mali and Togo, leading Ganade de Araújo et al (2014a) to suggest that deep-continental subduction took place in the region. The Forquilha eclogites occur between the Santa Quitéria magmatic complex to the east, that has long been proposed as a Cryogenian-Ediacaran (660-620 Ma) continental arc (Fetter et al 2003) and the Transbrasiliano-Kandi megashear zone, that crosses the Brazilian territory from the Pantanal area up to the Hoggar region of the Transaharan orogen in NW Africa in pre-drift reconstructions (Cordani et al 2013, Caxito et al 2020a. continental arc batholith of similar age in the NW border of the BP is interpreted as the telltale of a collisional suture related to the closure of the Goiás-Pharusian Ocean (Cordani et al 2013).…”

“…The Borborema Province (BP; NE Brazil), like other Neoproterozoic orogenic areas of Brazil, is part of the large system proposed by Almeida et al (1981), built-up through convergence of the São Francisco-Congo and São Luis-West African paleocontinents during the Brasiliano Orogeny (ca. 630--530 Ga; Brito Neves et al 2014, Caxito et al 2020a.…”

“…New alternatives proposing both the acting of typical modern-style plate tectonics processes and reworking of older basement blocks in the interior of the province have emerged (e.g. Oliveira et al 2010, Ganade de Araújo et al 2014a, Caxito et al 2016, 2020a reinforcing some aspects of previous models and highlighting problems that have not yet been detected or discussed. The goal of this contribution is to present an update of ideas mainly related to the accretionary model since the seminal work of Santos (1996) and future perspectives for the evolutionary dynamics of the BP.…”