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Geochemical and geochronological investigation of giant dike swarms associated with West Gondwana breakup: keys to geodynamical correlations between large igneous provinces in South America

Grant number: 22/03365-9
Support Opportunities:Scholarships in Brazil - Post-Doctorate
Effective date (Start): November 01, 2022
Effective date (End): October 31, 2024
Field of knowledge:Physical Sciences and Mathematics - Geosciences - Geology
Principal Investigator:Valdecir de Assis Janasi
Grantee:Antomat Avelino de Macêdo Filho
Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:19/22084-8 - The Paraná Magmatic Province: petrogenesis, chronology and environmental impact of Cretaceous tholeiitic, alkaline and silicic magmatism in the Brazilian Platform, AP.TEM

Abstract

The opening of the South Atlantic Ocean, and consequent West Gondwana breakup, triggered at the Early Cretaceous was preceded by dramatic tholeiitic magmatism (with minor associated silicic and alkaline occurrences) presently recognized from NE Brazil/western Africa (Nigeria) to the Falklands/South Africa. In SE South America and SW Africa, continental flood basalts and related plumbing systems constitute the Paraná-Etendeka Magmatic Province (PEMP). In NE Brazil, in turn, dike swarms and sill complexes compose the Equatorial Atlantic Magmatic Province (EQUAMP). The main component of the EQUAMP is the Rio Ceará-Mirim dike swarm (RCM), forming up to 1000 km-long arcuate plumbing system across the Borborema Province with prevalent high-Ti tholeiitic composition (TiO2 > 2 wt.%). Geophysical airborne data available at the Geological Survey of Brazil indicate that the magnetic anomalies of the RCM reach the NW sector of the São Francisco Craton, where they propagate up to the vicinity of the Barreiras town (Bahia state). From that sector onwards, the anomalies propagate to SSE to the Espinhaço region (Minas Gerais state), where Early Cretaceous-aged high-Ti tholeiitic dikes are named as the Transminas swarm. Another analogous situation is observed between the Early Cretaceous Riacho do Cordeiro and Vitória-Colatina swarms that host low-Ti tholeiites, suggesting continuity across the São Francisco Craton in the magnetic maps. All these observations support that the RCM and Transminas swarms, as well as Riacho do Cordeiro and Vitória-Colatina swarms, form large continental-scale plumbing systems that constitute the physical linkage between the two expressive large igneous provinces (LIP) of the Lower Cretaceous. This Post-Doctoral project aims to investigate Transminas and Vitória-Colatina dike swarms from northern PEMP, through the collection of new data combined with those available in the literature, to establish robust correlations with the Rio Ceará-Mirim and Riacho do Cordeiro swarms, both already well characterized in terms of geochemical-isotopic perspective. If the compositional and temporal link between these plumbing systems is confirmed, a connection between the Paraná-Etendeka and the Equatorial Atlantic provinces could be established, which together would constitute the largest plumbing systems and continental flood basalts reported for the Mesozoic.

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