Petrology of Cenomanian basalts on the Brazilian equatorial margin: Implications for the tectonomagmatic evolution of the drift phase

Author(s)

de Macedo Filho, Antomat Avelino ; Oliveira, Alisson Lopes ; Kloecking, Marthe ; Janasi, Valdecir de Assis ; Archanjo, Carlos Jose ; Lino, Lucas Martins

• Document type: Journal article
• Source: CHEMIE DER ERDE-GEOCHEMISTRY; v. 85, n. 1, p. 17-pg., 2025-03-06.

Abstract

Olivine basalts from the Serra do Cuo<acute accent> magmatism in the onshore Potiguar basin exhibit SiO2 = 46-53 wt%, MgO = 9-12 wt%, and total alkalis = 3.5-6 wt%, combined to elevated concentrations of large ion lithophile elements (Rb, Ba, Th, U, K), positive anomalies of Nb and Ta, and fractionated heavy rare earth elements. These lavas constitute a single volcanic event with evidence of fractional crystallization primarily involving olivine and pyroxene. Whole rock 40Ar/39Ar geochronology provided a minimum crystallization age of 99 +/- 1 Ma, which is chronologically compatible with other Albian/Cenomanian igneous activity in NE Brazil. Clinopyroxene geothermobarometry indicates a range of crystallization depths from 23 km to 6 km, supporting crystal growth in a magma plumbing system before the emplacement. Radiogenic isotopes reveal enriched mantle-type source, akin to Paleogene/Neogene alkali basalts elsewhere in NE Brazil. Rare earth element inverse modeling hints that Serra do Cuo<acute accent> melts originated at a mantle potential temperature of 1350 degrees C, approximately 60 km depth. The longlived alkali basaltic volcanism across the NE Brazil likely resulted from decompression melting of the mantle due to a combination of geodynamic factors, including episodes of hotspot influence and changes in South America's drift pattern. (AU)

• FAPESP's process: 22/03365-9 - Geochemical and geochronological investigation of giant dike swarms associated with West Gondwana breakup: keys to geodynamical correlations between large igneous provinces in South America
• Grantee: Antomat Avelino de Macêdo Filho
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 23/02630-3 - "(U-Th)/He thermochronology applied to active orogenesis and landscape evolution in the Amazonian Andes
• Grantee: Alisson Lopes Oliveira
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/22084-8 - The Paraná Magmatic Province: petrogenesis, chronology and environmental impact of Cretaceous tholeiitic, alkaline and silicic magmatism in the Brazilian Platform
• Grantee: Valdecir de Assis Janasi
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 23/06771-0 - Silicate liquid immiscibility in alkali-rich tholeiitic systems: the role of unmixing in the petrogenesis of intermediate intrusions and bimodal volcanic suites
• Grantee: Lucas Martins Lino Aguiar dos Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral