Submarine basalt xenoliths confirm the occurrence of post-rift volcanism in the Southern Santos Basin, SW Atlantic

Author(s)

de Mahiques, Michel Michaelovitch ; Schattner, Uri ; Riccomini, Claudio ; Janasi, Valdecir de Assis ; Lobo, Francisco Jose ; Vasconcelos, Paulo ; Thiede, David S. ; Ramos, Raissa Basti ; dos Santos, Rosangela Felicio

• Document type: Journal article
• Source: Journal of South American Earth Sciences; v. 132, p. 12-pg., 2023-10-24.

Abstract

We report here the finding and analysis of xenoliths of altered basalt clasts dredged from the top of two exhumed diapirs in the southern Santos Basin (SW Atlantic). The diapirs crossed the stratigraphic column from the Aptian and outcropped on the seafloor. Complemented by seismic data, these findings provide the first direct evidence of an Early Campanian post-rift magmatic event in the southern Santos Basin (SW Atlantic). One 82 Ma Ar-Ar age of these xenoliths indicates that the volcanism developed coeval with the intrusion of the Serra do Mar Alkaline Province rocks on land. The tholeiitic composition of the xenoliths excludes a genetic correlation with the alkaline province. Seismic reflection data indicate the possible source of the xenoliths from a 40-km-wide cluster of volcanic centers and sills located above the Aptian salt deposits (similar to 115 Ma), between the top-Turonian (90 Ma) and top-Campanian (72 Ma) interval. We suggest that salt diapirism peented the overlaying volcanic units and carried fragments upwards through the entire stratigraphic column to the ocean floor. Our findings stress that salt diapirism is an important mechanism for conveying unreachable subsurface fragments to the surface, particularly the ocean floor. With the expanding knowledge of the seascape worldwide, enhanced exploration of salt diapirism and its xenolith products has the potential of opening new windows to unknown parts of geologic history. (AU)

• FAPESP's process: 10/06147-5 - Increase of the research capabilities in oceanography and related sciences in São Paulo State, Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Research Program on Global Climate Change - Regular Grants
• FAPESP's process: 17/50191-8 - Dymamics of salt dome exhumation on the ocean floor, focusing on Santos basin offshore Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/06250-5 - Diapir exposure at the ocean floor as a new paleo-currents indicator: a case study from Santos Basin, offshore Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• 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