Geochronology (Ar/Ar and K–Ar) of the South Atlantic post-break-up magmatism

• Main Authors: M. C. Geraldes, A. Motoki, A. Costa, C. E. Mota, W. U. Mohriak
• Format: Dataset
• Language: unknown
• Published: 2016
• Subjects: Geology; South America platform; South America platforms; serpentinized mantle rocks; Cameroon Volcanic Line; magmatism; Cabo Frio Province; Cretaceous; mantle plumes; NE; Rio Grande Rise; Mafic dyke swarms; NW; South Atlantic opening; SE; magmatic; South Atlantic margin; Saint Paul Rocks; South Atlantic Ocean opening; Cabo Frio; Saint-Paul; St. Helena; South Atlantic Ocean
• Online Access: https://doi.org/10.6084/m9.figshare.3453263.v1; https://figshare.com/articles/Geochronology_Ar_Ar_and_K_Ar_of_the_South_Atlantic_post-break-up_magmatism/3453263

This work integrates the available geological information and geochronology data for the Cretaceous–Recent magmatism in the South Atlantic, represented by onshore and offshore magmatic events, including the oceanic islands along the transform faults and near the mid-ocean ridge. The analysis of the igneous rocks and their tectonic settings allows new insights into the evolution of the African and Brazilian continental margins during the South Atlantic opening. Following the abundant volcanism in the Early Cretaceous, the magmatic quiescence during the Aptian–Albian times is a common characteristic of almost all Brazilian and West African marginal basins. However, rocks ascribed to the Cabo Granite (104 Ma) are observed in NE Brazil. In West Africa, sparse Aptian–Albian ages are observed in a few coastal igneous centres. In the SE Brazilian margin, an east–west alkaline magmatic trend is observed from Poços de Caldas to Cabo Frio, comprising igneous intrusions dated from 87 to 64 Ma. Mafic dyke swarms trending NW also occur in the region extending from the Cabo Frio Province towards the Central Brazilian Craton. On the West African side, Early Cretaceous–Recent volcanism is observed in the Walvis Ridge (139 Ma), the St Helena Ridge (81 Ma) and the Cameroon Volcanic Line (Early Tertiary–Recent). Volcanic islands such as Ascencion (1.0–0.65 Ma), Tristão da Cunha (2.5–0.13 Ma) and the St Helena islands (12 Ma) most probably correspond to mantle plumes or hot spots presently located near the mid-Atlantic spreading centre. Within the South America platform and deep oceanic regions, the following volcanic islands are observed: the Rio Grande Rise (88–86 Ma), Abrolhos (54–44 Ma), the Vitória–Trindade Chain (no age), Trindade (2.8–1.2 Ma) and Fernando de Noronha (12–1.5 Ma). There are several volcanic features along the NW–SE-trending Cruzeiro do Sul Lineament from Cabo Frio to the Rio Grande Rise, but they have not been dated. The only known occurrence of serpentinized mantle rocks in the South Atlantic margin is ...