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Título

PETROGENETIC RELATIONSHIP BETWEEN THE ABROLHOS MAGMATIC PROVINCE (AMP) AND THE VITÓRIA-TRINDADE RIDGE (VTR) MAGMATISM, SOUTHEAST BRAZILIAN MARGIN, SOUTH ATLANTIC OCEAN

Texto do resumo

The Abrolhos Magmatic Province (AMP) is an igneous province with about 63,000 km2 located at the Continent-Ocean Boundary (COB), into the Southeast Brazilian Margin, encompassing the Espírito Santo, Mucuri, and Cumuruxatiba marginal sedimentary basins. The AMP emerges as five small islands, Santa Bárbara, Redonda, Siriba, Sueste, and Guarita. They integrate the Abrolhos Archipelago located about 55 km offshore Brazil, southeast of Caravelas city, Bahia state. To the southeast of the AMP lies the Vitória-Trindade Ridge (VTR), a west-east-trending volcanic aseismic ridge composed of more than 30 seamounts and banks. The AMP and the VTR show an eastward decreasing age pattern from the older ca. 60 Ma Abrolhos Province to the younger Martin Vaz and Trindade Islands (ca. 4 – 0.1 Ma), located ca. 1,200 km away from the Brazilian coastline. Based on whole-rock chemistry data and Sr-Nd-Pb isotopic compositions from AMP and VTR rocks, in addition to geochemical modeling, this work discusses a possible petrogenetic link between the AMP and VTR magmatism since there is an overlap of their geochemical and isotopic data, besides the age pattern. Our model mixing calculations suggest a mixture with a prevailing depleted asthenosphere mantle source (represented by DMM; ca. 80%) metasomatized by an enriched mantle I (EMI) component (≤ 10%) and a possible HIMU-type constituent (up to 10%) in the AMP genesis. The assimilation of subducted slabs of the oceanic crust associated with the HIMU signatures is possibly linked to the Brasiliano Event due to the range of the AMP Nd TDM model ages, from 407 to 767 Ma. A viable mechanism for the EMI end-member contribution could either be a physical detachment of the South American subcontinental lithospheric mantle during the breakup of the Gondwana or lithospheric delamination of the South American plate caused by an edge-driven convection mechanism. This petrogenetic model is similar to the one proposed for VTR source in previous studies. Thus, the volcanic alignment between the VTR and AMP, along with the overlap of geochemical and isotopic data of their different igneous rocks, cannot be a random feature but instead represent the sampling of similar shallow mantle reservoirs, thus suggesting a cogenetic relationship.

Palavras Chave

Abrolhos magmatism; Abrolhos Archipelago; Eocene-Pleistocene volcanism; Vitória-Trindade Ridge