Abstract
The Vitória Seamount (VTS), distant ~300 km from the Brazilian coastline at latitude 20°S, is the second closest offshore volcanic complex of the Vitória-Trindade Ridge (VTR) which corresponds to a ca. 1200 km long ridge of seamounts and islands composed of SiO2-undersaturated magmatic rocks commonly considered to be the volcanic track of the Trindade mantle plume in the South American Plate. Based on the first sample dredged from Vitória Seamount, new petrographic and electron microprobe analyses from its rock show an alkaline basalt with pseudotrachytic texture consisting of bytownite and salite phenocrysts, labradorite microliths, anhedral titanomagnetite, and a yellowish green pseudomorphic phase composed of MgO–Al2O3–SiO2–FeO. The fine-grained groundmass is mainly composed of strongly oriented lath-shaped labradorite microliths, opaque minerals, and vesicles filled by a yellowish green pseudomorphic phase. Whole-rock analyses of the Vitória Seamount rock reveal its SiO2 undersaturation (SiO2ca. 40 wt.%; normative nepheline = 13.8), enrichment in Cr, Co, Ni, V and Sc, along with depletion in Zr, La and Nd contents compared to the other seamounts of the VTR. VTS show a strong enrichment in light-REE (La/SmNca. 2.68) compared to heavy-REE (La/YbN = 20.79). Major and trace element evidence indicate that the melting of an enriched mantle source to generate the Vitória Seamount magma occurred dominantly in the garnet stability field. Trace element composition of VTS is consistent with ≤ 3% partial melting of the mantle source. Neodymium and Sr isotopic data suggest that the mantle source of the Vitória Seamount had been variably metasomatized by melts derived from enriched mantle component, which may have developed approximately 600 Ma, reconciling with the Brasiliano Orogeny, according to Nd age model. Modeling of the Nd–Sr isotope systematics points out that the primary melt was formed from an asthenospheric mantle (DMM – Depleted MORB [Mid-Ocean Ridge Basalts] Mantle) that underwent mixing with a continentally derived material (represented by EMI [Enriched Mantle I] component). This process can be explained by the mixing of melts from these mantle components during magma genesis.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
