Abstract
The Vitória-Trindade Ridge (VTR) represents important physiography in the South Atlantic Ocean. It is a 1200-km volcanic ridge running W–E in Vitória (Espírito Santo State) parallel about 20°S. It represents about 50 My volcanic episodes forming alkaline lava with undersaturated affinity regarding the silica content, with high MgO and incompatible element content (Cr, Ni, V, and Rare Earth Elements (REE) representing rocks from the nephelinite–basanite–tephrite series. Volcanic buildings in the VTR have variable REE ratios, indicating different depths and degrees of partial melting (e.g., Dy/Yb and La/Yb ratios), and variable mixtures of spinel and garnet-lherzolite facies, with lower and variable extents of partial melting (≤2%), which explains the incompatible element content of VTR. In addition, the approximately homogeneous Nd–Sr–Pb isotopic compositions, which are slightly more enriched than those of the Normal Mid-Ocean Ridge Basalts (N-MORB) indicate a depleted asthenosphere-type mantle source with the minor input of two enriched components (EMI and young "High μ; μ = 238U/204Pb (HIMU)" and "Focal Zone (FOZO)", the latter of which is invoked owing to radiogenic Pb isotopic compositions, which is the result of recycling of subducted dehydrated oceanic crust.
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