Trace Element Evidence of Subduction-Modified Mantle Material in South Mid-Atlantic Ridge 18–21°S Upper Mantle

Mid-ocean ridge basalts (MORBs), produced at mid-ocean where the continents and subduction zones are distant, product of partial melting upper mantle their chemical composition can provide information about itself. The geochemical characteristics MORBs enable us to be more informed geological processes below ridge, assist in understanding heterogeneity geodynamic processes. In this paper, new data major elements, trace Nd-Hf isotopes south mid-Atlantic (SMAR) 18–21°S presented. TAS diagram shows that samples belong subalkaline basalt compositional field. Trace elements (e.g., (La/Sm)N = 0.49–0.79) show N-MORBs. However, primitive mantle-normalized element patterns showed studied were clearly enriched Rb, U, Pb, other fluid-mobile elements. Meanwhile, ratios, such as Nb/U Ce/Pb, also significantly different from typical N-MORB. Combined with isotopic composition, we propose these anomalies not related continental crust material, delaminated subcontinental lithospheric (SCLM), recycled sediments, direct supply plume, nor they result directly affecting source, but caused by incorporation material modified subduction.