Recycling of subducted crust in the source of within-plate CAMP basalts from southeastern North America

Basaltic dykes and sills of the Central Atlantic magmatic province (CAMP) were intruded between 202 and 195 Ma in southeastern North America (SENA) during Pangea break-up. We aim to constrain the mantle source of these magmatic bodies and their evolution path with new combined geochemical data (major and trace elements, Sr-Nd-Pb-Os isotopes). While Sr-Nd isotopic compositions for SENA rocks (87Sr/86Sr200Ma 0.70438-0.70880 and 143Nd/144Nd200Ma 0.51251-0.51204) fall within the low-Ti CAMP field, Pb-Pb isotopes (206Pb/204Pb200Ma = 17.46-18.85, 207Pb/204Pb200Ma = 15.54-15.65, 208Pb/204Pb200Ma = 37.47-38.76) are peculiar for this area of the CAMP and span a wide range of compositions, notably extending towards low 206Pb/204Pb200Ma values. Based on the generally unradiogenic Os isotopic compositions (187Os/188Os200Ma = 0.127-0.144) and the lack of correlation between these and other geochemical markers, the role of crustal contamination in the evolution of SENA tholeiites is constrained to be less than 10%. Hence, the isotopic variation is interpreted to reside within the mantle source and a process other than crustal assimilation was responsible for conveying the observed continental trace element signature (positive anomaly in Pb and negative anomalies in Ti and Nb) to these magmas. For this process, we hypothesize shallow recycling of subducted lower and upper crustal materials within the upper mantle. Pseudo-ternary mixing models show that a maximum of 10% recycled crust is enough to explain both the SENA dyke trace element patterns and their isotopic heterogeneity. Furthermore, though a thermal contribution of a mantle plume is not completely excluded due to the relatively high mantle potential temperatures (1430°-1480° C) calculated from SENA primitive olivines, its chemical contribution was negligible (less than 5%).