New U-series isotope data for lavas from the East Scotia backarc spreading center span a large range in (230Th/232Th) and (238U/232Th). Most of the backarc lavas have (238U/230Th) 1 and are enriched in fluid-mobile elements, implying a recent addition of a U-rich slab-derived component. The data from one segment suggest an influence from an aqueous fluid from altered MORB, whereas samples from the other slab-influenced segment show addition of a sediment melt. The slab-influenced samples form a distinct trend in the equiline diagram between aqueous fluid and sediment melt that is suggested to be a mixing line rather than an isochron.

The quoted errors are 2 sigma errors.

Supplement to: Fretzdorff, Susanne; Haase, Karsten M; Leat, Philip; Livermore, Roy A; Garbe-Schönberg, Dieter; Fietzke, Jan; Stoffers, Peter (2003): 230Th-238U disequilibrium in East Scotia backarc basalts: Implications for slab contributions. Geology, 31(8), 693