(Table 1) Composition of volcanic glasses from the East Scotia Ridge

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, similar to the composition of mid-oceanic-ridge basalts (MORB). Lavas from two segments 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.

本数据集包含来自斯科舍海弧后扩张中心的熔岩的新型铀系同位素数据，其(²³⁰Th/²³²Th)与(²³⁸U/²³²Th)比值分布范围广泛。多数弧后熔岩的(²³⁸U/²³⁰Th)比值小于1，其组分与洋中脊玄武岩（mid-oceanic-ridge basalts, MORB）一致。来自两个段的熔岩(²³⁸U/²³⁰Th)比值大于1，且富集流体活动性元素，暗示近期有富铀板片衍生组分的加入。其中一个段的数据显示其受蚀变洋中脊玄武岩产出的含水流体影响，而另一受板片影响的段的样品则表现出沉积物熔体的加入特征。受板片影响的样品在以含水流体与沉积物熔体为端元的等线图（equiline diagram）上形成了一条独特的趋势，该趋势被认为是混合线而非等时线。