This study presents Ba isotope compositions of ocean island basalts (OIB) from the Azores Archipelago to investigate the origin of the enriched components within their mantle sources. These samples have large variations in radiogenic Sr-Nd-Pb-Hf isotope compositions, indicating that they tap highly heterogeneous mantle sources. They display two types of Ba isotope characteristics. Samples from the Faial, Pico, São Jorge, and São Miguel Islands exhibit homogeneous and MORB-like Ba isotope compositions, whereas samples from Terceira Island have variable Ba isotopes. The δ^138/134Ba values of the Terceira samples range from −0.03 to +0.24‰, extending to values significantly higher than those of the other islands.

The MORB-like Ba isotope composition of the São Jorge samples indicates that the enriched HIMU/FOZO material in the Azores mantle plume source has a homogeneous and MORB-like Ba isotope composition. In contrast, the Terceira samples are characterized by heavy Ba isotope compositions, which are likely inherited from subducted altered oceanic crust (AOC) and may reflect the presence of a shallower enriched source beneath Terceira. As the Azores archipelago is located at a triple junction far from any active subduction zone, the signature of subducted AOC must be an ancient feature, potentially derived from a recycled fluid-metasomatized mantle component now present beneath the Azores archipelago. The negative correlation between δ^138/134Ba and ²⁰⁶Pb/²⁰⁴Pb and the positive correlation between δ^138/134Ba and Ba/Th among selected Terceira samples likely reflect mixing between the mantle plume and shallower, recycled, fluid-metasomatized mantle components enriched in heavy Ba isotopes.

本研究介绍了来自亚速尔群岛的海岛玄武岩 (OIB) 的 Ba 同位素组成，以研究其地幔源中富集成分的来源。这些样品在放射性 Sr-Nd-Pb-Hf 同位素组成上有很大的变化，表明它们利用了高度异质的地幔源。它们显示出两种 Ba 同位素特征。来自 Faial、Pico、São Jorge 和 São Miguel 群岛的样品表现出均质和类似 MORB 的 Ba 同位素组成，而来自 Terceira 岛的样品具有可变的 Ba 同位素。Terceira 样品的 δ ^138/134 Ba 值范围从-0.03 到 +0.24‰，延伸到明显高于其他岛屿的值。

São Jorge 样品的类 MORB Ba 同位素组成表明，亚速尔群岛地幔柱源中富集的 HIMU/FOZO 物质具有均一且类 MORB 的 Ba 同位素组成。相比之下，Terceira 样品的特征是重 Ba 同位素组成，这可能是从俯冲蚀变洋壳 (AOC) 继承的，并且可能反映了 Terceira 下方较浅的富集源的存在。由于亚速尔群岛位于远离任何活跃俯冲带的三重交界处，俯冲 AOC 的特征一定是一个古老的特征，可能源自现在存在于亚速尔群岛下方的循环流体交代地幔成分。δ ^138/134 Ba 与²⁰⁶ Pb/ ^{204负相关在选定的 Terceira 样品中，Pb 和 δ 138/134} Ba 和 Ba/Th 之间的正相关可能反映了地幔柱与富含重 Ba 同位素的较浅、循环、流体交代的地幔组分之间的混合。