Abstract Calcium isotopes can potentially be used to trace many geological processes. Characterizing the Ca isotopic compositions of marine sediments is a precondition for using Ca isotopes to trace the recycling of marine sediments into the mantle and mantle-derived rocks. The best way to achieve this goal is to investigate different types of marine sediments that are adjacent to subduction zones and would undergo subduction in the future. Here, we present high-precision Ca isotopic data for marine sediments from the Deep Sea Drilling Project (DSDP) Sites 543 and 144 along the Lesser Antilles forearc region, to constrain the Ca isotope signatures of marine sediments with various components and assess their possible effects on δ44/40Ca of the local mantle and arc lavas via subduction. Our results show that the δ44/40Ca values of these marine sediments vary from 0.10 to 1.21‰ and depend on lithology. Carbonate-rich sediments from Site 144 exhibit δ44/40Ca values in the range of 0.10–0.58‰ with a weighted average value of 0.36‰, which is ∼0.6‰ lower than that of the mantle. In comparison, δ44/40Ca of clay-rich sediments from Site 543 range from 0.79 to 1.21‰ with a mantle-like mean value of 0.96‰. The data obtained here suggest that carbonate- and clay-rich marine sediments differ significantly both in Ca isotopic compositions and CaO contents. Recycling of these sediments will result in different effects on the isotopic compositions of the local mantle and probably affect the local arc lavas. Specifically, carbonate-rich sediments from Site 144 with high CaO contents and light Ca isotopic compositions can alter the local mantle to lower δ44/40Ca signatures, which is expected in the southern Lesser Antilles arc lavas.

中文翻译：

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来自小安的列斯群岛前弧的富含碳酸盐和粘土的海洋沉积物之间的显着 δ44/40Ca 变化及其对地幔非均质性的影响

摘要 钙同位素可用于追踪许多地质过程。表征海洋沉积物的 Ca 同位素组成是使用 Ca 同位素追踪海洋沉积物再循环到地幔和地幔衍生岩石的先决条件。实现这一目标的最佳方法是研究与俯冲带相邻并在未来会发生俯冲的不同类型的海洋沉积物。在这里，我们提供了沿小安的列斯群岛前弧区域的深海钻探项目 (DSDP) 543 和 144 位点海洋沉积物的高精度 Ca 同位素数据，以限制具有各种成分的海洋沉积物的 Ca 同位素特征并评估其可能的影响通过俯冲作用在局部地幔和弧形熔岩的δ44/40Ca上。我们的结果表明，这些海洋沉积物的 δ44/40Ca 值在 0.10 到 1.21‰ 之间变化，并且取决于岩性。Site 144 富含碳酸盐沉积物的δ44/40Ca 值在0.10-0.58‰范围内，加权平均值为0.36‰，比地幔低约0.6‰。相比之下，Site 543 富粘土沉积物的δ44/40Ca 为0.79～1.21‰，类地幔平均值为0.96‰。此处获得的数据表明，富含碳酸盐和粘土的海洋沉积物在 Ca 同位素组成和 CaO 含量方面存在显着差异。这些沉积物的再循环将对当地地幔的同位素组成产生不同的影响，并可能影响当地的弧形熔岩。具体来说，