Abstract Neodymium (Nd) isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean-water masses. Despite the general assumption that the Nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents, preferential dissolution of easily dissolvable phases may result in significant deviations in Nd isotopic composition between the solutes and the source rocks, with potential implications for the utility of Nd isotopes in paleoenvironmental studies. Here, we present the Nd isotopic compositions of leached and detrital fractions separated from bedrock and marine sediment samples from the Svalbard archipelago. Our goal is to further understand the behaviour of Nd isotopes during chemical weathering in glacial catchments and evaluate how glacier fluctuations and associated weathering congruency may have affected the export of dissolved Nd isotope signatures to seawater. Our results confirm that terrestrial weathering on Svalbard causes considerable Nd isotopic decoupling between the leached and detrital fractions of fjord sediments (△eNd), resulting from the preferential dissolution of marine precipitates in glaciated catchments dominated by sedimentary rocks. We also show that the degree of Nd isotopic decoupling has fluctuated in response to climate variability on Svalbard during the Holocene, which is also as suggested by the occurrence of generally higher △eNd values during periods of glacier advances in sediment cores retrieved from two different fjords (Dicksonfjorden and Woodfjorden). We posit that the high △eNd values can be ascribed to incongruent chemical weathering of fresh rock flour produced by glacial abrasion. This finding suggests that the degree of Nd isotopic decoupling could be used as a new proxy for tracing glacial fluctuations and associated glacier-derived nutrient inputs to the marine realm.

中文翻译：

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钕同位素对斯瓦尔巴特群岛化学风化和过去冰川活动的限制

摘要 海洋沉积物浸出的自生成分中的钕 (Nd) 同位素越来越多地被用作过去海洋-水团的示踪剂。尽管一般假设在化学风化过程中释放的溶质的 Nd 同位素组成是大陆上的烃源岩，但易溶解相的优先溶解可能导致溶质和烃源岩之间 Nd 同位素组成的显着偏差，这对Nd同位素在古环境研究中的应用。在这里，我们介绍了从斯瓦尔巴群岛的基岩和海洋沉积物样本中分离出来的浸出和碎屑部分的 Nd 同位素组成。我们的目标是进一步了解冰川集水区化学风化过程中 Nd 同位素的行为，并评估冰川波动和相关的风化一致性可能如何影响溶解的 Nd 同位素特征向海水的输出。我们的研究结果证实，斯瓦尔巴群岛的陆地风化导致峡湾沉积物的浸出部分和碎屑部分（△eNd）之间显着的 Nd 同位素解耦，这是由于海洋沉淀物在以沉积岩为主的冰川集水区中的优先溶解所致。我们还表明，在全新世期间，Nd 同位素解耦的程度随着斯瓦尔巴群岛的气候变化而波动，在从两个不同的峡湾（Dicksonfjorden 和 Woodfjorden）提取的沉积岩芯中，冰川推进期间出现普遍较高的 △eNd 值也表明了这一点。我们假设高 △eNd 值可以归因于冰川磨损产生的新鲜岩粉的不一致化学风化。这一发现表明，Nd 同位素解耦的程度可用作追踪冰川波动和相关的冰川衍生营养物质输入到海洋领域的新指标。