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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >Rare Earth Elements in early-diagenetic foraminifer 'coatings': Pore-water controls and potential palaeoceanographic applications
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Rare Earth Elements in early-diagenetic foraminifer 'coatings': Pore-water controls and potential palaeoceanographic applications

机译：早期成岩传染率的稀土元素的稀土元素'涂料'：孔隙水控制和潜在的古英语应用

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摘要

Rare Earth Element (REE) distributions in the ocean bear the fingerprints of several key environmental processes, including vertical particle/organic carbon fluxes, water column/pore-water oxygenation and ocean transports. The use of 'fossil' REE analyses in the service of palaeoceanography as redox, water transport or nutrient cycling 'proxies' has long been a tantalizing possibility. Here we demonstrate the application of a novel laser-ablation microanalysis approach for the rapid and accurate measurement of the REE composition of early diagenetic 'coatings' on fossil foraminifera. By applying this new method to a range of core-top and multi-core samples, we show that `authigenic' REE enrichments on planktonic foraminifer surfaces (REEfs) reflect a primary seawater signature that becomes overprinted during sediment burial due to early diagenetic processes that control the flux of REEs to pore-fluids. Thus 'light' REEs (LREEs), and eventually 'middle' REEs (MREEs) are generally enriched in foraminifer 'coatings' relative to seawater, while Ce-anomalies (Ce/Ce*) recorded in surface sediments are typically more positive than local seawater values and are further 'eroded' during burial with the onset of anoxic conditions in the sediment. Similar patterns have previously been observed in pore-fluid measurements. Indeed, we show that Mn and Fe concentrations measured in foraminifer 'coatings' track the availability of these elements in pore-water, indicating that they are not associated with a secondary oxide phase. We propose that these elements, along with REEs are instead adsorbed directly from pore-fluids. In contrast, U in authigenic coatings tracks the removal of this element from solution under sub-oxic conditions, supporting the use of U/Ca in foraminifer coatings as a redox proxy. Although our results confirm a significant early diagenetic influence on REEfs, we also demonstrate the potential utility of `Ce-enrichment' relative to expected seawater values as a
机译：稀土元素（REE）海洋的分布承担了几种关键环境过程的指纹，包括垂直粒子/有机碳通量，水柱/孔隙水氧合和海运。使用“化石的REE分析古生馆服务作为氧化还原，水运输或营养循环'代理人长期以来一直是诱人的可能性。在这里，我们证明了一种新型激光烧蚀微量分析方法的应用，以便快速，准确地测量化石传染率的早期成岩性“涂料”的REE组成。通过将这种新方法应用于一系列核心顶级和多核样本，我们表明，浮游动物的食物面积（珊瑚礁）的Ree浓缩反映了由于早期成岩工艺而在沉积物埋藏期间变为叠印的主要海水签名控制REES的助焊剂到孔隙流体。因此，“轻盈”Rees（LEREES），最终'中间'REES（麦饼）通常相对于海水富集，而在表面沉积物中记录的CE - 异常（CE / CE *）通常比当地更积极海水值，在埋葬中进一步“侵蚀”，沉积物中的缺氧条件发作。以前在孔隙流体测量中观察到类似的图案。实际上，我们表明，在面部素涂层的涂层中测量的Mn和Fe浓度跟踪孔隙水中这些元素的可用性，表明它们与二次氧化物相无关。我们提出这些元素以及REES，而是直接从孔隙流体吸附。相比之下，在Authigenic涂层中，追踪在亚氧化条件下从溶液中除去该元素，支持使用U / Ca作为氧化还原代理。虽然我们的结果证实了对珊瑚礁的显着早期成绩影响，但我们还证明了“CE-CE-CERICHENT”相对于预期海水价值的潜在效用

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