Rare earth element abundances in high phosphorus and low iron groundwaters from the Nishinomiya district, Japan: Variations in Ce anomaly, redox state and heavy rare earth enrichment
Rare earth element abundances in high phosphorus and low iron groundwaters from the Nishinomiya district, Japan: Variations in Ce anomaly, redox state and heavy rare earth enrichment
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日本西宫地区高磷低铁地下水中稀土元素丰度：Ce异常、氧化还原态和重稀土富集变化
DOI：
10.2343/geochemj.37.1
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发表时间：
2003
影响因子：
0.8
通讯作者：
Y. Terakado
中科院分区：
文献类型：
--
作者：
M. Otsuka;Y. Terakado
对日本西宫地区南部（宫水地下水）的高磷和低铁含量地下水进行了稀土元素 (REE) 和一些主要元素浓度的分析。这些地下水的球粒陨石归一化稀土元素模式的特点是相对于轻稀土元素有较强的重稀土元素富集，以及轻微到中度的负 Ce 异常。 Ce 异常的幅度随着 Fe 的减少以及 NO3- 含量和 pH 值的增加而增加。这种相关性可以通过氧化还原随该区域深度的变化来解释。球粒陨石归一化 REE 模式的重 REE 倾角与 Ca 和 Mg 含量呈正相关，与 Fe 含量呈负相关。重稀土富集是通过连续的水-岩石相互作用向水中提供稀土元素来解释的，其中颗粒物质对轻稀土元素的清除发生了差异。高磷特性是通过生物材料在氧化条件下的分解来实现的。这些地下水的低铁浓度归因于氢氧化铁的沉淀以及地下水流经含水层时随后的过滤。低磷和高铁地下水被认为源自经历还原条件的更深含水层。研究区地下水独特的地球化学特征可能与特殊的地质情况密切相关，即富含有机质层位于相对较浅的深度、渗透性较大的含水层中。
High phosphorus and low iron-content groundwaters from the southern Nishinomya district (Miyamizu groundwater), Japan, were analyzed for rare earth element (REE) and some major element concentrations. The chondrite-normalized REE patterns of these groundwaters are characterized by strong heavy REE enrichments relative to light REE, and slight-to-moderate negative Ce anomalies. The magnitude of Ce anomaly increases with decreasing Fe and increasing NO3- contents and pH. Such correlations are explained by the redox changes with depth in the area. The heavy REE inclinations of the chondrite-normalized REE patterns correlate positively with Ca and Mg contents and negatively with Fe contents. Heavy REE enrichment is explained by successive water-rock interactions supplying REE to the water in which differential scavenging of light REE by particulate matters occurs. The high P characteristic is achieved by the decomposition of biogenic materials under oxidizing conditions. The low Fe concentration of these groundwaters is ascribed to precipitation of Fe-hydroxides and their subsequent filtration as groundwater flows through the aquifer. The low P and high Fe groundwaters are thought to originate from a deeper aquifer experiencing reducing conditions. The unique geochemical characteristics of the groundwaters of the study area may be closely related to a peculiar geological situation in which an organic-rich layer is seated at relatively shallow depths within an aquifer of relatively large permeability.