皖北九顶山组灰岩稀土元素地球化学特征及对古海水的制约
Geochemical characteristics of REE in limestone of Jiudingshan Formation, northern Anhui Province and their constraint on the seawater
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摘要: 提要：采集皖北新元古代九顶山组灰岩进行了系统的岩石学和稀土地球化学分析，研究了灰岩中稀土元素的来源，并对海水的稀土配分模式进行反演，结果表明：灰岩中稀土元素主要受控于古海洋，基本不受陆源物质影响；灰岩样品中稀土含量很低，平均为8.54×10-6，轻重稀土分异明显，为正常浅海沉积；海水稀土配分模式与灰岩相似，为重稀土亏损，灰岩和海水的Y/Ho、Y/Dy值呈正相关；海水具有较高的Y/Ho比、Ce负异常，且海水的δEuNASC值小于1，表明了新元古代海水与现代海水的稀土元素特征基本相似。Abstract: Abstract：In this paper, petrological and rare earth element analysis was carried out for limestone collected from the Jiudingshan Formation in northern Anhui Province, the origin of REE in limestone was studied, and the rare earth elements distribution patterns of the seawater were inversed. The results imply that rare earth elements in the limestone were mainly controlled by ancient oceans, without the influence of detrital material, that the total rare earth elements (REE) content is rather low, only 8.54?鄢10-6 on average, and the light and heavy REE are strictly fractionated, indicating normal neritic deposit. The REE distribution patterns of seawater is depleted in HREE, similar to things of limestone, and a very good positive correlation exists between Y/Ho and Y/Dy (R2=0.97) in limestone and seawater. The seawater has high Y/Ho ratios and negative Ce anomaly, with the δEuNASC being lower than 1, suggesting that the ancient seawater was similar to modern seawater.
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