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Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2018-03-06 00:00:00 , DOI: 10.1021/acsearthspacechem.7b00124
Michael C. Cheshire 1 , David L. Bish 2 , John F. Cahill 3 , Vilmos Kertesz 3 , Andrew G. Stack 1
Affiliation  

This study investigates how saprolization influences inherent rare-earth element (REE) source rock signatures and how depositional environment(s) and diagenetic reactions ultimately impact the REE signature within sedimentary kaolin bodies. Rare-earth element geochemistry signatures are particularly useful for tracking element sources and mobility and are, therefore, powerful tools in the investigation of clay mineral formation and diagenesis. Rare-earth element and bulk chemical compositions were determined using discrete chemical analyses and chemical imaging. Saprolitic materials show an enrichment in the light and heavy REEs, compared with the parent material, with enhanced Ce/Eu anomalies. Light REEs within sedimentary kaolins are associated with phosphate mineralogy and have experienced variable degrees of diagenetic fractionation and mobilization. Cretaceous kaolins display more light REE mobility compared with Tertiary kaolins, which show very little REE fractionation. Degrees of REE fractionation are driven primarily by differences in sedimentary kaolin physical properties and the presence of organic acids in groundwater. Unfortunately, the provenance of the Georgia kaolins could not be determined based solely on the trace-element and REE compositions because fractionations during saprolization and diagenesis mask much of the inherent provenance signatures. Finally, implications for the REEs as an economic deposit and their beneficiation are discussed.

中文翻译:

高岭土成岩过程中稀土元素动员的地球化学证据

这项研究调查了腐烂作用如何影响固有的稀土元素(REE)源岩特征,以及沉积环境和成岩反应最终如何影响沉积高岭土体内的REE特征。稀土元素地球化学特征对于追踪元素来源和流动性特别有用,因此是研究粘土矿物形成和成岩作用的有力工具。使用离散化学分析和化学成像确定了稀土元素和大块化学成分。与母体材料相比,腐殖质材料在轻质和重质稀土元素中富集,铈/ Eu异常增强。沉积高岭土中的轻稀土元素与磷酸盐矿物学有关,并经历了不同程度的成岩作用分馏和动员。与第三级高岭土相比,白垩纪高岭土显示出更多的轻质REE迁移率,而第三级高岭土仅具有很少的REE分级。稀土元素分馏的程度主要是由沉积高岭土物理性质的差异和地下水中有机酸的存在所决定的。不幸的是,佐治亚州高岭土的来源不能仅仅基于痕量元素和REE组成来确定,因为在皂化和成岩过程中的分级分离掩盖了许多固有的来源特征。最后,讨论了稀土元素作为经济沉积物的含义及其选矿。与第三级高岭土相比,白垩纪高岭土显示出更多的轻质REE迁移率,而第三级高岭土仅具有很少的REE分级。稀土元素分馏的程度主要是由沉积高岭土物理性质的差异和地下水中有机酸的存在所决定的。不幸的是,佐治亚州高岭土的来源不能仅仅基于痕量元素和REE组成来确定,因为在皂化和成岩过程中的分级分离掩盖了许多固有的来源特征。最后,讨论了稀土元素作为经济沉积物的含义及其选矿。与第三级高岭土相比,白垩纪高岭土显示出更多的轻质REE迁移率,而第三级高岭土仅具有很少的REE分级。稀土元素分馏的程度主要是由沉积高岭土物理性质的差异和地下水中有机酸的存在所决定的。不幸的是,佐治亚州高岭土的来源不能仅仅基于痕量元素和REE组成来确定,因为在皂化和成岩过程中的分级分离掩盖了许多固有的来源特征。最后,讨论了稀土元素作为经济沉积物的含义及其选矿。佐治亚州高岭土的来源无法仅根据痕量元素和REE组成来确定,因为在腐烂和成岩过程中进行分级分离掩盖了许多固有的来源特征。最后,讨论了稀土元素作为经济沉积物的含义及其选矿。佐治亚州高岭土的来源无法仅根据痕量元素和REE组成来确定,因为在腐烂和成岩过程中进行分级分离掩盖了许多固有的来源特征。最后,讨论了稀土元素作为经济沉积物的含义及其选矿。
更新日期:2018-03-06
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