Redistribution and fractionation of rare-earth and other elements in a weathering profile
Redistribution and fractionation of rare-earth and other elements in a weathering profile
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DOI：
10.1016/0009-2541(80)90102-3
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发表时间：
1980
期刊：
影响因子：
3.9
通讯作者：
Lan R. Duddy
中科院分区：
文献类型：
--
作者：
Lan R. Duddy
澳大利亚维多利亚南部下白垩统火山成因砂岩风化剖面富含稀土元素（REE）、Y和Ba、Sr、Rb等元素。富集的稀土元素高达7倍的母岩值与铁浸出的成员蚀变对很少或没有富集在邻近的富铁成员。这些蚀变偶联在外观上与Liesegang带相似。在风化前缘新鲜岩石中形成的蚀变偶只涉及Fe（和P）的再分配，而不涉及REE、Y的再分配。Ba、Sr和Rb。在目前的土壤和蛭石的风化剖面的上部的原始矿物的分解释放稀土和相关元素到溶液中。该溶液向下移动并沿着剖面移动，直到在狭窄的风化前缘处接触到中性至碱性条件。在这里，稀土元素特别是吸收和明显固定在蛭石中形成的黑云母和云母为代价。(La+ Ce + Nd + Y）至多10.1重量%这种富集和分馏作用对沉积岩或任何岩石类型露头样品的稀土元素研究具有重要意义。
A weathering profile on a uniform Lower Cretaceous volcanogenic sandstone from southern Victoria, Australia is enriched in rare-earth elements (REE), Y and other elements including Ba, Sr and Rb. Enrichments of REE of up to 7 times parent-rock values are associated with Fe-leached members of alteration couplets with little or no enrichment in adjacent Fe-rich members. These alteration couplets are similar in appearance to Liesegang banding. The REE have been fractionated during accumulation, leading to relative enrichment of the light rare earths (LREE).The formation of an alteration couplet from fresh rock at the weathering front involves redistribution of only Fe (and P) and does not involve redistribution of REE, Y. Ba, Sr and Rb. Breakdown of original minerals in the present soil and degradation of vermiculite in the upper part of the weathering profile releases RE and related elements into solution. This solution moves down and along the profile until it comes into contact with neutral to alkaline conditions at the narrow weathering front. Here REE particularly are absorbed and apparently fixed in vermiculite forming at the expense of biotite and chlorite. (La + Ce + Nd + Y) up to 10.1 wt.% is recorded in degraded biotite grains with similar but lower contents in the degraded diagenetic chlorite cement.Such accumulation and fractionation have important implications for REE studies involving sedimentary rocks or for that matter outcrop samples of any rock type.