碳酸盐岩稀土元素是沉积环境示踪的理想参数，但由于自生沉积碳酸盐矿物的稀土元素含量远低于陆源黏土等其他矿物，在样品处理过程中少量陆源黏土矿物的溶解，将影响沉积环境的示踪。因此，如何在样品处理过程中避免陆源黏土矿物中稀土元素的释放，从而获得海洋环境自生沉淀形成的碳酸盐矿物中的元素方法非常重要。本文应用地层中常见的同一泥灰岩样品，分别用5%醋酸、5%盐酸、2%和5%硝酸浸取，采用0.5 h、1 h、2 h、3 h、6 h和24 h的反应时间，用X射线衍射法(XRD)分析酸不溶残渣矿物组成、电感耦合等离子体原子发射光谱法(ICP-AES)测定酸可溶相溶液的主元素和微量元素含量、电感耦合等离子体质谱法(ICP-MS)测定酸可溶相溶液的稀土元素含量，结果表明所有酸溶均可完全溶解泥灰岩中的方解石矿物，并有少量黏土发生溶解，导致稀土总量和Ce/Ce*增高，但对Eu/Eu*、LaN/YbN和Gd/Gd*等参数没有影响。泥灰岩中自生方解石的稀土元素理想溶样条件是5%醋酸反应1 h以内，溶液的ICP-MS分析结果适用于示踪沉积环境的氧化还原条件。%Rare earth elements (REEs) of sedimentary carbonate rocks are the best parameters to trace redox conditions of sedimentary environment. However, because the REE contents of authigenic carbonate minerals are much lower than that of terrigenous clays, a small quantity of terrigenous clays dissolved will affect true redox implication of sedimentary environment. Therefore, it is very important to conduct an analytical method to get the true REE contents of authigenic carbonate minerals deposited in marine environment without the contamination from clays. Here we use 5% CH3COOH, 5% HCl, 2% and 5% HNO3 to dissolve powder samples split from one marls that usually occurred worldwide for 0.5, 1, 2, 3, 6 and 24 hours, respectively. The results of XRD analysis of insoluble residues and ICP-AES and ICP-MS analysis of acid dissolved solution show that calcite was completely dissolved and small quantities of clays were also dissolved. These dissolved clays resulted in an increase of REE contents and Ce/Ce* ratio, but not affect Eu/Eu*, LaN/YbN and Gd/Gd* ratios. The better dissolution method of authigenic calcites of marls is to use 5%CH3COOH to dissolve powder samples for less than 1 hour. The results of ICP-MS analysis of acid dissolved solution are suitable to trace the redox condition of sedimentary environment.
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