地球化学標準物質（堆積物シリーズ）に逐次溶解法を適用した際に生じる鉱物組成変動

Abstract

We have applied the sequential extraction procedure developed by the Community Bureau of Reference (BCR) to eight Japanese geochemical reference materials. By using this method, we attempt to extract exchangeable and carbonate phases in step 1, extract iron hydroxide and manganese oxide in step 2, and extract metal sulfide and organic material in step 3. We use X-ray diffractometry (XRD) to measure untreated samples and the residue of samples after each step of the extraction process to determine whether the target material is satisfactorily decomposed during the procedure. For JSd-1 and JSd-3, XRD patterns do not change significantly by using the BCR procedure. Actually, most of the elements in these materials are scarcely extracted by BCR scheme. The peaks of calcite in JSd-4, JMs-1 and JMs2 disappear in the XRD patterns after the first extraction procedure. The result suggests that the target phase of step 1 process is fully decomposed. JLk-1 and JMs-2 show high concentrations of the Fe and Mn extracted in step 2. However, it is difficult to clearly confirm the full decomposition of iron hydroxide and manganese oxide in step 2 because these materials do not show distinct peaks in the XRD patterns. Pyrite in JMs-1 disappears in step 3 of the extraction, which suggests that sulfide is satisfactorily decomposed in this process. X-ray reflection intensities of some peaks for quartz and plagioclase in JSO-1 increase significantly after step 3 of the extraction. It is assumed that organic material thickly covered the mineral surfaces and reduced the X-ray reflection from the minerals prior to the third procedure. Although this evidence is indirect, we conclude that organic material is successfully decomposed and removed from the mineral surface during the third extraction procedure. On the basis of these results, it is confirmed that the BCR protocol can properly extract target materials from the geochemical reference materials.