| 概要 |
Chemical and mineral compositions of the Toyoma slate and the Nachiguro shale, both of good quality as expanding shale, have been investigated by means of electron probe microanalysis. Analalytical pr...ocedures for the whole rocks and constituent minerals were scanning analysis and spot analysis, respectively. The chemical compositions of the whole rocks are shown in Table 1, together with the average of 277 shales. Compared with the average, they are rich in Si02 and poor in CaO. Constituent minerals are identified under the microscope, by the electron probe microanalyzer, and X-ray powder method. They are quartz, plagioclases, illites, and chlorites, and small amounts of sphene, apatite, pyrrhotite and carbonaceous mineral are included. In the Toyoma slate, the plagioclase belongs to albite (Ab_95An_5), whilethe Nachiguro shale includes various kinds of plagioclases, such as albite (Ab_95An_5), andesine (Ab_66An_34), and labradrite (Ab_49An_51). Illites of the Toyoma slate are similar to muscovite according to chemical composition, while those of the Nachiguro shale are in agreement with illites in sediments. These characteristics of plagioclases and illites indicate that he Toyoma slate has been completely recrystallized, while the Nachiguro has not. This fact is conformable to their geological occurrences, fabrics, and physical properties. Chlorites, both of the Toyoma and the Nachiguro, are Fe-chlorite, the latter being slightly richer in MgO. Chemical compositions of quartz, plagioclases, illites, chloriles in the Toyoma slate and the Nachiguro shale were compared in Tables 2, 3, 4 and 5. On the basis of the chemical compositions of the whole rocks and constituent minerals, the mineral compositions of the Toyoma and the Nachiguro were calculated as shown in Table 7, and the results are compared with the average composition of 277 shales given by Wedepohl (1971) in Table 8. Quartz and silica minerals are remarkably richer in the Toyoma and slightly richer in the Nachiguro than the average, and both are deficient in carbonates, as inferred from the chemical compositions of the whole rocks. It seems that the recrystallization of illite resulted in the relative increase of quartz content and decrease of illite in the Toyoma slate.続きを見る
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Mendeley出力
