鉱物組成に基づく黄鉄鉱含有泥岩のスレーキング特性

The X-ray diffraction analysis (XRD) and wet-dry slaking test were examined to clarify mudstone weathering and slaking characteristics using drilling cores of the Lower Cretaceous Fujikawa Formation distributed in the Katsuura-gawa area, Tokushima, Japan. The drilling cores of the Fijikawa Mudstone were subdivided into three weathering grades as in the Fresh-zone, Slightly- and Strongly-weathered zones by naked-eye observations. The peaks of quartz, feldspar, calcite, illite and chlorite were detected by XRD analysis of the mudstone. The amount of calcite decreased in relation with the progressing of weathering grade, whereas the amounts of other minerals are constant during the weathering. Pyrite micrograins were extracted by the chemichal-etching process of mudstones. * The laboratory experiments and field observations revealed that the wet-dry slaking occurs in the Fujikawa Mudstone without swelling-clay minerals such as smectite. These characteristics of slaking originate from the changes of rock texture and physical properties of the mudstone with the oxidation of pyrite micrograins and dissolution of calcite under the oxidizing condition.