2011 Volume 64 Issue 5 Pages 309-318
Bentonite is widely used for various industrial fields. Many borings are carried out for investigation of subsurface bentonite bodies now. It is required to develop an effective method for bentonite exploration instead of the boring, which requires high cost and gives only local geology information. The resistivity of bentonite is generally very low because it contains a lot of smectite which has high conductivity. It means that the geoelectrical method is suitable for bentonite exploration. In order to confirm it, we conducted a DC resistivity survey experiment at the Dobuyama bentonite deposit, Miyagi prefecture, Northeast Japan. The analyzed 2-D resistivity sections indicate that low-resistivity zones correspond to the bentonite bodies confirmed by surface geology and many exploration borings in this area. We also considered the relation between resistivity and methylene blue adsorption that is used as an index of the quality of a bentonite. A good correlation was found between the resistivity and the methylene blue adsorption of bentonite-bearing samples. Using the correlation, we estimated the sections of methylene blue adsorption from the resistivity sections. The zones which show the high value of methylene blue adsorption correspond to the bentonite bodies found by the borings. This fact indicates that the geoelectrical method is effective for bentonite exploration and evaluation.
