Layer Charge Characteristics of Smectite from the Pohang Area

포항지역에서 산출되는 스멕타이트의 층전하 특성

The layer charge characteristics of smectites from the Tertiary basins in the Pohang area have been studied in detail using the alkyl-ammonium method. On the basis of layer charges, the smectite in the Pobang area can be classed as normal and high-charge (hc) smectite. The layer charge of the normal smectite averages 0.3, and ranges from 0.25 to 0.38/half unit cell. The hc-smectite collapses on K-saturation to become illite-like material and shows $10{\AA}$-series reflections on X-ray diffraction. The layer charge of the he-smectite ranges from 0.5 to 1. The layer cbarges of the Pohang smectite are in general heterogeneous. The layer charges distribute between 0.21 and 0.45, and the most frequent layer charge is 0.30~0.32. The layer charge and the layer charge distribution do not appear to be related to stratification or basins of occurrence. Thus, the layer charge may not have developed as a result of burial. Rather, it may have developed due to heat and hydrothermal solutions associated with volcanic activities. Volcanic sills and dykes are ubiquitous in the region.