THE CLAY MINERAL ASSOCIATION AND CHARACTERISTICS IN THE SHENNONGJIA MOUNTAIN AREA

In five types of soil with a vertical band spectrum on the north slope of the Shennongjia Mountain area, 2:1 type clay mineral is predominant, and there is a little kaolinite. The ratio of SiO_2/Al_2O_3 in clay fracions is about 3.0-3.4. There is a weak desllifieation in the soils. For yellow brown soil and mountain yellow brown soil, the main clay mineral is hydromica, and there is a certain amount of vermiculite, as well as a little 1. 4rim intergrade mineral and kaolinite. For mountain soil, 1. 4nm minerals (mostly being 1. 4nm intergrade mineral) are the major clay minerals, and there are certain amounts of hydromica and chlorite, and a little kaolintie or vermiculite. For soils examined, the higher the sampling place of the Shennongjia Mountains, the stronger the eluvial depotassium process of clay mineral in soil is. The contents of various activated iron, aluminum oxides and the ratio of Feo/Fed in the soils increase obviously, and the increasing extent of various alumnium oxides is larger than that of various iron oxides with the increasing altitude in the area.