THE CLAY MINERAL ASSOCIATION AND 14 A MINERAL OF THE ZONAL SOILS IN CENTRAL AND SOUTHERN CHINA
Huang Qiaoyun, Xu Finglin, Li Xueyuan( Huazhong Agricultural University, Wuhan)
The clay mineral association and 14A mineral of 9 soil profiles, derived from granite type parent material,in central and southern China,were studied. Results indicate that : 1 ) the content of kaolinite in yellow brown earth, red earth and latosol increased and the content of 2: 1 type clay mineral decreased in proper order, 2 ) yellow brown earth, the content of 14A mineral is high and it is vermiculite in profile No. Ⅰ, whereas part of it in profile No. 2 is intergrade 14A mineral and the another part is vermiculite. The content of 14A mineral in red earth is lower than that of yellow brown earth,but it is almost 14A intergrade mineral, 3) there is nearly no 14A mineral in latosol and, 4)for the amount of gibbsite, there is almost none in yellow brown earth, very little in red rearth or latosol.In correspondence with the soil clay association, the order of SiO2/Al_2O_3 ratio and the content of CaO, MgO and Na_2O in soil clay fraction is as follow : yellow brown earth,red earth and latosol, whereas the content of K_2O in clay fraction varies only a little with different soils, and the order for free degree of iron oxides in soil clay fraction is oppsitive.In terms of these results, the various weathering reactions of clay mineral and the formation, heat stability and identification of 14A intergrade mineral in examined soils were discussed.