Effect of Weathering and Parent Materials on Clay Mineralization Part-II.

The clays from the arid zone, e.g., Churu and Ludhiana having been formed in an alkaline earths ionic environment contain illite and chlorite. Kaolinite is likely to have been derived from K-feldspars. Under insufficient leaching condition in the semi-arid zone and under suitable calcium-magnesium environment montmorillonite is the dominant clay mineral in Annegeri soil. The small amount of kaolinite present in this clay seems to come from K-feldspar. The clays of both Machkund and Padwa soils contain mainly kaolinite with traces of illite, caused by pronounced leaching of weatherable feldspar in the semiarid to humid climatic conditions. The humid condition of Pasighat under alkaline and alkaline earths ionic environment favours illite as well as vermiculite formation. Kaolinite is the result of intense weathering. The highly acidic soils of Cherrapunji is kaolinitic but under favourable potassium equilibrium condition contains illite as well.