Kaolinite associated with Mesozoic sediments of Kachchh and alkaline igneous rocks are not well studied in view of its genesis. The petrography, EPMA and DTA studies support that the studied kaolinite samples formed by mature transformation from rhyolitic tuff by hydrothermal alteration in epithermal condition. Such postulation indicates that there was intermittent acid volcanic episode along with alkaline basic igneous magmatism in the Cretaceous of Kachchh basin, western part of India.