Report of 68 new chemical analysis data of granitic rocks collected during a preliminary field trip from Chungju to Busan through non-metamorphic part of the Ogcheon folding belt, Ryongnam land and Gyongsang basin is presented. Special attention is paid to characterize chemical composition of Jurassic and Cretaceous granites of the country. The studies hitherto performed show:
(1) Chemical evolution examined from (Na₂O+K₂O), total Fe as Fe₂O₃ and MgO variation of Jurassic granite is identical to that of Cretaceous one.
(2) For rocks having the same AL₂O₃/(AL₂O₃+total Fe as Fe₂O₃+MgO) index, Jurassic granite is less siliceous than Cretaceous one.
(3) Remarkable differences between Cretaceous and Jurassic granites are found in their petrographic texture and the sequence of crystallization of the constituent minerals.
Features enumerated above suggest that the two groups of granite separated by their ages differ also each other in their modes of emplacement.