The Arkansas alkalic province consists of Cretaceous intrusions that range from lamproite to syenite in composition and are parallel to the trend of the Tertiary onlap through central Arkansas. Ages obtained by K-Ar and fission track methods become younger toward the northeast, and rocks generally become more leucocratic. However, mineral compositions show little evolution throughout the belt. Whole-rock major and trace element data indicate that fractionation played a minor role in the transition from mafic to syenitic intrusions. Separate mantle sources and potassic metasomatism are important factors in the development of the Arkansas alkalic province.