Abstract: The formation of mortar lavas in the Gutian Xiwei area, Fujian, was controlled by the NE trending basement fault zone. They have a distinct vertical zoning extending horizontally. From the center to the borders, four rock types may be distinguished, i.e. intermediate acid and acid granular mortar lavas and acid felsitic cryptocrystalline lavas. They are the product of viscous magma extrusive effusive facies during the decline of Late Jurassic volcanic activity and the collapse of volcanic edifices. Mortar lavas and their synchronous granite porphyry and rhyolitic crystal tuff are the product of comagmatic differentiation and evolution and in space they form a trinity.