A suite of north-south-trending alkaline dykes occurs just south of the border with Bolivia near Santa Victoria and it may be related to an alkaline centre in Bolivia. It includes trachytes, porphyritic foyaites with analcime, basanite and limburgite. There are also two syenite bodies several km in diameter but the character of this syenite is not clear. The tinguaite dyke at Iruya (No. 2) is likely to be part of the same suite.