A wide zone of north-northwest-trending alkaline dykes traverses the Zebra Mountains northwest of Swartbooisdrif (No. 116-00-003). One dyke has a length of 35 km. They consist of syenite with calcite, biotite and what Menge (1986) refers to as "biotite-albite fenite" or carbonatite. These dykes are probably related to the Lupongola complex a short distance to the north in Angola (Angola No. 005-00-035).