One of the few alkaline provinces in the Andes. The interesting minerals are from a large dike, 2km long, 1 - 5m wide, of pegmatitic ankerite-sodalite-barite carbonatite, which cuts a nepheline syenite intrusion and the surrounding hornfels and slate. Source of all the sodalite beads found in Inca and pre-Inca ruins ranging from Quito (Ecuador) to Tucuman (Argentina).
