Lithospheric delamination may be the cause of volcanism in the area. The amount of magma generated is small, most of it is primitive mafic magma, and its ascent was controlled by local tectonic structures. In the case of Pasto Ventura, the composition of the magmas is influenced by fluids emanating from the downgoing Nazca Plate slab as well as by a relic mantle that already influenced magma composition during the Famatinian Orogeny c. 485 million years ago.