Volcanic rocks erupted at Payún Matrú resemble ocean island basalt volcanism, implying a deep origin of the magma although a shallow origin cannot be ruled out. Magnetotelluric observations indicate the presence of a plume-like structure that rises from depth close to the edge of the Nazca Plate slab to underneath Payún Matrú; it may indicate that magma erupted in the volcanic field originates at such depths which would explain the ocean island basalt-like composition.