The Cala iron deposit has been traditionally regarded as a classic iron skarn developed on Cambrian
limestone adjacent to a Variscan monzogranitic stock. Ongoing studies show that the geologic setting is
more complex and the mineralization is replacive on marble and calcsilicate and pelitic hornfels and
controlled by syntectonic hydrothermal activity with a pull-apart structure. The skarn only forms a part of
the hydrothermal alteration. Most of the magnetite is related to an biotite-quartz-ankerite-chlorite
assemblage, while the pyrite-chalcopyrite ore seems to be slightly younger, replacing magnetite along
extensional structures, sharing many features with the IOCG style of mineralization