Role of massive anhydrite bodies in the Cordilleran-type polymetallic mineralization of Morococha district, Peru: 3D geological modeling and Sr-S-O isotope constraints

In the Morococha district, anhydrite bodies hosted by carbonate rocks at the base of the Late Triassic Chambará Formation, Pucará Group, close to its unconformable contact with clastic and volcanic rocks of the underlying Triassic Mitu Group, show evidence of deformation and ascent during the Andean Orogeny. These bodies are often spatially associated with Cordilleran-type polymetallic replacement orebodies. We propose that impermeable anhydrite bodies acted as stratigraphic seals promoting carbonate replacement by the Miocene mineralizing fluids. Field evidence and the Sr-SO isotope composition of the anhydrite bodies suggest that they are Norian marine evaporites that partly have interacted with Miocene hydrothermal fluids.