The contact between the unit Porphyry Andesite and the Cajamarca Group is observed in the Tunel de la Linea section. The integration of petrographic, geochemical and textural (crystal size distribution, CSD) analysis allows description of physical and chemical processes that took place in the contact zone in order to propose a model for the intrusion. Material assimilation produced quartz enrichment towards pluton's boundaries associated to a simple process of melt injection. The difference between host rock and hot melt rheologies causedshear stress that produced crystal breaking, folding and foliation rotation.