Rock alteration to strata on the northern Yorke Peninsula, which appears to have been caused by an event which spanned the Palaeo-Mesoproterozoic boundary (~1600 Ma), was responsible for emplacing much of the mineralisation found in the Moonta-Wallaroo district. This alteration involved several processes which in a broad sense were imposed synchronously; deformation, the intrusion of granitoids, heating, metamorphism and the gross movement of chemical elements to form metasomatic lithologies and epigenetic sulphide-bearing bodies. Manifestations of the event were superimposed upon the crust from the northern Gawler Craton to the Curnamona Province and also the Mount Isa Block. The purpose of the present excursion is view aspects of the alteration system and to promote discussion about the current state of stratigraphic and tectonic understanding.