Fig. 4

Simplified representation of the evolution of the Hyrkkölä mineralization, which has been used as a natural analogue for indicating the rate of corrosion of copper canister in groundwater over a very long period of time (thousands of years; modified after Marcos 1996, Fig. 8). a The original bedrock consisting of quartzo-felspathic gneisses, amphibolites and granite pegmatites, ages of formation 1800–1700 million years. b The period of hydrothermal mineralization, age 1750–1200 million years, in which the cross-cutting veins filled with native copper (Cu^o), hematite and uraninite were formed. c The period in which uplift/erosion brought this part up into the zone of circulating groundwater and the formation of open fractures, at the latest 10,000 years ago (possibly long before). The native copper/smectite association (open fracture indicated with an arrow) shown in Fig. 3 represents this period. The copper corrosion data in Marcos (1996) represents this period in the evolution