Alteration and fluid characterization of the Hamlin Lake IOCG occurrence, Northwestern Ontario, Canada

Abstract

The Hamlin Lake area is located approximately 120km southwest of Thunder Bay, Ontario, in the Shebandowan Greenstone Belt of the Wawa Subprovince in the Superior Province. The area has been explored for its copper and gold mineralization for more than 50 years, but has only recently been treated as an iron-oxide copper gold (IOCG) occurrence. The aim of this study was to characterize the alteration at the occurrence through space and time, and to relate this paragenesis to the formation of mineralization. Localized field mapping and re-logging of drill core established several relationships between styles of alteration. Rocks were examined in hand specimen and thin section, and minerals were examined with scanning electron microscope (SEM) to identify mineral assemblages and associations. Consistent variations in space could not be mapped, so textural relationships were used to relate the timing between six styles of alteration and the local brecciation that hosts the potential ore. These are: (1) sodic, (2) early potassic, (3) calcic(-iron), (4) late potassic, (5) carbonate, and (6) silicic.