Characterization of alteration and mineralization at the Archean Grey Fox and Hislop magmatic-hydrothermal gold deposits, Matheson, Ontario

Abstract

The Abitibi Greenstone belt (AGB) is host to some of the world’s largest gold deposits and their study has led to various gold deposit models and classifications. The latter includes a syenite- associated deposit type, which was first recognized in the early 2000s. This type of mineralization is present at the Grey Fox and Hislop deposits, which are located 80 km east of Timmins, Ontario. A study of their geologic setting, alteration, mineralogy, mineral chemistry, veining styles, and metal associations, suggest that these deposits, as well as others in the area, developed in different zones of a larger magmatic-hydrothermal system associated with alkalic intrusions of probable Timiskaming age (i.e., <2680 Ma). As such, they formed relatively early in the deformation history of the belt and predate the formation of the more common orogenic or greenstone-hosted quartz- carbonate vein deposits, such as the nearby Black Fox, which make up much of the gold budget in the AGB. A strong host-rock control is present at both deposits and their complex alteration histories provide insights on the formation of multiple mineralization styles within a single system. These different mineralization styles are described here to provide guidelines for mineral exploration for this deposit type in the Abitibi greenstone belt, as well as in other greenstone belts globally.