Insights into the timing of mineralization and metamorphism in the North Caribou greenstone belt, western Superior Province

Abstract

Secondary ion mass spectrometry (SIMS) U-Pb depth profiles of unpolished detrital zircon were used in an attempt to resolve the timing of metamorphism and mineralization in the North Caribou greenstone belt of northern Ontario, which hosts the Musselwhite gold mine. Eleven samples located 10-75 km from the mine site were collected from metasedimentary rocks adjacent to structures that may have promoted hydrothermal fluid flow. Zircon rim material is commonly characterized by decreased Th/U concentrations (up to an order of magnitude), as well as generally possessing concordant ages. Rim ages obtained via this technique range from 2788-2703 Ma, up to 250 m.y. younger than zircon cores. The timing of zircon rim recrystallization overlaps with the timing of potassic alteration in the surrounding plutons, as well as regional gold mineralization in the North Caribou Superterrane. These zircon rims may represent the timing and potential distribution of Au-bearing fluids within and regional to the Musselwhite deposit.