A trace metal, stable isotope (H, O, S), and geochronological (U-Pb titanite) characterization of hybridized gold orebodies in the Missanabie-Renabie district, Wawa subprovince (Canada)

Mineralized shear zones in the Archean Missanabie-Renabie gold district (similar to 1.1 Moz Au; Wawa, Ontario, Canada) locally define composite orebodies that record three hydrothermal events: (1) a pre-orogenic Au(1)event (pre-D(1)and pre-prograde-metamorphic); (2) a syn-orogenic, post-peak-metamorphic Retrograde event (syn-D-3); and (3) a late syn-to post-orogenic Au(2)event (late syn- to post-D-4). Genetic considerations indicate the orebodies are hybrids with early intrusion-related (Au-1) and later orogenic (Retrograde + Au-2) events. Pearson product-moment correlation coefficients (log(10)) of whole-rock and LA-ICP-MS pyrite trace metal datasets distinguish Au(1)from Au(2)mineralization by Au-Ag, Au-Bi, and Au-Te correlations > 0.7 (p < 0.05) in the former, irrespective of sample medium and analytical method. An Au-Mo correlation in whole rock data (0.58-0.76;p < 0.05) further distinguishes Au(1)from Au(2)and supports an independently inferred intrusion-related origin for Au-1. Sulfur isotope data is similar for both Au(1)and Au(2)pyrite with average delta S-34 values of - 5.5 parts per thousand +/- 0.2 parts per thousand (1 sigma) and - 3.5 parts per thousand +/- 0.3 parts per thousand (1 sigma) and average Delta S-33 values of 0.4 parts per thousand +/- 0.1 parts per thousand (1 sigma) and - 0.3 parts per thousand +/- 0.2 parts per thousand (1 sigma), respectively. SIMS delta(18)O(quartz)values for the Au-1, Retrograde, and Au(2)events largely overlap and, like delta(18)O(carbonate)values of previous studies, tend to be lower than values typical of Archean gold deposits. The results of this study suggest that correlation coefficients in trace metal datasets are useful in discriminating and characterizing different gold events. Caution is emphasized with the use of S- and O-isotope datasets for these purposes. The presence of low delta O-18 values in vein quartz and carbonate is best explained by an(18)O-depleted fluid formed during the Retrograde hydrothermal event. The latter is inferred at 2580 +/- 21 Ma based on U-Pb geochronlogy of hydrothermal titanite, and relates to deformation and metamorphism in the nearby, amphibolite- to granulite-grade Kapuskasing metamorphic belt. Geochronological and geochemical evidence suggest that the(18)O-depleted fluid may have formed via the devolatilization of biotite-bearing granitoids during deep-crustal metamorphism.

Automated summary

By tracking mineralized shear zones in orebodies and analyzing trace metal, sulfur isotope, and oxygen isotope data in pyrite, this study reveals the nature and genesis of different gold events, providing important clues for understanding Archean gold deposits.