Abstract
Regional and detailed mapping at Gordon Lake has closely outlined the structural timing of a km-scale refold and linked this event to the formation gold-bearing quartz–breccia zones. Early (F1) isoclinal folds, that were refolded (F2) during a secondary (D2) deformation event coeval with peak regional metamorphism, lead to the development of a pervasive (S2) regional cleavage and sub-vertical (L2) stretching lineation. Tightening and increased strain within the east limb of the Gordon Lake refold structure occurred during D3 along with the development of a localized (S3) crenulation cleavage and an episode of quartz–breccia mineralization. The nearby Spud Lake pluton intruded the region post-peak metamorphism. New in situ Rb–Sr geochronology on white mica from the pluton defined an overdispersed regression date of 2573 ± 17 Ma, which overlaps an existing 40Ar/39Ar date of 2592 ± 14 Ma and other U–Pb zircon ages for nearby granitic plutons of the Prosperous Suite. Rb–Sr geochronology of biotite from a sample of quartz–breccia mineralization yielded a single population regression at 2480 ± 53 Ma. This date is significantly younger than a previous 40Ar/39Ar date of 2564 + 14 Ma, perhaps indicating the incorporation of excess 40Ar available during the mineralization event. The Rb–Sr date from the quartz–breccia is consistent with field relationships that indicate the mineralization post-dates peak metamorphism.
Published Version
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