Preliminary report on new gold deposits in the Clarence Stream area of southern New Brunswick: Anomaly "A" - distal deposits of an intrusion-related-gold system?

Abstract

Gold-bearing mineralized zones in Ordovician turbidites of the Kendall Mountain Formation (St. Croix Terrane) in southwestern New Brunswick occur within shallowly dipping brittle high-strain zones. The gold zones, commonly several metres wide, are defined by stockwork, massive, and multiply brecciated quartz-sulphide veins containing arsenopyrite, pyrrhotite, pyrite and stibnite, and are enveloped by locally auriferous, weakly to intensely altered wall-rock. Vein paragenesis includes: 1) early (barren?) quartz-chlorite veins that are largely the product of migration of quartz from domains of cleavage-parallel pressure solution into extensional structures; 2) cross-cutting, multiphase, vuggy quartz-sulphide veins that contain most of the gold and are interpreted to be controlled by late-D2 thrust faults; 3) late cross-cutting, non-gold-bearing veins containing various combinations of laumontite, chlorite, muscovite, quartz, fluorite and base-metal sulphides. These late veins constrain the upper time limit of gold mineralization to Late Devonian based on their widespread association with nearby plutons of that age. Alteration associated with gold is lithology-specific and notably carbonate-poor and appears to reflect overprinting of several events. Major elements removed during alteration include Si, Na, Mn, Mg; minor and trace elements include Co, Li, Sc and possibly Sr, Ni and Zn. Minor and trace elements added include Au, Ag, As, Sb, S, and possibly F, Cu, Pb and Zr. The gold-mineralized zones appear to be the product of a protracted structural history that culminated with late-D2 thrust-faulting, and which facilitated gold mineralization. The gold deposits of Anomaly A are tentatively interpreted to be affiliated with intrusion-related gold deposits in the Clarence Stream Main Zone area.