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.

Gold Mineralization at the Anomaly A Deposit, Clarence Stream Area, Southwestern New Brunswick: Distal Deposits of a Syn-Deformational Intrusion-Related Gold System?

“…1; Thorne and Lentz, 2001;Thorne et al, 2002), and the Anomaly A zone, 3 km to the northwest of the Main zone, hosted by Ordovician turbidites of the St. Croix belt ( Fig. 1; Watters et al, 2003). The setting and characteristics of gold mineralization at the Main zone are consistent with an intrusion-related genetic model (Thorne and Lentz, 2001;Thorne et al, 2002Thorne et al, , 2008.…”

“…This model is reinforced by the signature of granite-related elements such as Bi and Te in mineralized veins (Thorne et al, 2002). The rocks hosting Anomaly A, although polydeformed Watters et al, 2003), are not as intensely or pervasively sheared and mylonitized as those in the Main zone deposit. Therefore, this area has better potential for evaluating the relationship and timing of gold-mineralizing events to regional structure.…”

Temporal relationships between plutonism, metamorphism, and gold mineralization in southwestern New Brunswick: U-Pb and 40Ar/39Ar geochronological constraints

“…A number of gold occurrences have been reported in the study area (McLeod, 1990;McLeod and Fyffe, 2002;Thorne and McLeod, 2003a;Watters et al, 2003). The most signifi cant occurrences have been interpreted to be genetically related to Early Devonian granites near Clarence Stream, Jimmy Hill, and Tower Hill (Fig.…”

“…Recent research (e.g. McLeod and McCutcheon, 2000;Chi et al, 2001;Thorne and Lentz, 2001;Thorne et al, 2002a;Chi, 2002Thorne and McLeod, 2003a;Watters et al, 2003) and exploration work highlight the poten tial for intrusion-related gold systems in southwestern New Brunswick. Many of the southwestern New Brunswick gold occurrences are comparable to the intrusion-related gold systems found in the Tintina Belt of Alaska and the Yukon Territory (see Lang and Baker, 2001 for a review), and a simi lar exploration model may apply.…”