Gold mineralisation in a chemically reactive host: the Archean Gold Mineralised Vickers Dioritic Intrusive Complex, Nunavut Canada.

Abstract

The Vickers albitised dioritic intrusion (VDI, 2668 ± 6 Ma), located in the central Hearne sub- domain of Nunavut, hosts a significant gold discovery (2012; e.g., hole PB-12-09 164.41 m @ 5.39 ppm Au). The intrusion (equilibrated to lower-greenschist-facies) is located in the northern part of the 2.72 to 2.65 Ga Tavani greenstone belt, an area that has been interpreted to contain the Pistol Bay Corridor, a west-northwest-trending brittle/ductile deformation zone. The VDI is an elliptical (900 x 600 m) heterogeneous igneous intrusion emplaced into the siliclastic Evitaruktuk Formation, part of the sedimentary Kaminak Group, and contains highly anomalous Au mineralisation focused along its northeastern contact. Pyrite and arsenopyrite, spatially associated with gold mineralisation, occur proximal to quartz- carbonate± chlorite veins that increase relative to the severity of hydrothermal alteration. Several gradational alteration assemblages are present in the mineralised zone, including chlorite- (CF1+CF2) and silica-facies (SF1I + SF2I) that are restricted to the VDI, and sericite-facies (SF1FW+SF2FW) in the footwall. By integrating petrographic observations, LA-ICP-MS analysis (sulphide mapping, Pb isotopes), in situ SIMS δ18Oquartz and δ34Spyrite, arsenopyrite, and other geochemical data (whole rock, SEM, etc.), a working model is proposed. The preferred model suggests that a metamorphic fluid carrying Au as a bi-sulphide complex was focused along a rheologically favourable contact and subsequently reacted with the Fe-oxide - rich VDI and precipitated Au via sulphidation reactions.