STRUCTURAL SETTING OF PB-ZN SULPHIDE VEINS HOSTED BY SILURIAN SEDIMENTARY ROCKS OF THE NICHOLAS-DENYS PROPERTY, BATHURST MINING CAMP: GENETIC IMPLICATIONS

Pb-Zn veins containing gold and silver occur in the Nicholas-Denys property of Puma Exploration Inc., located between the Rocky-Brook Millstream Fault (RBMF) and the Main Fault, two major EW-striking strike-slip faults of the Bathurst mining camp (BMC) in New Brunswick. The Upper Devonian Nicholas-Denys intrusion (ca. 380 Ma) lies just a few hundred meters to the north of the RBMF. The regional geological structures belong to the Nigadoo River Synclinorium, which is part of the Chaleur Bay Synclinorium. The sedimentary rock sequences hosting the Pb-Zn veins were deformed during the Middle Devonian Acadian orogeny. Along with other world-class sulphide deposits (Half Mile Lake, Brunswick 12) of the Miramichi Anticlinorium, lying south of the Main Fault and hosted by Cambrian-Ordovician volcanic and volcaniclastic rocks, the studied Pb-Zn-Au-Ag veins has brought the interest of economic geologists for several decades in the Nigadoo River area. This contribution presents a summary of sulphide deposits of the area; a summary of the structural characteristics of the Puma Exploration mining properties and detailed geological maps of historical exploration trenches as well as recently discovered deposits

The polymetallic veins crosscut limestone and siliciclastic rocks of the La Vieille and Simpsons Field formations, and are presumably genetically related to the Nicholas-Denys granodiorite, which is known to contain molybdenum, copper, gold as well as silver. Alternative hypothesis for mineralisation processes, such as regional deformation-related hydrothermalism, are however still to be evaluated. Different types of mineralised fractures have been recognised and seem to be related to three relatively large dextral shear zones trending NW-SE, along which the mineralising fluids are thought to have circulated and migrated along subsidiary shears/fractures and favourable porous sedimentary horizons. Limestone is commonly silicified and excludes lead-zinc deposits but is crosscut by mineralised strike-slip faults. The mineralisation appears to be confined to hornfels (metagreywacke, metasiltstone...) where they occur most frequently next to fractures. In mineralised zones, galena is the predominant sulphide over sphalerite and arsenopyrite.