Structurally controlled iron oxide mineralization in the Iron Range Mountain and Mount Thompson region, British Columbia

Abstract

Structurally controlled iron oxide alteration occurs within and along the Iron Range fault, a steeply west-dipping normal fault. Iron oxide alteration occurs as massive lenses, breccia infilling, and veins in a cataclastic quartz-albite breccia. Textures in thin section suggest multiple episodes of magnetite, hematite, quartz, and pyrite growth. Fluid-inclusion studies indicate two dominant, twophase fluid-inclusion assemblages within predominantly quartz and albite, i.e. brine + H2O vapour and brine + CO2 vapour. Chlorite thermometry from six microprobe analyses indicates temperatures of 275 to 325°C. The voluminous early sodic and relatively limited potassic alteration accompanied by ironoxide-rich and sulphide-poor alteration in the Iron Range deposit appears to be consistent with basinal brine fl uid-source models (with no magmatic component) for iron oxide-copper-gold-type mineralization.

Deep transverse basement structural control of mineral systems in the southeastern Canadian Cordillera1Geological Survey of Canada Contribution 20110294.

“…Massive sulphide mineralization in the Foreland Belt are mainly MVT deposits localized along Middle Cambrian or Devonian facies changes or vein deposits (e.g., Höy 1982;Richards and McMechan 2007;Richards 2009). Mesoproterozoic intrusion-and fault-related Ag-Pb-Zn and Cu-Ag veins (Höy 1993;Paiement et al 2007), Mesozoic shear and vein gold and associated placer gold (Höy 1993;Thompson 2009), stratabound Cu-Ag, an iron oxide, copper, gold (IOCG) deposit (Iron Range Mountain;Staples et al 2008), and a magnesite deposit also occur within the study area.…”