Daniel Castano Madrigal, MSc
D. Castano Madrigal1, A. Arribas1
1Department of Earth, Environmental and Resource Sciences, The University of Texas at El Paso, El Paso, Texas, USA
The Iskut project in northwestern British Columbia, Canada, is hosted in Triassic–Jurassic volcano-sedimentary rocks intruded by Cretaceous intrusive bodies associated with hydrothermal activity. At the Snip North prospect, multiple vein systems crosscut the hornfelsed volcano-sedimentary host rocks and record at least three mineralization stages. The earliest stage comprises <1 cm magnetite–pyrite–chalcopyrite–carbonate veins, mainly in the deepest part of the deposit and at shallower levels to the east. A second stage is characterized by pyrite–carbonate–quartz–chalcopyrite veins, sometimes with potassic stronger alteration halos. A late, coarse-grained stage consists of thicker quartz – pyrite – chalcopyrite – sphalerite – galena – carbonate veins in a white-mica alteration zone, commonly displaying intense white-mica halos up to 20 cm thick. Along the contact between the volcano-sedimentary rocks and the monzonite intrusions (~850 m), an additional vein type is developed, consisting of fine-grained quartz with molybdenite.
U-XRF and thick-section studies indicate that copper is associated with quartz-carbonate veins and is less disseminated in the host rocks, predominantly chalcopyrite-bearing. SEM analysis reveals electrum-style gold and scarce uranium-rich minerals within the volcano-sedimentary units. High concentrations of massive magnetite, together with localized hematite zones, record variations in oxidation conditions during hydrothermal activity. Overall, the volcano-sedimentary units that host the veins and mineralization are hornfelsed and affected by secondary biotite alteration, locally overprinted by white-mica and late chlorite replacement.
The timing of the hornfels-forming event is still under investigation, and ongoing microthermometric analyses of fluid inclusions will provide further constraints on the evolution of the Snip North system.