Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The Silbak Premier silver-gold deposit in the north Coast Range of British Columbia consists of sulphide-bearing stockwork veins and breccia zones marginal to, and crosscutting, conjugate sets of irregular to tabular plugs and dykes of Early Jurassic age pottassium-feldspar porphyritic dacite.;Distinct precious metal and later base-metal rich mineral assemblages are concentrated in subparallel stockwork veins and breccia zones. In general, base-metal sulphide minerals are more prominent at depth in the deposit and precious metal minerals are more prevalent closer to surface. Analyses of fluid inclusions indicate vein-hosted base and precious metals were deposited at pressure-corrected temperatures of 250 to 260{dollar}\sp\circ{dollar}C at a depth of 500 metres.;Each vein has abundant potassium feldspar and sericite in its immedial wall rock. This grades outward into an assemblage of chlorite, epidote, calcite, and apatite which occupy the sites of original hornblende and plagioclase. Sericite and calcite are more abundant in hanging walls to veins. Chlorite is patchy in distribution, but commonly more prominant in footwalls.;Pre, syn- and post-mineralization fractures are interpreted as rotated and dilated R and P shears oblique to the principle direction of movement along regional transpressional strike slip faults. This dilation allowed sequential access of porphyritic dacite, followed by ore-forming fluids into diffuse areas of in situ breccia at margins of the dacite and subsequent crosscutting conjugate fault sets.;Both base and precious metals are most soluble in hot, reduced fluids. Sulphide deposition occurred by cooling and oxidization upon mixing with meteoric waters in the upper levels of fractures. Restricted lateral distribution and upward change from barren to base metal-rich and precious metal-rich assemblages coincide with declining thermal and salinity gradients. The Silbak Premier deposit is epithermal in character and is part of a distinct metallogenic province in which mineral deposits are structurally-controlled, locally stratabound and have a large base metal component with precious metals.



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