Feasibility Study and Technical Report - Pretivm

Previously, some of the rocks straddling the Brucejack Fault were mapped as intrusive(e.g. Davies et al. 1994). Based on drilling and detailed mapping across the Propertyover the last three years, Pretivm now interprets the majority of the rocks on the Propertyas being extrusive. Most of the bodies of massive fine-grained rocks contain localfragmental layers, which are interpreted to represent interflow block tuff or flow-breccia.In addition, there is little or no evidence in the vicinity of the larger masses for associateddykes, and little evidence for contact aureoles. In a number of outcrops, there is clearevidence for the incorporation of large, angular fragments of these bodies, which aretexturally distinctive (they typically contain abundant fine- to medium-grained hornblendeand/or feldspar phenocrysts within an aphanitic groundmass) within marginal and/oroverlying fragmental units. Furthermore, the relatively massive rocks are commonlyinterlayered with clastic sedimentary rocks near their basal contacts, and locally theycontain fragments of lithologies known to be Upper Triassic in age. The various EarlyJurassic hornblende feldspar-phyric rocks display variable ages over a range of 15 Ma, asdetermined from preliminary uranium-lead dating, which is more consistent with anextrusive interpretation.The polylithic conglomerate and overlying pyroclastic fragmental units appear to havebeen favourable sites for channelling hydrothermal fluids due to the presence ofnumerous stratiform intensely silicified zones within these relatively porous andpermeable rocks. Intense silica flooding with an associated cross-cutting network ofcrack-seal and hydraulic fractures filled with cryptocrystalline quartz indicates that thesezones may have acted as local pressure caps during fluid infiltration that induced localoverpressure conditions and subsequent hydraulic fracturing. The presence of multiplezones of intense silicification that are effectively stratiform and that are present atdifferent stratigraphic levels within the conglomerate and younger fragmental unitssuggests a continuum of fluid infiltration, silica ponding, over-pressurization, andhydraulic fracturing. A Late Triassic uranium-lead age obtained by Pretivm on one ofthese silicified zones hosted within these Early Jurassic volcano-sediments thereforereflects the detrital age of one of the pebble or cobble clasts (most likely rhyolite). Theintensely silicified zones have been intersected in VOK (particularly on the southern limbof the VOK syncline), as well as in West Zone, Gossan Hill, and Golden Marmot. Theseunits were previously variably interpreted as submarine rhyolite flows (which isirreconcilable with the geochronology), dykes, sills, or chert horizons (McPhearson et al.1994).Pretium Resources Inc. 7-13 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC