Feasibility Study and Technical Report - Pretivm

quartz-sericite-pyrite altered rocks. Most of the defined mineral resources on theProperty are located within the intensely altered zone.7.3.1 LITHOLOGY AND STRATIGRAPHYTRIASSIC STUHINI GROUPRocks of the Upper Triassic Stuhini Group, which are typically fine-grained and wellbedded siltstone and mudstones with minor micritic limestone, conglomerate, andsedimentary breccia, are limited to the western parts of the Property, west of theBrucejack Fault. These rocks are intruded by a number of mafic to felsic predominantlyalkalic intrusions, a number of which have been dated as Early Jurassic in age. TheUpper Triassic clastic rocks have been folded across steep northerly-trending folds andrelated faults and were deformed and eroded prior to deposition of the lowermost rocksof the Hazelton Group.LOWER JURASSIC LOWER HAZELTON GROUPThe majority of the lithological units mapped on the Property appear to correlatereasonably well with those of the Unuk River and Betty Creek Formations of the EarlyJurassic lower Hazelton Group, as described by Britton and Alldrick (1988). However,Pretivm has elected not to assign formation-level regional stratigraphic names to theserocks until the current detailed field mapping is complete, due to the existence ofcomplicated lateral facies variations and the diachronous nature of many of the units.Unconformably overlying the Triassic rocks are rocks of the Lower Jurassic HazeltonGroup, which comprise five principal intercalated rock types:1. heterolithic volcanic conglomerate, most common at the base and typicallycoarse-grained (Jack formation)2. massive and locally well-layered medium to dark green volcanic siltstonecontaining common carbonate concretions, and subordinate litharenite andlocally-derived pebble conglomerate3. hornblende and/or feldspar-phyric volcanic rocks, principally flows and relatedcoarse fragmental rocks4. weakly stratified heterolithic green to dark green volcanic pebble to boulderconglomerate, sandstone and local mudstone, containing zones of intenselysilicified conglomerate5. pyroclastic rocks, including medium- and coarse lapilli tuff and tuff-breccia, withminor intercalated intensely silicified zones.The flows include several subtypes that can be distinguished by the grain size andcompositions of their phenocryst assemblages (generally fine- to medium-grainedhornblende and plagioclase feldspar, ±medium- and locally coarse-grained potassiumfeldspar) the flows are typically rich in groundmass potassium feldspar, and areessentially latites to trachydacites or trachyandesites.Pretium Resources Inc. 7-12 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC