Feasibility Study and Technical Report - Pretivm

Altered Stuhini Group rocks and Mitchell intrusions are the main host rocks to porphyrystylemineralization at the Kerr (copper-gold), Sulphurets (gold-copper), and Mitchell(gold-copper-molybdenum) deposits. Mineralization at the KSM deposits occurs within agold-enriched copper porphyry system controlled by a series of dikes, sills and plugs, andis associated with quartz veinlet stockworks and sheeted quartz veinlet arrays mainly inthe altered host rocks adjacent to the intrusions. Pyrite and chalcopyrite are thedominant sulphide minerals, with minor molybdenite, and trace amounts of tennantite,bornite, sphalerite, and galena. All mineralization is hypogene, except for small remnantsof preserved weak supergene at higher elevations.7.2.3 STRUCTURAL SETTING AND METAMORPHISMRocks in the Sulphurets Mining Camp have been affected by folding, faulting, penetrativecleavage formation, late stage quartz vein formation, and low-grade lower greenschistfacies (or lower) regional metamorphism. Rocks of the Stuhini Group were subjected tointense ductile deformation during the Late Triassic to Early Jurassic prior to thedeposition of the Hazelton Group rocks. Ductile deformation during the Late Jurassic toLate Cretaceous development of the SFB resulted in the formation of the major structuralculmination of the McTagg anticlinorium and associated fold and thrust structures thataffected the Stuhini Group through Bowser Lake Group rocks in the Sulphurets MiningCamp.Penetrative cleavage (foliation) development was associated with the Late Jurassic toLate Cretaceous event and affected most of the altered and unaltered rocks in the area,where host rock mineral assemblage (i.e. the presence and concentration ofphyllosilicates in the rock) permitted its development. Age dating (argon-argon) ofsericite within pressure shadows about pyrite provide a minimum age for thisdeformation at 110 ±2 Ma. Foliation orientations, while variable within the SulphuretsMining Camp, are dominantly east-west trending on the Property (Figure 7.4). This is incontrast to the more regional scale north-northwest to north-east orientation of structuralfabrics (particularly foliation) that is more in accordance with typical Cordilleran structuraltrends. The east-west trending foliation orientations coincide with a distinct westwardoriented"kink" in the McTagg anticlinorium (Figure 7.3), which is possibly a reflection ofthe warping of this structure about a protrusion of more strain-resistant rocks inboard ofthe culmination, that resulted in apparent north-south compression in this part of thearea. The existence of such a strain resistor might also have resulted in the developmentof the southeast-vergent fold-induced thrusts during strain accommodation to the east ofthe anticlinorium axis. The Snowfield Deposit is considered to be part of the upperMitchell Deposit that was thrust southeastward over lower Hazelton Group rocks duringthe Late Jurassic to Late Cretaceous deformation.Pretium Resources Inc. 7-7 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC