Download this Presentation - Geoscience BC

Alkalic Porphyry Deposits inBritish ColumbiaDeposit- to District-scale characteristicsFionnuala Devine, October 2011

Acknowledgements• Geoscience BC – Porphyry Integration Project– Peter Kowalczyk– Dave Heberlein– Fion Ma• Claire Chamberlain, Teck Resources• Teck Resources & Eastfield Resources• Thompson Creek Metals

Porphyry occurrences in BCMapped TerranesQuesnelStikineGalore CreekLorraineMount MilliganPorphyry OccurrencesAlkalic: producer/past-producer,developed prospect, prospect/showingCalc-alkalic: producer/past-producer,developed prospect, prospect/showingMount PolleyIron MaskCopper Mountain

Magma Series and Deposit Type16Na 2 O + K 2 O (wt%)1284Cu-AuCu-AuCu-AuCu-Au(-Mo)high-K calcalkalicCu-Molow- to medium-Kcalc-alkalic040 50 60 70SiO 2 (wt%)Modified from Lang et al. 1995Highland Valley, BCC. Chamberlain, photo

Calc-alkalic porphyry – alteration modelLithocapHigh-sulfidation mineralizationPyrite root haloDistal propyliticPropylitic halo(epidote subzone)Compositeporphyry stockPropylitic halo(actinolite subzone)Potassic core(mag + or -)Modified from C. Chamberlain, 2010

Alkalic porphyry – alteration modelAlkaliclithocapSodicSkarnpropylitic500 mSkarnDistal propylitic±sodic/calcicOuter propyliticInner propyliticOuter calc-potassicInner calcpotassicCalc-potassic orpotassic coreModified from C. Chamberlain, 2010Controls• Clusters of deposits, variations• Pipe shaped geometries• Multi-stage intrusions, multistagehydrothermal events• Reactivity of host rocksMineralization/alteration• Complex alteration:Na, Na-Ca-Fe, Ca, K, K-Ca-Fe• Mt-rich core, distal hematite• Replacement, veins, breccias• Low sulfide (+Au, enriched PGE)• Sulphide zonation• Oxidized fluids (anhydrite)

Examples from theDuckling Creek Syenite Complex

Duckling Creek Syenite ComplexAlkalic ClusteringTeck Cominco, 2006

LorraineTeck Resources (Teck Cominco)Eastfield ResourcesLorraine Copper Corp.

Multi-stage intrusive systemLorraineStage 1pyroxenite –leucosyenitedyke swarm,late porphyrymineralizationTilting40-60 degreesto the NE180 MaShearingLocal shear zoneformation,sinistraldisplacementStage 2NW trendingpyroxeniteleucosyenitedyke swarm178.5 Ma

Alkalic IntrusionsLorraineStage 1:pyroxenites andsyenites,mineralizedcutbyStage 2:pyroxenitesand syenites,locallymineralizedCpy+bnStage 3:leucosyenite &pegmatite dykes,local cpy inquartz veinsPhase 1Phase 2cutby

Multi-Stage Mineralized SystemsLorraine – Rock Evidence

Reactivity of Host RocksLorraineStage 1pyroxenite dykes

Sodic AlterationEarly Timing?Photos: C. ChamberlainEarly albite alteration cut by magnetite, in turn cutby cc-qtz-cpy vein with K-spar haloEarly albite alteration ofphenocrysts, LorraineEarly albite alteration cut byqtz-bt, Mt Milligan

Calcic and Calc-Potassic Alteration“Core” Hydrothermal FaciesDiops-mt-gn-anhydrite veincutting monzoniticmegacrystic K-spar porphyry,Galore Creek (photo: K. Byrne)Diops-mt-bn cutting albitealteredpyroxenite, LorraineMt-actin-cpy-cc (with laterhem-epi-chl-c-py,) Afton(photo: C. Chamberlain)18

Mineralization StylesSilica UndersaturatedBn-diops-mt-apatite veinscutting syenite, Lorraine(Photos: C Chamberlain)Bn-cpy-anhyd CM’tedbreccia, Mt Polley(Photo: C. Chamberlain)Gn-diops-mt-cpy CM’tedbx, Galore Creek (J.Micko)Heterolithic matrix supported brecciawith bt-mt-cpy, SW Zone (K. Byrne)19

Sulphide ZonationTeck Cominco, 2007

Sulphur Isotope Zonationδ 34 S:~ +1 o / ooδ 34 S:~ -5 o / ooδ 34 S:~ -15 o / ooδ 34 S:~ +3 o / ooδ 34 S:~ -5 o / ooTeck Cominco, 2007

Alkalic porphyries – exploration criteriaC. Chamberlain, 2010

Alkalic porphyries – exploration implicationsAlkaliclithocapSodicSkarnpropylitic500 mSkarnDistal propylitic±sodic/calcicOuter propyliticInner propyliticOuter calc-potassicInner calcpotassicCalc-potassic orpotassic coreDeposits occur as clusters• Camp-scale targets• Variations between deposits are thenormMulti-stage magmatichydrothermalepisodes• Multiple events at deposit-scale• Deposit-scale observations criticalPredictable zonation patterns• Sulphide zonation simple, useful• Wider-scale silicate zonation• Cognisant of paragenesis!• Assists in geometry and vectoringModified from C. Chamberlain, BC alkalic porphyry presentations

Importance of Scalewww.cumtn.com

Copper MountainTertiary volcanic rocksCretaceousmonzoniteLate Tr –Lost Horse Intr. - syeniteLate Tr –Voight StockdioritemonzoniteUpper Tr –Nicola Group Volcanic RocksTertiaryvolcanic rockssyenitepegmatiteLate Tr –Copper Mtn Stockgabbro &diorite2 kmGeology Map:BCGS Geoscience Map 2004-3: Nixon, Preto, MacDonald

Magnetite-bearing mineralizationPit 1&3 Historical production:97 MT @ 0.66%CuPit 2 Historical production:30 MT @ 0.38% Cu2 kmAlteration zones modified from:Stanley et al., 1995

MAGENTICSStrongly magnetic intrusive rocks2 kmData:NRCAN 1971, 805 m line spacing

MAGENTICSStrongly magnetic intrusive rocks2 kmData:NRCAN 1971, 805 m line spacing

Late TriassicNicola Groupvolcanic rocksRADIOMETRICSLate TriassicIntrusive complex:Potassic alteration &Cu-Au mineralizationLate Triassicsyenite intrusionGlaciofluvial & glaciolacustrine deposits2 kmK/ThData:NRCAN Hydraulic Survey 2005, 500 m line spacing

TITAN 24Pit 1&3 Historical product97 MT @ 0.66%CuPit 2 Historical production30 MT @ 0.38% Cu2 km

TITAN 24Plan View of the Chargeability Model2 km2D Section of 3D Chargeability Modelhttp://www.quantecgeoscience.com/Tech/CopperMountainMine.php

GEOCHEMISTRYEarly Jurassic–Porphyry intrusionsUpper Tr –Nicola Group Volcanic Rocks

Mount MilliganSoil geochemistry - Mitzi LakeAuCuElevated Bi, Mo, Pbindicate a blindporphyry system?Elevated As, Sb, Th butno Cu indicate that theepithermal level ispreserved?Pb Zn AsMaps: Assessment report 31930 – Terrane Metals 2010, Author: D. Heberlein

Alkalic porphyries – exploration implicationsAlkaliclithocapSodicSkarnpropylitic500 mSkarnDistal propylitic±sodic/calcicOuter propyliticInner propyliticOuter calc-potassicInner calcpotassicCalc-potassic orpotassic coreDeposits occur as clusters• Camp-scale targets• Variations between depositsMulti-stage magmatichydrothermalepisodes• Multiple events at deposit-scale• Complex district-scale geology• Multiple mineralization stylesPredictable zonation patterns• Sulphide zonation simple, useful• Wider-scale silicate zonation• Cognisant of paragenesis!Modified from C. Chamberlain, BC alkalic porphyry presentations

Alkalic porphyries – exploration implicationsConsider scale• In interpreting exploration datasets,and planning detailed, targetedsurveys• Smaller footprint deposits• Subtle geophysical (IP) targets, needgeological controlUse deposit-scale observationsto develop mineralization modelsfor the district• Deposit-scale observations critical tounderstanding relationshipsbetween geology, geophysical, andgeochemical responses

Alkalic Porphyry Deposits inBritish ColumbiaDeposit- to District-scale characteristicsFionnuala Devine, October 2011