Geology of theKettleRiverArea,Almond Mountain Project, Southern British Columbia (NTS 082E/07) T.Höy,Consultant,Sooke,BC,[email protected] Höy,T.(2016):GeologyoftheKettleRiverarea,AlmondMountainproject,southernBritishColumbia(NTS082E/07);inGeoscienceBC SummaryofActivities2015,GeoscienceBC,Report2016-1,p.23–34. Introduction ure2.TheareaappearsontheKettleRivermapsheet(east half),mappedatascaleof1:253440(1inchto4miles)by TheAlmondMountainproject,fundedbyGeoscienceBC, Little (1957), and is included in the Penticton map area includes geological mapping and compilation of a large (NTS082E),mappedandcompiledatascaleof1:250000 part of the 1:50 000 scale Almond Mountain map area byTempelman-Kluit(1989).Thegeologyofareasimmedi- (NTS 082/07), located in the Monashee Mountains of atelytotheeastmappedatascaleof1:50000hasbeenpub- southern British Columbia(BC). Theprojectisan exten- lishedbyHöyandJackaman(2005,2010and2013),based siontothewestofmapping,compilationandmineral-po- on new mapping and on compilation of previous studies, tential evaluation of the east half of the 1:250 000 scale mostnotablythoseofDrysdale(1915),Preto(1970),Acton Pentictonmaparea(NTS082E),whichincludedtheGrand et al. (2002) and Laberge and Pattison (2007), and in the Forks(NTS082E/01),DeerPark(NTS082E/08)andBur- northernpartofthearea,extendingintotheBeaverdellcamp, rell Creek (NTS 082E/09) map areas (Figure 1; Höy and byReinecke(1915). Jackaman,2005,2010,2013).Thisproject,andthecontin- uationtothenorthintheChristianValleymaparea(NTS GeologicalmappingintheAlmondMountainmapareain 082E/10)in2016,focusesmainlyonthestructural,strati- 2014and2015wasfocusedalongthewesternsideofthe graphicandmagmaticcontrolsofbase-andprecious-metal areashownon1:20000scaleTRIMmapareas082E/036 mineralizationinareasdominatedbyTertiary1extensional and 082E/046. This work is based on approximately tectonics. 40daysoffieldworkaswellascompilationofmappingby TheAlmondMountainprojectinvolvedmainlygeological Reinecke(1915),GreigandFlasha(2005),andMasseyand mapping at a scale of 1:20 000 in the western part of the Duffy(2008a,b).Furtherworkwillincludecompilationin studyarea(Figure2),whichisdominatedbyTertiaryfault- digital format of all regional geological, geophysical and ing that produced a complex north-trending graben filled geochemicaldatacollectedundertheNationalGeochemi- withEocenevolcanicandsedimentaryrocks.Theseuncon- cal Reconnaissance and the BC Regional Geochemical formablyoverliePaleozoicbasementrocks,andMesozoic Surveyprograms.Thiswillbecombinedwithmineraloc- andEoceneintrusiverocks.Thegrabenhostsavarietyof currence and geology databases to produce 1:20 000 and mineral occurrences, most notably base- and precious- 1:50 000 scale maps, suitable for directing and focusing metalveinsthathavesimilaritiestodepositsintheBeaver- mineralexploration. dellminingcamptothewestandtheGreenwoodcampto thesoutheast. ExplorationintheAlmondMountainmapareawasinitially based on thesuccessfuldiscoveryand exploitation of the Geological and Exploration History base- and precious-metal deposits in the Beaverdell and Greenwoodcamps,andmorerecentlyofgolddepositsin TheresultsofgeologicalmappinginthevicinityoftheAl- the Republic District of northern Washington. Mining in mondMountainmaparea(NTS082E/07)areshowninFig- theBeaverdellcamp,locatedapproximately5kmwestof themaparea(Figure2),operatedfrom1913to1991and, 1‘Tertiary’isanhistoricalterm.TheInternationalCommission based on MINFILE information (BC Geological Survey, onStratigraphyrecommendsusing‘Paleogene’(comprising 2015),producedapproximately99.2milliongAg(35mil- thePaleocenetoOligoceneepochs)and‘Neogene’ (comprisingtheMioceneandPlioceneepochs).Theauthor lionoz.)and481941gAu(17000oz.)fromnarrow,high- usedtheterm‘Tertiary’becauseitwasusedinthesource gradelead-zincveins.DepositsinthePhoenixmineareain materialforthispaper. the Greenwood camp, 30 km to the southeast (Figure 2), Keywords:geology,regionalcompilation,RepublicDistrict,Ju- produced more than 2.5 million g Au (910 000 oz.) and rassic–Eocene intrusions, Eocene extensional tectonics, 116.7 million g Ag (5.9 million oz.) until its closure in PentictonGroup,base-andprecious-metalmineralization 1978,andseveralotherdepositsinthecampcontinuetobe Thispublicationisalsoavailable,freeofcharge,ascolourdigital files in Adobe Acrobat® PDF format from the Geoscience BC actively explored (e.g., Dufresne and Schoeman, 2014). website:http://www.geosciencebc.com/s/DataReleases.asp. Explorationelsewherecontinuestobeactive,particularly GeoscienceBCReport2016-1 23 Figure1.Locationofthe1:50000scaleAlmondMountainmaparea(NTS082E/07)insouthernBritishColumbia;modifiedfromBC MapPlace(BCGeologicalSurvey,2015). withtherecentdiscoveryofnewzonesofepithermal-gold Regional Geology mineralization in a similar geological setting at the Brett property, approximately 30 km west of Vernon (Caron, TheAlmondMountainareaisunderlainbyQuesnelterrane 2014). rocksintrudedbyavarietyofigneousrocksranginginage from Jurassic to Eocene. Paleozoic metasedimentary and Exploration in the immediate area is summarized mainly metavolcanic rocks within the Quesnel terrane form a fromMINFILE data and fromprovincial government as- subterranethatcanbesubdividedintotwodistinctsucces- sessmentreports.Thisexplorationresultedinthediscovery sions,theoceanicOkanagansubterrane,whichincludesthe ofanumberofbase-andprecious-metalveinsandbreccia KnobHillGroupandAnarchistSchist,andthearc-related zoneslargelyrestrictedtothegrabeninthewesternpartof HarperRanchsubterrane(Wheeleretal.,1991).Overlying themaparea.Workonthesehasincludedconsiderablegeo- arc-volcanicrocksincludetheTriassicNicolaGroup,ex- logical mapping, soil sampling, ground geophysical sur- posedintheGreenwoodareatothesouthandthroughout veysandlimiteddrilling(summarizedinGreigandFlasha, theThompsonPlateauareatothewest(Preto,1979),and 2005). theEarlyJurassicRosslandGroupalongthesoutheastern 24 GeoscienceBCSummaryofActivities2015 Figure 2. Geology of part of the Penticton area, showing the location of the Almond Mountain (NTS 082E/07) and Christian Valley (NTS082E/10)mapareasinsouthernBritishColumbia(modifiedfromTempelman-Kluit,1989). marginoftheQuesnelterrane(HöyandDunne,2001).Ju- base-andprecious-metaldeposits.Theseincludetheveins rassicgranodioriteoftheNelsonplutonicsuite,andJuras- in the Beaverdell camp immediately west of the Almond sicandEocene(?)graniteandgranodioriteoftheOkana- Mountainareaandnumerousstructurallycontrolledmin- ganbatholithunderliealargepartofthePentictonmaparea eraloccurrencesthroughouttheKettleRiverarea. (Tempelman-Kluit,1989). Geology of the Kettle RiverArea RegionalextensionduringtheTertiaryhadaprofoundef- fectonthephysiographyandmetallogenyofsouth-central TheKettleRiverarealiesalongthewesternmarginofthe BC,withlow-angledetachmentfaultsexhumingProtero- AlmondMountainmaparea((NTS082E/07;Figure1).Itis zoicandPaleozoicgneissicandplatformrocksthatformed underlainbyacomplexnorth-trendinggrabenthatexposes themetamorphic-corecomplexesofthesouthernMonashee Paleozoic metasedimentary and metavolcanic rocks in- Mountains,includingtheGrandForkscomplex(Preto,1970). trudedbyJurassicdioriteandgranodiorite.Theseareover- Extensioninthehangingwallterrane,betweentheGranby lainunconformablybyanEocenesedimentaryandvolca- faultatthewesternmarginoftheGrandForkscomplexand nic succession that constitutes the graben fill. Eocene theOkanagandetachmentfaulttothewest(Figure2),re- stocks, including alkalic rocks of the Coryell suite and sulted in the intrusion of alkalic plutons of the Eocene megacrysticgranite,arelocallyexposedwithinthegraben, Coryell intrusive suite; the formation of north-trending asisasuiteofgenerallynorth-trendingdikes.Anumberof grabensfilledwithEoceneandyoungercoarsesediments base-andprecious-mineralveins,relatedtoEoceneexten- and alkalic volcanic rocks; and the localization of both sion,arefoundwithinthegraben. GeoscienceBCReport2016-1 25 Wallace Group tions of younger undifferentiated, fine-grained intrusive diorite. TheWallacegroupwasinitiallydefinedbyReinecke(1915) to include Paleozoic metasedimentary and metavolcanic Minor-andtrace-elementanalysesofvolcanicrocksofthe rocksthatlieinthenorthwesternpartofthearea(Figure3), Crouse Creek member and within the siltstone/volcanic- extendingwesttowardthetownofBeaverdell.Theserocks rocksectionsuggestthatthesePaleozoicrocksareacalc- havebeenassumedtobepartoftheAnarchistSchist,but alkalinevolcanic-arcsuccession(Massey,2010).Theydif- because of considerable lithological differences, Massey ferconsiderablyfromthetholeiiticrocksoftheKnobHill and Duffy (2008a) preferred to retain the term ‘Wallace GrouportheAnarchistSchist(Massey,op.cit.)andmaybe group’,ausagethatisadoptedinthispaper. partofthearc-relatedHarperRanchsubterrane. TheWallacegroupintheKettleRiverareaisdescribedby Triassic–Jurassic Intrusive Rocks MasseyandDuffy(2008a).Theynotedthataconsiderable partoftheareathatisunderlainbyWallacegrouprocksin Middle Jurassic and Triassic granodiorite and diorite un- original mapping (Reinecke, 1915) includes younger Ju- derlie a considerable part of the Almond Mountain map rassicand/orTertiaryrocks.Otherworkersinthearea,no- area.IntheKettleRiverarea(Figures3and4),Jurassic(?) tablyGreigandFlasha(2005),alsorealizedthedifficultyin diorite occurs as two isolated stocks between the Crouse distinguishingbetweenPaleozoicmetavolcanicrocksand CreekandChristianValleyfaultsinthenorthernpartofthe recrystallizedorfinergrained,youngerintrusions.Thedis- maparea.Isolatedbodiesofgranodioriteinthenorthwest- tributionoftheWallacegroup,asshowninFigures3and4, ernpartofthemaparea(unitJgdinFigure3)arepartofthe isbased,inpart,onmappingundertakenduringthisstudy Westkettle batholith (Reinecke, 1915), which hosts many andonattemptstoreconcilepreviouswork. oftheveinsintheBeaverdellcampaswellassomeveinsin the central part of the Kettle River area. These intrusive AlargepartoftheWallacegroupcomprisesinterbedded, rockshavebeencorrelatedwiththeJurassicNelsonpluton- laminatedargilliteandsiltstone(unitPw).Thesearecom- icsuite,asdefinedbyTempelman-Kluit(1989)andLittle monlyhornfelsedandrecrystallized,maskingoriginalsed- (1961). However, U-Pb zircon analysis of the Westkettle imentarystructures.Siltstonebedsaretantogrey,whereas batholith,fromasamplelocatedjustwestof1:20000scale argillitebedsaredarkgreytoblack.Somesectionsoflami- maparea082E/049,returnedadateof213.5Ma(Masseyet nated ‘siltstone’ are light green and may represent thin, al.,2010),similartoaTriassicageobtainedfromanintru- mafic tuffaceous layers. Disseminated pyrite and quartz- sionintheChristinaLakearea,informallynamedthe‘Josh carbonateveins,withminorpyrite,arecommonand,inar- Creekdiorite’(Actonetal.,2002).Additionalsamplesof easofinterbeddedplagioclase-phyric‘flows’,thepresence these units, as well as from other intrusions in the Kettle ofmalachitestainingandchalcopyritewasnoted. Riverarea,arebeingsubmittedtothegeochronologylabo- ratoryoftheUniversityofBritishColumbiafortestingby MasseyandDuffy(2008a,b)differentiatedalimestoneand the40Ar/39Armethodofagedetermination. agreenstonememberintheWallace.Theinformallynamed ‘Larse Creek limestone member’ (unit Pl; Massey and UnitJgdcomprisesdominantlylightgreytomediumgrey, Duffy,op.cit.)occursinthenorthernpartof1:20000scale medium-to coarse-grained granodioriteand lesserquartz TRIMmaparea082E/046,immediatelysouthofBeaver- diorite(Figure6).Quartzcontentrangesupto20%andthe dellCreek(Figure3).Thisdistinctive,lightgrey-weather- maficminerals,hornblendeandbiotite,fromtypically10to ing limestone, with numerous calcite-quartz veins and 30%. These rocks are locally altered to pale green, and pods, ranges from massive to well bedded, to locally in- veinedwithquartz,chloriteandepidote. tenselyfolded(Figure5). Diorite (unit Jd) is exposed in two irregular stocks in the Thelimestoneisoverlainbymassivemaficflowsofthein- centralpartofthenorthern1:20000maparea(082E/046). formallynamed‘CrouseCreekmember’(unitPv;Massey The southwestern stock includes medium-grained to lo- and Duffy, op. cit.). The flows locally include vague callyporphyriticdioriteandlessergranodioritecomposed amygdules and feldspar or pyroxene phenocrysts. Inter- mainlyofplagioclase,hornblendeandupto20%quartz.It beds of siltstone or laminated mafic tuffaceous rocks are is fractured and chlorite altered adjacent to the Crouse common.Massivemaficflowsarealsomappedasasepa- Creekfault.Porphyriticgranodioritecontainseuhedralto rateunitontheeasternsideoftheKettleRiver(Figures3 subhedralphenocrystsofwhitefeldsparuptoseveralcenti- and4)andarereferredtoaspartoftheCrouseCreekmem- metresinsizeinagranularfeldspar-hornblende-quartzma- ber,althoughdirectcorrelationisnotknown.Aswell,the trix. The northeastern stock is similar, but includes a dis- largesectionofundifferentiatedWallacegroupinthecen- tinctive unit, termed a “hornblende crowded feldspar tralpartofbothmapareas(unitPw)containsconsiderable diorite”byGreigandFlasha(2005).Thedioriteishostto maficvolcanicrocks,butitispossiblethatitincludessec- many of the base- and precious-metal veins in the Triple 26 GeoscienceBCSummaryofActivities2015 Figure3.Geologyof1:20000TRIMmaparea082F/046,showinglocationofselectedmineraloccurrencesintheKettleRiverarea. GeoscienceBCReport2016-1 27 Figure4.Geologyof1:20000TRIMmaparea082F/036,showinglocationofselectedmineraloccurrencesintheKettleRiverarea.Notall unitsandsymbolsshownonthelegend,whichaccompaniesFigures3and4,appearonthisfigure. 28 GeoscienceBCSummaryofActivities2015 Figure 5. Banded grey and white limestone of the Larse Creek Figure6.Medium-grained,relativelyfreshgranodioriteofunitJgd, member,Wallacegroup,KettleRiverarea. fromtheKettleRiverarea. Lakesarea(Figure3).Similarplagioclaseporphyryisex- chlorite-altered, fractured and veined adjacent to the posednearthemouthofCanyonCreek(Figure3). CrouseCreekfault. Granite (unit Tg) Numerous, generally north-northeast-trending dikes and small stocks (unit Jdp) cut the diorite stock and host Graniteandgranodioriteofthe‘Cretaceousand/orJurassic’ WallacegrouprocksintheTripleLakesarea.Theseinclude Okanagan batholith underlie a large part of the Almond fine-grainedtoporphyriticdiorite,lithologicallysimilarto Mountainmaparea,eastoftheGreenwoodfaultandwest unit Jd, and plagioclase porphyry latite and hornblende- of the Kettle River area in the footwall of the Okanagan plagioclaseporphyrydikes.Theagesofthesedikesarenot fault(Tempelman-Kluit,1989).Basedonlithologicalsimi- known; some have a distinctive pink cast, suggesting the laritiestotheporphyriticgranite(unitEg)andtheEocene presenceoffine-grainedK-feldsparinthematrix,andmay ‘Ladybird’graniteintheDeerParkandBurrellCreekareas, bepartofthealkalicEoceneintrusivesuite. unitTgisassumedtobeEoceneinage. Porphyritic Granite (unit Eg) Exposures of the granite immediately east of the Green- wood fault (Figures 3 and 4) comprise mainly medium- Distinctivecoarse-grainedmegacrysticgraniteoccurswest grained, massive to porphyritic quartz-orthoclase-plagio- oftheCrouseCreekfaultandinisolatedexposurestothe clasegranite,withminorbiotiteandhornblende.Porphy- east and south. The granite is correlated with the ‘Creta- ritic phases, similar to unit Eg, are common near David ceous’ValhallacomplexintrusionsofLittle(1957)and,in Creekinthesouthernpartofthearea. subsequentpapers,theseintrusionsaregenerallyreferred toas‘Jura-Cretaceous’(e.g.,Tempelman-Kluit,1989).In Eocene Coryell (unit Ec) theKettleRiverarea,themegacrysticgraniteintrudesthe ThealkalictosubalkalicCoryellplutonicsuiteconsistsof WallacegroupandMiddleJurassicgranodioriteandisun- MiddleEoceneintrusions.Theyunderliealargepartofthe conformablyoverlainbyEocenePentictonGrouprocks.A Almond Mountain map area, but within the Kettle River K-Ardateof49.4±1.9Mawasobtainedfromalithologic- areaarerestrictedtoasmallplutoninthenorthernpartof ally similar megacrystic granite south of Beaverdell 1:20000scalemaparea082E/046,referredtoasthe‘Col- (Church, 1996) and a U-Pb zircon date of 56.0 ±1.0 Ma lierLakestock’(MasseyandDuffy,2008a).Thestockisa (Parrish, 1992) as well as a hornblende 39Ar/40Ar date of porphyritic syenite, with phenocrysts of pink K-feldspar. 52.8±1.6Ma(Höy,2013)forasimilargraniteintheBurrell Itseasterncontactisachilled-marginphaseoffinergrained Creek area. Hence, pending further radiometric analysis, material, whereas the southern contact with unit Jgd is theKettleRivermegacrysticgraniteisassignedanEocene coarsegrained,suggestingafaultedrelationship. age,followingtheleadofMasseyetal.(2010). Penticton Group The granite is typically medium to coarse grained, with large,pink,euhedralK-feldsparphenocrystssetinagranu- TheTertiaryPentictonGroupisdescribedanddefinedby larmatrixofK-feldspar,plagioclaseandupto10%biotite Church(1973)ascomprisingsixformationmembers:basal and hornblende. It is generally fresh, although bleached SpringbrookandcoevalKettleRiverformations,volcanic and fractured beneath the sub-Tertiary unconformity, and rocksoftheMarronand‘McNamara’formations,anddom- GeoscienceBCReport2016-1 29 inantlysedimentaryrocksoftheWhiteLakeandSkahafor- oftheKettleRiverFormation(Figure8),whichistypically mations. In the Kettle River area, three units are recog- wellbeddedandlightcoloured,formingwhitecliffsvisible nized,abasalsuccessionofconglomerateandsandstoneof fromadistance(Figure9).Thinshaleorargillitebedsoccur the Kettle River Formation, the Marron Formation and locally,andplagioclase-phyricflows,typicaloftheMarron overlying basalt, referred to as the ‘Kallis formation’by Formation,occasionallyoccurintheupperpartoftheKet- MasseyandDuffy(2008b). tleRiverFormation.Elsewhere,coarsegritorsandstonedi- rectlyoverliesJurassicgranodioriteor,nearthemouthof Kettle RiverFormation (unit Epk) Crouse Creek (Figure 4), the megacrystic granite of unitEg.Here,thegritisderivedentirelyfromthegranite TheKettleRiverFormationandoverlyingMarronForma- anditisdifficulttodeterminetheexactlocationofthecon- tion occur within a well-defined, north-trending graben tact between the two units as the granite is very friable, thatextendsfromtheRockCreekareawestoftheGreen- weatheredandbleached. woodcamp(Figure2)throughthewesternpartoftheAl- mondMountainmaparea,andnorthwardintotheChristian TheKettleRiverFormationissimilartobasalsuccessions Valleymaparea.IntheKettleRiverarea,italsooccursin ofthePentictonGroupdescribedelsewhere,includingthe several isolated exposures immediately west of Kettle SpringbrookFormationintheWhiteLakebasin(Church, River. 1973)andtheKettleRiverintheGreenwoodarea,whereit isdescribedasa“discontinuousbasalconglomerate,above The formation is well exposed on the eastern side of the whichiswhitetobuff,locallyplantbearingarkosicsand- KettleRiver,nearPaturagesCreek(Figures3,4),whereit stone, siltstone, and minor shale and conglomerate, all unconformably overlies volcanic rocks of the Wallace largely derived from acid volcanic and granitic rocks” group. It comprises a basal unit of coarse conglomerate, (LittleandMonger,1966,p.67). with large rounded boulders of dominantly granite and greenstoneinamediumgreengrit-sandstonematrix.The basalpartoftheKettleRiverFormationinthesouthernex- posure on the western side of the Kettle River is also a coarse conglomerate, with dominantly granitic clasts in a fine-tomedium-grainedgritmatrix(Figure7).IntheCan- yonCreekarea,2to3kmtothenorth,thebasalpartofthe Kettle River Formation is a thick (approximately 100 m) successionofimmatureconglomerate,withcoarseangular clasts of dominantlygreenstone and diorite typicalof the underlyingWallacegroupandunitJd. Basal conglomerate grades upward into coarse-grained, tan-colouredgrit,sandstoneandsiltstonethatformthebulk Figure7.Coarseconglomeratethatforms thebasal partofthe KettleRiverFormation,insouthernBritishColumbia;notelarge Figure8.Interbeddedconglomerateandgritlayersinthebaseof angulartosubroundedclastsofgranodiorite,whichissimilarto theKettleRiverFormation,insouthernBritishColumbia.These that shown in Figure 6, and a medium-grained, chlorite-altered gradeupintobeddedtomassivegritandsandstone,moretypical groundmass. oftheKettleRiverFormation. 30 GeoscienceBCSummaryofActivities2015 Figure9.Viewtothesoutheast,lookingacrosstheKettleRiver,insouthernBritishColumbia. NotecliffformingexposuresoftheKettleRiverFormationonthenearslopes;theseunconform- ablyoverlievolcanicrocksoftheWallacegroupandareinturnoverlainbyMarronFormation volcanicrocksapproximately5kminthedistance.Aneast-dippingTertiarynormalfaultfollows approximatelytheKettleRivervalley. Marron Formation (unit Epm) Structure The type section of the Marron Formation in the White The structure of the Kettle River area is dominated by LakebasinareaisdescribedbyChurch(1973)andiscorre- north-trendingnormalfaultsthatrecordaperiodofTertiary latedwithasimilarsectionintheGreenwoodarea(Church, extensioninsouth-centralBC(Parrishetal.,1988).Anear- 1986).TheMarronFormationdirectlyoverliestheKettle lier deformation, present only locally in the Paleozoic RiverFormationor,locally,olderpre-Tertiary‘basement’ Wallacegroup,contrastswithpenetrativedeformationthat rocks. In the Burrell Creek area, the contact between the hasbeenrecordedinPaleozoicrockselsewhere,notablyin Kettle River and Marron is locally unconformable (Höy, theKnobHillGroupandAnarchistSchisttothesouth(e.g., 2013),andhencetheabsenceofthebasalpartoftheKettle Massey,2006,2007).IntheGreenwoodarea,thePaleozoic River Formation may record either nondeposition or ero- Attwood Group, Knob Hill Group and Triassic Brooklyn sionpriortovolcanismoftheMarronFormation. Formation are locally tightly folded within a series of northward-dippingthrustsheets(Fyles,1990). TheMarronFormationcomprisesathicksuccessionofvol- canicrocksthatvariesincompositionfromalkalicbasaltto Thelackofprominentmarkerunitsandtheabundanceof trachyte,andrangesfromlavaflowstowell-bandedmafic intrusiverocksinmostoftheWallacegroupprecludesade- tuffs and blocky tephra. In contrast with Wallace group tailed structural interpretation of these rocks. As well, flows, volcanic textures, including amygdules, vesicles, hornfelsingandveiningadjacenttointrusionsfurthermask phenocrysts and clasts, are well preserved. A section of both their structures and primary sedimentary features. blacktoredshalesafewtensofmetresthickoccursinthe Tight minor folds were noted in the ‘basal’Larse Creek centralpartoftheMarronFormation,westofThoneLake. limestonejustsouthofBeaverdellCreek,butalargepartof the Wallace group lacks structures or regional metamor- Kallis Formation (unit Pk) phismthatcouldbeattributedtoaregionaldeformational TheKallisformationispreservedinisolatedtopographic event.Thrustfaults,similartothosedescribedintheGreen- highsthroughoutthearea.ItliesontheMarronFormation wood area (Fyles, 1990), are also not recognized here; and represents the remnants of widespread Neogene pla- serpentinitesthatmarkthethrustfaultsandfoldingcharac- teau basalt. It consists typically of a black, fine-grained, teristicofthethrustsheetsatGreenwoodappeartobealso aphyricorolivine-phyricbasalt. absent. GeoscienceBCReport2016-1 31 Acomplexnorth-trendinggraben,boundedbyhigh-angle Creekfault,southofBeaverdellCreek(Figure3),contains Tertiarynormalfaults,extendsfromnearRockCreekinthe apronouncedshearandmylonitezonealongit;aprominent south,throughtheKettleRiverareaandintotheChristian topographic linear feature that extends to the southeast, Valley map area (NTS 082E/10). The Paleozoic Wallace across the Crouse Lake fault and following a branch of group forms a tectonic high in the Kettle River area, and CanyonCreek,maymarktheextensionofthisfault. TertiarygrabenfilloftheKettleRiverandMarronforma- tionsonlapWallacebasementrocksandexposedJurassic Thenortheast-trendingCrystalCreekfaulthasnetnormal andEoceneintrusions. west-side–downmovementalongit,withKettleRiverFor- mation in its hangingwall juxtaposed with Jurassic and A west-dipping, north-trending normal fault, the Green- Eoceneintrusiverockstotheeast(Figure3).Farthersouth, woodfault,formstheeasternmarginofthegraben.Itjuxta- the Hoodoo Lake fault defines a pronounced northeast- poses Tertiary granite on the eastern side against Marron trending linear feature within the granite. Several expo- and Kettle River formations and Wallace group rocks on suresimmediatelynorthwestofHoodooLakeindicateright the western side. Exposures of the fault surface were not lateralmovementalongasteep,west-dippingfaultsurface. seen,butobservedgraniteandgranodioriteontheeastern sideofthefaultwerelocallysheared,withshearzonesdip- Numerousotherfaultsandshears,generallytoosmalltobe ping relatively steeply (40–50°) to the west. The western shown on the maps, occur within the central part of the marginofthegrabenismarkedbyaneast-dippingnormal graben. These are marked by outcrop shear zones, brec- faultthatfollowsthetrendoftheKettleRiversouthtothe ciation,alterationand,commonly,sulphidemineralization. CrouseCreekarea,andthereitisoffsettothewestbythe northtonorthwest-trendingCrouseCreekfault. Mineralization The Crouse Creek fault (Figure 10) is a brittle structure An importantfocus of this studyis to determinetherela- marked by considerable shearing, brecciation and mainly tionships,onbothalocalandregionalscale,betweenbase- chloritic alteration (Greig and Flasha, 2005). It trends and precious-metal mineralization and structures, and north-northwest and generally dips at a high angle to the magmatism. Previous work in the Deer Park and Burrell west. The amount of displacement on the fault is not Creekareastotheeast(Höy,2010;2013)underscoredthe known;itisassumedtobeobliquewithleft-lateralandnor- importanceofJurassicandEocenemagmatismaswellas malwest-side–downmovement,basedmainlyontherela- Tertiary structures, in localizing mineralization. To the tivelevelsofthePentictonGroupexposuresatthesouthern west,shear-hostedsilver-richveinsintheBeaverdellcamp endofthefault.Anorthwest-trendingsplayoftheCrouse appeartobeEoceneinage,whereastheCarmiveinsimme- Figure10.ViewtothesouthoftheCrouseCreekvalley,andlocationoftheCrouseCreekfaultin southernBritishColumbia;theKettleRivervalleyisapproximately8kminthedistance.Abbrevi- ation:Eg,megacrysticporphyriticgranite. 32 GeoscienceBCSummaryofActivities2015