Geology of the Kettle River Area, Almond Mountain

12 Pages·2015·0.94 MB·English

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