GEOLOGY OF THE NOAXE CREEK MAP AREA* (920/02) By J. K. Glover, P. Schiarizza and J. I. Garver

KEYWORDS: Regional geology, Noaxe Creek, Warner Pass, The '&aughton 'kough: Marine sedimentary strata of he BridgeRiver terrane, Cadwallader terrane, Tyaughton Middle Jurassic to Lower Cretaceous Relay Mountain GrrNugl trough. Yalakom fault, Shulaps ultramafic complex, wrench and the mid-Cretaceous Taqlor Creek and Jackass Mountain faults. groups (Jeletzky and Tipper, 1968). An Upper Cretaceous succession, which comprises her- INTRODUCTION ally discontinuous, nonmarine basinal deposits that grade up into continental volcanicarcrelated rocks, overlies theo13e: The Noaxe Creek map area lies 200 kilometres north of marine strata of the the Tyaughton trough with local pro- Vancouver on the eastern margin of the Coast Mountains, nounced angular unconformity (Glover and Schiarizra, and covers an area of 1000 squarekilometres within the 1987). Chilcotin Range. The topography and vegetation vary from The BridgeRiver terraneand Tyaughton trough are alpine tosubalpine in thewest, southeast and northeast, thought to have been offset from their correlatives to thc: where elevations range up to 2850 metres, to rolling tree- south, the tiozameen Group andMethow basin, by at leas170 covered ridges with intervening broad river valleys in the kilometres of right-lateralstrike-slip movement along the central part of the area. north-trending Fraser - Straight Creek fanlt system during Approximately 70 per cent of the area, mostly north of Late Cretaceous (?) and Early Tertiary time (Monger, 19U). Tyaughton and Noaxe creeks, was mapped at ascale of Earlier, post-Albian fragmentation of the Tyaughton-Methow 120 000 by a four-person field crew duringthe 1987 season. basin occurred along the Yalakom-Hozameen fault system, This was augmented by results from independent detailed along which 80 to 190 kihmetres of right-lateral offset has mapping in the westem partof the areaby Paul Umhoefer and been postulated (Tipper, 1Y69). The Yalakom fault crosses in the western and southern parts of the area by John Garver the map area fromsoutheast to northwest, from where it has during1985, 1986and 1987. been traced, north of Taseko and Chilko lakes, to the T3tl.z Approximately 50 rock samples were collected from zones Lake area in the Mount Waddington map area (Tipper, 1969, of alteration and mineralization for trace element analysis. 1978; McLaren, 1986, 1987). This report covers the second year of a 4-year regional Mesozoic strata areintruded by mid-Cretaceousquartz mapping project, hegun in 1986, and funded by the Canada/ diorite to quartzmonzonite of the Coast piutonic compler i.1 British Columbia Mineral Development Agreement in order thesouthwest part of the belt (McMillan, 1976) and by to provide 150 000-scale geology maps and mineral poten- widespread equigranular and porphyritic granitic stocks and tial overlays of the Taseko-Bridge River area as an aid to dykes of probable late Crelaceous and Eocene age; they are exploration. unconformably overlain by Eocene volcanic and sedilren- tary rocksand by Plioceneand Mioce~ne plateau basalts (Mathews and Rouse, 1984). REGIONAL GEOLOGY The study area is underlain by Mesozoic sedimentary and LOCAL GEOLOGY volcanic rocks that lie within a northwest-trending, struc- Figure1-9-2 outlines the general geology of the Noaxe turally complex zone along the western margin of the Inter- Creekmap area. Previous regionalmapping by Tipper montaneBelt, to the east of theCoast plutonic complex (1978) and detailed biostratigraphy (Tozer, 1967; Jeletzky (Figure 1-9-1). This zone comprises several fault-hounded and Tipper, 1968) form thebasis of divisions within mucn cd tectonostratigraphicunits, some of which are coeval, as the Mesozoic strata; division of Cretaceous rocks into the outlined below: Taylor Creek and Kingsvale groups, defined for the Taseko TheBridge River Terrane: Oceanicrocks of the lower Lakes map area by Jeletzky and Tipper, has been modified Jurassic and older (?) Shulaps ultamafic complex and Middle based on field relationship:; recognized during the 1986 and Triassic to LowerJurassic Bridge River complex (Potter, 1987 seasons. Results from two independent structural and 1986). stratigraphic studies of the Tyaughton and Relay Mountain groups by P.J. Umhoefer, and of the Taylor Creek Group by The Cadwallader Terrane: Volcanic arc-relatedrocks of I. 1. Garver are incorporatedin Figure 1-9-2 (Umhot:fer, theUpper Triassic Cadwallader and Tyaughton groups Garver and Tipper, in preparation), toget.her with a limited (Rusmore, 1987),and lower to middleJurassic sediments amount of data from assesmentreports. The geology along (H.W. Tipper, personal communication, 1987). the southern marginof the map sheet has been compiled from

~ * This projccl is a canlnhution 10 the CanaddBntish Columhla Mineral Development Agreemenl. British Columhm Ministry of Energy. Mines and Petroleum Resources, Geological Fieldwork. 1987. hpcr 1958-1 IO5 previous work(Caimes, 1943; Leech, 1953: Tipper, 1978; Range,southwest of the Yalakom River andnorth of the Rusmore, 1983, with the addition of data supplied by B.N. Bridge River. The complex and its contact relationships were Church (Church et al., this volume). first studied in detail by Leech (1953), whoconcluded that it was an intrusive body, emplaced in Late Triassic or Early LITHOLQGY Jurassic latertime, and redistributed, possibly by solid flow, THE SHULAPS ULTRAMAFIC COMPLEX AND along fault zones to the west and northwest. Later workers RELATED SERPENTINITE ZONES (Monger, 1977; Nagel, 1979;Wright etal., 1982) suggested The Shulaps ultramafic complex, which extends into the that theShulaps ultramaficand Bridge River complexes southeastern part of the map area, is located in the Shulaps together constitute a dismembered ophiolite. Potter (1983, LEGEND MIOCENEPLIOCENE UPPER TRIASSICTO LOWER JURASSIC 191 plateau lava. basalt flow PIAUGHTON GROUP (Unit 1) E O CE NE (UnitEOCENE 8) limestone:Massive red congiomerate: ,grit and > > > Aphyric to porphyritic andsitk to dacitic flows: conglomerate interbtdded with gmnsandstone rhyoiii (lorn and flow bmcclab;minw volcanic andshale: darkgmy to black shale and argillite sandstom andsiltstone UPPER TRIASSIC UPPERCRETACEOUS CADWALLADER GROUP (IJnit UTc) BATTLEMENT RIDGE GROUP (Units6 and 7) Malic vdurnlcs and tvoicanidastis: m#glom- Potymict conglomerate, sandstons; epiclash; crate: llmsstone andgmy to bfackargiWe andesitic RQws. volcanic bfema and lapilli luff LOWER CRETACEOUS MIDDLE TRIASSICTO LOWER JURASSIC (Unit TAYLORCREEK GROUP (Units 4 and 5) BRc) aShale. siltstom andsandrtom; volcanic BRIDGE RIVER COMPLEX conglomerafe: chett-pebble conglomerate: micamow aRibbon andmassirs chefk:greensfon~e; sandsfone argdiacsous mdlangr,, argiliite andlimestone; JACKASS MOUNTAINGRWP (Unit 3) minoraltefedgabbm lo dorite Lithic sandstoneand wacke: arkosic sandstone: PLUTONIC ROCKS pofymict conglomerate and mnglomeratk sandstone: siltstone andshale EOCENE AND OLDER MIDDLE JURASSICTO LOWER CRETACEOUS m Equigranular to pxp9yritk qua& dlorile to quam RELAY MOUNTAIN GROUP (Unit2) monzonite lnterbddeddark grey shale, grey-brownsiktons, [email protected]. @mite, serpsntinlzsd gmn-gmygreyacke and lithic san&tone;grit and panhbte mglomerate Figure 1-9-2. Generalized geology map, Noaxe Creek map area. 107 1986), working along itssouthern margin, documented a and melange. They are rarelytraceable for more than 20 thrust zone at the base of the complex which juxtaposes it metres, hut one, located north of the confluence of Relay against underlying rocks of the Bridge River complex that Creek with Mud Creek, extendsfor a strike length of 3 contain an inverted metamorphic gradient and a transposed kilometres. Melange comprises pods and lenses of all the foliation; he concluded that thrusting occurred during mid- above lithologies in a foliated argillaceous matrix; the fabric Jurassic time while the ultramafic rocks were still hot. is generally coplanar with bedding in adjacent ribbon chert. Only the northeastern margin of the Shulaps ultramafic These rocks, together with the Shulaps ultramafic complex, complex has been mapped during the present study; here, its are interpreted as an accretionary prism of oceanic prove- contact with rocks of the Jackass Mountain Group to the nance (Price et a/., 1985; Potter, 1986). No fossils have been northeast is defined by a broad, poorlyexposed zone of obtained from the complex in the studyarea, but to the south, serpentinization along the Ydlakom fault. This zonecon- on the north side of Carpenter Lake, conodonts from carbo- tinues to the northwest of the complex for a distance of 16 nates and radiolaria from cherts give a range in age from kilometres. Two other slivers of serpentinite occur Middle Triassic to EarlyJurassic (Cameron and Monger, elsewhere: along the Yalakom fault in the northwestern part 1971:Cordey, 1986). of the map area,and along a fault zone onthe west margin of a panel of Bridge River complex, in the vicinity of Tyaughton THECADWALLADERGROUP Creek. (UNIT UTc) Leech (1953) estimated the main body of the complex to Rocks of the Cadwallader Group areconfined to two areas comprise 85 per cent harzburgite,with dunite making up the along the southern margin of the map sheet,neither of which remainder; variable serpentinization of these rocks is uhiq- was mapped during thepresent study; theirdistribution, uitous. Pods and lenses of relict harzburgite within foliated outlined on Figure 1-9-2, is based on previous work. serpentinite were observed in the study area north of Quartz The Cadwallader Group, as defined by Roddick and Mountain alongthe Yalakom fault zone, and at the con- Hutchison (1973) for the Pemberton (east half) map area, to fluence of Mud Creek with Relay Creek, along the fault zone the south of the present study, comprises the Noel, Pioneer west of the Bridge River complex. and Hurley formations of Cairnes (1937, 1943). Subsequent Serpentinized ultramafic rocks associatedwith some of the work by Rusmore (1985, 1987) indicates that the Noel For- major faults in the map area areextensively carbonatized and mation is not a coherent unit and should be abandoned. The silicified. These rusty to orange-weathering rocks are com- revised stratigraphy of the group, based on sections south of posed of silica and magnesian carbonate with fuchsite. Tyaughton Creek and west of Eldorado Mountain (map sheets Quartz, some of which is chalcedonic, occurs in anastamos- 920/02 and 921115). comprises a mafic volcanic unit, the ing veinlets and irregular massesin a carbonate matrix, with Pioneer Formation, at thebase, overlain by a lower vol- some late, crosscutting veinlets of euhedral magnesite. All caniclastic member and an upper turbidite member of the stages of hydrothermal alteration of serpentinite can be found Hurley Formation; an estimated total thickness of at least in these zones. 2000 metres (Rusmore, 1987). Conodonts from the Hurley Formation give a range in age from latest Carnian or earliest THE BRIDGE RIVER COMPLEX Norian to Middle Norian (Rusmore,1987). (UNIT BRC) Rocks of the Cadwallader Grouphave been mapped along The Bridge River complex (Potter, 1983) includes all rock the southwest margin of the Shulaps Range by various work- types previouslyassigned tothe Bridge River Group by ers (Leech, 1953; Roddick and Hutchison, 1973; Church et Roddick andHutchison (1973) and theto Fergusson seriesby a/.,this volume). However, contact relationships with adja- Cairnes (1937, 1943) and later, by Church (1987). In this cent rocks of the Bridge River and Shulapsultramafic com- report the term complex is preferred because internal struc- plexes are poorly defined. tural complexities and small-scale variability of lithology prohibit measurement of a meaningful type section. THE TYAUGHTON GROUP (UNIT 1) This unit outcrops in the southern andsoutheastern partsof the area where its thickness is unknown. It comprises, in Cairnes ( 1943) originally confined the Tyaughton Group to order of decreasing abundance, intercalated and structurally rocks of Triassic age. We also include a distinct unit of juxtaposed ribbon chert, greenstone, melange, black ar- overlyingLower toMiddle Jurassicsediments. following gillite, limestoneand minoraltered gabbroor diorite.Ribbon Tipper (1978),pending its formal separation as agroup chert is generally grey, with less common red, brown and (H.W. Tipper,personal communication, 1987). The green varieties. Individual beds vary from I to 10 centimetres Tyaughton Group is exposed in the southwest partof the map thick and are separated by argillaceous partings, but massive area where it occurs within a structurally complex panel on chert occurs locally. Greenstone is grey-green to chocolate- the north and south sides of Tyaughton Creek. brown weathering, generally massive, with rare pillows, and The lower part of the group is the most extensively exposed is fine grained, hut locally contains amygdules and altered andhas a minimumcomposite thickness of 500 metres, ferromagnesian phenocrysts; volcanic breccias occur in based on two measured sections north of Tyaughton Creek places. These rocks represent submarine volcanismof proba- (P.J. Umhoefer, personalcommunication, 1987). It com- blebasaltic toandesitic composition. Scatteredpods and prises red-weathering interheds of conglomerate with lime- lenses of light grey, massive crystalline limestone, generally stone and volcanic clasts, conglomeratic sandstone and sand- less than IO metres thick, occur within ribbon chert, argillite stone at the base, overlain by light grey to buff-weathering, 108 massive to thinly bedded limestone with corals and megalo- The mostwidespread exposures of Upper Jurassic tmd dont bivalves. This is in turn overlain by limestone con- Lower Cretaceous strata of Ithe Relay Mountain Group occur glomerate with a sandymatrix. The upperpartof this unit has in the western part of the area within fault-hounded hlo:ks a green-weathering sandstone with conglomeratic seams that extend into the eastern part of the Warner Pass map area containing volcanic clasts, overlain by green sandstone inter- (Tipper,1978; Glover and Schiarizza, 1987). A faunal calated with coquina beds of Cassianellu lingulura (the assemblage of Tithonian (Latest Jurassic:l age (T. Poultm, “Cassianella beds” of Tozer, 1967). At the top, green sand- personal communication, 1987) was collected from strata of stone and conglomeratic sandstone with pebbles of volcanic the Relay hlountain Group In a fault sliver that strikes north- rock occur. The depositionalenvironment of these rocks west from Mud Creek. These rocks comprise intercalated fluctuated between shallow marine and fluvial; provenance greenish grey lithic wacke and lithic sandsl.one, rusty hrown- of the clastic rocks was probably a volcanic arc, perhaps weathering grey-brown siltstone, dark gp?y shale, grit :in11 related to the Cadwallader Group (Rusmore. 1987). The age thin conglomerate interbeds with well-rounded volcarlic, of this lower unit is from mid to latest Norian (Late Triassic). granitic and sedimentary clasts. Minor thin limy interhzds The upper part of the Tyaughton Group is exposed along and concretions occur in places. They are characterized by thesouthwest and northeast margins of the belt and in a abundant and well-preserved huchias, belemnites and to ;i structural window along Tyaughton Creek. Its contact with lesser extent ammonites, which provide the hasis for (]if- the lower unit is either faulted or not exposed. It also outcrops ferentiation of Upper Jurassic from Lower Cretaceous strata, within an apparently isolated fault sliver to the east of the although, in general, Lower Cretaceous rocks appear to be main belt (H.W. Tipper, personalcommunication, 1986). more shaley in the study area. The thickness of this unit is unknown due to poor exposures and small-scale folding. It comprises dark grey to black JACKASS MOUNTAIN GROUP calcareousshale and argillite that containammonites of (UNIT 3) Sinemurian(Early Jurassic) to Early Bajocian (Middle The Jackass Mountain Group (Selwyn, 1872; Duffell Jurassic) age (Tipper, 1978). McTaggart, 1952) comprlses clastic sedimentary rocks, which outcrop over most ofthe map area lying northeast of THE RELAY MOUNTAIN GROUP the Yalakom fault. These rocks range in age from Barremian (UNIT 2) to Alhian (Early Cretaceous);they are therefore coeval with rocks of the Taylor Creek Group and (?) the: uppermost part of Marine strata of the Relay Mountain Group were first the Relay Mountain Group,,which outcro:p southwest of the described in detail by Jeletzky esti- and Tipper (1968); they fault (Duffelland McTaggart, 1952; Jel’etzky and Tipper, mated a total thickness of 1500 to 2700 metres in sections Rocks of Unit 3 xe unconformahly overlain by north of Relay Mountain. Lithological divisions are, on the 1968). Eocene volcanics at Red whole,difficult to implement because of lateralfacies M.ountain and bf Miocene plateau lavas near the headwaters of Dash Creek. They are locally in changes and lack of distinctive marker units, with the excep- fault contact with upper Cretaceous volcanic rocksof Unit 7, tion of a lower shaley unit of Middle Jurassic age; divisionof but are separated from other Mesozoic units by the Yalakom the overlying strata is facilitated by a well-defined paleon- fault. tologicalzonation that ranges from Late Oxfordian (Late Jurassic) to Barremian (EarlyCretaceous), based on Buchia, Continuous sections of strata assigncd to the Jackas ammonites and Inoceramus species(Jeletzky and Tipper, Mountain Group are not pment in the map area; moreover, 1968). The Relay Mountain Group is undifferentiated in fossilscollected fromthis group are as yet unidentified. Figure 1-9-2, but the threefold divisionof Tipper (197R) into Consequently, the proposed stratigraphic relationships be- Middle Jurassic,Upper Jurassic andLower Cretaceous strata tween lithologic units described below are preliminary: Lnit is followed on the open file map of the Noaxe Creek map 3v, believed to he at the base of the succession, comprise:s sheet (Glover er al.. in preparation). predominantlymassive, marine, volcanic-rich sandstone; this is locally overlain by fluvial to shallowmarine.organic- The thicknessof the mid-Jurassic part of the Relay Moun- rich sandstones of Unit 3f in some places these are overlain tain Group isdifficult to ascertain because of poor exposures by marine boulder-cobble conglomerates of Unit 3cg; domi- and structural complications, hut probably ranges from 300 nantly arkosic turbidites of Unit 3ak locally appear to sit to 600 metres (Tipper and Jeletzky, 1968). It is most exten- stratigraphically above Unit 3v, and may, in part, he equiv- sively exposed to the west, on the Warner Pass map sheet alent to or younger than Unit 3cg. The distribution of these (Glover and Schiarizza, 1987): hut also occursat the base of a units is shown in Figure 1-9-3. section northof Relay Mountain and in nmow fault-bounded slivers to the south. Similar rocks of uncertain age occur alongthe Relay Creek road and have beententatively UNIT3v assigned to this unit. Rocks of this unit comprise recessive, Rocks of Unit 3v outcrop in a northwesterly trending belt, variably rustyweathering dark grey to black shales with bounded by the Yalakom fault and related splays to the minor thin beds of siltstone; sparse lenticular concretions of southwest, and extending from Poison Mountain to the north- dark siliceous shale andsiltstone occuras discontinuous beds west boundary of the map uea. This unit consists predomi- or isolated pods. A mid-Callovian to early Oxfordian age is nantly of massive, greenvo:.canic-lithic sandstones. Bedding attributed to this unit, based on Cordioceras sp. in the upper- is rarely evident, hut locally may be defined by subtle varia- most beds in two sections studied by Jeletzky and Tipper tions in grain size or by trains of siltstone i~ntraclasts.Loc:~lly (1968, page 16). the sandstone occurs as thick graded beds with flutes ,md 109 Plate 1-9-1. Interbedded polymict conglomerate and sandstone of the Jackass Mountain Group (Unit 3cg); north of Red Mountain, Noaxe Creek map area.

Plate 1-9-2. Arkosic sandstone turbidites of the Jackass Mountain Group (Unit 3ak); Dash Creek, Noaxe Creek map area. 110 *1 5 4. Taylor !5. Relay Creek Mountain1-, Creek 1

Lizard Formation

11 Paradise 13 Formation I; I-

Figure 1-9-3. Stratigraphic sections and correlations within the Cretaceous succession, Noaxe Creek and Warner Pass map areas. grooves that suggesta turbiditic origin. Dark grey, fine- was correlated with similar conglomerates, east of the Frr.ser grained sandstone andsiltstone are commonin theupperpart faultsystem by Jeletzky and Tipper (1968). The cx- of the unit where it underlies Unit 3f along the lower reaches glomeratescontain poorly sorted, predominantly w,:ll- of Lone Valley Creek. Several fossil collections, comprising rounded clasts of mainly granitic and intermediate volcanic ammonites, pelecypods and gastropods, were made from this rocks, together with metamorphic and foliated plutonic area. rocks, chert and clastic sed~xnentaryrocks. In the vicinity of Red Mountain, the conglomerate occurs as beds upto several UNIT 3F metres thick whichare commonly inverse to normally graded Unit 3f comprises grey to mottled greenish white-weather- and pass upward into sandlitone and siltslone (Plate 1-9.1). ing, locally crossbedded, volcanic-lithicsandstone which These conglomerates probablyrepresent channel deposits contains abundant tree branches, coal seams, full length fern within a proximal submarine fan environment. The contact fossils and other fossil plants. These sediments aretypically with underlying nonmarine to shallow-marine sandstones of arranged in fining-upward sequences with basal crossbedded Unit 3f is abrupt and may be an erosional onconformity.lhis sandstones. Sedimentary structures, facies and fossils sug- may represent an important time of uplift and subsidencz gest fluvial deposition. Unit 3f outcrops north and northwest associated with tectonism. of Red Mountain, along Lone Valley and Churn creeks south of their confluence, and asa narrow northwest-trending belt UNIT 3AK west of Poison Mountain. It underlies conglomeratesof Unit 3cg in all of these areasand sits above sandstones of Unit 3v Unit 3ak consists mainly of huff-weathering grey arkosis sandstones and gritty pebbly sandstones, together with in the northern localities; underlying rocks arenot exposed in to the Red Mountain area. minor amounts of pebble conglomerate, siltstone and shk In most olaces. its contacts with adiacent unitsof the Jackass Mountain Group are faulted. However, in the Dash Creek UNIT 3CC wherearea, the base of the unit is marked by granitic petlble Boulder tocobble conglomerate of Unit3cg is themost conglomerates,Unit 3ak apparently sit:; stratigraphic:illy distinctivelithology within the Jackass MountainGroup. It abovemassive volcanic-lithic sandstones of Unit 3v. 111 Figure 1-9-4. Distribution of Cretaceous rocks and late Cretaceous and Eocene structural features, Noaxe Creek map area.

Thesandstones of Unit3ak are predominantly come- THE TAYLOR CREEK GROUP grainedarkoses with subordinate volcanic-lithic wackes, (UNITS 4 AND 5) commonly containing hornblende, mica (biotite and minor muscovite)and magnetite.Gritty andpebbly sandstones, The Taylor CreekGroup (Cairnes, 1943; Jeletzkyand togetherwith rare beds of pebble conglomerate, contain Tipper, 1968)comprises about 2800 metres of lower to upper clasts of feldspar, quartz, granitic rocks, aphyric and feld- Albian (mid-Cretaceous) clasticrocks which outcrop south- spar-phyric intermediatevolcanics, chertand siltstone. In west of the Yalakom fault. Unbroken stratigraphic sections exposures along the Yalakom Riverand Dash Creek, the are not present anywhere in the study area; the stratigraphy sandstones comprise thick to medium-bedded turbidites with bas been erected using numerous local sections, facies and partial and complete Bouma sequenceswell displayed (Plate provenance analyses and faunal control. The most complete 1-9-2);a limitednumber of measurementssuggests that sections are shown in Figure 1-9-4. In this study, the Taylor transport was to the west and southwest. Northeast of the Creek Group is subdivided into three informal formations Yalakom River these turbidites comen upward into thick- defined principally by the composition of clastic material: bedded sandstone with pebbly seams, Elsewhere they occur the Paradise formation (Unit4a), at the base, overlain by the mostly asthick, massive orgraded sandstone beds with Dash conglomerate (Unit 4b),which is in turn overlainby the minor shale. Precisestratigraphic relationships cannot be Lizard formation (Unit 5). The dominantly marine strata of defined between structural panels, butthe entire unit belongs the Taylor Creek Group are overlain by a thick section of to an extensive submarine fan depositional system and may nonmarine conglomerates at the base of theUpper Cre- be in part a facies equivalent of Unit 3cg. taceous sequence. 112 LEGEND

SOUTHWESTOFTHE VALAKOM FAULT NORTHEAST OFTHE VALAPDM FAULT

UPPER CRETACEOUS

BATTLEMENT RIDGE GROUP

POWELL CREEK FORMATION

SiLVEROUiCK FORMATION (Unit 6) Pebble lo cobble polymiclconglom- erams and minor sandstone:mbbie lo boulder wlcanic congimeraler and volcanic sandslone

. LOWER CRETACEOUS TAYLOR CREEK GROUP 'JACKASS MOUNTAIN GROUI'

PARADISE WRMATiON (Unit&) Silklone. bhala. sandrlmns and polymictconglomsrale

THE PARADISE FORMATION(UNIT 4A) shale and minorinterbedded tuff. Northwest of Relay Morln- The Paradise formation is at least 950 metres thick, com- tain, on theeastern margin of the Warner Pass map area, the prising a sequence of siltstone, shale, thin-bedded sandstone Dash conglomerate passes upward from turbiditic sands and and conglomerate, all of which were depositedin a sub- conglomerates to fossiliferous shallow-maine tononmarine marine fan environment. The conglomerates are dominated fan-deltaic deposits. The cojnglomerates contain 70 per cent by intermediate volcanic clasts but alsocontain minor meta- chert and metachert, 25 per cent felsic volcanics, and 5 [er volcanic, plutonic andchert detritus. Sparse paleocurrent cent greenstone. Sandstones are dominate:d by chert, w!th data suggest transport was to the south and southeast. The minor sedimentary and felsic to mafic vokanic grains, and base of thissection is marked by at least 100 metres of quartz-mica tectonites. Chromite, iron oxides, garnet and concretionary shales which appear topass transitionally from aluminosilicates dominate the heavy mineral fraction. l)p- the underlyingHauterivian shales of the Relay Mountain ical of fan-deltaic deposits, the paleocumnts are scattered, Group, but this contact is not exposed. Northwest of Relay but suggesta general westward transportdirection. The Mountain thin-bedded turbidites of the upper portion of the abundance of chert, metachert, sedimentary rock fragments Paradise formation pass transitionally into the overlying and common detrital chrom:ite suggests that the source area Dash conglomerate. Similarity in composition and a north- was the locally upliftedBridge River and S:hulaps ultramzic to-south transport direction suggest that this unit may he the complexes. lateral equivalent of the volcanic-rich sediments of the Jack- assMountain Group (Unit 3v), northeast of the Yalakom fault. LIZARDFORMATION (IIm 5) The Lizard formation, at rhe top of the sequence, sharply THE DASHCONGLOMERATE (UNIT 4B) overlies the Dash conglomerate. The ba.sa1 deposits are The Dash conglomerate comprises at least 900 metres of characterized by at least 100 metres of shale; the unit passes chert-pebble conglomerate, cherty sandstone, siltstone, upward into thin to medium-hedded muscovite-ri(:h 1 I3 quartzofeldspathic sandstones and shales which were deposi- deposited in a submarine fan environment. This unit also ted in an extensive submarine fan system.In the Taylor Creek occurs in the core of a syncline, northeast of Relay Creek, on drainage theLizard formation is 850 metres thick (Section4, the Noaxe Creek map sheet. Figure 1-9-4); furtherto the west, near Relay Mountain, it is The upper member of the Silverquick formation includes about 500 metres thick. The sandstones arerich in quartz (28 similarbraided river deposits but the conglomeratesare to 41 per cent), plagioclase (23 to 35 per cent), intermediate dominated by basic to intermediate volcanic clasts that vary to felsic volcanic clasts (14 to 31 per cent) and minor meta- from cobble to boulder size. Although many beds are com- morphic clasts; detrital chert is almost absent. Metamorphic posed exclusively of these lithologies, they are clearly inter- clasts, 2.5 per cent muscovite and minor garnet, indicate a bedded with chert-rich conglomerates typical of the lower partial source of schistose metasedimentary rocks. Paleo- member. The upper member is only exposed in the Taylor currents are to the northeast everywhere in the basin; mea- Creek area on the Noaxe Creek map sheet, where it grades surementswere taken from both overturnedand upright upward into volcanic breccia of the overlying Powell Creek panels.These shales and turbiditesrepresent a rapid and formation. It is correlated with the dominantlyvolcaniclastic widespread deepening of the basin that was probably tec- rocks of Unit 6a in the Warner Pass map area (Glover and tonically controlled. The Lizard formation is sharply over- Schiarizza, 1987). lain by predominantly nonmarine conglomerates of the Sil- verquick formation. THEPOWELL CREEKFORMATION (UNIT 7) THE BATTLEMENT RIDGE GROUP This formation is equivalent to Units 6b and 6c, in the (UNITS 6 AND 7) Warner Pass map area (Glover and Schiarizza, 1987); the proposed type section,northwest of Powell Creek, has a total The Battlement Ridge group is proposed as an informal thickness of 1550 metres, but the top is not exposed. It name for sedimentary, volcaniclastic and volcanic rocks of comprises dominantly volcanicbreccia and lapilli tuff of latest Albian (?) (mid-Cretaceous) to late Cenomanian (Late andesitic to basaltic composition, intercalated with finer Cretaceous) age,previously assigned to theKingsvale Group grained tuff, basaltic to andesitic flows and epiclastic sedi- (Rice,1947) by Tipperand Jeletzky(1968). Thorkelsen ments. It can be locally subdivided into a lower massive unit (19851, working in the type area near Kingsvale, south of and an upper bedded unit; the latter is dominated by andesitic Merritt, has shown that rocks previously attributed to the lahars and epiclastic sediments. Theseunits are best exposed Kingsvale Group are partof the SpencesBridge Group, based in the vicinity of Powell Creek and Battlement Ridge in the on field relationships and radiometric age determinations. Warner Pass map area, but also occur northeast of Relay This group comprisesa sequence of intercalated andesitic to Creekon the Noaxe Creekmap sheet. Elsewhere in the rhyolitic lavas and clastic rocks of mid-Cretaceous age. It present study area the lower and upper parts of the Powell may, in part,be time-equivalent to theBattlement Ridge Creek formation are undifferentiated. Group of this report, butis separated from the study area by major tectonic boundaries such as the Fraser and Yalakom VOLCANIC ROCKS OF PROBABLE fault systems. EOCENE AGE (UNIT8) The Battlement Ridge group is informally subdivided into This unit comprises predominantly andesites to rhyolites; a clastic unit at the base, theSilverquick formation (Unit 6), it extends from Red Mountain to the northeastern comer of and a gradationally overlying volcanicunit, the Powell Creek the maparea, where it attains a thickness of about 800 formation (Unit 7). The base of the group is defined by an metres. These rocks lieunconformably above conglomerates angular unconfomity that separates it from the underlying of the Jackass Mountain Group (Unit 3b). They comprise Mesozoicstrata; this relationship is well exposedin the mainly reddish brown-weathering, platy to massive, aphyric Warner Pass map area(Glover and Schiarizza, 1987), and its andesitic to dacitic flows; they are locally vesicular and/or presence is inferred at the base of the group in the Taylor amygdaloidal and are columnar jointedin places. Flow brec- Creek basin, on the Noaxe Creek map sheet (Figure 1-9-4). cias and/or brick-red regolith zones locally mark flow con- tacts. Massive andesite flows at the baseof the succession are THESILVERQUICK FORMATION (UNIT 6) porphyritic,and contain phenocrysts of pyroxene, The Silverquick formation comprises two members; the hornblende andplagioclase. Discontinuousunits of light lower member is composed of poorly stratified, clast-sup- grey to white-weathering flow-banded rhyolite, commonly portedand locally crossbedded pebble to cobble con- with phenocrysts of quartz and/or feldspar, occur at three glomerates with minor sandstone interbeds (lessthan IO per different stratigraphic levels within the Red Mountain suc- cent). Sandstones are commonly maroon weathering. Finer cession. The most extensive unit is locally more than 150 grained intervals contain abundantstick and leaf fossils.The metres thick. The rhyolites includesignificant zones of flow conglomeratescontain mainly chert clasts, together with breccia, vesicular glass and glassy breccia. Siliceous sinter sedimentary and intermediate volcanic clasts, and a minor (?) deposits displaying botryoidal growth structures occur proportion of metamorphicand plutonic clasts. Paleo- locally. currents suggest derivation from the east. This member at- Sedimentary rocks are uncommon in the Red Mountain tains a maximum thickness of I500 metresin the Taylor succession. They comprise lensesof rusty brown and chalky Creek area; here, these rocks areinterpreted as braided river white-weathering thin-bedded volcanic sandstone and silt- deposits. To the northwest,in the northeast partof the Warner stone which range up to several tens of metres thick. They Pass map area, this member is thinnerand was probably occur along rhyolite-andesite contacts, or as lateral equiv- 1 I4 alents of rhyolite. Volcanic conglomerate outcrops at one volcanics of the Powell Creekformation (Unit 7) of this locality, 2.5 kilometres northeast of Red Mountain summit, report, and to he in part Early Tertiary in age. This will be where it separates a rhyolite unlt from underlyingandesite. It tested by potassium-argonage determinations on sampler. comprisesunsorted, angular dacitic to andesiticvolcanic collected from both Warner Pass and Noaxe Creek map arcas clasts, up to 80 centimetresin size, within a friable siltstone during the past summer. matrix. North-northeast-trending dykes of andesite and fel- Hornblende feldspar porphyry also occurs in the south- site are locally common. Dykes of the same orientation and eastern comer of the map area,where it cuts ultramafic rocks plugs, composed of quartz-biotite-hornblende-feldspar por- of the Shulaps complex, mainly east and southeast of Ilig phyry, appear to grade into flow-handed rhyolite in places. Dog Mountain. These porphyries locally contain hlotite 5.nc. The Red Mountainvolcanics are not dated. Theyare grade into equigranular diorite and quartz diorite (Leech. assigned an Eocene age on the hasis of their unconformable 1953). Weakly sheared hornblende feldspar porphyry dykes relationship to underlying Jackass Mountain Group rocks, from which a sample was taken for radiometric dating, also and their lithologic similarity to volcanic rocks to the north occur locally within theYalskom fault zone, east of Blg E'oE; and northeast whichhave yielded several Eocene radiometric Mountain. ages (Mathews and Rouse, 1984). These Eocene volcanics Light grey to white-weatheringporphyritic bodies con-. host the Blackdome epithermal gold deposit10 kilometres to taining variable proportions, of feldspar, hornblende, hio:ite the north. and quartz phenocrystsintrude the Eocene(?) volcanic rock!; at Red Mountain. Similar porphyries oc,:ur at Big Sht:ep MIOCENE PLATEAU LAVAS Mountain, where they may he associated with felsic extrusivt: rocks (Leech, 1953), and as several stocks and plugs north of (UNIT 9) Tyaughton Creek. These porphyritic bodies are commonly Flat-lying plateau hasalts of Unit 9 unconformahly overlie carbonate altered, and locally contain zonesof argillic altera- older rocks in the western part of the map area. The hasalts tion. They are probably Eocene in age, based on their clost: occur asmedium to dark grey, commonly rusty brown- association with Eocene (?:I volcanic rocks at Mount Shhi weathering flows intercalated with minor amounts of vol- (Glover and Schiarizza, 1987) and at Red Mountain. S2m. canic breccia and volcanicconglomerate. They outcrop most plesfrom these two areas, and of si~nilarporphyries extensively along the western edge of the map area, north of elsewhere in the map area, were collected for radiomerir: Relay Creek,where they overlapthe Yalakom fault and dating. adjacent rock units alongan erosional surface with a shallow Intrusive rocks in the vicinity of Poison Mountain conlist regional dip to the north. The unit is ahout 350 metres thick of hornblende feldspar porphyry and hornblende-biot~te- in this area.The hasalts cap several ridges to the south, feldsparporphyry. They occur asthree sep,uate stocks which including Relay Mountain, where 300 to 350 metres of outcrop south, southwest a~ndwest of the summit. A foLrtll volcanic flows are exposed. stock, which is dominantly feldspar-phyric. occurs 3 k lo- metres to the east. Porphyrly copper-gold ~nineralizationDC- INTERMEDIATE TO FELSlC curs within and adjacent to the outer portion of the sorlth- INTRUSIVE ROCKS western stock, where hioti1.e partially replaces hornblende. Severalpotassium-argon dates obtained on hiotite and Porphyritic to equigranular intrusiverocks, ranging in hornblende from the mineralized stockgin: ages of 57 and 51) composition from diorite to granodiorite,occur as small Ma (Late Paleocene to Early Eocene) (W.J. McMillan, per. stocks, plugs and dyke swarms distributed sporadically sonal communication, 198'7). through the map area. Mostof these are EarlyTertiary and (?) Late Cretaceous in age. A smallstock, composed of equigranularhiotite- hornblende quartz dioriteand granodiorite, occurs along the STRUCTURE southern boundary of the map sheet,and outcrops mainly to the west and south of'Eldorado Mountain.It intrudes thefault OVERVlEW contact between the Taylor Creek Group on the east and The Yalakom fault divides the map into two parts. North- Cadwallader Group on the west. An age of 63 Ma (Early east of the fault relatively widely spaced northwest and north- Paleocene) has recently been obtained by potassium-argon east-trendingfaults dominate the map pattern in an area dating of biotite from the stock (K.M. Dawson, personal mosty underlain by gent1.y dipping sandstones and cmm- communication, 1987). glomerates of the Jackass Mountain Group.To the southwest, Hornblende feldspar porphyry occurs asdyke swarms and an intricate network of northwest-trend:lng anastamosing small plugs within Units 5 and 7 between Relay Creek and faults, some of which merge with the Yal!akom fault, sepa- the Yalakom fault. It comprises variable proportions of rates most of the map units into relatively small, structurally hornblendeand feldspar phenocrysts, up to several milli- discrete, lenticular blocks. Bedding attitudes are gener;ill:y metres in size, withina massive, grey aphaniticmatrix. steep to vertical, especially close to high(-angle faults, ,and Carbonate and propylitic alteration is common within the their strikes are commonly to the northwest, hut northeast porphyry and adjacent countryrocks. Theserocks are similar trends occur locally in fault slices, probably due to rotalion to hornblende feldspar porphyries which outcropextensively during strike-slip movement. Small-scale .folds only occur in in theWarner Pass map area (Unit A of Gloverand the less competent units and are generally disharmonic; lold Schiarizza, 1987). There, they were thought to he related to axes vary in plunge hut usually trend toward the northwst. 1 I5 This map pattern,together with the nature andorientations Several northeast-trending faults were mapped in the of small-scale structures, kinematic indicators and the gen- southeastern part of the belt, where they are inferred on the era1 lack of any penetrative deformation, indicate that Meso- basis of abrupt truncations of lithologic units or changes in zoic rocks in thearea undenventa protracted period of major facing direction. Faults of this group were also observed in dextral wrench faulting under brittle conditions at high outcrops along Churn Creek. in the north-central part of the crustal levels area. The orientation of these faults is that expected for The mid-Cretaceous deformational event, documented by antithetic left-lateral strike-slip faults related to right-lateral structures in rocks of the Taylor Creek Group and older units displacement along the Yalakom fault.Left-lateral move- in the Warner Pass area (Glover and Schiarizza, 1987), is ment was demonstrated locally along minor faults of this obscured by the later dextral wrench faulting in the present orientation northeast of the Yalakom River. study area. However, there is some evidence for pre-middle An east-trending syncline occurs withintheJackass Moun- Jurassic deformation in the older rocks of the Tyaughton tain Group north of the Shubdps ultramafic complex, where it Group, Cadwallader Group and Bridge River complex. is outlined by exposures of Unit 3akturbidites along the Yalakom River; this fold is apparently truncated to the west POST-MIDDLE CRETACEOUS STRUCTURES by the Yalakom fault. An easterly trending syncline is infer- red from opposing dip andfacing directions within Unit 3ak THEYALAKOM FAULT on either side of Dash Creek. Its probable extension to the east of a northwest-trending fault was mapped in rocks of The Yalakom fault has a length of at least 230 kilometres; Unit 3f along Chum and Lone Valley creeks. These folds estimates of dextral strike-slip offset along the fault range may comprise part of a right-handed fold set (Campbell, from 80 to 190kilometres (Tipper, 1969).Monger(1985) has 1958; Wilcoxet al., 1973) related to dextral movement along correlated the Yalakom and Hozameen faults across the the Yalakom fault. Fraser fault system, to which he attributed 70 to 90 kilo- Rocks of Units 3 and 8 are bounded to the west by the metres of dextral strike-slip displacement that occurred dur- north-northwest-trending Red Mountain fault. This fault ap- ing Late Cretaceous and/or Early Tertiarytime. Potter (1983, parently truncates or offsets a number of northeast-trending 1986) proposed that the Yalakom and Fraser faults belongto faults. One of these earlier faults, which separates Units 3cg the same system and suggested that significant dextral dis- and 3ak. north of Poison Mountain, can be matched with a placement occurs on both from 40 to 45 Ma. similar fault on the opposite side of the Red Mountain fault, In the map area the fault is poorly exposed, but its trace east of the upper Yalakom River. If this correlation is valid indicates that it is steeply dipping. For much of its length it is then the Red Mountain fault may have 4 kilometres of appar- the locus of a narrow discontinuous zone of selpentinized ent right-lateral displacement along it. peridotite. The most compelling evidence for transcurrent Bedding attitudes in the volcanic succession of Unit 8 at movement along the fault derives from the presence of con- Red Mountain are generally shallow dipping. The structure trasting mid-Cretaceous successions oneither side, a feature within these rocks is dominated by north-northeast-trending that waspointed out by previousworkers (forexample, extensional faultsand fracturesthat are probably Eocene and/ Kleinspehn, 1982, 1985). Kinematicindicators such as fibrous mineral growth and slickensides along and adjacent or younger in age (Figure 1-9-51, These may have developed in conjunction with dextral wrenchfault along theFraser fault to the fault, northeast of Mud Creek, indicate that at least system (Mathews and Rouse, 1984; Price et al., 1985). some of this movement was right lateral in nature. North of Red Mountain an easterly trending fault is infer- Volcanic rocks of the Powell Creek formation, truncated red separating sandstones of Unit 3 from volcanic rocks of by the fault in thenorthern part of the area, providea Unit 8 which outcrop along the northern edge of the map probable upper limit of Cenomanian (earliest Late Cre- area. This probably represents a vertical displacement of a taceous) for transcurrent movement along the fault. Plateau few hundred metres, hut the fault is not exposed and itsdip is hasalts of probable Miocene age,which truncate the fault in unknown. This fault was interpreted as part of the Hungry the Dash Creek area, currently provide the only lower con- Valley thrust by Tipper (1978), andwas inferred to extend to straint in the Noaxe Creek map area.However, forthcoming the west, across Churn and Dash creeks. Here,a northwest- potassium-argon radiometric dates of hornblende from por- trending fault that separatesthe Jackass Mountain Group phyry dykes, emplaced along thefault zone southwest of the from the Powell Creek formation is closely constrained by Yalakom River, may provide a minimum age for the early outcrops along thesecreeks; highly fractured rocksof Unit 3 history of movement. are cut by northwest-striking, predominantly steeply dipping fault surfaces which locally display shallowly plunging STRUCTURESNORTHEAST OF THE slickensides. These features indicate strike-slip movement YALAKOM FAULT along this fault zone rather than thrusting, as proposed by Tipper. In this area, the structural pattern is dominated by north- west and northeast-trendingfaults and by east-trending folds which are probably related to dextral movement along the STRUCTURESSOUTHWEST OF THE Yalakom fault system. Around Red Mountainfaults that trend north-northwest to east-northeast may be younger YALAKOMFAULT structures related to Eocene and/or later dextral movement Three majornorthwest-trending faults of probable along the Fraser fault system. regional extent that occur southwest of the Yalakom fault can 116 he traced acrossthe map area: the Relay Creek fault, the Mountain Group along the fault from Noaxe Creek to Relay Castle Pass fault andthe Tydughton Creek fault. To the Creek (Figure 1-9-6). The .timing of movement along this northwest these faults strike subparallel to the Yalakom fault fault is poorly constrained. hut the Marshall Creek fault, its hut all swing sharply to the south at about the latitude of the correlative in the Bridge River area, displaces probattle Shulaps ultramafic complex. Thereis evidence that these are Eocene volcanic rocks and is itself truncated by the Mission wrench faults; aminimum right-lateral offset of 8 kilometres Ridge pluton (Potter, 1983), biotite from which has yielded a along two of them is proposed potassium-argon date of 44 Ma (Woodsworth, 1977). Thus, this part of the fault system was active in the Middle Eocene. The Relay Creek Fault The Relay Creek fault has been traced along Relay Creek The Castle Pass Fault from east of Big Creek on the Warner Pass map sheet (Glover This fault was traced from near Gravey,ard Creek, in the etal., 1987). to the southeast, across the present study area, Warner Pass map area (Glover el al., 1987) to the southeast, from where it probably merges with the Marshall Creek fault into the Noaxe Creek map area,where it forms the northe,lst (Roddick and Hutchison, 1973; Woodsworth, 1977; Potter, boundary of theprincipal :xposures of Tyaughton Group 1983, 1986). If this correlation is valid, it would give the rocks. South of Tyaughton Creek it truncates rocks of the Relay Creek - Marshall Creek fault system a total length of at Cadwallader Group on the west; east of the fault a 5-ki.o- least 145 kilometres to its truncation by the Fraser fault metre-wide. overturned, ear,terly dipping panel, comprising system, south of Lillooet (Potter, 1986).In the northwest part rocks of the Taylor Creekand Battlement Ridge groups, of the Noaxe Creek map areathe Relay Creek fault separates provides evidence for post-Cenomanian large-scale folding steeply dippingto vertical, northeast-facing strata of the of rocks in this area. A recmt potassium-argon radiometric Taylor Creek Group on the northeast from older, generally age determination of 63 Ma (Paleocene) om biotite from {he southwest-facing strata of the Relay Mountain Group on the Eldoradostock (K.M. Dawson, personal communication, southwest. 1987), which truncates the Castle Pass fault along the souk A minimum estimate of 8 kilometres right-laterdl offset is em margin of the map area, provides a lower age limit .:or obtained by using the truncation of the Upper Jurassic Relay movement along the fault.

Fipe 1-9-5. Tertiary structures. Red Mountain area; Noaxe Creek map area 117 A complex array of upwardly fanning high-angle reverse suggestsa post-Cenomanian age.This is contraryto our faults, similar to that described by Wilcox et al. (1973), is previous interpretation of largely vertical movement along rooted along the Castle Pass fault in the western part of the this section of the fault, and furtherwork is required in order map area (Umhoefer and Garver, 1987, in preparation) and to test these hypotheses provides evidence for transcurrent movement along the ma- jor fault. However, the magnitude of displacement is Other Post-middle Cretaceous Structures unknown. Southwest of the Yalakom Fault North-northwest-trendingfaults of shorter strikelength The ’Qaughton Creek Fault merge with or are truncated by the major faultsand are This fault is poorly exposed for most of its length from east distributedthroughout the intervening panels. In general, of Lorna Lake, in the Wamer Pass map area (Glover et al., these faults juxtapose progressively younger rocks to the 1987) to Spruce Lake in the southwest part of the Noaxe west. Their orientation relative to the major faults matches Creek map area, from whereit apparently swings tothe south that of early-formedsynthetic dextral strike-slip faults (Cairnes, 1943; Tipper, 1978). The Tyaughton Group occurs (Wilcox et al., 1973) which is, in general, supported by mostly on thenortheast side of the fault, but an isolated measurements of fibrous mineralgrowth and slickenside klippe of rocks attributed to this unit south of the fault near orientations along them.However, many of these faults show Lorna Lake (Glover and Schiarizza, 1987) indicates aright- evidence of late dip-slip movement. lateral offset in the order of IO kilometres (E to B’, Figure In the panel northeast of the Relay Creek fault, bedding 1-9-6); supportingevidence is provided by matchingthe attitudes outline a complex, northwest-trending, doubly truncations of an older, northeast-trending fault on the plunging syncline in rocks of the Silverquick formation(Unit Wamer Pass map sheet, which gives a right-lateral offset of 6),which are surroundedby and in fault contact with rocks of 8 kilometres (C to C’ , Figure 1-9-6). the Powell Creek formation (Unit7). This contact is defined The timing of movement along this fault is unknown, hut by northwest-trending faults that are subparallel to the possible transcurrent offset of the Powell Creek formation Yalakom and Relay Creek faults on the northeast and south- along its western extension in the Wamer Pass map area, west limbs of thefold. However, alongthe northwestern

Figure 1-9-6. Robahle piercing points and resulting right-lateral offsets along the Relay Creek and Saughton Creek fault zones, Noaxe Creek and Warner Fass map areas. 118 closure of the syncline, where rocks of Unit 7 apparently season. The principal occurrences of this type elsewhere on structurally underlie rocksof Unit 6, their contact may repre- themap sheet are theupper Relay Creek claims and the sent an early thrust that was subsequently folded. Theoutline Poison Mountain deposit, described below. of this syncline is reflected on a broader scaleby stratigraphic and structural facing in the older rocks of the Taylor Creek UPPER RELAYCREEK Group to the northeast and southwest. This fold probably Alteration and mineralization upp:r Relay Creek are formedbefore or duringthe early stages of strike-slip along associated with a swarm of sills, dykes and smallplugs which faulting. intrude volcanic and sedimentary rocks (of Units 5 and 7. Interest in the area dates back to 1970 wbcn it was explored PRE-MIDDLE CRETACEOUS STRUCTURES for porphyry copper-molybdenum mineralization. More re- In the southwest part of the map area, excellent exposures centexploration by ConsolidatedBarrier Reef Resources and the well-defined internal stratigraphy of the Tyaughton Ltd. (now MFC Mining Finance Corporation) and by Esso Group permit detailed mapping of thrust faults, which are Minerals Canada, the present operator, has concentrated on folded about axes with quite variable orientations; thesefolds the area’s gold potential. Cubonate alteration is widespr:ad are, in turn, truncated by north-northwest-trendinghigh- within both intrusive and country rocks; if:is locally accom- angle faults, some of which have dextral strike-slip along panied by chlorite-epidote alteration, silicification and minor them (P.J. Umhoefer, personal communication, 1987). The clay alteration.Disseminated pyrite and/or pyrrhotite are complexstructural pattern that results impliespolyphase common within and adjacent to theporphyries, and arc deformation. Rusmore (1987) concluded that two phases of locally accompanied by minor amounts of chalcopyrite, mo- folding existed in rocks of the Cadwallader Group to the lybdenite,arsenopyrite and sphalerite. More intense south. Similarly,Potter (1986), working to the southeast, pyritization is commonly a!;sociated with zones of silicifica- found evidence for twophases of deformation in rocksof the tion. Present interest is focused on the northwestern end of BridgeRiver complex. These workerspropose that these the altered belt,where gold values of 1 to IO grams per tonne older rocks underwent a major deformational event in mid- have been obtained from niurow quartz-carbonate and chal- Jurassictime (Umhoefer et a[., 1987). Small-scalenorth- cedony veins which occur in association with broader zones easterly directed thrust faults observed in the Bridge River of elevated gold values in the range of 50 to 300 parts per complex at the confluence of Noaxe and Tyaughton creeks billion, and anomalously high values of arsenic (Dawson, may also belong to this phase of deformation. However, the 1981, Assessment Reports 9876, 11037). The narrow zones complexity of structures typically associated with zones of of higher grade mineralizatl.on reported to date are of lim. ted major strike-slip faulting, which the Noaxe Creek map area extent. undoubtedly represents,precludes thisconclusion at this point in our study. POISONMOUNTAIN The Poison Mountain copper-molybdenum-gold porphyry MINERAL OCCURRENCES deposit occurs on southwestthe slopesof Poison Mountain, .3 kilometresnortheast of ths: Yalakom fault. The fist Me Mineral occurrences in the Noaxe Creekmap area fall into claims were staked in 1935, after placar gold had been two distinct groups: (I) generally low-grade gold and base discovered along Poisonmount Creek in 1932 (Minister of metal occurrences withpyrite, minor arsenopyrite and/or Mines Annual Reports, 1933, pages A186 to A191; 1946, pyrrhotite, associated with granitic intrusive rocks; and (2) pages AI01 to A102). Diamond drilling and trenching, ,:a~- minorcinnabar, stibniteand/or scheeliteoccurrences,associ- ried out by various companies between 1956 and 1971, ated with fault zones. delineated a mineral inventory in the ortler of 175 million tonnesaveraging0.33percantcopper,O.O15percentmolyb- LOW-GRADE GOLD ANDBASE METAL denumand 0.3 gram per tonne gold (Seraphim ;and OCCURRENCES Rainboth, 1976). Additional drilling was carried outby Lcmg Nearly all these occurrences appearto k small, with the Lac MineralExploration Ird. in 1979 and 1980 (Brown, exception of PoisonMountain, where significant chal- 1981, Assessment Report 8874), but no updated reserves copyriteand molybdenite mineralization, with associated were published. low gold values, occurs in a porphyry setting. Many of these Mineralization at Poison Mountain is associated with :wn prospects are hosted by carbonars andlocally argillic-altered granodiorite to quartz diorite stocks whit-h intrude Jackass granitic stocks and dykes that aregenerally porphyritic. Mountain Group sedimentary rocksof Unit 3ak. The stacks Some of the larger stocksexhibit chlorite-epidote alteration. compriserelatively unaltered cores of hornblendepla- Many of thedykes are structurallycontrolled by north- gioclase porphyry which .grade outwards into biotite ]]la- westerly trending faults. These mineral occurrences appear gioclase porphyryin whichthe biotite is an alteration product to range from an epithermal setting, for example,Big Sheep of hornblende. The highest grade minaralization occurs Mountain, to a porphyry setting, such as Poison Mountain. within the biotite-altered border phases and adjacent biotite The associated intrusive rocks are probably Tertiary in age. hornfels. It consists rnainl:, of pyrite, chilcopyrite, molyb- The Blue Creek occurrences, Big SheepMountain andshow- denite and bornite, whichCECUT as disseminations and fracc- ings near Eldorado Mountain appear to be of this type ure fillings, and in veins a.ssociated with quartz (Seraphim (Cairnes, 1943; Dawson, 1982) but fall within the southern and Rainboth, 1976). Calciteand gypsum also occur as part of the map sheet, not covered during the 1987 field hydrothermal minerals, and pyrite, together with magnetite 119 and hematite, formsan irregular halo around the mineralized western margin of a panel of serpentinized peridotite and zone. Chlorite-epidote alteration occurs sporadically within vanable lithologies of the Bridge River complex. Narrow, Jackass Mountain Group rocksfor several kilometres around carbonate-altered feldspar porphyry dykes,that occur locally the deposit, but is not distinctlyconcentrated around the along the fault zone, may be related to these mineral occur- mineralized porphyries.Intrusion, potassic alteration and rences. These prospectsinclude theTungsten King andTung- mineralization at Poison Mountain is about 58 Ma in age sten Queen,where scheelite was discovered in 1939and (Paleocene)as indicated by potassium-argon dating of which produced a small tonnage of high-grade ore over the hornblendes and biotites from the mineralized system (W.J. following two years (Cairnes,1943). The property was inter- McMillan, personal communication, 1987). mittently explored for tungsten and antimony up to 1984. The showings comprise scheeliteand stibnite in a stockwork MERCURY, ANTIMONY AND TUNGSTEN of quartz and calcite veins that cut a carbonatealteration zone OCCURRENCES containing mariposite. Previous workers have thought that Cinnabar, stibnite and/or scheelite mineralization is found the protolith was limestone within lenses in the Bridge River associated with some of the major fault zones in the area. complex. However, the mineralized zone is on strike with Most showings are hosted by orange to rusty weathering partially carbonatized serpentinite, and, although limestone carbonatized and silicified serpentinite that locally contains lenses do occur nearby, there is no indication of skarn de- up to 5 per cent greenfuchsitic mica, mainly between Noaxe velopment. Apex, a mercury showing in a similar setting, and Mud creeks (Figure 1-9-7). They are located along or occurs northeast of Quartz Mountain, and is hosted by car- close to a north-northwest-trending fault zone that forms the bonatized and silicified serpentinite withinthe Yalakom fault

Figure 1-9-7. Mineral occurrences and alteration zones, Noaxe Creek map area. I20 zone. There are no goldvalues known to be associated with eastern part of the map area, this later regime produced these showings. thenorth-northwest-trending Red Mountain fault and The Manitou or Empire Mercury mine is located at the north-northeast-trendin::-tensional faults and fractures confluence of Mud Creek with Tyaughton and Relay creeks together with minor faults that match the orientation!; (Figure 1-9-7). Theearliest record of underground workings expected for synthetic and antithetic strike-slip faults is 1931; up to the endof 1940, twenty flasks of mercury had been produced (Cairnes, 1943). A substantial program invol- ACKNOWLEDGMENTS ving refurbishing of some underground workings and a 7000- The authors would like to thank Drs.Howard Tipper and metre percussion drilling program was completed by Empire Terence Poulton of theGeological Survey of Canadafor Mercury Corporation Ltd. in 1966 (Minister of Mines An- providingfossil identifications, together with theircontinuetl nual Report, 1966). This property was not visited, but cin- advice and support. We are grateful to Dr. Margaret Rusm,m nabar was reported by Cairnes to occur along north-north- of Occidental College, Los Angeles, for her guidance in the west and east-trending shear zones in volcanic rocks of the field through rocks of the Cadwallader Group. We thank Dr, Bridge River complex. The Silverquickmercury showing Neil Church of theBritish Columbia Geological Suriey (Minister ofMines, Annual Report,1964) south of Branch for showing us thrcsugh the geology of the north:nl Tyaughton Creek occurs along a northwest-trending shear part of the Bridge River mining camp. Discussions with Dr. zone in conglomerates of the Silverquick formation. No gold Lawrence Dick of Chevron Minerals Limited have proved values have been reported from these mercury, antimony and extremely useful; he hashe:lped us to question the economic tungsten showings. implications of this regional study, forwhich we are gratelul. Paul Umhoefer of the University of Washington has made a considerable contribution to our understa~ndingof the swat- TECTONIC IMPLICATIONS igraphy and structure in the: Tyaughton aoi Relay Mountain Much of the NoaxeCreek maparea is underlain by rocks of groupsand their tectonic implications. .lanet Riddell :mi Cretaceous age; this reportdocuments thecharacter and Dorothy Payne are gratefully acknowledged for their tena- distribution of lithologic units in thissuccession, and,in part cious assistance in the field and for their independent map- establishestheir internal and external structural and strat- ping contribution, without which we would still be in the igraphic relationships. The tectonic implicationsof this study bush. are summarized as follows: (I) The thick sequence of Taylor Creek Group sediments REFERENCES represents a period of major tectonic activity during the Brown, R.F. 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