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-lateral strike-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- Figure 1-9-2 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-related rocks 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 middle Jurassicsediments 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 rarely traceable 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.