TREK Mapping Project Year 2: A Structural Framework for the northern Interior Plateau J.J. Angen1, C.J.R. Hart1, J.M. Logan2, R. Kim1,M. Rahimi1 1Mineral Deposit Research Unit, The University of British Columbia, Vancouver; 2Consulting Geologist 126°W 125°W 124°W 123°W ( ( a) Preliminary Bedrock Geology of the TREK Area IV. CRETACEOUS DEFORMATION b) ( ( 4 a) 4 ( Quesnel WMC4 4 ( ( 4 350000 E 375000 E 400000 E 425000 E Stikine ( The Jurassic strata south of the Tatuk Fault were deformed during ENE- ( ( Terrane 125°30'0"W 125°0'0"W 124°30'0"W 124°0'0"W 6000000 4 ( ( Terrane 4 4 Francois !( & ! VOLCANIC AND SEDIMENTARY ROCKS OTHER FEATURES ( 5Prince 4 !(!(NIT!(HI MOUNTAIN Vanderhoof 54°0'0"N and WSW-vergent fold and thrust deformation (Figure 5a). This is likely 4 4 Lake ! ( 4 !( !(!( Miocene to Holocene City ( 4 !(!( 4 !( !( 4 4 !( 54°N Plutonic 4 4 4 George Anahim Volcanics ( ( Pinchi Fault Road Fraser-Straight Creek Fault 4 4 4 !( 4 !( !( !( Basanites to basaltic trachyandesites and trachytes 4 4 ( River related to the 700 km long fold and thrust belt that anks the east side of ? ( 4 450000 E 4 4 4 4 4 Miocene to Pliocene 4 4 ( Lake 4 4 4 4 4 ( 5975000 N Cabin 5975000 N 4 4 Chilcotin Group 4 4 4 I. INTRODUCTION 4 Lake 4 4 4 4 the Coast Belt (Rusmore and Woodsworth, 1991; Evenchick et al., 1991; VMC 4 4 Olivine basalt lava flows ( 4 4 4 4 4 4 Mineral Occurrences 4 4 4 4 4 GF 4 Eocene to Oligocene 4 4 4 !( Tatuk Fault ( 5950000 4 4 4 4 4 Porphyry Cu-Au: vein, breccia Bobtail Shear Zone 4 ") 4 4 4 The Targeting Resources through Exploration and Knowledge 4 4 Endako Group !( Schiarizza et al., 1997; Rusmore et al., 2000). Field structural evidence and 4 4 4 4 Porphyry Mo (Low F- type) 4 4 4 4 4 ( 4 Basaltic andesite and andesitic lava flows )" 4 4 4 4 4 4 4 Epithermal Au-Ag-Cu: high sulphidation 4 *# 4 4 4 4 (( 4 4 ") 4 4 4 )" 4 ") 4 Eocene 4 Epithermal Au-Ag: low sulphidation 4 4 project is a multidisciplinary project aimed at bringing 4 4 ")!(") 4 HOLY CROSS 4 ' geophysical anomalies exhibit a curvature from NNW-SSE to WNW-ESE 4 ( ") 4 ") 4 Ootsa Lake Group Subvolcanic Cu-Ag-Au (As-Sb) 4 4 Stikine 4 4 53°30'N 4 4 4 XW 4 Rhyolite to andesite flows and volcaniclastic rocks Polymetallic veins Ag-Pb-Zn+/-Au 4 ( 4 4 4 4 4 Frank Lake ") 4 4 XW Carbonate-hosted disseminated Au-Ag ( 4 together a variety of datasets in order to improve our ( 4 Upper Cretaceous 4 !( 4 +$ 4 4 pluton with proximity to the Tatuk Fault (Figure 2; Figure 3b,c). The Terrane 4 4 !( 4 Cu skarn 4 4 4 4 4 4 Kasalka Group +$ 4 4 Kenney Dam FSR 4 Fe skarn 4 4 4 4 4 4 4 4 Hornblende andesite #* 4 4 Ultramafic-hosted asbestos 5900000 understanding of the geological framework and mineral 5950000 N 4 4 5950000 N 4 predominantly volcanic and plutonic rocks to the north of the Tatuk Fault 4 Crystal-lithic tuff 4 4 Cache 4 GF 4 Lignite 4 4 c) ") 4 Vitric tuff 4 Volcanic redbed Cu 4 4 4 ( 4 4 4 4 4 4 4 4 Grizzly ( 4 Creek 4 4 Flow-laminated rhyolite potential of the Interior Plateau. In particular, little is known 4 pluton 4 4 appear unaected by the mid-Cretaceous deformation so it behaved as a 4 ( 4 ( 4 4 Undifferentiated andesite to rhyolite flows and volcaniclastic rocks ") 4 123°30'0"W 4 4 4 53°N 4 4 ( Terrane 4 Lower Cretaceous 4 4 4 4 4 Figure 5: a) Example of fold and thrust 4 ") 4 4 4 4 about the structural framework of this region. This region 4 ") 4 4 4 Skeena Group 4 sinistral fault to accommodate the shortening within the basin. The 4 4 4 4 4 ( 4 4 4 4 4 4 4 Yalakom Fault 4 4 4 Chert- and quartz-rich sandstone and conglomerate deformation in thin bedded mudstone and 4 4 4 4 ( 4 4 4 4 475000 E 4 4 4 4 Upper Jurassic 4 4 4 4 4 4 encompasses southern Stikine terrane, Cache Creek terrane, 4 ( 53°30'0"N ") 4 Nazko-Redstone belt, along the eastern margin of this fold and thrust tu of the Entiako Formation, looking 5850000 4 4 4 4 4 4 4 Nechako Formation 4 !( 4 ( ( 4 4 4 ( 4 4 ( 4 4 4 4 Pyroxene- and hornblende-phyric basalt 4 southeast; b) Bedding measurements within 4 4 4 4 ( Knewstubb Lake 4 4 4 Bobtail Shear Zone 4 Natalkuz Fault 4 ( 4 Cadwallader terrane, and several metamorphic complexes ( 4 ( 4 Middle and Upper Jurassic 4 belt, is interpreted to have formed similar to the Sustut Basin to the north. 5925000 N 4 4 4 4 4 ") 20 km of the Tatuk Fault; c) Bedding ( 4 4 Bowser Lake Group ( ( 4 4 Nechako Reservoir 4 4 ( Tatuk Fault 4 ( 4 4 PICKLE Chert pebble conglomerate, sandstone, siltstone and mudstone 4 Cadwallader( 4 measurements more than 20 km from the 4 4 4 ( 4 (Figure 1). These are extensively mantled by 4 4 TLMC ? 4 *# ( ( Deformation continued at least until the Campanian as indicated by 4 ( Stikine terrane 4 LIESEGANG 4 Tatuk Fault. 52°30'N ( Terrane( ( 125°30'0"W 4 ( CHU Lower and Middle Jurassic 4 4 !( 4 Sinkut Detachment volcanosedimentary overlap assemblages and thick glacial ( ( ( Hazelton Group ") !( 4 palynology of well logs showing Albian to Cenomanian strata on top of CH 4 CPC ( 5800000 4 ( 350000 E Fawnie pluton 4 Naglico Formation ( ( Dome ( 4 Pyroxene-phyric basalt, lapilli tuff and sedimentary rocks CAPOOSE ( 4 till. Publicly available aeromagnetic and gravity data have 4 Capoose Campanian strata (Riddell, 2011). ( ( 4 4 4 ( Entiako Formation 4 4 ' 4 pluton 4 ( 4 4 ( 4 ( +$ 4 4 Crystal-lithic tuff 4 4 4 4 ( 4 Red tuff 4 been integrated with bedrock mapping to develop a 4 4 4 4 4 ( Red dacite 300000 350000 400000 450000 500000 5900000 N 4 V. EOCENE DEFORMATION 4 ") Blackwater 4 Liesegang basalt Kluskus Blue FSR 4 4 4 ( structural framework for the northern Interior Plateau. This Prince George Access Rd 4 !( Undifferentiated sedimentary and bimodal volcanic sequence 4 4 Malaput FSR 4 !( 4 !H !( 4 ") 4 G 4 Eocene deformation was characterized by extension that can be separated into two phases. The BLACKWATER ( !( Telkwa Formation ") 4 4 4 !( Laidman ( 4 4 Rhyolite to basalt flows and volcaniclastic rocks 4 4 4 4 new framework outlines several major faults that were batholith BLACKWATER SOUTH( 4 4 125°30'0"W !( 4 4 Undifferentiated 4 ( 4 4 early phase of nearly E-W extension is recorded by NW-SE striking dextral faults, including KEY WEST 4 4 ( Rhyolite to basalt flows and associated volcaniclastic rocks Continental 4 4 4 4 325000 E ") ( 4 Arcs previously unidentied. These faults, in part, controlled the ")!( 4 4 ( Triassic KEY 4 4 !( 4 4 OIB ( 4 4 Limestone 4 reactivation of the Tatuk Fault, and N-S striking normal faults, including reactivation of some 4 ( 4 4 4 HAVANA Blackwater 4 4 4 Cache Creek terrane 4 ( 4 4 development and inversion of the marine Nechako Basin. 4 4 pluton 4 ( !( XW 4 4 Permian – Triassic 4 4 3TS 4 4 4 mid-Cretaceous thrust faults (Bordet, 2014). It accompanied eruption of the Ootsa Lake Group ( ( Capoose 4 Metasedimentary rocks and basalt 4 4 4 4 4 Kluskus 4 4 4 Vancouver stock 4 ! 4 Serpentinite 4 4 4 Nazko !H 4 4 4 4 4 4 4 Ootsa FSR 4 (Bordet, 2014) and exhumation of the Tatla Lake Metamorphic Complex (Friedman and 4 4 4 Victoria 4 4 4 PLUTONIC ROCKS 4 4 !H 4 4 4 4 4 4 Eocene Th/Yb E-MORB 4 4 4 4 4 4 4 4 Quanchus Plutonic Suite Armstrong, 1988). The late phase represents NW-SE extension recorded by N-S striking dextral 4 4 4 4 Figure 1: Location of the study area with tectonic domains and major structures based on a combination of 4 4 4 4 4 Biotite-hornblende granodiorite to tonalite Oceanic 4 4 4 4 MORB-OIB 4 4 4 Arcs 4 4 Assumed Eocene mafic intrusions inferred from aeromagnetic data 4 4 4 British Columbia map compilation, airborne magnetic and gravity data. Some of the structures presented 4 4 Array 4 4 faults, NE-SW striking normal faults, and exhumation of the Vanderhoof Metamorphic Complex 4 4 4 Late Cretaceous 4 4 4 4 4 here have not previously been documented. The red line corresponds to the extent of the TREK 4 4 4 4 4 Blackwater Plutonic Suite 4 4 4 4 4 4 4 4 4 4 Biotite-hornblende quartz monzonite to monzogranite 4 along the Sinkut Detachment (Figure 2a; Wetherup and Struik, 1996). It is assumed that the aeromagnetic survey. TLMC - Tatla Lake Metamorphic Complex, VMC - Vanderhoof Metamorphic Complex, 4 N-MORB 4 4 4 4 4 Plagioclase-phyric diorite 4 4 4 4 4 4 4 4 4 WMC - Wolverine Metamorphic Complex, CPC - Coast Plutonic Complex. 4 Jurassic to Paleogene 4 4 4 4 ") 4 4 4 Bobtail Shear Zone accommodated some amount of dextral shear at this time given the current 4 BAEZ 4 4 Coast Plutonic Complex 4 4 4 4 ITCHA - 4 Diorite to granodiorite related volcanic rocks 4 4 4 CLISBAKO 4 4 4 ") ILGACHUZ PARK 4 4 4 4 4 4 Late Jurassic to Early Cretaceous 4 475000 E 4 juxtaposition of geological units and its orientation parallel to other late Eocene dextral faults.