Rockin Out from Main Street in Smithers: A Geologic History of the Bulkley Valley and the Importance to us.
Jeff Kyba, Regional Geologist, Smithers
Summary of the Geology of British Columbia
The geological history of western North America has been, and continues to be, shaped by its position on the eastern rim of the Pacific Ocean. The modern Pacific Ocean’s basin is the successor of the original ocean which split Laurentia - our continent’s cratonic core - away from the rest of the Precambrian supercontinent Rodinia, an ocean that widened until in late Paleozoic time, it became Panthalassa, the World Ocean. Unlike the eastern side of the continent, where continental collision was followed by re-opening of the Atlantic Ocean - the “Wilson cycle” - western North America has always faced the same active ocean basin. Its tectonic evolution has always been that of an active margin, affected first by multi-episodic rifting, and then by plate-margin subduction and transcurrent faulting, over a 700 million year period of time. Throughout this long interval, fluctuating regimes determined by relative plate vectors have created the complex and varied geology and topography of the region; its thrust belts, volcanoes, and granite canyons; its scarps, plateaus, and cordilleras.
The geological history of this area can be viewed as four distinct plate-tectonic phases. The Rifting/Open Margin phase lasted from initial breakup at about 700 Ma (late Proterozoic) until 400 Ma (Middle Devonian), when widespread subduction began along the margin. The Oceans and Islands phase commenced as subduction built arcs and the continent retreated away from them, creating a scenario like the modern southeastern Pacific ocean. This phase lasted until about 180 Ma (Early Jurassic), when opening of the Atlantic ocean reversed the motion of North America such that it drove strongly westward relative to the long-standing subduction zones off its west coast, creating a broad zone of compression in the offshore arcs and ocean basins as well as its own miogeocline (Collisional/Orogenic phase). The final, Post-Collisional phase commenced during the Early Tertiary when parts of the East Pacific Rise subducted under the continent and turned the plate margin from pure subduction to a regime with both transcurrent faulting and continued subduction of short, remnant segments. Industrial mineral deposits formed during each of these tectonic phases. Combined effects of two or more phases were required to form some of these deposits.
The Cordilleran miogeocline developed during the Rifting/Open Margin phase, from its inception with deposition of the late Proterozoic, syn-rifting Windermere Supergroup, through the deposition of the thick sequences of Paleozoic-early Mesozoic carbonate and terrigenous siliciclastic strata that are now beautifully exposed in the Canadian Rocky Mountains. The Mt. Brussilof magnesite deposit is hosted by Middle Cambrian carbonate within this continental shelf sequence. Equivalent platformal strata are best exposed in the southwestern United States, the Grand Canyon being a world-renowned example. The opening of Panthalassa was not a single event in western North America: convincing Cambrian as well as late Proterozoic rift-related sequences occur, and alkalic to ocean-floor basalts in the miogeocline range through Ordovician into Devonian age. The implied protracted nature of this rift event, in contrast to the short-lived and efficient opening of the Atlantic Ocean, continues to puzzle. The exact identity of the missing twin continent or continents, also provides grounds for lively debate, with Australia, Australia/Antarctica, and Siberia attracting the most adherents.
The Oceans and Islands phase began in Devonian-Mississippian time with the first widespread arc volcanism and plutonism along the continent margin: these rocks are recognized from southern California to Alaska. West of the North American miogeocline, a large portion of California, Oregon, Washington, British Columbia, and most of Alaska are made up of rocks of intra-oceanic island arc to oceanic affinity that occur in relatively coherent packages separated from each other by faults. These assemblages, famously termed a collage of “suspect terranes” by Peter Coney and Jim Monger, had uncertain relationships to the North American continent during at least part of their history. Most of them have now been shown either to contain faunas of eastern Pacific affinity (an excellent example can be viewed at the Lafarge limestone quarry near Kamloops, B.C.), or to exhibit sedimentological, geochemical and/or historical aspects that link them, however distally, to the continent. Some, however, are more convincingly exotic imports: the Cache Creek Terrane of central British Columbia with its Tethyan, Japanese-Chinese, late Permian fusulinid fauna; Wrangellia and Alexander, a linear belt on the coasts of B.C. and southeastern Alaska, with its late Paleozoic cold-water, Baltic-affinity fauna; and fragments of continental crust in Alaska with Precambrian ages that are unknown in North America.
At present, the Pacific Ocean is highly asymmetric, its west side festooned with island arcs, its east side bare, bordering a continental margin made up of fragments of just such arcs and marginal oceans. It is reasonable to suppose that both sides of the Pacific were once mirror images. However, opening of the northern Atlantic Ocean at about 180 Ma destroyed that symmetry. Although earlier compressional events affected the suspect terranes, their thrusting on top of the North American miogeocline dates from the latest Early Jurassic, roughly 183 Ma - the same age as early rift basalts on the eastern seaboard. From that time until the end of the Mesozoic, both suspect terranes and sedimentary strata of the miogeocline were stacked into a complex but overall easterly-tapering thrust wedge. Oceanic terranes incorporated into the wedge have provided both asbestos (Cassiar Mine) and jade deposits. During this Collisional/Orogenic phase, successive Jurassic and Cretaceous magmatic arcs draped across the growing accretionary collage. Numerous dimension stone quarries exploit granites from this phase. The notably voluminous mid- Cretaceous arc was probably linked to an episode of rapid subduction around the entire northern Pacific Rim. Broad plutonic provinces of this age occur from China, through Russia, into Alaska and British Columbia and south into California and Mexico - a spectacular example of the global geological consequences of relative plate motion.
Towards the end the Collisional/Orogenic phase, dextral (Pacific-northward) transcurrent motion became an increasingly important part of tectonic development, with at least hundreds of kilometres of displacement along faults such as the Denali, Tintina, Pinchi and Fraser. By early Tertiary time, thrusting in the Canadian Rockies and Foreland Belt had ceased, and crustal extension was accompanied by volcanism and graben development in southern British Columbia and northern Washington-Idaho. At about 38 Ma ago, the edge of North America began to impinge on the East Pacific Rise, shutting off subduction along increasingly long sections of the margin. Major dextral faults - the San Andreas, Queen Charlotte, and Denali faults - began to express the strong component of lateral motion between the American and Pacific plates. Some 300 kilometres of crustal extension related to this lateral motion generated the Basin and Range Province in the western United States. Limited subduction continues today off the coast of Washington, giving rise to the Cascade volcanoes; and the westward turn of the continent margin in Alaska creates a continuing collision zone in the Wrangell and Alaska Ranges, resulting in North America’s highest summits. Late Cenozoic uplift, perhaps due to mantle heating events, has rejuvenated the Canadian Rockies and the Coast Mountains. In terms of industrial mineral deposits, late Cretaceous and Cenozoic volcanic and terrestrial deposits of bentonite, diatomaceous earth, pumice, zeolites, and opals have attracted exploration and mining interest.
The saga continues, with the recent earthquakes along the Queen Charlotte Fault rattling our knick-knack shelves and causing short term cell-phone and 911 overloads. This west coast is by nature Pacific Rim, not just in cultural orientation, but in terms of day-to-day tectonic reality as well.
Other Links: Geological Survey of Canada, Canadian Cordillera Geoscience Nelson, J. and Colpron, M. (2007): Tectonics and Metallogeny of the British Columbia, Yukon and Alaskan Cordillera, 1.8 Ga to the present, Special Publication No. 5, p. 755-791.
ELGCTM SCALE TIME GEOLOGIC
1) W.B.Harlandet al. , 1990 - Phanerozoic 2) Lumbers & Card (Geology, Vol. 20, 1991) - PreCamb. 3) R.D. Tucker & W.S. McKerrow, 1995 - Ord.-Sil. 4) R.D. Tucker et al. 1998 - Devonian CENOZOIC MESOZOIC PALEOZOIC 5) Palfy et al. , 1998 - Jurassic Age Age Age 6) S.A. Bowring & D.H. Erwin, 1998 - Permo-Triassic EPOCH / STAGE PERIOD EPOCH / STAGE Ma PERIOD EPOCH / STAGE Ma PERIOD Ma ERA 251 ±0.4 PRECAMBRIAN Holocene Changxingian QUATER 0.01 65.0 ±2 Longtanian 253 ±2 Age -NARY Pleistocene Calabrian L Capitanian 256 ±5 PERIOD 1.64 Maastrichtian 264 ±2 Ma L Wordian 543.9 Piacenzian 3.40 ±1.35 74.0 ±3 Roadian 269 ±7 Ediacaran E Zanclian 565 Pliocene Artinskian 5.2 ±1.5 Campanian 280 ±4 Messinian 6.7 ±2.3 L 83 ±4 E Sakmarian Varangian Santonian 86.6 ±3 285 ±10 605 Coniacian 88.5 ±2 PERMIAN L Turonian Asselian Hadrynian Tortonian 90.4 ±2 Gzhelian 300 ±4 Cryogenian Cenomanian 303 ±3 10.4 ±1.5 97.0 ±2 (late) 850 Kasimovian 306±5
L Moscovian Neoproterozoic Serravallian 311 ±3 Tonian M Albian 14.2 ±1.8 Bashkirian 1000
NEOGENE Langhian PENNSYLVANIAN 314 ±5 16.3 ±1 112 ±2 Miocene Serpukhovian Stenian 327 ±6 1200 Burdigalian CRETACEOUS Aptian Helikian E E E Visean 124.5 ±13 (middle) Ectasian 21.5 ±1.8 Barremian 342 ±3 1400
MISSISSIPPIAN Aquitanian CARBONIFEROUS Tournaisian 23.3 ±1 131.8 ±8 Calymmian
Hauterivian Mesoproterozoic 135.0 ±8 Famennian 355 ±4 Valanginian L 376.5 1600 L Chattian 140.7 ±13 Frasnian Berriasian Givetian 383 Statherian 144.8 ±3.1 M Eifelian 387.5 Emsian 394 1800 29.3 ±1.5 Tithonian Aphebian L Kimmeridgian 151.5 ±1.2 Pragian 409.5 Orosirian 154.7 ±1.0 E 413.5 Oxfordian 156.6 ±2.3 Lochkovian (early) Oligocene E 2050 Rupelian DEVONIAN Callovian 159.7 ±0.5 Pridolian 418 Bathonian 419 Rhyacian M 166.0 ±1.1 L Ludlovian Paleoproterozoic 2300 TERTIARY 35.4 ±1.4 Bajocian 423 L 174.0 ±4.1 E Wenlockian 428 Siderian Priabonian Guidelines” Reporting “Geoscience from,
Aalenian SILURIAN Llandoverian 2500 38.6 ±1.5 178 ±1.5 443 Toarcian Ashgillian 449 Neoarchaean 2003 May Grant, Brian by Compiled Bartonian L 183.6 ±1.5
JURASSIC (late) 42.1 ±1.8 Caradocian 2800 E Pliensbachian 458 M 192.0 ±4.5 M Llandeilian 464 Mesoarchaean Sinemurian Llanvirnian (middle)
PALEOGENE Eocene Lutetian 470 197.0 ±2.7 3200 Hettangian Arenigian 199.6 ±0.7 E Paleoarchaean ORDOVICIAN 485 (early) 50 ±1.5 Rhaetian 209.6 ±4.1 Tremadocian 3600 495 E Eoarchaean Ypresian L Norian Late 220.7 ±4.4 505 (earliest) 3800 Middle 56.5 ±1.4 Carnian 518 Toyonian 522 L 227.4 ±4.5 Botomian Thanetian 525 TRIASSIC Ladinian Atdabanain M 239.5 ± 6.5 528 60.5 ±2.3 Anisian Tommotian Spathian 244 ±4 E 531 E Danian Smithian CAMBRIAN
Paleocene E Dienerian 247 ±4 Nemakit - Daldynian base not defined ~4400 Ma 65 ±2 Griesbachian 251 ±0.4 543.9 May 2003, compiled by Brian Grant, Geoscience Reporting Guidlines - Distributor: Prospectors & Developers Association of Canada - Tel: 416-362-1969 E-mail: [email protected] Geology and Mineral Deposits of the Skeena Arch, West-Central British Columbia: A Geoscience BC Digital Data Compilation Project1
By Don MacIntyre2
KEYWORDS: dig ital data, GIS, Skeena arch, mineral de - base, using Mani fold 6.5 GIS software, for use by pos its, ge ol ogy explorationists; vari ous data formats will be pro- duced in or der to make the data as widely use able as INTRODUCTION pos si ble; data will be made avail able on CD and possi bly over the Internet in standard GIS format; The Skeena arch is a northeast-trending belt of uplifted and Ju ras sic and older rocks that transects cen tral British Co- • spatial analy sis of the data and defi ni tion of explo ra - lumbia. This uplift is believed to have formed in the Middle tion tar gets based on cor re la tion of pos i tive in di ca- Juras sic and resulted in sepa ra tion of the Bowser and tors, such as geo chem i cal and geo phys i cal anom a- Nechako basins (Yorath, 1991). Rocks exposed along the Skeena arch rep re sent a long-lived mag matic arc that has lies and strati graphic set ting. produced a diverse range of mineral depos its in a wide vari - The pro ject will gen er ate the fol low ing de liv er ables ety of geolog i cal set tings. This area repre sents some of the over a two year period: most richly endowed terrain in BC and has been the site of • Updated and standard ized 1:100 000-scale geolog i - mineral explo ra tion for the past 125 years. Since 1985, the cal, geo chem i cal and geo phys i cal com pi la tion maps BC Geo log i cal Sur vey and the Geo log i cal Sur vey of Can- ada have been involved in regional mapping projects along for the maps sheets cov ered by the pro ject area the Skeena arch, first as part of the Whitesail and Smithers (Fig. 1) pro jects (e.g., Mac In tyre et al., 1989) and more recently as • A CD con tain ing re ports doc u ment ing the re sults of part of the Inte rior Plateau (Diakow et al., 1997) and the project and new explo ra tion targets, plus a com- Nechako NATMAP (Mac In tyre et al., 1996a, 1996b, 1997, plete suite of data files and maps in GIS format for 1998; MacIn tyre 1998, 2001a, b; MacIn tyre and use in Mani fold 6.5 GIS and other popu lar GIS Villeneuve, 2001) projects. This work has resulted in a pack ages (ArcView®, MapInfo®, AutoCAD® Map, much better un der stand ing of the geo log i cal evo lu tion of etc.); the CD will also contain 1:100 000-scale digi - the arch, partic u larly during the metallogenically impor tant Ju ras sic through Cre ta ceous time pe ri ods. Al though there tal maps in PDF format por traying the geol ogy, min- are gaps in the map cov er age, a large part of the pro ject area eral oc cur rences, geo chem is try and geo phys ics of (80%) has now been mapped in detail. These data were the pro ject area, and as sessed ex plo ra tion po ten tial origi nally compiled at 1:100 000 scale as part of the Min- for key mineral deposit types eral Po ten tial Pro ject (Mac In tyre et al., 1994) and re vised • Updated MINFILE (2005) occur rences, as re- and updated as part of the Dig ital Geol ogy of BC Project quired. (Massey et al., 2003, 2003a). The Skeena arch Project will provide a means of bringing this and other digi tal datasets Pro jected re lease of fi nal re port, maps and da tabase to gether as a se ries of stan dard ized, dig i tal geo log i cal maps files is Octo ber 2006. with linked da tabases for struc ture, mineral oc cur rences, geo chem is try, geo phys ics, geo chron ol ogy and pa le on tol - ogy. A new series of 1:100 000-scale maps will be produced LOCATION OF THE PROJECT AREA for the area and made available in digi tal and hardcopy for- The area cov ered by the Skeena Arch Project is shown mat. in Figure 1. The area includes all of the Hazelton (93M), The aim and scope of this proposed two-year project is Smithers (93L) and Whitesail (93E) maps sheets, and the to promote new explo ra tion along the Skeena arch by: south half of the McConnell Creek (94D), east half of the • com pil ing all ex ist ing data rel e vant to min eral ex - Terrace (103I) and south east cor ner of the Nass River plora tion along the arch and building a GIS data - (103P) map sheets.
KEY DATASETS AND PRODUCTS 1 Geoscience BC contribution GBC007 2 Consulting Geologist, D.G. MacIntyre & Associates Ltd., New ge ol ogy and ex plo ra tion-po ten tial maps will be Victoria, BC com piled and re leased as digi tal products for each of the This publication is also available, free of charge, as colour map tiles shown in Fig ure 1. The dig ital files will include digital files in Adobe Acrobat PDF format from the BC Ministry bed rock ge ol ogy and ex plo ra tion po ten tial for spe cific of Energy, Mines and Petroleum Resources internet website at mineral-de posit types, such as epither mal veins, Eskay http://www.em.gov.bc.ca/Mining/Geolsurv/Publications/catalog/ Creek – type VMS, porphyry Cu and Mo, etc. Poten tial for catfldwk.htm hydro car bons may also be included if suf ficient data can be
Geo log i cal Field work 2005, Pa per 2006-1 303 Fig ure 1. Skeena Arch Project area, showing map tiles to be com piled and lo ca tion of MINFILE oc cur rences. ob tained. Dig i tal com pi la tion prod ucts will be de rived ever, dig ital ele va tion data are available for free from the from the datasets shown in Table 1. A key cri terion for the Gov ern ment of Can ada GEOBASE website, and these will project is that all datasets used to produce the deriv a tive ge- be used to gener ate contour maps and hillshade surfaces for ol ogy and ex plo ra tion-po ten tial maps and da ta bases are the project area using the capa bil i ties of the Mani fold 6.5 available to the public for free. Unfor tu nately, this means GIS software. Mani fold was cho sen as the GIS platform for that TRIM topo graphic data can not be used in this project this project because of its excep tional function al ity and low because of its high cost and distri bu tion restric tions. How- cost (currently selling for around $300 Ca nadian). In addi -
304 Brit ish Co lum bia Geo log i cal Sur vey TABLE 1. KEY DATASETS TO BE USED IN THE SKEENA ARCH COMPILATION PROJECT Name Description Source Geology Bedrock geology polygons, faults and related databases BCGS Quaternary Quaternary cover polygons BCGS Age Dates Isotopic ages BCGS Minfile Mineral occcurrence locations and related databases BCGS ARIS Assessment report locations and descriptions BCGS RGS Regional silt, water and till geochemistry sample locations and related databases BCGS Minpot Mineral potential tracts, location of known resources and related databases BCGS Geophysics Airborne geophysical surveys GSC DEM Digital elevation model points (used to generate contours and hillshade relief maps) GEOBASE
Rivers Major rivers as lines and polygons GEOGRATIS Lakes Major lake polygons GEOGRATIS Sea Ocean polygons GEOGRATIS Roads Road network GEOGRATIS FSR Logging road network BCMOF Cities Cities, towns and communities GEOGRATIS Ice Cover Areas of ice cover GEOGRATIS Parks Location of parks BCMENV Grid 250K NTS map sheet grids for 1:250K and 1:50K maps GEOGRATIS Grid 20K Map sheet grid for BC 1:20K TRIM maps BCMENV
tion to the Man ifold data for mat, however, all files will also Richards 1980, 1990). Most of these faults formed during be made available in ESRI shapefile, MapInfo® MIF and Late Cre taceous to Eocene or youn ger block-faulting AutoDesk® DWG for mat. All file formats will be avail able events (Mac In tyre et al., 1997, 1998). In most parts of the in three pro jec tions: geo graphic, Uni ver sal Trans verse project area, rocks of the Stikine Terrane display broad Mercator and BC Albers. These pro jec tions will be based open fold patterns. The oc cur rence of a pene tra tive cleav - on the North Ameri can Datum 1983. age and meta morphic grade higher than lower greenschist fa cies is rare. TECTONIC SETTING GEOLOGY The project area is within the Intermontane Belt, which at this lati tude in cludes the volca nic-arc Stikine (Stikinia) The geol ogy of the Skeena Arch Pro ject area is based Terrane and a small part of the oce anic Cache Creek on a recent compi la tion completed by the BC Geolog i cal Terrane. The Stikine Terrane comprises Car bon if er ous to Sur vey (Massey et al., 2003a, b). This infor ma tion has been Mid dle Ju ras sic is land-arc vol ca nic and sed i men tary rocks used to gener ate Figures 2–5. Figure 6 is a schematic cross- and re lated plutonic suites (Schiarizza and Mac In tyre, sec tion, extend ing from the Skeena arch to the Bowser ba- 1999). The Stikine Terrane is believed to have evolved in sin, that shows the rela tion ships of major lithostratigraphic the eastern Pacific of the northern hemisphere and moved map units. Also shown are the stratigraphic posi tions of northward to dock with ances tral North America sometime geo chron ol ogi cal and paleontological age con trols. dur ing the Mid dle Ju ras sic (Mon ger et al., 1972, 1996). Most of the project area is under lain by the Stikine The Stikine Terrane is well ex posed along the Skeena arch. Terrane, which here in cludes the Carbon ifer ous to Perm ian North of the Skeena arch, the Stikine Terrane is overlain by Asitka Group island-arc meta volcan ic rocks and limestone; postaccretion Late Ju ras sic to Early Cre taceous marine and Mid dle to Late Tri as sic augite-phyric ba salt, an de site and nonmarine sed imen tary rocks of the Bowser Basin. The re lated island-arc marine sedi men tary rocks of the Takla southern part of the Skeena arch is overlapped by Late Cre- Group; and Early to Mid dle Ju rassic andesitic vol canic, taceous and Eocene con tinen tal vol ca nic arc and re lated volcaniclastic and re lated ma rine sed imen tary rocks of the sedi men tary rocks of the Ootsa Lake and Endako groups. Hazelton Group is land-arc to con ti nen tal-arc as sem blage The pro ject area spans the zone of west ward-di rected (Fig. 2; Thorkelson et al., 1995; Richards 1980, 1990). The thrust faulting that marks the boundary between the Stikine strati fied rocks are cut by the granodiorite and quartz and Cache Creek ter ranes (Struik et al., 2001). This struc- diorite of the Late Tri as sic to Early Ju ras sic Topley in tru - tural imbrication occurred prior to 165 Ma (Schiarizza and sive suite and the newly recog nized Early to Middle Juras - Mac Intyre 1999), as indi cated by isoto pic ages for sic Spike Peak in tru sive suite (Mac In tyre et al., 2001), postkinematic plutons that cut both terranes. Folds and which are prob a bly comagmatic with the Takla and thrust faults re lated to this imbrication are off set by a com- Hazelton vol ca nic-arc suc ces sions. plex pattern of high-angle faults. This pattern of faulting is In the northwest corner of the project area, the Stikine not unique to the boundary between Stikine and Cache Terrane is over lain by marine to nonmarine clastic sed i- Creek terranes, as it is observed throughout the Smithers men tary strata of the Late Ju ras sic Bow ser Lake and Early and Hazelton map sheets (Tipper and Richards 1976a, b; Creta ceous Skeena groups (Fig. 3). These rocks were de-
Geo log i cal Field work 2005, Pa per 2006-1 305 Fig ure 2. Dis tri bu tion of Tri as sic and Ju ras sic vol ca nic and plutonic rocks of the Stikine Terrane.
306 Brit ish Co lum bia Geo log i cal Sur vey Fig ure 3. Dis tri bu tion of Ju ras sic and Cre ta ceous sed i men tary rocks of the Bow ser and Skeena bas ins.
Geo log i cal Field work 2005, Pa per 2006-1 307 Fig ure 4. Dis tri bu tion of Cre ta ceous and Tertiary volca nic-arc rocks and lo ca tion of MINFILE oc cur rences.
308 Brit ish Co lum bia Geo log i cal Sur vey Figure 5. Distri bu tion of Tertiary volca nic cover.
Geo log i cal Field work 2005, Pa per 2006-1 309 Overlap Assemblages Extension, block faulting Miocene Endako 50 Sustut P 50-53 L. Cret.- Newman Basin Eocene Kasalka 50-53 Eocene 78 Babine Sustut P Folding, uplift Arc Bulkley U. Cretaceous Rocky Ridge Skeena 107 L. Cretaceous Skeena Bowser Trout Crk. F Arch Basin Ashman U. Jurassic F 172-166 F 175 Smithers F 176 P M. Jurassic 184 F Hazelton Saddle Hill 178-176 Arc Spike Peak Nilkitkwa F L. Jurassic Telkwa 194
Folding, uplift 208 Takla Topley 219 Takla F Arc F 218 Triassic Asitka Stikine Terrane Arc Asitka Permian F
U-Pb Ar-Ar F Fossil P Porphyry Cu
Figure 6. Schematic stratigraphic rela tion ships, northern Skeena arch. posited in a fluvial-deltaic to nearshore shelf envi ron ment MINERAL DEPOSITS along the south eastern mar gin of the Bowser Basin (Bassett, 1991; Bassett and Kleinspehn, 1996; Evenchick, The Skeena Arch Pro ject area is richly endowed with 1999). A detailed discus sion of these overlap assem blages me tal lic min eral de pos its, with over 800 oc cur rences listed is presented in MacIn tyre (1998). in the BC Geolog i cal Survey’s MINFILE da tabase. The dif- ferent de posit types that have been recog nized in the area are listed in Ta ble 2. Of these, the most impor tant types are In the western half of the pro ject area, Late Cre taceous polymetallic veins (268), subvolcanic Cu-Ag-Au-(As-Sb) to Early Eocene por phy ritic an de site, ba salt, rhy o lite and (153), porphyry Cu±Mo±Au (140), vol canic redbed Cu re lated pyroclastic and volcaniclastic con tinen tal-arc rocks (86), porphyry Mo (66), in trusion-re lated Au pyrrhotite un conform ably overlie both folded and up lifted rocks of the Stikine Terrane and Late Ju ras sic to Early Cre taceous sedi men tary rocks of the Bowser Basin (Fig. 4). The youn- TABLE 2. MINERAL DEPOSIT TYPES OCCURRING IN THE ger vol canic rocks are preserved in grabens or as erosional SKEENA ARCH PROJECT AREA rem nants on ridge tops. The Late Cre taceous rocks in clude Profile Name Count por phy ritic an de site flows and lahars of the Kasalka Group Code and coeval granodiorite and quartz diorite plutons of the I05 Polymetallic veins Ag-Pb-Znÿ±Au 268 Bulkley plutonic suite (MacIn tyre, 1985; Carter, 1981). In L01 Subvolcanic Cu-Ag-Au-(As-Sb) 153 the vicin ity of Babine Lake, the Stikine Terrane is uncon - L04 Porphyry Cuÿ±Moÿ±Au 140 form ably overlain by porphy ritic an desite flows of the D03 Volcanic redbed Cu 86 Early Eocene Newman Forma tion and is cut by porphy ritic L05 Porphyry Mo (low F- type) 66 I02 Intrusion-related Au pyrrhotite veins 38 granodiorite to quartz monzonite plutons of the Babine K01 Cu skarns 20 plutonic suite. In the south ern part of the project area, small G06 Noranda-Kuroko massive sulphide Cu-Pb-Zn 7 porphy ritic quartz monzonite and related felsic intru sions E04 Sediment-hosted Cu 6 consti tute the Nanika plutonic suite. Im portant porphyry H05 Epithermal Au-Ag (low sulphidation) 6 copper depos its are asso ci ated with the Bulkley, Babine I01 Au-quartz veins 6 and Nanika intru sive rocks (Carter, 1976, 1981; Carter et M01 Flood basalt - associated Ni-Cu 4 al., 1995; MacIn tyre and Villeneuve, 2001). H04 Epithermal Au-Ag-Cu (high sulphidation) 3 I06 Cuÿ±Ag quartz veins 3 I12 W veins 3 In the east and south east parts of the project area, the K03 Fe skarns 3 Stikine and Cache Creek terranes are uncon form ably over- K04 Au skarns 3 E14 Sedimentary exhalative Zn-Pb-Ag 2 lain by Early Eocene ba salt and rhyo lite flows and re lated G04 Besshi massive sulphide Cu-Zn 2 pyroclastic rocks of the Endako and Ootsa Lake Groups J01 Polymetallic manto Ag-Pb-Zn 2 (Fig. 5; Grainger and Ander son, 1999; Grainger et al., K02 Pb-Zn skarns 2 2001) and Miocene basalt flows of the Chilcotin Group. L02 Porphyry-related Au 2 These younger rocks have also been block faulted and tilted L03 Alkalic porphyry Cu-Au 2 during an Eocene or younger extensional tectonic event. 827
310 Brit ish Co lum bia Geo log i cal Sur vey veins (38) and Cu skarns (20). Most of these depos its are re- Co lum bia; in Porphyry De posits of the North west ern Cor - lated to the Late Cre taceous Bulkley and Eocene Babine dillera of North America, Schroeter, T.G., Edi tor, Ca na dian and Nanika plutonic suites. These intru sions are part of a In sti tute of Min ing, Met al lurgy and Pe tro leum, Special Vol- long-lived magmatic arc that forms the core of the Skeena ume 46, pages 247–255. arch. A schematic dia gram showing the evolu tion of Creta - Diakow, L.J., Webster, I.C.L., Richards, T.A. and Tipper, H.W. ceous and Tertiary volca nic centres is shown in Fig. 4. (1997): Ge ol ogy of the Fawnie and Nechako Ranges, south - Redbed Cu oc cur rences are mostly as so ciated with ba saltic ern Nechako Pla teau, cen tral Brit ish Colum bia flows of the Takla and Hazelton Groups. (93F/2,3,6,7); in Inte rior Plateau Geoscience Project: Sum- mary of Geo log i cal, Geo chem i cal and Geo phys i cal Stud ies, In recent years, poten tial for the discov ery of Eskay Diakow, L.J. and New ell, J.M., Edi tors, BC Min is try of En- Creek – type volcanogenic massive sulphide depos its has ergy, Mines and Pe troleum Re sources, Pa per 1997-2 and been recog nized. The most prospec tive targets are Middle Geo log i cal Sur vey of Can ada, Open File 3448, pages 7–30. Juras sic subma rine volca nic rocks of the Hazelton Group Evenchick, C.A. (1999): Depositional and struc tural his to ries of (Massey, 1999; Massey et al., 1999) and mid-Creta ceous the north ern two-thirds of the Bow ser Ba sin/Skeena Fold bimodal vol canic rocks of the Rocky Ridge Forma tion Belt, north ern Brit ish Co lum bia: re cords of terrane in ter ac- (Mac In tyre, 2001). tions; in Terrane Paths 99, Circum-Pacific Terrane Confer - ence, Abstracts and Program, Evenchick, C.A., There is currently only one deposit in produc tion in the Woodsworth, G.J. and Jongens, R., Edi tors, Geo log i cal Sur- project area: the Huckle berry porphyry Cu-Mo deposit at vey of Can ada – Geo log i cal As so ci a tion of Can ada, pages Tahtsa Lake, 90 km south of the town of Houston. Two 30–32. other depos its are in the advanced stages of feasi bil ity stud - Grainger, N.C. and An der son, R.G. (1999): Ge ol ogy of the Eocene ies: the Davidson (a.k.a. Gla cier Gulch or Yorke-Hardy) Ootsa Lake Group in north ern Nechako River and south ern porphyry Mo deposit at Smithers and the Morri son por- Fort Fraser map area, central British Colum bia; in Current phyry Cu deposit at Babine Lake. Re search 1999-A, Geo log i cal Sur vey of Can ada, pages 139–148. Grainger, N.C., Villeneuve, M.E., Heaman, L.M. and Ander son, CONCLUSIONS R.G. (2001): New U-Pb and Ar/Ar iso to pic age con straints on the tim ing of Eocene magmatism, Fort Fraser and This pro ject will help to stimu late min eral ex plo ra tion Nechako River Map ar eas, cen tral Brit ish Colum bia; Ca na - by provid ing mineral explorationists with a com prehen - dian Jour nal of Earth Sciences , vol ume 38, pages 679–696. sive, up-to-date, all-in clu sive GIS-com pat i ble com pi la tion Mac Intyre, D.G. (1985): Ge ol ogy and mineral de posits of the of exist ing geoscience data in one of the most prospec tive Tahtsa Lake district, west-central British Colum bia; BC ar eas of BC. The cur rent da tabase for this area is a mixture Min istry of En ergy, Mines and Pe troleum Re sources, Bul le - of digi tal and nondigital data from a wide range of projects tin 75. that were done at differ ent times and scales by differ ent Mac In tyre, D.G. (1998): Babine Porphyry District Pro ject: bed - gov ern ment agen cies and ex plo ra tion com pa nies. The data rock ge ol ogy of the Nakinilerak Lake map sheet (93M/8), from these projects need to be compiled, inte grated and Brit ish Co lum bia; in Geo log i cal Field work 1997, BC Minis - stan dardized into a format that can be used in a GIS. Build- try of En ergy, Mines and Pe tro leum Re sources, Pa per 1998- ing such a data base will help explorationists identify new 1, pages 2-1–2-18. ex plo ra tion tar gets and re-eval u ate ar eas of known min eral Mac In tyre, D.G. (2001a): Geo log i cal com pi la tion of the Babine oc cur rences us ing new geo log i cal and met al lo gen ic mod - por phyry cop per dis trict; BC Minis try of Energy , Mines and els. Partic u lar focus will be directed toward porphyry Mo Pe tro leum Re sources, Open File Map 2001-3. and Eskay Creek – type depos its. In addi tion to provid ing a Mac In tyre, D.G. (2001b): The Mid-Cre ta ceous Rocky Ridge For - com pre hen sive stan dard ized da ta base, this pro ject will also mation — a new target for sub aque ous hot-spring de posits an a lyze the data and gen er ate a list of po ten tial tar get ar eas (Eskay Creek – type) in cen tral Brit ish Colum bia; in Geo - for con sid er ation, thus as sist ing the ex plo ra tion com mu - log i cal Field work 2000, BC Minis try of Energy, Mines and nity in their eval u ation of the po tential for new discov er ies. Pe tro leum Re sources, Pa per 2001-1, pages 253–268. MacIn tyre, D.G., Ash C. and Britton, J. (1994): Nass-Skeena (93/E, L, M; 94/D; 103/G, H, I, J, P; 104/A, B), BC Min is try REFERENCES of En ergy, Mines and Pe troleum Re sources, Open File 1994- Bassett, K.N. (1991): Pre limi nary re sults of the sedimentology of 14. the Skeena Group in west-cen tral Brit ish Colum bia; in Cur- Mac In tyre, D.G., Desjardins, P. and Tercier, P (1989): Juras sic rent Research, Part A, Geo log i cal Sur vey of Can ada, Paper strati graphic re la tion ships in the Babine and Telkwa ranges; 91-1A, pages 131–141. in Geo log i cal Field work 1988, BC Minis try of Energy, Bassett, K.N. and Kleinspehn, K.L. (1996): Mid-Cre ta ceous Mines and Pe troleum Re sources, Pa per 1989-1, pages 195– transtension in the Ca na dian Cor dil lera: evi dence from the 208. Rocky Ridge volcanics of the Skeena Group; Tec ton ics, Vol- Mac In tyre, D.G. and Villeneuve, M.E. (2001): Geo chron ol ogy ume 15, pages 727–746. and tec tonic set ting of mid-Cre ta ceous to Eocene Carter, N.C. (1976): Regional set ting of por phyry de posits in west- magmatism, Babine por phyry cop per dis trict, cen tral Brit ish cen tral Brit ish Co lum bia; in Porphyry De posits of the Ca na - Co lum bia; Ca na dian Jour nal of Earth Sciences , Vol ume 38, dian Cor dil lera, Suther land-Brown, A., Ed i tor, Ca na dian pages 639–655. In sti tute of Min ing and Met al lurgy, Spe cial Vol ume 15, Mac In tyre, D.G., Villeneuve, M.E. and Schiarizza, P. (2001): Tim- pages 227–238 ing and tectonic set ting of Stikine Terrane magmatism, Carter, N.C. (1981): Por phyry cop per and mo lybde num depos its, Babine-Takla lakes area, central British Colum bia; Ca na - west-cen tral Brit ish Co lum bia; BC Minis try of Energy, dian Jour nal of Earth Sciences , Vol ume 38, pages 579–601. Mines and Pe tro leum Re sources, Bul le tin 64. MacIn tyre, D.G., Webster, I.C.L. and Bellefontaine, K. (1996a). Carter, N.C., Dirom, G.E. and Ogryzlo, P.L. 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Geo log i cal Field work 2005, Pa per 2006-1 311 work 1995, BC Min istry of En ergy, Mines and Pe tro leum ta tion, dis place ment and ac cre tion of suc ces sive North Re sources, Pa per 1996-1, pages 11–35. Amer i can plate-mar gin arcs; in Ge ol ogy and Ore De posits MacIn tyre, D.G., Webster, I.C.L. and Bellefontaine, K. (1996b). of the Amer i can Cor dil lera, Coyner, A.R. and Fahey, P.L., Ge ol ogy of the Fulton Lake map sheet (93L/16), BC Min is- Ed i tors, Geo log i cal So ci ety of Ne vada, Sym po sium Pro- try of En ergy, Mines and Pe troleum Re sources, Open File ceed ings, Reno/Sparks, Ne vada, April 1995, pages 1133– Map 1996-29. 1152. MacIn tyre, D., Webster, I.C.L. and Desjardins, P. (1998): Bed rock Rich ards, T.A. (1980): Ge ol ogy of the Hazelton map area (93M); ge ol ogy of the Old Fort Moun tain map area, north-central Geo log i cal Sur vey of Can ada, Open File 720. BC; BC Min is try of En ergy, Mines and Pe troleum Re- sources, Open File Map 1997-10. Rich ards, T.A. (1990). Ge ol ogy of the Hazelton map area (93M); Geo log i cal Sur vey of Can ada, Open File 2322. MacIn tyre, D.G., Webster, I.C.L and Villeneuve, M. (1997). Babine Por phyry District Pro ject: bed rock ge ol ogy of the Schiarizza, P. and Mac Intyre, D.G. (1999): Ge ol ogy of the Babine Old Fort Mountain area (93M/1), Brit ish Colum bia; in Geo - Lake – Takla Lake area, central British Colum bia; in Geo - log i cal Field work 1996, BC Min is try of En ergy, Mines and log i cal Field work 1998, BC Min istry of En ergy, Mines and Pe tro leum Re sources, Pa per 1997-1, pages 47–67. Pe tro leum Re sources, Pa per 1999-1, pages 33–68. Massey, N.W.D. (1999): Volcanogenic massive sul phide de posits Struik, L.C., Schiarizza, P., Orchard, M.J., Cordey, F., Sano, H., in Brit ish Co lum bia; BC Min is try of En ergy, Mines and Pe - Mac In tyre, D.G., Lapierre, H. and Tardy, M. (2001): Im bri - tro leum Re sources, Open File 1999-2. cate ar chi tec ture of the up per Pa leo zoic to Ju ras sic oce anic Massey, N.W.D., Alldrick, D.J. and Lefebure, D.V.L. (1999): Po- Cache Creek Terrane, cen tral Brit ish Colum bia; Ca na dian ten tial for sub aque ous hot-spring (Eskay Creek) de posits in Jour nal of Earth Sciences , Vol ume 38, pages 495–514. Brit ish Co lum bia; BC Min is try of En ergy, Mines and Pe tro - leum Resources , Open File 1999-14. Thorkelson, D.J., Mortensen, J.K., Marsden, H. and Tay lor, R.P. (1995): Age and tec tonic set ting of Early Juras sic ep i sodic Massey, N.W.D., MacIn tyre, D.G. and Desjardins, P.J., (2003b): vol ca nism along the north east ern margin of the Hazelton Digi tal ge ol ogy map of Brit ish Colum bia: tile NN9 north Trough, north ern Brit ish Co lum bia; in Ju ras sic Magmatism coast BC; BC Min is try of En ergy, Mines and Pe tro leum Re - and Tec ton ics of the North Amer i can Cor dil lera, Miller, sources, GeoFile 2003-13, scale 1:250 000. D.M. and Busby, C., Edi tors, Geo log i cal So ci ety of Amer - Massey, N.W.D., MacIn tyre, D.G. and Desjardins, P.J., (2003a): ica, Spe cial Pa per 299, pages 83–94. Dig i tal ge ol ogy map of Brit ish Colum bia: tile NO9 north- cen tral BC; BC Min is try of En ergy, Mines and Pe tro leum Tip per, H.W. and Rich ards, T.A. (1976a): Ju ras sic stra tig ra phy and Re sources, GeoFile 2003-18, scale 1:250 000. his tory of north-cen tral Brit ish Co lum bia; Geo log i cal Sur- vey of Can ada, Bul le tin 270, 73 pages. MINFILE (2005): MINFILE BC mineral de posits da ta base; BC Min istry of En ergy, Mines and Pe troleum Re sources, URL Tip per, H.W. and Rich ards, T.A. (1976b). Ge ol ogy of the Smithers
312 Brit ish Co lum bia Geo log i cal Sur vey