GEOLOGY BETWEEN NINA LAKE AND OSILINKA RIVE,R, NORTH-CENTRAL BRITISH COLUMBIA (93N/15, NORTH HALF AND 94C/2, SOUTH HALF) By Filippo Ferri and David M. Melville KEYWORDS: Regionalmapping, Germansen Landing, The northern and eastem sections of the map are bounded, Omineca Belt. Intermontane Superterrane, Slide Mountain respectively, by the Osilinka and 0mine:ca rivers. At lheir Group, Paleozoicstratigraphy, lngenika Group, metamor- confluence the terrainis a relatively subdued and tree covzred phism, lead-zinc-silr,er-baritemineralization area. This is in contrast to the Wolverine Range east oithe OminecaRiverand arugged, unnamedrangeof mountai'ls to the southwest. The southern part of the map area was first mapped at a INTRODUCTION 6-mile scale in the 1940s by Amstrong; (1949).Gahrlelse (1975) examined the northem half in the course of 1:250 000 In 1989 theManson Creek 150 000 mappingproject mapping of the east half of the Fort Grahame map area. encompassed the north half of the Germansen Landing map Monger (1973), and Monger and Patersan (1974) described area (93Ni15) and the south half of the End Lake map area rocks in the map area during a reconnaissance sunfey of (94Ci2). As with previous years, the main aims of this project Paleozoic stratigraphy. To the northwest, Roots (1954) pub- were: to provide a detailed geologicalbase map of the area, to lished a 4-mile map of the Fort Graham west-half sheet. update the mineral inventory database, and to place known Many ofthe correlations made in this paper arewith stratigra- mineral occurrences within a geological framework. phy described by Gabrielse (1963, 1969:1,Nelson and Eirad- ford (1987) and other workers in the Casiar area whera: the The centreof the map area is located some 260kilometres miogeoclinal stratigraphy is quite similar and well known. north-northwest of Prince George, immediately north of the settlement of Germansen Landing (Figure 1-1 1-1). Primary access is via all-season gravel roads from Fort St. James or Mackenzie which connect to secondary roads along Nina REGIONAL GEOLOGY Creek, Nina Lake and the Osilinka drainage. A four-wheel- The map area lies along the western e(jgeof the Omineca drive road along Nina Lake provides access to lead-zinc- Belt, one of the five morphogeological belts of the Canadian silver showings northwest of Echo Lake. A major logging Cordillera (Wheeler and McFeely, 1987). Thisarea contains road along the Osilinka River services secondary logging rocks which are part of the Intermontane Superterrane (i.e. roads providing access to the northern third of the map area. accreted) and displaced North American rocks (Wheeler and The remainder is reached on foot or by helicopter. McFeely, ibid; Figure 1-1 I-1). Rocks of the Foreland Iklt lie I Figure 1-1 1-1. Location of the map area with respect to the five morphogeological provinces of the Canadian Cordillera with an expanded view in the right half of the diagram. Geological Fieldwork 1989, Paper 1990-1 101 EARN GROUP INGENIKA GROUP Upper Devonian- Proterozoic Lower Miwissippian Stelkuz Formation MCDAMEGROUP Middle Devonian SANDPILE GROUP Silurian - Lower Devonian ROAD RIVER GROUP Ordovician - Silurian \ Kechika Group - Cambrian -Ordovician ATANGROUP Lower Cambrian 200 base not 3001 exposed loo j Limestone 0Siltstone 0Feldspathic wacke 0 metres Dolomite metres Shale Orthoquartzite Sandy dolomite Calcareousshaledolomite Sandy Impure quartzite, sandstone j : Figure 1-1 1-2. Generalized stratigraphic column of formations within the map area. (Includes material on facing page.) I02 Brirish Columbia Geological Survey Branch Southern Part of Mapsheet Southwest of MountainWhiscler HARPERRANCH Razorback Mountain GROUP FAULT (?) SLIDEMOUNTAIN GROUP ...... +j... ............. -4- v- 1000, metres kgillite siltstonebasalts, Massive 0.... minorgabbro 0 Pillowed Chert basalts ,,-(wehrlite)Ultramafite Gabbro to the east,across the Rocky Mountain Trench (now separates Quesnel rocks from middle Paleozoic to Triassic Williston Lake). rocks of the Cache Creek Terrane. In the study area, the Intermontane Superterrane is repre- Para-autochthonous rocks of North American affinity sented by volcanic and sedimentary rocksof the Quesnel and within the study area are part of a Proterozoic to Misssip- Slide Mountain terranes. Quesnel rocks are composed of a pian carbonate and siliciclastic miogeo,:linal wedge which volcanic and sedimentary assemblage of the Upper Triassic includesstrata of theProterozoic Ingtmika Group to the to Lower Jurassic Takla Group (Monger, 1977) and a poorly Devono-Mississippian Earn Group (Figure 1-11-2). 'ID the defined sedimentaryand volcanic suite belonging to the east, the lower parts of thissequena: are highly Ineta- Upper Paleozoic Harper Ranch Group which is basement to morphosed (sillimanite grade) and deformed, and are incor- the Takla Group. The Slide Mountain Terrane is composed of porated within the Wolverine complex, one of several core oceanic rocks of the Upper Paleozoic Slide Mountain Group. complexes found along the length of the Omineca Belt. The west side of theQuesnel Terrane is intruded by the The rocksabove the garnet isograd roughly definea multiphase, Triassic to Cretaceous Hogem batholith (Gar- southwest-dipping package which is d'eformed by various nett, 1978) bounded to the west by the Pinchi fault which generations of folds and faults. The most notable structure is Geological Fieldwork 1989, Paprr 1990-1 I03 KILOMETRES Figure 1-1 I-3a. Geology of the map area with location of known mineral occurrences described in Table 1-1 1-1 the Manson fault zone, located along the Nina Creekvalley STRATIGRAPHY: NORTH AMERICAN (Figure 1-11-3a). The oldest rocks, the Proterozoic Ingenika ROCKS Group, lieto the northeast. In this map area thecontact betweenthe Slide Mountain Group andNorth American INGENIK.4 GROUP(PROTEROZOIC) rocks is not a west-side-downnormal fault as shown by Ferri The Ingenika Group is predominantlya clastic sequence and ~~l~ill~(1988) inthe M~~~~~ Creek area, lts exact withlesseramountsofcarbonate. This package is inexcess of nature is indeterminate but, in accordance with observations 3.5 kilometres thick and composed of feldspathic and quartz wackes, siltstones, slates, sandstones, limestones and their madeelsewhere along this contact, is assumed to be a layer- higher grade metamorphic Four subdivisions of parallelthrust fault betweenlowermost Slide Mountainrocks the lneenika G~~~~(as bv M~~~~ and Gabrielse. .~~~~~~ 0~~~~~~~~ ~ ~ .\ and uppermost North Americanstrata (Nelson and Bradford, 1978) have been recognized in the area; these are, in ascend- 1987). ing order, Swannell, Tsaydiz,Espee and Stelkuz formations. I04 British Columbia GeologicalSurvey Branch t LEGEND l ClalQUr DEVONIAN LOWER TO ORDOVICIAN alluvium AND RIVER ROAD SANDPILE, KECHlK4 GROUPS: Sandpile Group: up,9erpan is sandy dolomife, dofomife and minor quamite, lower m.sssive to thickly bedded limestone to dolomiflc limesfone [x,:z,AK€YOLCANICS: masshrebasalt, volcanic Road River Group: slate, calcareous dale Kechika Group: dark greyargil1acsou:r dolomite UPPERTRIASSICLOWERJURASSIC TO LOWER CAMBRIAN volcanic sandsfone, augite porphyy basalts, agglomerate, minor siirsrone, argiliite BOYA FORMAilON: basal orthoquamite succeeded by dive green siltstones and D EVO NIAN TOTRIASSIC(?)DEVONIAN shales. minor sandstone HARPER RANCH GROUP:argiilire, siifsrone PROTEROZOIC I Pin INGENIKAGROUP PENNSYLVANIAN TO PERMIAN , Undifferenfiared; garnet. staurolite - siilimanils SLIDE MOUNTAIN GROUP Schist and gneiss, marble and caicisiiicafe UPPER DIVISION volcanic STELKUZKIR~ATiON:basaip~~ris~h~I~, FJSlitstone gradi,?~ up to sandstone and minor limestone CheR, argiilite endgabbra ESPEE FORMATION:massive to fhinly bedded iimeslones and rscrysla;lized limesfone. marble. 1 PP~mueI Uitramatite TSAYDIZ FORMATION: grey green dales, . IT]phyilrfes, mmor sritstone, wackes and LOWER AND MIDDLE DlViSlON limestone Gabbro F] SWANNELL FORMATION:shale, phyiiire, feidspathk wacke, iimesrom, gernitiferous schists, gneis:i Argiliile at base, siliceous argiilile, massive to m.nbbon cheR, mimrgabbro MINERAL ISOGRADS UPPER DEVONIAN TO MISSISSIPPIAN -ct BiOTlTE EARN GROUP; blue grey iissile shale, argiiiite, "-+ GARNET mlnor sandstone --cC STAUROLITE -SILLIMANITE MIDDLE DEVONIAN MCDAME GROUP; dark grey ferid dolomite. grey doiomhe and limestone, breccia Figure l-ll-3b. Geological legend to accompany Figure l-ll-3a SWANNELL FORMATION composed primarily of ihin to thickly bedded, very me.- to The Swannell Formation is the most areallyextensive medium-grained quartz andfeldspathic wackes (feldspar formation of theIngenika Group, occupying roughly the content is typically less than 15 per cent). Subordinate t,) northeastern third of the map area. The exact thickness is these lithologies are very fine grained impure sandstones, difficult to deduce dueto polyphase deformation and lack of siltstones, grey to white marble, greenish slates and::reen t: continuous outcrop. It is upwards of 2 kilometres thick and is grey phyllite and schist. These rocks are metamorphosed t: tectonically thickened to the northeast. The basal part of the garnet,staurolite and sillimanite grade, with themet?. formation is poiydeformed, metamorphosed to sillimanite morphic grade increasing to the northeast. Schistjsin th.; grade and intruded by pegmatite and related granodiorite. vicinity of Garnet Creek commonly contain distinct r.eedlcs, Three generalsubdivisions of the SwannellFormation of metamorphic tourmaline in associ;ltion with large PO: have