.... v CANADA DEPARTMENT OF MINES AND RESOURCES MINES, FORESTS AND SCIENTIFIC SERVICES BRANCH GEOLOGICAL SURVEY OF CANADA MEMOIR 251 McCONNELL CREEK MAP-AREA, CASSIAR DISTRICT, BRITISH COLUMBIA BY C. S. Lord OTTAWA EDMOND CLOUTIER, C.M.G., B.A., L.Ph., KING'S PRINTER AND CONTROLLER OF STATIONERY 1948 Price, 25 cents No. 2488 PLATE I LU :t: t;- . -· - .- " - - .. - ·~ . ~;-~. -~i;1ff!:~ ~ /)?:.,""' ~.~.-~}:~T~·~ )f.~h~~~~'.':~~::~~~ ~-.,-~-;- j."':! ''-·., ~:-r .............t..,. .. · _~;:·;t'~'l'~ ~ ~ "~:«- . -- Lo o kin ~ south1•aslcrly from the norll11rnst end of Connelly Hangc. The µ:e ntlr in tli ned, 'rell-strati fic<l rocks a rc typical members of the Sustut group. In the centre distance is The Thumb, a projecting plug of Tcniarr basalt. The outlet of Bear Lake lies in the right middle distance. CANADA DEPARTMENT OF MINES AND RESOURCES MINES, FORESTS AND SCIENTIFIC SERVICES BRANCH GEOLOGICAL SURVEY OF CANADA MEMOIR 251 McCONNELL CREEK MAP-AREA, CASSIAR DISTRICT, BRITISH COLUMBIA BY C. S. Lord OTI'AWA EDMOND CLOUTIER, C.M.G., B.A., L.Ph., KING'S PRINTER AND CONTROLLER OF STATIONERY 1948 Price, 25 cents No. 2488 CONTENTS PAGE Preface......... .. .. ... ... ....... .... .. .... ... .................... v CHAPTER I Introduction...... 1 General statement . .. ... 1 Accessibility. 1 History............. ...... ... ..... ................... .... .... ..... 2 Physical features..... .. .. ...... .. ............ .. ... ........ .... 3 Glaciation. 4 Climate.. ... .. .............. ....... .. .. ... ...................... .... 5 Flom and fauna. 6 Bibliography. 7 CHAPTER II General geology ...... ... ..... .... ...... ............ .... .. .. .......... 8 Summary statement .............. .... .... ... .. .... .. ......... 8 Table of formations ........ ... ........................ ............ 8 10 Asitka group.Di~t;ib~ti~~.".".".". ". :: : : : : : ::: :::::::::::: ::: ::: :::: : : :::: :: : 10 Lithology ............. .. ............. .... ....... .... 10 Structure ....................... ....... ..... ... .... 11 Fossil collections ... .. ........ ......... .. ... .. ........ 11 Age and correlation ............... ...... .. ............. 13 Cache Creek group .................................................... 13 Distribution .. ... .. .............. .. ..... .. ............. 13 Lithology .... ... ...... ............. ................... 13 Structure .... .. ....... ............. ......... .. .... ... 14 Age . ... .. ....... .. ... ·········· · ········· · · ··· ····· ·· 14 Takla group . .... .. ..... ... .............. ... .. ...... .. ..... .... 15 15 ~tlfvi~r~~e·~·e-~~._-_._._.::::::::::::::::::::::::: : : : : : : : : : : : : : : : : : : 15 Andesitic and basaltic tuffs, agglomerates, flows, and tuffaceous argillites ................ .. .. .. .. ... ... ............... 15 Distribution ..... .. .......... ... .. .. .. .. ............. 15 Lithology ........... ... ...... ...... .. ......... .. ... .. 15 Meta-andesite and meta-basalt, greenstone, basalt, hornblende schist, and gneiss ... .. .......... ... ....... ................ 17 Distribution . ........ .. .. ...... .. ... .. ... .. .. ....... 17 Lithology .. .. ...... ..... ..... ...... ........... .. .. ... 17 Lirn:e~t~me, tuff, and argillite ... .. .... ..... .. ....... ... ..... 19 Upper div1s10n .... ....... ...... ... ...... ............... ..... ..... 19 Distribution .............. ....... .. .. ... ........ ...... 19 Lithology ...... ... .. .. ... ........... .. ... .. .. ...... 19 Fossil collections ... ... ... ..... ...... .... ...... ..... .. 22 Structure of the Takla group .. ... ... .. ...... .. .. .. .... ....... ... .. 25 Internal structural relations ....... .... ... .. ....... .. ..... 25 External structural relations ......... .................... .. ... 26 Age ............ ..... ............ ····.············ · ······ · ······· 27 Gabbro, peridotite, pyroxenite, dunite, and serpentine ...... .. .. .. ........ 28 Distribution ....... ...... .... .. ........ .......... ... .. 28 Lithology ............ .. ...... ..... .... ... ... .. ... ... .. 28 Structure .... ..................................... ... 30 31 Omineca i ntru~~;~.". .. ". ".:::::::::::: ::: : ::: :::: : :: ::: ::::::::::::::: : : : : 31 D istribution . ............... .. ............... ......... ... 31 Lithology ........................................... .... 31 Structure ... .. ... ... .... .. ... .. ... ..... .. ... .. ... 32 34 Sustut group.~~~.·::::::::::::::::::::::::::::::::::::::::::::::::::::: 34 Distribution . ................ ... ........ .. .... ... ..... 34 Lithology .... .... .... ... ..... .. ..... .. .. .... ... ..... 34 Metamorphism ... ... .. ............... .. .... .... ..... 37 Internal structural relations ..................... .. ...... 37 15410-1~ iv CHAPTER II-Cone. PAGE External structural relations .. .. ................... .... 38 Fossil collections ....... ... .. ...... ... ....... .... ..... 39 Age ......... ... .. ... ..... .. .... · · ·· ·· · ·· · ······· · 41 Kastbcrg intrusions . ............... .. ... .. .. ... ... .. .. ...... 41 Distribution ....... .. .. ... .. ... ...... .. ......... ... 41 Lithology ....... .. ................. ...... .......... 41 Structure ............... .. .............. ... .. ....... 42 Age ............................. ..... ·· · ·············· ·· 43 Basalt necks, dykes, lavas, and pyroclastic rockt> .. ..... .. ... ...... 43 Distribution . .. ............... ...... ........ ...... 43 Lithology ..... ... ..... .. .. .. .. ..... .. .. .. ...... 43 Structw·e . ...... .. .. .. ............ ... ... ....... .... 44 Age .... .. ......... .. ....... ...... ·· . ·.···· · · ········ 45 Pleistocene and Recent .. ....... ...... ... ... ... ... .............. 46 CHAPTER III Structure. 48 ' Faults........ ............... ..................................... 48 General description. 48 Detailed description. 49 Saiya fault. .. 49 Carruthers fault . ........... ..... ....... :...... .. .......... 49 Ominicetla fault. 49 Omineca fault. 50 Quenada fault. 51 Genlyd fault.... ... ... ... ............................. 51 Red Creek fault . 52 Asitka fault.......... ... ..... .. .. .. ... ... ............. 52 Driftwood valley. 52 Age of faults . 53 Folds.. .. .... .. ... ....... .. .... .. ... ...... ..... ... ....... 53 CHAPTER IV Historical geology. 54 CHAPTER V Economic geology . 56 General statement...... .. .......... .. .. .. ... ..................... 56 Metalliferous deposits .... ..... ........ .. .. .. ... .... ...... ....... , . 56 Placer gold deposits. 56 Lode deposits.... ......... ... ..... .. .............. ......... .... 58 Gold.. .... ..... .. ....... .. .. ... .. .. ................. 58 Copper and silver. 61 Lead and zinc. 63 Berylliwn. ... ....... ...... .... .............. .. .......... 64 Chromite. 64 Molybdenite. 64 Non-metallic deposits . 64 Coal ...... .. .............. .. ... .... ...... ...... .......... 64 Prospecting notes. 66 Index................ .. ... .. ........ ...... ... ..... ............ ....... 69 Illustrations Map 962A. McConnell Creek, Cassiar district, British Columbia ............. In pocket Plate I. View looking southeasterly from the northwest end of Connell y . Range. Frontispiece v PREFACE McConnell Creek map-area lies in a mountainous, relatively inaccess­ ible region near the centre of the northern half of British Columbia. Little was known about it until 1907-08 when placer gold was discovered on McConnell Creek. This activity, and that of a later rush of placer miners in 1932, quickly waned, without disclosing commercial mineral deposits or material geological information. Subsequent investigations by the Geolog­ ical Survey in areas to the south succeeded, however, in drawing attention to the McConnell Creek area as a possible source of lode deposits. Accord­ ingly, field work was commenced there by Dr. Lord in 1941, and, although interrupted by more urgent wartime duties, was completed by him in 1945. The present report is descriptive of the geology, structure, and economic features of the area. Granitic intrusions, both of Mesozoic and Tertiary age, are described, and the presence, in this part of the province, of a large area of Upper Cretaceous and Paleocene strata is noted for the first time. A belt of strong, post-Paleocene faults, in part continuous with the Pinchi fault zone, traverses the area from southeast to northwest, and probably extends far beyond. Many occurrences of gold, silver, copper, coal, and other minerals, found in the course of geological mapping and resultant active prospecting, are described. Although none of these is yet known to be commercially valuable many are of sufficient interest to warrant further search. As an aid to the prospector, Dr. Lord has listed the more favourable host rocks, and has defined the areas within which mineral occurrences are most concentrated. GEORGE HANSON, Chief Geologist, Geological Survey of Canada OTTAWA, March 25, 1948 McConnell Creek Map-Area, Cassiar District, British Columbia CHAPTER I INTRODUCTION GENERAL STATEMENT McConnell Creek map-area lies in the mountainous central part of northern British Columbia between latitudes 56 and 57 degrees, and longitudes 126 and 127 degrees. It includes about 2,600 square miles. Geological mapping was begun by the writer in 1941 and continued by him during 1944 and 1945. No previous geological mapping had been done in the area by the Geological Survey, although Malloch (1914) 1 briefly visited Sustut Valley in 1912 and correlated certain coal-bearing strata found there with his Skeena series of the Groundhog