Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

BCGS: Carbonatites, Nepheline Syenites & Related Rocks in British Columbia (Chapters 7&8) (Pell, 1994)


Published on

In 1994, British Columbia Geological Survey Geologist Jennifer Pell released a report on the potential for exploration of several minerals in British Columbia.

  • Be the first to comment

  • Be the first to like this

BCGS: Carbonatites, Nepheline Syenites & Related Rocks in British Columbia (Chapters 7&8) (Pell, 1994)

  1. 1. ,.., ~ ~~~~ ~ Ministry of Energy, Mines and Petroleum Resouxes KIMBERLITES IN BRITISH COLU1M:BIA THE CROSS KIMBERLITE (82J/2) et al., 1986; Ijewliw,1986,1987; Pell, 1987) and reader the is referred to those works for additional details. The Cross diatremeis exposed at an elevation of 2200 The Cross diatreme intrudes Pennsylvanian-Pennian metres on the north side of Crossing Creek, 8 kilometres Rocky Mountain Snpergroupstrata(Hovdebo,19.57). It out- northwest of Elkford (latitude 5O0O524W, longitude crops on steep face and an of approxitmate1:y by 15 a area 55 114"5948W). It is 60 kilometres east of the Rocky Moun- metres is exposed. Its western contact is wall exposed and tain Trench, or approximately20 kilometres east of the axis clearly crosscuts shallow-dippingcrinoidal dolo!:tones and of the zone containing the other intrusions in the Elk River dolomitic sandstones (Figure 82). Aminor s:hearzone forms - Bull River areas (Figure 73). It represents the only true the eastern contact. No thermal effects 011 the wallrocks were observed. kimberlite known in the province to date. Access is by heli- copter or by four-wheel-drivevehicle and a hike along an undriveable road. It has previously been reported on (Meeks, 1979;Robertsetal., 1980;Grieve. 1981,1982;Hall @ Creek f Crossing kirnberllts / 10.00 I 5.00 0.00 0.00 5.00 10.00 15.00 20.00 -25.00 3 . 00 03 + Crorrtng Creek 25.00 kirnberllte @ Averoga klrnberlile 20.00 1 ponolitlc barmillto lephrite Iarnprophyre 50 .0 bora11 0.00 " 20.00 30.00 40.00 50.00 60.00 70.00 SI02 Figure 83. Major element discriminant plots, Cross kirnberlite. Figure 84. Major element ternaryplots, Cross kinlberlite - Bulletin 88 103
  2. 2. ~~ ~ Ministry of Energy, Mines and P e t r o o Resources ECONOMHC CONSIDERATIONS AND EXPLORATION POTENTIAL Many metals and industrial minerals are either pro- al., 1986). The other British Columbia carbonatite com-duced from alkaline rocks or are known to occur in eco- plexes which have been examined all have averageNbzOsnomically significant amounts in alkaline rocks. Alkaline values of 0.30% or less, but there is excellent potentia1 forrocks are a major sourceniobiumand rare-eartb elements of the discovery of other carbonatites with potential ore-gradeamong the metals and of nepheline, barite, vermiculite, co- niobium concentrations.rundum and diamond among nonmetals. Molybdenum, the Tantalum is not abundant British Columbi:l carbona- inzirconium,copper, fluorite, wollastonite and apatite are also tites. Most of the complexes have NLxTa ratios typical ofrecovered from alkaline rocks. The important features of carbonatites, approaching 1OO:l or more ana niobiumeconomicallysignificant materials in alkaline rocks in Brit- grades are never sufficient to result in signifi.cant concentra-ish Columbia are outlined in the following summary. tions of tantalum. Carbonatites in the Blue River area have anomalous Nb:Ta ratios, in the order of 4:l and tantalumNIOBIUM AND TANTALUM analyses of up to 2400 ppm are reported (Aaqui:.t, 1982b). On average, however, theniobium grades Blue River are at Carbonatites contain the bulk ofthe worlds reserves of low, ranging between 0.06 to 0.1% NbzOs and, therefore,niobium, a metal whichis used in the production of high- even with anomalous NbTa ratios, currently suteconomictemperature speciality steels and superalloys for nuclear, with respect to tantalum.aerospace, heavy equipment pipeline applications. Nio- andbinm also has important potential as a superconductor of RARE-EARTH ELEMENTS ANDelectricity at cryogenic temperatures (Cunningham, 1985a).The principal niobium mineral carbonatites is pyrochlore, in YTTRIUMalthough other niobium-bearing species such as columbite Rare-earth elements are concentratedl in all alkalineand fersmite may also be present. The majority of the rocks. In carbonatites they are present mainlyin the form ofworlds niobium, approximately 85% of total production, the cerium subgroup, or light rare earths. A considerablecomes from Araxa, Brazil, where pyrochlore has been con- concentration of rare-earth elements may be contained incentrated by residual weathering and grades arc in the order common minerals such as calcite, dolomite, pyrochlore,of 3% NbzOs. In Canada, niobium is mined by Niobec Inc. fluorite, apatite, sphene and zircon. Rare-earth carbonate(Teck Corporation and Cambior Inc.) at St. 1Ionor6, near and fluorocarbonate minerals such as bastnaesite andChicoutimi, Quebec, where grades 0.5 to 0.67% NbzOs. are parisite, or phosphate minerals such as monazit: or xeno- Tantalum is a relatively rare, heavy, inert metal that is time, may also be present in alkaline suites a.nd contain rare-used in electronics, chemical processing equipment, metal- earth elements. Yttrium, although not strictly a rare earth, iscutting tools and high-temperaturesteel alloys. It is recov- commonly grouped with them its chemical properties are asered principally as a coproduct of other metal mining, similar to the heavy rare earths.associated with tin lodes, tin placers and beryllium-tin-nio- These elements are used principally in petroleum-biumpegmatites (Cunningham,1985b). Tantalum may also cracking catalysts, iron, steel and other metal-alloyingbe present in significant amounts in carbonatites, generally agents, glass-polishing compounds and glass add Itives, per-in the mineral pyrochlore. In alkaline rocks the Nb:Taratios manent magnetsand phosphors for television and lightingcommonly exceed 100,whereas in granitic rocks theyaver- (Hendrick, 1985). The rare earths also have importantpo-age 4.8 (Cume, 1976b). tential in the manufacture of superconducsm ar.d applica- Carbonatites in British Columbia areall anomalous in tions in advanced ceramics and lasers, piuticnlarly yttrianiobium. The Aley carbonatite complex appears have the to (Wheat, 1987). The U.S.A., Australia and China are the ma-greatest niobium potential of any of the complexes so far jor producers of rare earths (Griffiths, 1984; Hendrick,discovered. Work by Cominco Ltd. since 1982, which in- 1985). Most of the economic recovery the U.I .A. comes includes surface exploration and diamond drilling, has de- from the Mountain Pass carbonatite in Califonia, whichfined extensive zones in both the rauhaugite core and grades 7 8% total rare-earth oxides, predominiatly of the tosovites, containing between two-thirds and three-quarters of cerium subgroup. Bastnaesite is the principal ole mineral.a percent NbzOs (K.R. Pride, personal communication, InAustraliarareearthsarerecoveredfromnlonaziteplacers;1986) and grades which rival the St. Honor6 complex easily in China rare earths are recovered fromtabular magnetitein Quebec. Local areas containing greater than 2% Nbz0s iron ores, fluorite-quartz-carbonate and tungsten-quartzhave been outlined in the Aley complex. At Aley,the nio- veins, pegmatites and placers (Lee, 1970). Recently, the tinbium is present mainly in the minerals fersmite and pyro- greatest demand has been for samarium and nedymium tochlore; columbite is also present in minor amounts (Pride et be used inthe magnet industry and for yttrium in:?hosphors, - _"Bullelin 88 107
  3. 3. _" British Columbia " The diatreme is lithologically heterogeneous and, lo- between phases be gradational or sharp. Athin dike, 10 may tally, very friable. The west end o the outcrop is a light f to 30 centimetres wide, cuts the central breccia phase green, strongly foliated rock containing some red hematized Ultramafic xenoliths are almost entirely serpentinized clasts, abundant pelletal lapilli and cobble-sizedpellets, as pseudomorphs of olivine and pyroxene. The original pres- well as autobreccia fragments (western breccia phase). Fo- ence of olivine is indicated by the typical olivine outlin e and liation is at a high angle to bedding in adjacent sediments. fracture pattern; the grains, however are completel. 1 ser-1 This grades eastwards to a massive, inclusion-poor light pentinized. Some relict pyroxene, with characteristic c:leav- green unit (western massive phase) in turn grades into which age and birefringence, is preserved. Talc replaces pyroxene a rock with 40% inclusions, 5 to 10% of which are ul- to a limited extent and also rims and veins sapentinized tramafic xenoliths (central breccia phase). The inclusions grains. Interstitial spinels are also present in minor amounts. often form the cores of accretionary lapilli (Plate 55). Far- ther east the rock is a dark green, massive, unfoliated unit The interstitial spinels analysed on the energy dispersive withfewerclasts but containing abundant,randomly distrib- system of the scanning electron microscope are in the chro- uted phlogopite books and ultramafic xenoliths (eastern mite-hercynite solid solution series and can best be ~epre- massive phase). Bright red hematization is progressively sented by the formula (Fe, Mg) (Cr, A1)204 (Ijewliw, 1987). more evident toward top and the centre of the outcrop where The xenoliths may be broadly classified as spinel lher- entire mineral or xenolithic fragments may be hematized. zolites. Also preserved, although not abundant, are : m e t as € Pyrite is present as discrete grains in the groundmass and as lherzolites and glimmeritexenoliths (Hall et al., 1986,). rims surrounding clasts where it may, in turn, be enveloped The macrocryst population (0.5 to 5.0 mm insize:)con- by ragged, bright red hematite spotted phase). Contacts (red sists of completely serpentinized olivines, partially altered garnets, garnets with kelyphitic rims andphlogopites. They may be or round, oval lath shaped in random orientation and TABLE 18 make up 10 to 20% of the rock volume. Garnets sf~ow a CHEMICALANALYSIS moderate to high degree alteration or dissolution in reac- of CROSSING CREEK KIMBERLITE tion with the matrix. None are enhedral. They are rounded ~~~ ~ and irregular in shape and surrounded kelyphitic rims or by _wr % _ 1 2 3 reaction coronas of opaque iron oxides (Ijewliw, 198711.The Si02 Ti02 A1203 Fe203T 30.04 1.28 2.23 6.89 30.74 1.45 2.31 8.28 30.02 1.29 2.21 5.31 1.44 2.10 7.48 I;: 7.70 garnets arepyrope rich. Phlogopites are occasionally zoned, with rims darker and morestrongly pleochroic than cores and often displayingreversepleochroism (Halletal., 1986). The phenocryst population comprised of completely is MnO 0.12 0.16 0.09 0.11 MgO 25.03 27.72 23.54 27.75 0.151 23.84 serpentinized olivine, together with phlogopite and :;pinel CaO 13.48 9.78 14.94 9.55 14.21 (Plate 56). Phlogopite grains vary insize, are randomly ori- Na20 0.07 0.09 0.03 0.02 ented, square to rectangular in shape and relatively unal- K20 1.37 1.01 1.47 1.26 1.22 0.05I tered. Reddish brown translucent spinels are disseminated LO1 17.87 15.38 17.04 15.4 17.37 no5 0.99 1.06 1.03 0.99 in the groundmass and show magnetite reaction rims - 0.14 S 0.23 0.09 0.12 (Ijewliw, 1987). The groundmass composed ofca1ci:e and is Total 98.68 98.22 97.88 98.35 serpentine with minor apatite and anatase. ppm Ni 1000 1000 10W 1300 X90 Cr 12941398 1369 1747 1728 co 60 56 54 70 55 Rb 56 40 53 57 54 Sr 1177 1073 1171 1452 14921 Ba 3237 2642 3497 2648 3442 Zr 292 322 301 313 367 Nb 187 207 200 199 %30 Y 18 22 21 21 La 134 157 126 132 197 Ce 258 300 239 266 363 Nd na na na na na Yb 2 1 3 0 .:-I sc 20.323.1 23.7 20 25.1 Ta 7 14 9 11 11 iu !"c j u Th 14 73 1 18 14 196 54 19 196 24 15 208 50 2 18 ; 51 All amlyss8 b;vXRF, B.C. G.S.B.analytical laboraforv 4 41 1. .CX5-6 K n i . . 0.00 400.00 800.00 1200.00 1600.00 2. - CX57BHemotire-spotred kimberlite: red-sparredphase: Cr ppm ~- 3. - CX5-8A Kimberlife, easrem massivephase: 4. - CX6-Dl Fine-grained crosscutting, inclusion-free dike; Figure 85. "Average" values from Wederhal Maramatsu 1979. and 5. - CX5.7Micaceouskimberlite, red-sparfedphase. Ni vs Cr plot, Cross kimberlite. 104 Geological Survey Itranch
  4. 4. Ministry of Energy, Mines and Petroleum ResourcesGEOCHEMISTRY GEOCHRONOLOGY TheCrossdiatreme is the only trne kimberlite so far Rubidium-strontiumdating of micaseparateshasrecognized in the province. It fits both the petrologic and yie,ded Pemo-T~assicages of 240 244 k,a for thegeochemical definitions of a kimberlite (Figures 83 and 84; Cross kimberlite (Grieve, 1982; Smith, 1983; F:all et al.,Table 18 ). Although it appears to bequite a heterogeneousintrusion, analyzed were all v e similar geochemi- ~ 1986 ). Both the Cross kimherlite and its hostrocks are sig-cally. It is characterizedby low silica, high magnesium, high nificantly younger than other British Cohtmbia diatremestrontium and high nickel and chrome(Figure 85; Table 18). suites. ~~-Bulletin 88 105
  5. 5. ~-106 Geological Survey Eranch
  6. 6. engineering ceramics and superconductors(Roskill Infor- he 1 to 4 metres wide and over metres long. Mafic syenite 30mation Services, 1988). dikes in the area generally contain lower concentrations of Significant enrichment in rare-earth elements is re- rare earths than the pegmatites; local concentrations up toported from five localities in British Columbia, the Aley 4.26% total rare earths have been found (Halleran andcomplex and Rock Canyon Creek, both Rocky Monn- in the Russell, 1990). Very little work has been done the IvIount intains; the Wicheeda Lake area along the Rocky Mountain Bisson area and preliminary results indicate some potential;Trench near Prince George; Kechika River area in the the this area might warrant further work in the future, particu- Cassiar Mountains; and the Mount Bisson area in the larly if the demand for cerium and lanthanum incream.Omineca Mountains. Aley narrow At dikes enrichedin rare- The presence of these five highly anomalous occur-earth elements, and locally fluorite, cnt the altered sedi- rences indicates that British Columbia is highly prospwtivements peripheral to the main complex. Samplescontaining for economic accumulations of carbonatite-related rare-in excess of 2.1% total rare-earth oxides are present. The earth elements.rare earths are contained in carbonate minerals as bast- such naesite, burbankite, cordylite and huanghoite (Miider, ZIRCONIUM 1987). These dikes are thin and sporadically developed and,although worthy ofnote, not of major economic interest. Zirconium is strongly concentrated in some alkaline At Rock Canyon Creek a metasomatically altered (feni- rocks and comprise up 2%. The main zirconium may to min-tized) zone rich in rare earths and fluorite, measuring ap- erals present in these rocks are zircon, eudyialite (Na-Zr sili-proximately 1000 by 100 metres, has been identified. cate) and haddeleyite (ZrOz), with alkaline rocks beir,g the Samplescontaininginexcessof 2.7%total rare-earthoxides only known source of substantial amounts of haddele yite. (predominantly cerium and lanthanum oxides) have been The major application of zirconium is in four driesobtained from outcrops this zone.The rare-earth fluoro- of where it is in mineral form facing for molds for metal used ascarbonate minerals hastuaesite and parisite, and gorceixite, casting. It is also used in refractories, nuclear powerappli-a phosphate mineral, have been identified. At RockCanyon cations and chemical processing equipment. increasing Of Creek, locally high rare-earth values at surface, the size of importance is the application of zirconium inadvanccd ce-the zone and lack of extensive work suggest that further the ramics which have suchdiverse uses as heat-resistant tiles,work is warranted. sensors and automobileexhausts. The principal sources of zirconium are zircon recovered as a hyproducl. from tita- In the Wicheeda Lake area a series of alkaline rocksincluding carbonatites, syenites and leucitites are exposed. nium placer deposits and haddeleyite produced as a copro- duct from apatite mining ofthe Palabora carhonatite, SonthWork by TeckCorporation has indicated that one carhona- Africa and of niobium mining Araxa and Pocos C aldas at detite plug locally contains in excess of 4% total rare-earth carhonatites in Brazil (Adam, 1985).elements and one trench, across part the carbonatite, ex-posed material grading 2.60% total rare earths over its 42- Zircon is a ubiquitous phase in carbonatitc: andmetre length (Betmanis, 1988). These valnes are nephelinesyenite gneiss complexesin BritishCo1umb.a andpredominantly in light rare earths, in particular cerium and crystals often exceed 1 centimetre in length. The Aley com-lanthanum,however, the results are favourahle and area this plex, Paradise Lake syenite, Verity carhonatite, Tjidentmight warrant further work in the future, particularly ifthe Mountain syenite and Lonnie and Vergil complexes all con-demand for cerium and lanthanum increases. tain coarse zircon inexcess of 1%. In the Lonnie. and Jergil complexes, the syenitic rocks may contain 3 to 15% zircon In the Kechika River area, alkaline rocks consisting of locally. Althoughit is unlikely that any of these rocks couldsyenites, malignites, breccias and fenites are intermittently compete with placer deposits, it is possible that zircceiumexposed along a northwest-trending zone in excess of 15 could he produced as a hyprodnctof niobium 0.r rare..earthkilometres in strike length. During a recent exploration pro- mining and should hetested for.gram, samplescontainingin excess of 3.77% total rare-earthoxides (mainly cerium snhgronp elements) werecollectedfrom carhonatite dikes; other samples containing up to PHOSPHATES 1.13% Y203, 0.30% NdzO3, 0.11% Sm2O3 and 0.14% Ultrabasic alkaline igneous complexes commonly con-Dy2O3 were taken from phosphate-richsegregations, con- tain high concentrations of phosphate, largely in the fcrm oftaining upto 19.3% P2O5, in a mylonitized syenitekrachyte themineralapatiteandapproximately 18%ofallphos&hates(Pel1 et al., 1990). Rare-earth elements and yttrium in the mined come from igneous complexes. Apatite: from car-Kechika River area are present mainly in monazite, xeno- bonatites is mined at Palabora, South Africa; Dorowa, Zim-time and other phosphate minerals. The size of this zone, babwe; the Kola Peninsula in the U.S.S.R.; and Araxa andlack of detailed work and presence of anomalous concen- JacupirangainBrazil (Currie, 1976a;Russell, 1987; Feman-trations of heavy rare-earth elements suggest additional that des, 1989). Grades as low as 4% P2O5 are currently recov-work is warranted. ered. Approximately 90% all the phosphatemined i:; used of Light rare-earth elements, particularly cerium and lan- in the fertilizer industry; other uses include organicm d in-thanum, are concentratedin allanite pegmatites and allan- organic chemicals, soapsand detergents, pesticides, :nsec-ite-hearing mafic syenite dikes that are associated with large ticides, alloys, animal-food supplements, ceranics,fenite zones in the Mount Bisson area. Some of the pegma- beverages, catalysts, motor lubricants, photographic mate-tites reportedly contain up to 14.5% total rare earths and can rials and dental cements.108 Geological Survey 1:ranch
  7. 7. ~ ~ M n s r of Energy, Mines and P e t r e Resources iity In British Columbia, all carbonatites contain some apa- 1989). The remote location of this body, howeve!; severelytite. The Aley complex and carbonatites in the Blue River limits its economic potential.area are more enriched in apatite than many of the othercarbonatites, containing, on average, 5 to 15% apatite, with VERMICULITEP205 contents up to 11% (Tables 1 and and averaging 9) 3.5to 5%. The Ren carbonatite also has an average120s content Vermiculite is a mineral which expan& whm heated.of approximately 3.5%, with maximum values of 4.2% (Ta- It is formed from alteration o biotite or phlogopite and a f isble 12). Carbonatitedikes cutting ultramafic rocks of the Ice characteristic accessory in ultrabasic rocks associated withRiver complex locally contain np to 8% PzOs (Table 3). carbonatites. Vermiculite is present in minor amounts asso-Syenitic mylonites in the Kechikaarea contain small zones ciated with carbonatites in the Blue River area, but is notwhich assay as high as 19.3% P20s and haveapatite as one reported from other areas. The potential for vermi<:ulite pro-of the major rock-forming minerals. contin.uity of The these duction from carbonatites in British Columbia is :xtremelyphosphate zones is unknown and it is unlikely that they limited.would be exploited for phosphate alone. MOLYBDENUM It has been estimated that the Aley complex may con-tain as much as 15 billion tonnes of 5% P2O5, while other Molybdenum is generally associated with granitic ascarbonatites probably contain only a few million tonnes of opposed to syenitic rocks, but,in some c a w , it may bepre-phosphate reserves (Butrenchnk, in preparation). Produc- sent in alkaline complexes (Currie, 1976a). In British Co-tion of phosphates from these carbonatites as a primary lumbia, the nepheline syenite gneisses associate1 with thecommodity is unlikely in light of competition from sedi- Frenchman Cap domecommonly contain nlolybdenite andmentary deposits, but byproduct recovery apatite might of the Mount Copeland showings the focns of r.ignificant wereprove feasible, particularly in the case of Aley, if niobium exploration and development work inthe late 1960s (Fyles,were to be mined. 1970). Current economics,however, do natfavour exploi- tation ofmolybdenum from such deposits.NEPHELINE AND NEPHELINE SYENITE WOLLASTONITE Nepheline and nephelinesyenite are of major impor- Wollastoniteis an important mineral nscd primar- fillertance in the glass and ceramicsindustries due to their high ily in the paint and ceramics industries. It #:an b,: found inalumina contentin the presence of abundant sodium; these two main geological environments:contact .metarnorpbicorelements act as a flux which affects the rate and temperature metasomatic (skarn) deposits and in carbonatite!:, as a pri-of melting, the flnidity of the melt andthe physical proper- mary, magmatic mineral. Most world production comesties of the finished product. Small amounts also used in are from contact deposits (Harben andBates, 1990).paints and as fillers in plastics. Canada is currently the larg- Wollastonite has not been recognized in any carbona-est free-world producer of nepheline syenite which is all tites in British Columbia; however, it is worth looking forquarried in the Blue Mountainregion of Ontario. in fntnre discoveries. Nepheline syenite occurs in large volumes in a numberof areas of British Columbia; the Ice River complex, Bear- TITANIUMpaw Ridge, Paradise Lake, Trident Mountain, the Perry Titanium-bearing minerals are present in a inumber ofRiver area and Mount Copeland.With the exception of the the carbonatite and alkaline rock complexesin Rritish Co-latter, most are relatively inaccessible. TheMonntCopeland lumbia. Sphene,perovskite and ilmenite have all been rec-syenite gneisses, which are located 25 kilometres northwest ognized. As well, knopite, a rare-earth emiched variety ofof Revelstoke, may be reached by old mining roads. Onav- perovskite, has been reported from the Ice R.iver areaerage they contain moreiron, manganese, calcium andpo- (Ellsworth and Walker, 1926).In most cases, these titaniumtassium, and less sodium, silica and aluminum than thoseat minerals are present in relatively low concent:ations; atBlue Mountain (Table 11; Currie, 1976a). In general, the Howard Creek, however, sphene is a rock-forming mineralMount Copeland syenites are medium to coarse grained and in a melteigite of limited spatial distribution. It is unlikelyit was considered that many of the impurities (ferromagne- that titanium could be produced from any of th,:se wcur-sian minerals - in particular biotite) could potentially be rences.removed by crushing and magneticseparation techniques;however, beneficiation tests failed to produce a product with DIAMONDa low enough iron content to meet industry specifications(White, 1989). Some of the other syenites, such asthe Para- Diamonds were traditionally considered to be prcsentdisesyeniteorthelargehodyonTridentMountain,arequite in economic concentrations in kimberlites oniy. Recentsimilar in composition to those being minecl in Ontario. studies have shown that they may also be recosered fromBeneficiation tests run on samples from Trident Mountain lamproites, and they havealso been reported fro:n such di-indicate that this syenite is low in magnetic impurities, has verse rock typesas peridotites and even carbonaites. Onlya high recovery rate of nonmagnetic materials and, there- one true kimberlite has been discovered Briti:;h Colum- infore, has good potential to produce a commercial-grade bia, the Cross diatreme, but no results of laboratoly research anepheline syenite product with brightness of 85% (White, or on mineral composition diamond recovery have been re- _"Bulletin 88 109
  8. 8. ~British Columbia "Stevens, R.D., Delahio, R.N. and Lachance, G.R. (1982):Age De- sition of Three Basaltic MagmaTypes; in Kimberlites, Dia- terminations and Geological Shldies, K-AI Isotopic Ages, tremes and Diamonds: Their Geology, Petrology and Geo- Report 16;Geological Surveyo Canada, Paper 82-2. f chemistry,American Geophysical Union, Procwdings oftheStewart, J.H. (1972): Initial Deposits in the Cordilleran Geosyn- Second International Kimherlite Conference, Volume 1, cline: Evidence of Late Precambrian (R my) Continental pages 300-312. Separation; GeologicalSociefyofAmerica,Bulletin,Volume Wheat, T.A. (1987):Advanced Ceramics Canada; in Canadian In- 83,pages 1345-1360. stitute ofMining andMefaNurgy,Bulletin, Volume 80,Num-Stewart, J.H. and Poole, F.G. (1974):Lower Paleozoic and Upper- ber 900,pages 43-48. most Precambrian Miogeocline, Great Basin, Western Wheeler, J.O. (1962): Rogers Pass Maparea, British Col~mbia United States; in Tectonics and Sedimentation, Sociefy of and Alberta;Geological Survey o Canada, Map 43-1 f 962. Economic Paleontologists and Mineralogists,Special Puh- Wheeler, J.O. (1963): Rogers Pass Map-area, British Colmhia lication 22,pages 28-57. and Alberta;Geological Surveyo Canada, P a p 62.32. fSymons, D.T.A. and Lewchuk, M.T. (in press): Paleomagnetism Wheeler,J.O.(1965):BigBendMapArea,BritishColumhia;Geo- of the MississippianHP Pipe the Western Marginof the and logical Survey of Canada, Paper 64-32. North American Craton; American Geophysical Union, Monograph Series. Wheeler, J.O., Campbell, R.B., Reesor, J.E. and Mountjoy. E.W. (1972): Structural Style of the Southern Canadian C!ordil-Taylor, G.C. and Stott, D.F. (1979): Monkman Pass (931)Map lera; International Geological Congress, Excursion A-01- Area, British Columbia; File Report 630. GeologicalSurvey o Canada, Open f xo1. White, G.P.E. (1 982):Notes on Carbonatites in CentralBriti ;h Co-Thompson,R.I.(1978):GeologicalMapsandSectionsoftheHalf- lumbia; in Geological Fieldwork1981,B.C. Ministry of En- way River Map Area, British Columbia (94B); Geological erg3 Mines and Pefroleum Resources, Paper 1!>82-1, pages Survey o Canada, Open File Report f 536. 68-69. (1987)Extension andThompson, R.I., Mercier, E. and Roots, C. White, G.P.E. (1985): Further Notes on Carhonatims in C!entral its Influence onCanadian Cordilleran Passive-margin Evo- British Columbia;in Geological Fieldwork1984,B.C: Min- lution; in ContinentalExtensional Tectonics, Howard, M.P., istry of Energ3 Mines and Petroleum Resources, Paper Dewey, J.F. and Hancock,P.L., Editors, GeologicalSociety, 1985-1, pages 95-100. Special Publication 28,pages 409-417. White, G.V. (1989):Feldspar and Nepheline Syenite Potertial inVaillancourt, P. and Payne, J.G. (1979):Diamond Drilling Report British Columbia;in Geological Fieldwork1988,B.C Min- on the LonnieRitch Claims, MansonCreek Area, Omineca istry o Energy, Mines and Petroleum Resources. Paper f Mining Division; B. C. Ministry ofEnergy, Mines and Petro- 1989-1, pages 483-487. leum Resources, Assessment Report7515. Wooley, A.R. (1982):ADiscussion of CarhonatiteEvoluticm andvon Knorring, 0. and du Bois, C.G.B. (1961): Carbonatite Lava Nomenclature and the Generation of Sodic :md Potassic from Fort Portal Area in Western Uganda;Nature, Volume Fenites; Mineralogical Magazine,Volume 46,pages 13-17. 192,pages 1064-1065. Woyski, MS. (1980):Geology of the Mountain Pass CarbmatiteWarhol, W.N. (1980): Molycorps Mountain Pass Operations; in Complex - A Review; in Geology and Mineral Weatk ofthe of Geology and Mineral Wealth the California Desert, South California Desert, South Coast Geological Society, pages Coast Geological Sociefy, pages 359-366. 367-377.Wedepohl, K.H. and Mnramatsn, Y (1979):The Chemical Com- . the position of Kimberlites Compared with Average Compo- -~124 Geological Branch
  9. 9. ported by industry.Microdiamonds have, however, report- have also been reportedfrom alkaline lamprophyre dikes inedly been recovered from of the lamprophyre diatremes two the Golden - Columbia Icefields area. One of the pipes Nepheline syenites are known from a localities in fewreported to have yielded microdiamonds from concentrates B.C. (e&, Paradise Lake, Ice River, etc.). These areas havecollected and processedat two different times, from differ- not been evaluated for their potential to contain gem corun-ent laboratories. Asignificant amount additional research of dum. Alkaline lamphrophyres are present in the Rcckiesis necessary to establish if economic concentrations are pre- (e.g., Golden cluster) and couldalso be prospected fa: gemsent. corundum varieties. Blue corundum crystals (star sapphires) up to 1 to 2GEMSTONES centimetres in size, have recently been discovered in the Corundum (sapphire, ruby) is a common accessory Slocan Valley withina syenitic phase o the Valballa Gneiss fmineral in silica-undersaturated, alumina-rich rocks as such Complex, part of the Passmore Dome. These gneisser alsonepheline syenites and nepheline-feldspar pegmatites. In contain sphene and amphibole and, in outcrop, resemblethe Bancroft area of Ontario,corundum occurs nepheline- in fenites in the Blue River and Perry River (Z.D. Hora, areas ofbearing rocks and marginal zones nepheline syenite in- personal communication,1993). Fenites are widesprer.d, as-trusions at Blue Mountain and elsewhere. Nepheline sociated with carbonatites and syenite gneiss complexessyenites at Cabonga Reservoir, Quebec contain blue corun- within metamorphosed rocks or the Ominica Belt anddum crystals mantled by biotite (Currie, 1976a). Sapphires for should be prospected gem corundum. _"110 Geological Survey 3ranch
  10. 10. Ministry ojEnergy, Mines and Pelruleurn Resources SUMMARY AND CONCLUSIONSCARBONATITESAND SYENITE are sill-like bodies with extensive fenitic aureolss. WorkGNEISSES done to date indicates moderate enrichment in rare-earth elements, with or without niobium. Carbonatites and syenite gneisses crop out inthreebelts There appears to be a relationship between depth ofparallel to the Rocky Mountain Trench. The intrusions in the emplacement, degreeof associated metasonratism and en- eastern Rocky and Cassiar Mountain are middle Paleo- belt richment in economically interesting elements suchas nio- zoic, predominantly Devono-Mississippian in age, hosted bium or rare earths. All of these factors are prohabl y relatedby lower to middle Paleozoicstrata and therefore are rela- to the original volatile content of the magma.. The most fa-tively high-level intmsions. They can be large and elliptical vourable areas for additional exploration for these slements in shape and have significant alteration halos (e&, Aley car- would appear to bethose underlain by lower to middle Pa-bonatite), consist simply of metasomatic alteration zones leozoic strata of North American affinity. The western or (e.& Rock Canyon Creek showing), be extensive linear Rocky Mountains and some regions of the eastern 13minecabelts comprising numerous and lithologically varied sills, Belt, close to the Rocky Mountain Trench, have the best dikes and plugs (e.g. the Wicheeda Lake and Kechika River potential. Byproduct recoveryof apatite and zircon should showings). The carbonatites in the eastern belt can be sig- also be considered when assessing the niobium or me-earth nificantly enriched in niobium, fluorine, yttrium and rare- potential of any prospects. earth elements. Commercial-grade nepheline syenite could pcttentially The central belt lies within the Omineca Belt, immedi- be produced from the Trident Mountain syenite, however,ately west ofthe Rocky Mountain Trench. The intrusions in current inaccessibility precludes immediate exploitation. Ifthis belt are also Devono-Mississippian in age, hut are this area were everto become moreaccessible, through thehosted by Precambrian strata; they were not emplaced as development of good loggingroads, the nepheline syenitehigh in the stratigraphic succession as those in the eastem potential of this body would warrant serious exar.lination.belt. The carbonatites in the Omineca Mountainsare thin, Other compositionally similarsyenites are presentin Britishdiscontinuous, sill-like intrusions generally with narrow Columbia, but are also in remote locations and remain un-fenite alteration halos. With one exception Mount Bis- (the tested.son intrusions), they are not enriched in niobium, as fluorineor rare-earth elements as their eastern counterparts. KIMBERLJTES, LAMPROPHYRES AND The western belt, also within the Omineca Mountains, OTHER ULTRABASIC DIATREMEScomprises intrusive and extrusive carbonatites and Ultrabasic diatremes have been recognized areas in fivenepheline syenite gneisses hosted by the autochthonous of British Columbia; the Kechika River and Ospika Rivercover sequence of the Frenchman Cap gneiss dome. The areas of northern British Columbia, the Goldan, Bull Riverenclosing metasedimentary rocks of uncertain age, how- are -Elk River and Elkford areas of the Kcatenays. Iri the Os-ever, recent studies suggest that they mayhave been depos- pika River area north of Mackenzie, and in the Columbiaited in a period which spans Precambrianto Eocambrian late Icefields area north of Golden (Figure Z, the diatrwnes are )time (HOy and Godwin, 1988). A single radiometric date, characterized by macrocryst-rich breccias and dikes. Theobtained on one of the alkaline intrusive bodies (Mount macrocryst population consists of clinopyroxene, phlo-Copeland syenite) which occurs near the base of the man-tling gneiss succession, indicates an age of emplacementof gopite, green diopside, spinel and olivine, with either py- roxene or phlogopite as the most abundantphase. In somecirca 770 Ma for that intrusion (Okulitch et al., 1.981).This cases, microphenocrystic feldspars are present :,.nsmallgives a minimum age for the basal part of the succession. amounts. These rocks aretentatively classifi,ed as lampro-Much higher in the mantling gneiss stratigraphy, overlying phyres; the HPpipe in the Golden area and the Ospika pipethe carbonatitehorizons, a strataboundlead-zincdeposit has can he classified as aillikites, which are members c f the ul-yielded an Eocamhrian to early Cambrian lead-lead date. tramafic lamprophyreclan based on their modal mineralogyThis suggests that the highest stratigraphic levels of the and, to a lesser extent, the chemistry. The other ultrabasicmantling gneiss succession are Early Cambrian and the in- intmsions in the Golden area are more difficltlt to classify;tervening stratigraphy was deposited between Late Protero- they appear to be most similar to amphibole-free alkalinezoic and early Paleozoic time. The extrusive carhonatites lamprophyres.In all cases the breccia pipes commonly con-are located relatively high in the mantling gneiss stratigra- tain multiple phases of intrusion characterized by variablephy, approximately 100 metres below the lead4nc layer proportions of xenoliths, macrocrysts and accretionaryand, like the lead-zinc deposit, are probably Eocambrian in lapilli or spherical structules. The breccia matrix in someage. cases is clearly magmatic. These pipes are characteristic of The carbonatites in the western belt comprise high- the diatreme facies material, as described from kilnberlitelevel intrusions and extrusives. The carbonatite intrusions pipes and/or hypabysal-facies (Clement and Reid, 1986).Bullelin 88 111
  11. 11. . ~~ Brirish Columbia ~~~~ “ They formed from extremely volatile-rich magmas, so rich, diatreme-facies tufflsitic breccias. Some pipes bneached the in some cases, that as they reached the surface and vesicu- paleosurface andthe upper parts of the crater zone contain lated, the magmatic phase exsolved from volatiles and the beddedepiclasticorpyroclasticrocks.Anumhert~fthe])ipes actually formed the ‘bubbles’, as indicated by the spherical - in the Bull River Elk River area intrude Ordovician-Silu- stmctures (or globular segregations) and armoured xeno- rian Beaverfoot carbonate rocks and contain bedded cl’ater- liths. At Lens Mountain, Mons Creek and Valenciennes facies material which is unconformably overlain b., the River sandy tuffisitic or gas-stream breccias, with an insig- basal Devonianunit (MiddleDevonian) suggesting anl3arly nificant recognizable igneous component, are present. also Devonian age of emplacement of approximately 4oC Ma. Rubidium-strontium and potassium-argon dates of Other pipes and flows apparently underlie and predate the 3381r3 and 323f10 Ma have been obtained from phlogopite Beaverfoot Formation, but cut middleSilurian rocks and, separates from the Ospika pipe. These dates indicate that therefore, must be approximately 455 Ma in. age. The emplacement occurred inDevono-Mississippiantime, as is Kechika pipe is also hosted by Ordovician to Silnrian litrata the case for the most of the carbonatites in the eastern and and associatedwith bedded tuffs whichmust be of the Same central belts. Aillikites and alnoites arenoted for their affili- age as the host strata (possibly circa 450 Ma.). ation with carbonatites (Rock, 1986). Pipes and dikes from The craters containing these breccias are envisaged to two areas north of Golden have also been dated. In area, that have a ‘champagne glass’ structure, similar to that of lam- most of the diatremes were emplaced slightly earlier, in proite or basaltic craters, with no extensively developedrmt Early Devonian time (circa 400 Ma). Zircons from ultra- zone. The breccias are commonly associated with cro5 scut- basic rocks in the Mons Creek yielded concordant area lead- ting porphyritic dikes and flows, characterized by the pres- lead ages of 469 Ma; ifthese zircons are not xenocrystic, it ence of phenocrystic olivine and titanaugite, with ahwdaut may indicate that there was athird period of emplacement feldspar (plagioclaseorpotassiumfeldspar),titanaugite and in the Late Ordovicianto Early Silurian. opaque oxide microphenocrystsin a fine-grained ground- Intrusions in the Bull River and Kechika are dis- areas mass. These rocks are extremely difficult to classify: they tinctly different than those in the Golden or Ospika areas. are ultrabasic, and locally quite potassic, feldspar-bearing They are characterized by chaotic breccias containing abun- rocks that can contain vesiculated glass lapilli and are gen- dant vesiculated glass lapilli, juvenile lapilli and rare altered erally devoid of hydrous mafic minerals and feldspathoids. olivine, altered pyroxene, feldspars and chromian spinel They may have originated in volatile-enriched systems, but macrocrysts and by theabsence of primary micas. The ma- not to the extent of the previous diatremes; as ihey n:ared trix of these breccias is not magmatic; they are crater and the surface the volatiles exsolved fromthe maglna and not Figure 86. Structural position diaEemes, B - Bush River;C -Lens Mountain; D - Mons Creek;E - Valenciennes River;P HP pipe; G of - Shatch Mountain;H - Russell Peak;I - Blackfoot;J - Quinn Creek; K - Summer :L - Crossing Creek, Geology modified from Wheeler (1963),Wheeleretal., ( 1972),Leech (1979), Price(1981). ~~ 112 Geological Survey haranch
  12. 12. Ministry of Energy, Mines and Petrnleum Resourresthe reverse. In some cases they maybe tentatively classified North America, it is unlikely that significant concentrations as limburgites, in others they appear to be most similar to of diamonds can found in nonkimberlitic rock!: originat- be members of the alkaline basalt family, but gmerally are ing so far from the stable craton; however, the we.;tern con-more basic than typicalalkaline basalts which suggests that tinental margin at the time of diatreme emplacement wasthey are verging towardsnephelinites. probably significantly more complex than theone proposed The last distinct rock typeis represented by one exam- in Haggerty’s model for South Africa. The locat ion of theple, the Cross kimberlite, located at Crossing Creek, nortb of westem edge the continental mass at that time is unknown of Elkford. As the nameimplies, it is a true kimberlite, the and the depth to the lithosphere-asthenosphere bcandary isonly one so far recognized in the province. It is apparently also uncertain, therefore, the proposed constraints on dia-a deeply eroded pipe remnant and contains two generations mond genesis may be not directly applicable.of olivine, phlogopite, pyroxene, garnet and spinelmegacrysts as well as garnet and spinel lhemlite nodules TECTONIC IMPLICATIONS (Hall etal., 1986). Rubidium-strontiumisotopic ratios indi-cate that the pipe was emplaced in Permo-Tiiassic time, The emplacement of carbonatites, kimberlites andcirca 245 Ma (Grieve, 1982; Hall etal., 1986). other alkaline rocks in the Canadian Cordillera appears to be related, in part, to extension and rifting along t t e western At this point it is difficult to completely assCss the depth continental margin that produced and deepened the basin of origin and diamond potential of theserocks. The Crossing into which the miogeoclinal succession ‘was t.eposited.Creek kimberlite apparently originated deep in the mantle, Sedimentological and stratigraphic evidence inc.icate thatit contains abundant pyrope garnets and has sampled mantle the western continental margin was tectonically activelithologies including garnet lherzolites. This suggests that it throughout much of the Proterozoic and Paleozc,ic eras. Itmay have originated at depths generally considered suffi- does not appear have behaved entirely in a passive man- tocient to be in the diamond field; however, diamond genesis ner and therefore may not be strictly analogous lo the pre-apparently depends on oxygen fugacity as well as pressure sent day Atlantic margin, as earlier workers proposedand depth origin alone is not sufficient to predict thedia- of (Stewart, 1972; Stewart andPoole, 1974); rather it appearsmond potential of a pipe (Haggerty, 1986). The pipes inthe that several superimposed ‘passive margin-type’ :;equences other arms of British Columbia do not appear to have origi- are present as a result of periodic extensional activity (Pellnated as deep in the mantle as the Crossing Creek kimberlite. and Simony, 1987; Thompson e t al., 1987). During theseThey contain no good evidence of deep mantle xenoliths; periods of extension, deep faults and fractures in the crustthe xenolith and xenocryst populationsare generally con- may have released pressure and triggered partial melting,fined to crustal material: rare eclogites, spinel. lberzolites, whichultimatelyresultedinalkalinemagmatism(Tab1e19).chrome spinels and very rare pyrope garnets (Northcote, 1983a, 1983b). This suggests an origin in the spinel lher- The earliest event recorded alkaline activi:y in west- byzolite field of the uppermantle, which is generally consid- ern Canada is represented by the Mount Copelandsyeniteered to be at pressures below those required for diamond of Late Proterozoic in age (circa 770 to 750 Ma);it mayformation. Microdiamonds reportedly found in two of the record extension or rifting of the North Ame:rican (craton andpipes in the Golden swarm suggest that these pipes may the initiation of the Late Proterozoic Windermere basin. Di-have sampled the uppermost levels of the diamond field. abase dikes and sills of similar age (770 Ma) in northern Canada also record extension preceding Windemlere depo- When comparedto current models, it appears that theprobability of British Columbia diatremescontaining eco- sition (Armstrong et al., 1982). Slightly younger datas ofnomic concentrations of diamonds is low. From craton to 728 and 741 Ma (U-Pb, zircons) have been obtained frommargin, a sequence of kimberlite with diamond, kimberlite granitic gneisses which appear to be basemen1 for Win- dermere Supergroup strata in north-central and central Brit-without diamond(e&, Cross) and diamond-free ultrabasic ish Columbia ( Parrish and Armstrong, 1983; Evznchick efdiatremes (nonkimberlitic) is commonly proposed (Hag-gerty, 1986). In an attempt to establish the original positions al., 1984). This implies that rifting began as early as 770 Ma in some areas, but that the event spanneda pericd of timeof the diatremes relative to the North Americancontinent, and, locally,Windermere sedimentation not beginuntil didtheirpositions have beenprojectedonto cross-sections (Fig- after 730 Ma.ure 86). If these sections were restored to predeformationalconfigurations, the pipes contained in the most westerly Sedimentary loading and synsedimentary faulting (Listhrust sheet would have been the farthest outboard. The and Price, 1976; Eisbacher, 1981; Root, 1.983; Bond andCross kimberlite is in the Bourgean thrust sheet and is the Kominz, 1984; Devlin and Bond, 1984) accoun:ed for theeasternmost of the diatremes. The ultrabasic diatremes in deepening of the basin and the continuation of depositionthe Bull Riverarea are carried by the Bull River Gypsum - into the early Paleozoic. Minor extensional activity is alsofault (Figure 86), which is west of the Bourgeau thrust. As indicated by the presence of acid to basic volcanic andin-the faults are traced to tbe north, the Bull River- Gypsum trusive rocks throughoutthe Hadrynian to early Paleozoicthrust apparently dies out and the displacement is accom- sedimentary wedge (Simony and Wind, 1970; Raeside andmodatcdby the Simpsons Pass thrust. The alnoitic rocks and Simony, 1983; Pell and Simony, 1987; Sevigny, 1987).alkaline lamprophyres north of Golden are carried on a Extrusion of theMount Grace carbonatiteandintrusionthrust (the Mons fault) which lies west of the Simpsons Pass of shallow-level carbonatites, accompanied by :he forma-thrust and apparently originated the farthest outboard of the tion of extensive zones of fenitization, probably occurred incontinent. If Haggerty’s model is applicable to western Eocambrian to Early Cambrian time (Htiy and Godwin,Bulletin 88 113
  13. 13. Minisfry of Eneqy, Mines and Pet,%l Resources 1988). These rocks occur a relatively thin cover-succes- in ported from the mid-Devonian to early M:ississippian se-sion above core gneisses of the Frenchman Cap dome, quence in the northern and central Canadian Cordillerawhich suggests that the dome may reflect a tectonic high in (Gordey, 1981; Mortensen, 1982; Gordey et al.. 1987) aslate Precambrian to Early Cambrian time. Emplacement of well as in the southern Canadian Cordil.lera :Wheeler,the alkalic rocks may have coincided with foundering of an 1965).extensive Lower Cambrian platform to the east. This period The Devono-Mississippian extension was synchronousis also interpreted by many workers as the time of the rift- with, or slightly postdated, compression to the south thatto-drift transition along the western continental margin was associated with Antler the orogeny. Devono- Mississip-(Bond and Kominz, 1984; Devlin and Bond, 1984; pian granites and granitic gneisses have also been docu-Thompson et al., 1987). In the southwestern United States, mented inthe Canadian Cordillera and Alaska (Okulitch etcarbonatites of Eocambriau to Early Cambrian age are re- ab, 1975; Dillonefal., 1980; Montgomery, 1985: Okulitch,ported from a number localities (Figure 87); for example, of 1985;Mortensen 1986;Mortensenetal., 19117).Theserocksthe McClure Mountain carbonatite-alkalic complex, the crop out west of the alkaline intrusions and are believed toGem Park and the Iron Hill carbonatite complexes in C o b have intruded near the western edge of the Paleozoic Cor-rado and the Lobo Hills syenite and carbonatite in New dilleran miogeocline (Okulitch er al., 1975). Aso duringMexico (Fenton and Faure, 1970; Olson et al., 1.977; Loring Devono-Mississippian time,a mixed volcanic and sedirnen-and Armstrong, 1980; Annbrustmacher, 1984; McLemore, tary sequence, termed Eagle Bay assemEdage, was the form- ). 1984; 1987; Although these intrusions are structurally in- ing o f fthe western contintental margin; these rocks recordboard of the Mount Grace carbonatite, their emplacement a change from an island arc environment at the base of themay be related to the same large-scale extensional tectonic sequence, where calcalkaline volcanics wen: forning aboveevent. a subductingplate, to a rift environment wbicb alkaline in Anumberofperiods ofPaleozoic extension areinferred volcanism and sedimentation took place 6:Schi;lrizza andalong the western continental margin; however, additional Preto, 1987).dating is necessary to clearly define these periods and elimi-nate possibilities of overlap. The earliest event is Late Or- Thesedatasuggestthatacomplextectonicre,:imemustdovician to Ordovician-Silurianin age (circa 450 Ma) and have pertained at the end of the Devonian and it was not thatis recorded by the emplacementof some ultrabasic diatre- simply a timeof extension. A more complex mollel is nec- essary to explain westerly sources for Devono-:Mississip-mes and alkaline lamprophyres in the southern RockyMountains and the Golden area of British Columbia. The pian miogeoclinal sediments, obduction a1 the latitude ofBearpaw Ridge sodalite syenite (eastern belt, Figure 1) may present-day northern California and southern OIegon, andalso prove to be Ordovician to Early Silurian in age as was emplacement of granites in southern British Colnmbia, theoriginally proposed by Taylor and Stott (1980). who be- Cariboo and Alaska approximately the same timeas ex- atlieved it to be a subvolcanic pluton related to alkaline basalt tension and alkaline intrusion were taking placl: near theflows in the Silurian Nonda Formation. Syenites, trachytes, eastern margin ofthe Canadian Cordilleran miog:ocline. Acarbonatites and ultrabasic diatremes and tuffs in the sequence of events may have occurred which culminated in the development of an incipient continental back:arc rift atKechika area may also be of a similar age. Carbonatites of a complex, attenuated margin (see Struik, 1987). as local-approximatelythe same age are found Lemitar Moun- in the ized obduction (and possibly subduction) occurred to thetains of New Mexico (McLemore,1987). south and outboard. Subduction probably resulted inpartial A secondperiod of alkaline igneous activi.ty along the melting and genesis of granite and calcalkaline volcanicwestern margin of North America occurred in Early De- rocks; this compressional regime was ap;parently super-vonian time (circa 400 to 410 Ma). Most of the ultrabasic ceded by an extensional regime. Alternatively, e:ctensionaland alkaline lamprophyres in the Golden area and somenl- basins may have resulted from strike-slip faulting: outboardtrabasic diatremes in southern British Colnmbia were em- of the preserved marginof the miogeocline, as pr,>posed byplaced at this time. Diatremebreccias in the Yukon Territory Eisbacher (1983) and Gordeyet al. (1987:1; however, this(e.g., Mountain diatreme, R.L. Armstrong, personal com- scenario does notexplain the intrusion of g:raniter.munication, 1988) of the same age. In a more continental aresetting (Figure 87). Early Devonian kimherlites are reported The last Paleozoic extensional event is inferred liomfrom thecolorado-Wyoming State-Linedistrict (McCallum the presence of Permo-Triassic kimberlite in the Rockyet al., 1975; McCallum and Marbarak, 1976; Hauselet al., Mountains. Although only one example known, it is is pos-1979). sible that other alkaline intrusions of simihu age exist and A third Paleozoic extensional event at the end of the that other evidence for extension may be discovered. AsDevonian (circa 350 to 370 Ma)resulted in the intrusion of with theprevious event, Permo-Triassic extmsion occurredcarbonatites into the miogeoclinal successionin the Fore- approximately synchronously with compression in theland and Omineca belts. Aillikite diatremes(ultramafic lam- southern Cordillera (Sonomau orogeny).prophyres) and dikes in the Ospika River area were also In Late Jurassic to Early Tertiary time, orogmesis oc-emplaced at this time. The tectonic instability resulting from curred when a compressional regime established on the wasthis major Devono-Mississippian extensional event is also Pacific margin whilerifting and the opening: ofthe Atlanticevident in the stratigraphic record (Thompsonet al., 1987); took place on the opposite side of the continent. During OIO-volcanic rocks (someperalkaline in composition),synsedi- genesis the continental margin prism was telascoped the andmentary block faults and chert-pebble conglomerates are re- alkaline igneous rocks were deformed, metamorphosed andBulletin 88 115
  14. 14. ; Tom LEGEND WILLIAM HENRYBAY . I: LEGEND MOUNTAIN DIATREME i SALMON BAY KECHIKA PIPE ! KECHIKA , ALEY i LONNIE F MOUNT BISSON 1 WICHEEOA LAKE i BEARPAW RIDGE IO BLUE RIVER AREA II TRiOENT MOUNTAIN I2 PERRY RIVER-MOUNT GRACE I3 MOUNT COPELAND 14 THREE VALLEY GAP I5 ICE RIVER 16 ROCK CANYON CREEK 17 RAINEY CREEK I8 BEARPAW MOUNTAINS I9 RAVALLliLEMHl COUNTIES !O IRON HILL. GUNNISON COUNTl !l WET MOUNTAINS CUSTER AND FREMONT COUNTIES !Z GEM PARK/MsLURE MOUNTAiN !3 MONTE LARGO 24 LEMITAR MOUNTAINS !5 MOUNTAIN PASS SYMBOLS SYMBOLS 19+ 0 Age unknown Age unknown v Tertiary (-50 & -30Ma) 01Tsriiary (Eocans) -50Mo + UpperCretocsour -90-95Ma X Oevono-Mirrirrlplon -350Ha # Permo-Trioaric -245Mo UNITED X Dewno-Uisriraippian 0 Ordorician-Silurian -450Ma 350-375Ma A EarlyDevonian -4OOMo OCEAN 0 Ordoviclon-Silurlon -45OMa STATES t Placediamond r Ioc~lity I Lower Cambrion-EoCombrlon :D) MlsrodlomondIoEOlity 520-58OMo t L o bp r o t e r o r o l s -770Mo A Mid-Pmlerozolc 1400-15OOM 23 M C o r d l l l e r o n front ,---Western limit of the .. miageoc1ino1 rtrato .I MEXICO 0 . ":i KILOMFTRLI 1 I:!
  15. 15. Minisfry o Energy, Mines and P e t r e Resoumes ftransported eastwards in thrust sheets. Their present distr- Cordillera, however, young calcalkaline lamprophyres,bution near the Rocky Mountain Trench is due to original strongly alkaline basalts and miaskitic syenite complexeslocation along a rifted continental margin, not to later tec- such as KrugerMountain, Copper Mountainand theCoryel1tonics. No syn or postorogenic carbonatites or alkaline nl- intrusions are present.tramafic diatremes have been discovered in the CanadianBulletin 88 I17
  16. 16. British Columbia "118 Geological S~rrvey 3ranch
  17. 17. Ministry of Enevy, Mines andP e t l w Resources REFERENCESAaquist, B.E. (1981): Report on Diamond Drilling on the AZ-1 Barlow, A.E. (1902): Nepheline Rocks of Ice River, British Co- Claim Group,Kamloops Mining Division; B.C. Ministry of lumbia; Ottawa Naturalist, June 1902, page 70. Energy,MinesandPetroleumResources,Asse!;smentReport Bending, D. (1978): Fluorite Claims, Golden :Minin,: Division; 9923. B.C. Ministry of Energy, Mines and Petndeum Resources,Aaquist, B.E. (1982a): Assessment Report on Verity First I, 2, 3 Assessment Report 6978. B.C. Claims, Blue River, British Columbia: Ministry of En- Betmanis, A.I. (1987): Report on Geological, Geochemical and eqy, Mines and Petroleum Resources, Assessment Report Magnetometer Surveys on the Prince and George Groups, 10955. Carib00 Mining Division; B.C. Ministry of Encrgy, MinesAaquist, B.E. (1982b): BlueRiver Carbonatites, BritishColumbia, and Petroleum Resources, Assessment Report1.7 944. Final Report 1981; B.C. Ministry of Energy, Mines andPe- Betmanis,A.I.(1988):SamplingEvaluation,l?G.NiobiumProject troleum Resources, Assessment Report 10 274. (Prince and George Groups); unpublished repixi for TeckAaquist, B.E. (1982~): Assessment Report, Blue River Carbona- Explorations Limited. tites, 1982; B.C. Ministry of Energy, Mines and Petroleum Bond, G.C. and Kominz, M.A. (1984): Constnlction of Tectonic Resources, Assessment Report 11 130. Subsidence Curves for the Early Paleozoic Miogeocline,Adams, W.T. (1985): Zirconium and Hafnium; in Mineral Facts Southern Canadian Rocky Mountains: Implications for Suh- and Problems, 1985 Edition, United States Department of sidence Mechanisms, Age Breakup and C N S ~ Thinning; of ;.~ the Interior, Bureau ofMines, Bulletin 675, pages 941-956. Geological Society ofAmerica,Bulletin 95, pag:s 155-173.Ahroon, T.A. (1979): Airborne Helicopter Magnetometer-Spec- Bonney, T.G.(1902): On a Sodalite Syenite (Ditroit:) from Ice trometer Survey on the Blue River Carbonatite Project, Brit- River, British Columbia; Geological Ma(:azine Volume 9, ishCo1umbia;B.C. MinistryofEnergy, MinesandPetroleum pages 199-213. Resources, Assessment Report 8216. Brown, R.L. (1980): Frenchman Cap Dome, Slmswap Complex,Ahroon,T.A. (1980): Geological Reporton theBlueRiverProject, British Columbia; in Current Research, PaR A, Geological British Columbia: B.C. Ministry of Energy, Mines and Pe- Survey o Canada, Paper XO-IA, pages 45-51. f troleum Resources, Assessment Report 9566. Butrenchnk, S.B. (in preparation): Phosphate Deposits in BritishAllan, J.A. (1911): Geology of the Ice River District, British Co- Columbia: B.C. Ministry of Energy, Mims and Petroleum lumbia; Geological Survey of Canada, Summary Report, Resouzes. 1910, pages 135-144. Campbell, EA. (1961): Differentiation Trends: in th: Ice RiverAllan, J.A. (1914): Geology theFieldMap-area, 13ritishColum- of Complex, British Columbia;American Journal of Science, bia and Alberta:Geological Survey of Canada, Memoir 55. Volume 259, pages 173-180.Alonis, E. (1979): B.C. Fluorite Claims, Golden Mining Division: Clement, C.R. and Reid, A.M. (1986): The Origin of Kimberlite. MinistpojEnergy, MinesandPetroleum Resources,Assess- Based on a Synthesis of Geological Pipes: An Interpretation ment Report7830. Features Displayed by South African Occurrences; Geologi-Armbrustmacher, T.J. (1979): Replacement and Primary Mag- cal Society of Australia,4th International Kimlmlite Con- matic Carhonatites from Wet Mountains Area, Fremont the ference, pages 167-169. and Custer Counties,Colorado;Economic Geology, Volume Clement, C.R., Skinner, E.W.M. and Scon-Snuth, B.H. (1984): 74, pages 888-901. Kimberlite Redefined; Journal of Geology, Volume 92,Armbrustmacher,T.J. (1984): AIkalineRockCompIexesinthe Wet pages 223-228. Mountains Area, Custer and Fremont Counlies, Colorado; Cunningham, L.D. (1985a): Columbium; in Mineral Facts and UnitedStates Geological Survey, Professional Paper 1269. Problems, United States Department Interioi; Bureau of ofArmbrnstmacher, T.J., Brownfield, I.K. and Osmonson, L.E. Mines, Bulletin 675, pages 185-196. (1979): Multiple Carbonatite Dike at McClure Gulch, Wet Cunningham, L.D. (1985b): Tantalum:in Mineral Facs and Prob- Mountains Alkaline Province, Fremont County, Colorado; lems, United Stares Department ojrnnlerior, Bureau of Mountain Geologist, Volume 16, Number 2, pages 37-45. Mines, Bulletin 675, pages 811-822.Armstrong, J.E., Hoadley, J.W., Muller, J.E. and Tipper, H.W. (1969): Geology, McLeod Lake, British Columbia (933); Currie, K.L. (1975): The Geology and Petrologyof the Ice River Geological Survey of Canada, 1204A. Map Alkaline Complex; Geological Survey 01Canada, Memoir 245.65 pages.Armstrong,R.L.,Eisbacher,G.H.andEvans,P.D.(1982):Ageand Stratigraphic-Tectonic Significance of Proterozoic Diabase Cunie, K.L. (1976a): The Alkaline Rocks Cmada: Geological of Sheets, Mackenzie Mountains, Northwestern Canada; Ca- Survey of Canada, Memoir 239. nadian Journal of Earth Sciences, Volume 19, pages 316- Cnrrie, K.L. (1976b): Notes on the Petrology of Nepheline 323. Gneisses near Mount Copeland, British Columbia;Geologi-Baadsgaard, H., Folinsbee, R.E. and Lipson, (1961): Potassium- J. cal Survey of Canada, Memoir 265. ArgonDatesofBiotitesfromCordilleranGranites;Geologi- Dawson, G.M. (1885): Preliminary Report on the Fhysical and cal Society ofAmerica, Bulletin, Volume 72, pages 689-702. Geological Featuresof that Portion of the Rockit Mountains -Bulletin 88 119