BCGS: Carbonatites, Nepheline Syenites & Related Rocks in British Columbia (Chapters 2&3) (Pell, 1994)

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Historical report by the British Columbia Geological Survey on carbonatites and related rocks. Ther report was completed by geologist Jennifer Pell who has spent several years studying rare metals in British Columbia's Rocky Mountain Rare Metal Belt.

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BCGS: Carbonatites, Nepheline Syenites & Related Rocks in British Columbia (Chapters 2&3) (Pell, 1994)

  1. 1. Ministry o Eneqy, Mines and Petroleum Resources f CARBONATITES AND SYENITE GNE,ISS COMPLEXES IN METAMORPH0SE:D PRECAMBRIAN TO EARLYCAMIBR1:A:N STRATA. OMINECA BELTMANSON CREEK AREA (93N/9) been deformed and metamorphosedto lower amphibolite facies. The hostrocks include psammitic semipelitic mica to Syenite, monzonite and calmnatite occur together on schists,micaceousquartzitesandsomemarbleswhichstrikeboth the Lonnie (Granite Creek) andVergil (Brent) claims. southeasterly (15Oo-17O0)and dip steeply to the southwestThe two showings arelocated 3 kilometres apart, approxi- (7Oo-8O0)on average.mately 8 kilometres east of the placer mining village of The various rock units within each intrusive zone areManson Creek, 230 kilometres northwest of Prince George. distributed in interfingering lenses (Hankinson, 1958;Exposures are in trenches, between loo0 and 1.100metres Rowe, 1958; Halleran, 1980). The Lonniecarbonatite is upelevation, on wooded slopes; elsewhere outcrop is sparse. to 50 metres thick and traceable for nearly 500 metres (Fig-TheLonniecarbonatitecanbereachedbyanoldroad,which ure 27);theVergil showing is approximately30 mftres thickis passable by four-wheel-drivevehicle to within 1 kilome- and canbe traced for a few hundred metres.The effects oftre of the showing (latitude 55”40’45”N, longitude alkali metasomatism(fenitization) can be detected for a few124°23’15”W). The Vergil showing,approximately5.5 kil- tens of metres beyond the intrusions.ometres from the nearest road, is accessible by helicopter oron foot (latitude 55”42’45”N,longitude 124°25’15”W). CARBONATITES At both showings, theintrusive rocks occurin single, W o varieties of carbonatite are present within the Lon-northwest-trending, sill-like sheets within uppermost Pre- nie complex: one is aegirine sovite in which the principalCambrian metasedimentary rocks the Wolverine Complex of components are calcite, microcline, perthite and aegirine;(Lang ef al., 1946). Both intrusive rocks and hostrocks have the other is biotite sovite, comprising calcite, b.iotite and ~~ ~~~~ _- ~~~~~ LEGEND S y e n i t em o n z o n i t em o n z a d i o r i t e , , Aegerine-amphiboleenite f Mylonitized biotite sovite Biotite sovite Aegerine sovite lnferiayered ovife nd emipelitic chisl s a s s Wolverine omplex iotite sammit?, C b p s e m i D e l i t i c c h i s tm i n o a u a r t z i l e s , r Figure 21. Geological map of the Lonnie (GraniteCreek) carbonatite complex (contours metric), after Rowe, 1958Bulletin 88 37
  2. 2. usually plagioclase. Only biotite sovite occurs at the Vergil tain accessory muscovite, biotite, calcite and apntite.showing. Both the biotite and aegirine sovites are variably Nepheline syenite is also locally present and contains: sig-foliated and containapatite (up to 20%). magnetite and py- nificant amounts of zircon (3-15%).rochlore as accessory minerals. The biotite sovite may alsocontain zircon; columbite, ilmenorutile and ilmenite have FENZTESalso been reported (Hankinson, 1958). At the Lonnie show-ing, aegirine sovite occurs along the southwestern margin Pods andlayers of fenite occur within both the Lonnieof the complex and biotite sovite along the northwestern and Vergil intrusive complexes. The fenite is medium to dark green in colour and rusty weathering. It consists ofmargin (Figure 27). The biotite sovite is variably myloni- aegirine and sodic amphibole (Plate 14) with microcline.tized, with the most intense shearing near the contact withthe country rocks. Enrichmentin zircon, pyrochlore, colum- plagioclase and calcite in varying amounts. The amphibolebite, pyrite and pyrrhotite has been noted nearthe contacts is strongly pleochroic, x -turquoise, y - colourless, z - PNS-of the sovites with syenites (Hankinson, 1958). sian blue, with colour strongest at the rims. It issimilar to the amphibole at the Aley complex, which has been itlenti- fied as magnesio-arfvedsonite(Miider, 1986, 1987). ‘TraceSILICATE PHASES constituents in fenites include pyrochlore, magnetite and Feldspathic intrusive rocks, monzodiorite, monzonite zircon.and syenite, outcrop as lenticular masses separating the car- The hosting psammitic and semipelitic schists arc rec-bonatite units (Figure 27). These intrusive rocks consist of ognizably fenitized for a fewtens of metres beyond the in-potassium feldspar (orthoclase or microcline) and plagio- trusive contacts. Microcline, plagioclase and quartz areclase in varying proportions; plagioclase greatly exceeds major constituents, with aegiriue and arfvedsonite dissemi-potassium feldspar in the monzodiorites,in the monzonites nated throughout, presumably replacing the original maficthe proportions approach equality and potash feldspar silicate minerals. Biotite is present in trace amounts only.greatly exceeds plagioclase in the syenites. All phases con- Calcite, apatite, magnetite and zircon may be present andPlate 14. Blue pleochroic amphibole (rnagnesio-arfvedsonite)and finer grained aegirine (light green) in ultrafenite, Lonnie area. Longdimension of photomicrograph is2.5 millimetres, (colourpkoto,page 135).38 Geological Survey €!ranch
  3. 3. ~~~ ~ ~~~ ~ ~~~ ~~ ~~ ~ ~ coarse-grained arfvedsonite, magnetite andfeldspar segre- gations are developed locally. GEOCHEMISTRY Carbonatites in the Manson Creek area are all true sovites, no magnesio- or ferrocarbonatites were observed (Figure 28; Table7. Aegirine sovites are depleted in silica ) and aluminum and enriched strontium, relative to biotite in sovites. Fenites are notably enriched in iron and sodium, relative to other lithologies (Figure 29; Table 7. With in- ) creasing degree of fenitization, that is from recognizable metasedimentsto ultrafenite, the rocks exhibit a systematic increase in iron and alkalis relative to calcium (Figure 30a) and fenitization appears to be a combination of typical iron-magnesium andalkali fenitization trends. The fenites, even ultrafenites (aegirine and arfvedsonite rich) are en- riched in sodium relative to typical pyroxene-amphibole fenites (Figure 30b). J Syenitic rocks are quite vaned in composition (Figures Figure 28. CaO-MgO-Fez03t+MnO carbonatite pht, Lonnie 29and31;Table7)but,onaverage,plotwithinthemiaskitic complex. TABLE 7 CHEMICAL ANALYSES OF ALKALINE ROCKS, MANSON CREEK AREA " ~ ~~~ ~ ~ ~~ ~~~ ~ Syenites and contact syenites Fenite 7 6 8 9 10 141113 12 15 15 - Si02 1.70 12.70 12.00 13.70 7.81 4 0 56.70 53.77 36.44 1.0 51.09 32.88 44.5035.9638.8273.1557.82 Ti02 0.02 0.67 0.71 0.01 0.08 0.03 0.02 0.530.03 0.40 0.20 0.66 0.38 0.28 0 6 0.83 .4 3.653.26 7.46 0.367.573.06 16.70 15.38 12.14 2.4811.61A12036.792.2214.30 14.93 11.74 Fe203T 1.40 6.21 5.70 0.37 5.39 1.44 0.57 0.80 4.84 0.59 2.63 19.60 6.91 18.63 11.66 4.52 0.59 0.37 0.24 0.16 0.28 0.23 0.11 0.26 0.15 0.25 0.37 0.24 0.30 0.34 0.24 0.115 0.31 2.20 1.85 0.60 1.21 0.17 0.12 1.73 0.18 1.36 1.15 2.48 2.11 1.13 1.11 2.112 CaO 52.90 36.10 43.72 6.09 9.78 20.19 36.60 48.29 16.30 8.85 23.12 10.90 14.56 0.34 24.21 1.34 Na20 0.44 1.21 0.99 5.57 2.46 5.79 10.33 3.48 4.97 5.37 10.30 5.55 0.36 6.94 3.53 3.99 0.12 2.45 2.04 0.49 0.19 5.36 5.84 1.89 4.82 1.50 4.43 0.24 0.50 1.14 1.61 0.ZI 4.417.48 17.89 7.9817.47 6.56 18.06 0.46 11.48 0.77 0.61 1.05 1.29 1.65 0.34 0.76 0.71 1.13 0.05 0.04 99.27 98.8298.7498.24 99.8985.9399.2799.5599.5998.13 ppm Ni <2 <2 <2 2 9 8 4 4 4 33 7 28 5 65 5 Cr e20 7 9 <20 e 20 36 52 1415 < 20 <20 153 24 34 77 6: 7 8 co 10 10 7 5 3 12 11 9 9 < 5 2 8 3 8 3 1 Sr 12009 6643 7959 6907 8780 4125 1110 1940 3143 2303 5360 5095 6738 233 1506 3: Ba 9861097662 14551926 26341191 22302479 1321215 27522084 387 129 4: Zr 76 127 10363 154 77 385 2030 1062 170 298 322 756 641 198 2324 311 Nb < 5 78306 2 43 1444 358 8831589 1274884 2465 19 253 387 1756 33 44 78 46 77 Y 66 54 69 62 53 16 19 36 YO 11 La 247 345 43 371 135347 398 401 222 265 88 254 102 1 0 173 9 22 Ce 600 172 426 483 130 392 107 673 325 470 286 176 398 660 741 31 Nd 245 179 206 102 35 56 Yb 6.27.7 5.2 3.5 3.8 2.1 sc 30 17 4.8 23 16.820.5 7.24.1 37 46 16.318.5 8.4 41 11.2 31 Ta c2 2 4 < 2 11 c 2 37 17 25 9 3 < 2 <2 <2 8 <2 Th <<6 <66 <66 < 25 28 17 8 < 6 18 6 8 65 244 19 I-LA179C oegirine sovite, Lonnieclaim 12- ultrafenire, LA174B Lonnie claim 2-01242B biotite sovite, Vergil claim 13- ultmfenite, LA197E Lonnie claim 3-011184 biotite sovite,Lonnie claim 14- LAl79E banded, calcareous fenite, Lonnie claim 4-LA242C white. massive sovite, Vergil claim IS- l.4178 fenitired metasediment with carbonaiite 5-LA252 carbowrite breccia, Vergil claim veinle:, Lonnie claims 6-l.41978 syenite, Lonnie claim 16- l.41740fenirired mefasediment, Lonnie claim 74.42408 syenite, Vergil claim Samples 1,2,3.6,7,12%- majorelementsnmlyred 8-01250 syenitic breccia, Vergilclaim by ICAP; trace elements by XRF; 9-LAl74A marsive syenite, Lonnie claim REE by INAA at Bondar-Clegg. IO-LA248 mixed syenitdcarbonatite, Vergil claim Sampbs4, 5,8,9,10,11.13,14,15,16,- II-LA197D carbonatitdsyenife contact, Lonnie claim Major and tmce elements byXRF. Bulletin 88 39
  4. 4. %% carbonatites A fenite 0 syenite trend Creek "normal.. fe-Mg fenite trem pyroxene amphibod< fenitesFigure 29. Majorelementternary plots, MansonCreekarea Figure 30. Ternary fenite plots, Manson Creek area carbsnatitccarbonatite complexes. complexes.syenite field (Figure 31). These rocksmay contain signifi- GEOCHRONOLOGYcant amounts of zirconium, upto 1.23%, and are enriched The Lonnie and Vergil carbonatites contain zircm, p yin barium and niobium relative to other igneous andmeta- rochlore and other uranium-bearing minerals arc: ame-- thatsomatic rocks the area. Niobium pentoxide in values of be- nable to uranium-lead geochronoIogy. Zircons fromtween 0.1 and 0.3% have been reported from the Lonnie samples collected from the Lonnie andVergil carbonatite-showing. Azone in the centre of the property averages 0.3% syenite complexes are generally large crystals that areNbzOs across a width of 7.6 metres and a length of 240 equant and clear. Analyses fromthese samples are ciscor-metres (Vaillancourt and Payne, 1979). dant, but indicate a uranium-lead age of 340 Ma anc. lead.. Rare-earth element abundancesrocks in the Manson of lead ages of 351 to 365 Ma (Appendix which is similar 2),Creek area are uniformly low, compared to those at Aley, to the age of the zircons from the Ice River complexin theKechika River and Rock Canyon Creek (Appendix and, 1) Rocky Mountains. Preliminary uranium-lead syste~natic!ias indicated by the shallow slope on chondrite-nomalized do not yield precise ages for these zircons, but do suggestplots, the light rare-earth enrichment is not as marked (Fig- that the Lonnie and Vergil carbonatites were emplaced iuure 32). Late Devonian early Mississippiantime. to __40 Geological Survey .3ranch
  5. 5. Ministry of Energy, Mines and Petmleum Resources CHONDRITE-NORMALIZED REE PLOl average Lonnie syenite 105 Lonnie & V e r g iS h o w i n g s l X overagemonzonite - Monson C r e e k r e a A . . . Carbonatite A Fanile 104 - D syenite . . . . .Subalkaline basalt Alkali rocks mmrr 30.00 40.00 50.00 60.00 70.01 Si02 Agpaitic 1 !O.OO- syenite La Ce Pr Nd Sm Eu Tb Dy Ho lm Yb LI family Rare-Earth lements E Mlaskitlc __ syenite family Figure 32. Chondrite-normalized REE plots, Lonnie and Vergil 5.00 showings, Manson creek area. Nephelinite family The alkalic rocks are hosted by high-grade metarnor- phic rocks assigned to the Wolverine complex, 0 ; probable 0.00- late Proterozoic age, and are exposed in a 5 hy 10kilometre area, south andeast of the Manson River, in the Wolverine Ranges of the Omineca Mountains. Within this arxa,num- a - 0 ber of discrete alkalic dikes and dike swarms arepresent, 5.00- ." . Subalkaline associated with alkalic pegmatite dikes or segreg&ions,in- rocks trusive breccias and large metasomatic alteration halos U " (fenites); unfoliated, fine-grained quartz morzonite to 0.00 quartz syenite intrusions are also present, but may or may 30.00 40.00 50.00 60.00 70.0 not berelated to the alkaline syenites. The relationship be- Si07 tween the intrusion of alkaline rocks andmetamorphism is Figure 31. Alkali-silica and agpaitic index plots, Lonnie complex unclear from available literature. the silicate rocks. (A) Agpiatic index plot - Lonnie complex silicate The area is accessible from good logging roads run that rocks; (B) Lonnie - alkali vs silica diagram. along the west side of WillistonLake fromWindy Point,at the south tip of the lake, to Manson Creek. MOUNT BISSON - MUNROE CREEK AREA (93N/9; 930/5,12) ALKALIC DIKE ROCKS Alkalic syenites are exposed in the Mount Bisson - Three types of syenite dikes are present in the Mount Munroe Creekarea of north-central British Columbia (lati- Bisson - Munroe Creek area: the fzst rich in alkali feldspar; the second containing abundant aegirine-augitc:; and the tude 553100"N, longitude 124"0000W), 64 kilometres third a suite of rare-earthelement enriched dikes which con- northwest of the town of Mackenzie (Figure 1). They were tain allanite as the main rare-earth mineral. The alkali ield- discovered in 1986 and 1987 A.A.D. Halleran.The min- by spar dikes contain 90% potassium feldspar rimmed with eralogy andfield relationships were describedby Halleran plagioclase, and 10% mafic minerals, predominantly aegir- (1988) andHalleran andRussel1 (1990) and summarized are ine-augite. The aegirine-augite dikes contain, 011 average, from these works. 40 to 60% aegirine-augite grains, up to 1.5 centimetres " Bulletin 88 41
  6. 6. across, 35% perthite, 3% sphene with rare allanite inclu- gioclase (Anzz-uI), potassium feldspar, biotite, chloritz andsions, 1%apatite and traces of allanite, magnetite, chalco- traces of magnetite, allanite, apatite and zircon.pyrite and malachite. These dikes are banded, with mafic theminerals concentratedin thin, discrete zones. The allanitic GEOCHEMISTRYdikes are also rich in aegirine-augite: they consist of ap-proximately 80% aegirine-augite, 8% potassium feldspar,5% apatite, 3% allanite and 2%sphene, withaccessory cal-cite and biotite.PEGMATITES Two types of alkalic pegmatites are described by Hal-leran and Russell (1990),aegirine-augite pegmatites and al-lanite pegmatites. They occur in zones l to 4 metres wideby in excess of 30 metres long; it is unclear, however,whether they are distinct dikes or, simply, coarse-grainedsegregations or pods within fenite zones. The aegirine-augite pegmatites contain zoned antiperthite (Anz3), sub-hedral aegirine-augite grains [with inclusions of plagioclase(An34). sphene, hornblende and biotite], minor perthitic po-tassium feldspar, occasional elongate quartz crystals andlate, fracture-filling epidote. The allanite pegmatites consistof perthite, up to 35% allanite, 5 % sphene, plagioclase(Anzs.27). apatite and minor to trace amounts of aegirine-augite, quartz, zircon and opaques. Allanite crystals are 0.03to 2.0 centimetres in size and commonly occur with spheneand apatite. Late quartz veins, up to 5 centimetres wide, lo-cally cut the allanite pegmatites.INTRUSIVE BRECCIAS An intrusive breccia zone, over 40 metres long, is ex-posed in one area. It consists of intrusive clasts supportedby a fine-grained, green matrix which contains 25% relicpotassium feldspar, 10%plagioclase, altered blue-greenamphibole and traces of sphene and apatite. LEGENDFENITES Fenitized Wolverine Complex rocks are exposed over &@ A e uncertainplutonic rocks G r o n o d i k , quartzmonzonite, tonollle;iocaliy pegmolitica broad area. The fenites are generally banded, with melano-cratic layers consisting of aegirine-augite, sphene, allanite, Hadvnian- Windermere Supergroupapatite and minor hornblende, andleucocratic layers domi- Horsethief Creek Group, Upper Clastic Unit/Koza Group: granule conglomerote,nated by plagioclase or potassium feldspar and apatite. psammite; minorpeiife carbonate andBanding in the fenites reflects original bedding or layeringin the Wolverine rocks which the fenite zones grade into: a Horse!hie! Creek Group, Amphlboilte Middle ond Semipelile/ Marbleunils;melanocratic bands were probably amphibolite or biotite amphibolite, semipelite, marble, minorschist layers while the leococratic bands were probably peliteoriginal quartzofeldspathic layers. Fenites are differentiated Horsethief Creek Group, Aluminousfrom hostrocks the presence aegirine-augite and rare- by of Peiite unit: pslite predominates:mayearth element bearing minerals, an increase in alkali feld- also contain minoramounts of Lower Gril Unitspar and a decrease quartz. in Hadrynian Older and (Proterozoic) Malton gneiss: ortho and parogneissQUARTZ MONZONITESAND QUARTZSYENITES Geological contact .......... ----------- Fault .............................. Fine-grained, massive, leucocratic quartz monronite Thrust fouit .................... -7-cand quartz syenite intrusions are also present in the Mount Corbonatite/nepheiineBisson - Munroe Creek area. They are very fresh in appear- rvenite localities ............................ 0ance and maybe unrelated to the more alkaline rocks. There -are at least four large intrusions (1 by 3 km in size) and a Fig,ure33. Geology and CarbonatiteJsyenite localitiesin the Illuenumber ofsmaller satellite bodies. They contain quartz, pla- Ri rer m a .42 Geological Survey Branch
  7. 7. -~ ~~~~~~~~ ~ Ministry of Energy, Mines and Petmleurn ResouxesThese values represent total rare-earth concentrations; how- of Kamloops (Figures 1 and 33). All are sill-like bodiesever, the values are mainly in the light rare earths. Fenites which were intruded prior to the deformation and ~netan~or-contain 0.07 to 0.64% light rare earths over widths 1to 2 of phism associated with the Columbian orogeny. The car-metres. bonatites, syenites and hosting sedimentary rocks been have subjected to three phases of deformation (Plate: 15) andGEOCHRONOLOGY metamorphosed to upper amphibolite grade (kyanite to sil- No absolute dating has been done on the alkaline rocks. limanite zone). TheMudLake (83D/3, latitude52c07’55”N.They obviouslypostdate the Late Proterozoic rocks of the longitude 119°10’44”W), Bone Creek (83D/6: latitudeWolverine Complex; from published data, the timingof em- 52°17’09”N, longitude 119°09’42”W) and Verity (831Y6,placement relative to metamorphism is unclear and an upperlimit on the agedifficult to establish. Within the sequence, latitude 52”23’51”N, longitude 119”09’13’W) !showingsthe syenitic dikes appear to be the latest alkaline rocks em- (Figure 33) occurbelow treeline at elevations bet ween 600placed as they crosscut both the alkaline pegmatites andthe and 900 metres; consequently exposure limited. ‘ThePara- isfenites. dise Lake (83D/6, latitude 52”24’19”N, longitude Quartz monzonites and quartz syenites probably post- 119°05’47”W) and Howard Creek (83D17, latitudedate the alkaline rocks andmay he completely unrelated to 52”23’OO”N, longitude 118”53’26‘W) carbonatites arethem; angular fenite xenoliths are reported to occur within above treeline, well exposed and were mapped in datailthe quartz-hearing intrusions. From descriptions given, (Figures 34,35a and 35h).these intrusions sound as if theyare postorogenic; however, The Verity carbonatites can be reached by trails anduntil some radiometricdating is completed, their ages will logging roads which cross the North Thompson River andremain unknown. intersect Highway 5 at Lempriere Station, approxi.nately 40 kilometres north of Blue River. The Bone Creek showingsBLUE RIVER AREA (83D/3,6,7) are accessed from logging roadwhich leaves Highway 5 a A number of carbonatite and nepheline syenite layers approximately 23 kilometres of Blue River. The Mud northoccur within the semipelite-amphibolite division of the Lake carbonatite crops out along Red Sands road, which theHadrynian Horsethief Creek Group the Monashee Moun- in intersects Highway 5, three kilometres north of B lne River.tains near BlueRiver, approximately 250kilometres north All roads are passable with four-wheel-drive vehicles. The Plate 15. Fz folds in banded nepheline syenite, Paradise Lake.Bulletin 88 43
  8. 8. CARBONATITES Three types of carbonatite occur within this suite. One is a whitish weathering olivine sovite which contains pre- dominantly calcite (60-8556). olivine (3-20%) and apatite (2-20%). Accessory minerals which may be present are phlogopite (Plate 16), with either normal or reverse pleo- chroism (up to 8%). diopside (10% or less), magnetitz, il- menite, pyrite, pyrrhotite, pyrochlore, columbite, zircon, monazite, allanite and baddelyite. The sovite is usually me- dium grained and massive, but locally may contain pegma- titic phases with calcite and olivine crystals 2.5 to 3 centimetres long and magnetite clusters over20 centimtres in diameter. Zircon crystals up to 3 centimetres long have also been found. The second type is a buff-weathering dolomitic car- bonatite (ranhaugite) with accessory amphibole (5-1 S) %, apatite (2-10%). magnetite and minor phlogopite.Ilmenite, pyrochlore, columbite and zircon may be present in trace amounts. The amphibolemay be richterite, soda-tremolite, tremolite or actinolite. Apatite and amphibole, within the rauhaugite, define a foliation parallel to both the edg:s of the carbouatite and the external schistosity. Locally, compo- sitional banding with alternating apatite-amphibole-rich and carbonate-rich layers parallels foliation and contacts (Plate 17). Pegmatitic segregations are not found in the ranhaugite, but coarse pyrochlore and crystals ( 1-1.5 zircon cm long) may be present. Separate bands of sovite and rauhaugite occur at Verity, Paradise Lake and Hoxard Creek. Rauhaugiteis present at both the Mud Lake and I3one Creek localities. LEGEND The third type ofcarbonatite, biotite sovite, is found at Carbona{ite, ou{crop Bedding SYMBOLS F, fold axes Minor folds - ............... 4 y 2 ........16 .......... Paradise Lake only. It occurs as segregations or pods ;asso- ciated with nepheline syenite. Calcite, biotite, apatite and magnetite are the primary constituents and nephelinemay also be present. 4 Sohene-amohibalite Fault - ................... NEPHELINE SYENITES Contour Interval = 30m Nepheline and sodalite syenite gneisses crop out in the ParadiseLakearea (Figure 35). In general, the syenitescom- prise white to grey-weathering, medium-grained, layered yE:&ian Psarnmite, sernipelite, and foliated gneisses, concordant with hostrocks of the and amphibolite Hadrynian Horsethief Creek Group. Layering and foliation are parallel to the margins of the gneisses, to bedding inFigure 34. Geologicalmap of the Howard Creek carbouatite surrounding metasedimentary rocks andto regional lolia-occurrence. tion. These syenites are typically composed of micrcclineHoward Creek and Paradise Lake localities are reached by (25-35%). plagioclase (An30 - Ana, 25-35%), nephelinehelicopter, from Valemount. (10-30%) and biotite (7-15%). Accessory minerals may in- Carbonatites in the Blue River area have been exam- clude muscovite, sodalite, cancrinite, zircon and perthite. Trace minerals present are calcite, magnetite, pyrrbotitl:, py-ined periodically since the 1950s, for their vermiculite, ura- rochlore and uranopyrochlore. The syenite gneisses r e lo-nium, niobium and tantalum potential. Previous cally migmatitic, with massive, medium to coarse-grained,descriptions are given by McCammon (1951,1953,1955), of lensoidal leucosomesthat are composed either nephdine,Rowe (1958). Currie (1976a). Meyers (1977). Ahroon microcline, plagioclase and sodalite or large perthite crys- tals (Plates 18 and 19).(1979, 1980), Aaquist (1981, 1982a,1982b, 1982c), White(1982, 1985) and Pel1 (1987). Lithologies are very similar MAFIC SILICATE ROCKSthroughout this area and will be described by rock type Mafic and ultramafic silicate rocks are present atrather than locality. Howard Creek (Figure 34). The most common varicty is44 Geological Survey Branch
  9. 9. Ministry of Energy, Mines and Petroleum Resouxes Geologicalconloct Moraine or talus defined, assumed approx, .......-" "- INTRUSIVE ROCKS Orientation bedding of and parallel foliation (SI and S2) F2 Fold axis ............................................. - ................................................ c- ....................................... xp HOST ROCKS Hadrynian Minor F2 folds Fault....................................................... S I axid race t - Bonded amphibolite ~ syncline, anticline ................................ * I 0 .i Psammlte,semipelite. and thin omphibollte layers S 2 axial antiform trace, ......................... olcsilicate SI axial trace ......................................... Sa Il + Figure 35. (A) Geology of the area south of Paradise Lake; (Next page) Cross-sectionA-A, area south (B) of Paradise Lake.Bulletin 88 45
  10. 10. INTRUSIVE ROCKS A Figure 358 (continued) Plate 17. Well layered carbonatite, Howard Creek. Layering isPlate 16. Phlogopite in carbonatite with reverse pleochroism and produced bycompositional variation within the carbonatite and isdistinctive orange colour, from Verity. Long dimension of parallel to the marginsof the layer, external sedimentary b:ddingphotomicrograph is 2.5 millimetres, (colourphoto, page 136). and regional foliation.46 Geological Survey 3runclr
  11. 11. Plate 18. Migmatitic leucosome (tine-grained leucosyenite segregations) present in layered syenites, Paradise Lake calcite with or without biotite, allanite and apatite The rock is generally coarse grained with pyroxenecrystals exceed- ing 3.5 centimetres in length and sphene crystas up to 2 centimetres long. In the strongly foliated varieties, hom- blende predominates (50-55%), with aegirine-augite, sphene and biotite abundant and calcite, plagioc1ar.e. apatite, pyrite and sometimes nephelinetrace constituents. At one as locality, themelteigiteis transitional to, and locallycrosscnt by, a coarse-grained, massive urtite composed of :25 to 40% nepheline, 10 to 15% potassiumfeldspar, 8 to 15% plagio- clase, 8 to 15%aegirine, 15 to 20% hornblende and sphene, biotite and calcite. FENITES Mafic fenites, 1 to 30 centimetres thick, separate car- bonatites and host metasedimentaryrocks. They v a q from medium to coarse grained and massive to foliated. They are generally composed of amphiboles (hornblende-actinolite, 45-80%), clinopyroxene(generally diopside or augite, up to 35%). apatite and opaques.Accessory minerals which may be present are titanaugite, biotite, plagioclase, sphene, epi- dote, quartz (remnant) and calcite. In some loca:.itiesa bi-Plate 19. Migmatitic segregations of coarse perthite crystals in otite-vermiculite layer is developed in place of thelayered nepheline syenite gneiss, Paradise Lake. amphibole fenites. In all cases the metasedimentary rocks adjacent to the fenites appear unaltered.sphene-pyroxene-amphibolerock or melteigite, which maybe layered andfoliated or massive. It consists of aegirine- GEOCHEMISTRYaugite (approximately 50%), strongly pleochroic horn- The alkaline rocks in the Blue River area shclw distinctblende (x - honey-yellow, y - dark bluish green, z - dark major element trends of increasing alkalis from carbonatitesforest-green to opaque: 15.30%) and sphene (10-20%).Ac- to syenites, with fenites most similar in composition to thecessory minerals include nepheline, plagioclase, pyrite and carbonatites (Figure 36; Table 8). Carbonatites (b~th calciteBulletin 88 47
  12. 12. British Columbia - albiie fenite fieldFigure 36. Major elementternary plots, Blue River area alkaline;ocks. Figure 38. Ternary fenite plots, Blue River area rocks and dolomite-rich varieties) are distinct from marbles the in host Horsethief Creek Group;the carbonatites c0nta.n s i g nificantly less silica, aluminum and alkalis than the average marble and are enrichediron, phosphorus, strontium and in rare earths (Table 8). Enrichment in niobium and tartalum also occurs in the carbonatites (Table 8), %Os values of up to 0.46%(Aaquist, 1982b) and tantalum ppm (Aaquist, 1982c) have been values tc.2400 reported. Calcite carbona.. tites range fromme sovites to ferrocarbonatites. dolomitic carbonatites may be classified as magnesiocarborlatites (Figure 37). Fenites are all typical pyroxene-amphibolt: fenites, pIotting within pyroxene-amphibolefenite fields; the rnognesio- ferro- o n b o t h N a20-KzO-Fe203 a n d C a 0 - N a20i-KzO.. corbonatite corbonatite MgO+FezO3 plots (Figure 38a and b). Syenites frcm tht: Paradise Lake are miaskitic, generally compositionally area close to the average nepheline syenite (Figure 39a m d b).Figure 37. CaO-MgO-Fe203ttMnO carbonatite plot, Blue River Alkaline rocks contain anomalous amounts of rare:-eartharea. elements, but not to the extent of manyof the comp1t:xes in -48 Geological Survey Branch
  13. 13. TABLE 8 CHEMICAL ANALYSES,ALKALINE ROCKS, BLUE RIVER AREA 5 6 3.82 6.60 5.26 2.73 7.642.03 12.30 41.03 42.30 59.20 47.01 12.W 35.86 58.W 44.12 58.20 4530 31.80 50.80 47.10 55.80 41.80 46.60 60.50Ti02 0.16 0.80 0.62 0.02 00 .2 0.70 0.09 0.85 0.13 0.60 0.44 0.82 0.02 0.29 5.65 4.15 0.25 218 1.84 0.40 0.23 0.40 06 .0 0.64 0.65 0.72 0.15 0.15 on 0.24 0.22 2.22 9.62 6.51 10.51 I250 22.60 20.80 20.10 8.42 5.93 9.72 20.10 18.W 4.88 1.03 13.30 853 4.28 10.70 10.30 4.35 7.356.48 7.61 8.41 0.305.177.449.409.68 2.62 2.69 2.20 15.10 856 12.90 3.67 5.36 1.10 7.19 11.10 3.31 0.21 0.23 0.24 0.31 0.38 0.21 0.41 0.37 0 2 0.20 .0.22 0.27 4 0.18 0.01 0.M 0.03 0.41 023 0.12 0.34 0.06 0.15 0.19 0.20 0.03 2.60 6.88 5.59 14.50 19.W 14.80 16.30 15.W 2.65 11.12 9.23 10.76 2.02 0.W 0.310.17 7.14 459 1.40 11.70 1.44 1.W 1290 7.98 4.74 45.40 39.80 40.90 28.10 28.70 32.90 30.64 29.10 20.W 16.81 15.26 42.90 14.40 0.54 0.698.20 13.58 0.83 16.80 23.10 28.70 2. 3 9 14.90 11.50 5.35Na20 0.10 0.15 0.15 0.10 0.27 0.11 0.05 4.03 1.11 3.60 3.28 0.40 4.06 7.488.27 9.70 4.462.08 9.52 0.12 1.01 1.13 054 26 6 3.wK20 4.10 0.38 0 4 4.10 .8 02 .5 o . ~ 0.12 0.12 2: 0 0.59 0.64 153 ;:$ 1.66 3.78 8.W 5.49 5.08 1.201.71 3.50 4.10 1.69 09 .7 0.81 0.13 2.71 d 40.38 35.46 27.12 37.21 20.73 4.98 2.57 0.90 2.02 1.75 1.18 19.29 0.71 2.12 0.21 -.4 2 8 24~ 098 1.11 04 .4 0.23 4.W 4 9 . 0 4.W am 4.W $9.78 99.86 97.98 97.10 97.W lW.11 98.R 99.63 91.17 98.18 97.601 lW.48 99.31 98.98 99.46 99.29 lW.39 2 4 <2 1 24 6s 58 I7 5 9 92 <w 2 < 20 CW 75 88 52 IC4 124 I27 3w 16 16 10 18 28 32 18 22 8 22 25 3 6 1 1 9 7 46Sr 4223 2995 3372 4092 4459 IS25 3276 3549 5312 534 1334 I641 78 2W3 134 152 71Ba 248 316 315 157 127 427 113 87 467 196 803 810 31912161 238 367s I59 934 712 27 M 1118 50 28 159 734 276 462 63 119 155 M3 37Nb % 41 42 470 7w 1 W 491 117 E5 181 185 303 6 I64 3 16 1Y 76 68 67 IS 9 2 5 22 16 68 32 33 48 36 19 26 42 17La 280 254 171 241 103 134 m 174 2H 74 91 183 42 18 33 162 2cc 539 548371 530 208 279 415 339 470 169 187 370 32 70 302 164 I5Nd 234 223 147 119 81 114rn 4 4 1.4 1 1.8 12 39k 41 36 40 41 3 4 4 4 34 29 22T* 19 <2 CZ 12s I78 8 IO CZ c2 c2 <2?h- ~ ~~ ~ c6 0.11 6 6 c6 ~6 , c6 5 13 W ~ 1 Porndire&;
  14. 14. I Nephelinite CHONDRITE-NORMALIZEDREE PLOT PARADISE, VERITY,HOWARD CREEK lo5j SHOWINGS BLUE RIVER AREA i Carbmatife A Fenile 1 o4 Subalkaline rocks 00 I .0 30.00 I I I , , , I , I , I I , , I I I , , 40.00 50.00 ,,,,, I , , 60.00 ,,,, I , , , 70.C ,, Si09 0 nepheline syenite m eDlCore0"S nepheline syenile Agpaitic family syenite fornily Miaskilic t overage nepheline - .- - " syenite 1 1 ~ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 , 1 1 1 11, La Ce Pr Nd Srn Tb Eu Dy Ho Tm Yb LL 1 Rare-earth lements E -- Alkali basalt Subalkaline rocks Figure 40. Chondrite-normalized REE plot - Paradise, V:rity, Howard Creek showings Blue Riverarea. 30.00 50.00 40.00 60.00 70.0 Si09Figure 39. Alkali-silica and agpaitic index plots,Blue River areasyenites.50 Geological Survey Brmch
  15. 15. LEGEND 11 2 Nepheline syenite /IjHorsethief creek met ore dim en la^ rocks 1 Axial 7 trace o f early antiforms Figure 41. Geology of the Trident Mountain area, Selkirk Mountains(from Pell, 1986b; Perldns, 1983). IPlate 20. Coarse-grainedilmenitesegregationin leucosyenite.Trident Mountain. Plate 21. Typical banded nepheline syenites, Trident Mountain.
  16. 16. Plate 22. Leucosyenite dikescutting mafic, biotite-amphibolegneiss, Trident Mountain. - Carbonalile average 1 family . . 1.00- 1 < b ? 0 nepheline syenite bosolt Alkali rn mafic ~ ( ~ I c o r e o u ! ; nepheline family syenite 0.00 60.00 73.0 Si07 Figure 42. Alkali-silica and agpaitic index plots, Trident Mountain syenites.Plate 23. Xenolith of mafic gneiss inbiotite-rich syenite, TridentMountain.52 Geological Survey Branch
  17. 17. Minishy of Energy, Mines and Petmleum .Pesources "the Rocky and Cassiarmountains (Appendix Enrichment 1). More recent uranium-lead data have been obtainedin light rare earths is greater than in heavy rare earths, as from zircon separates and indicate a mid-Paleoz.oic (1%-indicated by the shallow slope on the chondrite-normalized vono-Mississippian) age of emplacement. A sample fromrare-earth element plot (Figure 40). Verity yielded an age of approximately 325 Ma (G.l.E. White, personal communication, 1984); a prelimi!~ary dateGEOCHRONOLOGY of approximately 328f30 was obtained from Mud Lake Early attemptsat dating did not providedefinitive re- samples (R.R. Parrish,personalcommnnication,1!)85).Zir-sults on the ageof the alkaline intrusions in the Blue River cons separated from Paradise Lake syenites, which were large, equant andclear, provided slightly discordant analy-area. Potassium-argon dates of 205f8 Ma on phlogopite ses which suggesteda uranium-lead age of apprc7ximatelyfrom Howard Creek, and 92.5f3.2 and 80.2S.8 Ma on 340 Ma and lead-lead ages of 351 and 363 Ma (Appendixrichterite from Verity were obtained (White, 1982). Suh- 2).sequently, potassium-argon dates of 20of7 Ma on phlo-gopite and 94.4+3.3Ma on hornblende from Howard Creekwere obtained (G.P.E. White, personal communication. TRIDENT MOUNTAIN (82M/16)1984). The young dates (circa 80-90 Ma) are most likely Nepheline syenites were first recognized in tk e Tridentrepresentative of the timing of metamorphism and not the MountainareabyWheeler(1965)andsubsequentkfmappedemplacement of the igneous rocks. byPerkins(l983).TridentMountain(latitude5lo.L~4N,lon- gitude 118"09 west) is located in the Big Bend cf the Co- lumbia River, about 85 kilometres northeast of Rxelstoke and 20 kilometres southeast of Mica Creek (Figwe The 1). 0 nepheline syenite area is very rugged; the syenites are exposed 011 cliffs at maficcalcareous elevations of 2200 to 3000 metres, adjacent to largc:icefields nepheline syenite (Figure 41). Access is by helicopter from Revelsbke. The syenite gneisses at Trident Mountain are whiteto grey weathering, medium grained and moderately to well foliated. They are composed of white to pinkish nucrocline TABLE 9 CHEMICAL ANALYSES OF TRIDENT MOUNTAIN SYENITES Si02 5i.59 56.66 57.64 53.72 41.76 T0 i2 0.02 0.802.04 0.26 41.04 21.69 22.39 22.35 15.45 24.36 A1203 81.59 6.24 0.17 2.71 13.15 Fez03 MnO 00 .1 0.44 0.14 00 .8 *>.01 MgO 0.05 1.59 3.10 0.46 i0.W cao 6.820.59 0.33 8 . 6 0 9 15 .1 Na20 1.72 8.16 6.27 75 .1 1.39 K207.527.968.22 1.986.94 Ni 3 6 11 4 8 CI 21 < 20 19 13 18 CO 16 18 13 14 18 Sr 1234 1713 625 730 1116 B3 E 2992 1211 1156 584 1520 zr 210 338 1562 57 43 Nb <5 358 229 249 33 Y 6 22 16 4 2 La 8 197 1 6 21 Ce 16 275 10 22 32 Nd Yb SC 0.1 99 . 0.4 <I Cl <2 2 11 12 1020 COOFigure 43. Major element ternary plots, Trident Mountain syenites. -Bulletin 88 53

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