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Home , Aenigmatite, Astrophyllite

779

The Canalian M ine ralo gist Vol. 34, pp. 779-801(1996)

OCCURRENCEAND COMPOSITIONSOF SOMETi.BEARING IN THESTRANGE LAKE INTRUSIVE COMPLEX. OUEBEC-LABRADORBOUNDARV1

TYSON C. BIRKETT2

Geological Survey of Canada, Quebec Geoscience Centre, P.O. Box 7500, Sainte-Foy, Quebec GIV 4C7

WALTER E. TRZCIENSKI, JR.

Ddpartement de G4ologie, UniversitC de Montr4al, Case postale 6128, Succursale Centre-Ville, Montreal, Quebec HjC 3J7

JOHN A.R. STIRLING

Geological Survey of Canada, 601 Booth Street, Onawa, Ontario KlA 0E8

Alsrr.acr

Ilmenite, bafertisiteand Ti-bearing silicatesof the StrangeLake peralkalinegranite complex,Quebec-Labrador boundary, preservea history of crystallizationand reactionwith the residualmagma. Early-formed and aenigmatiteprogressively gave way to astrophyllite, neptunite,and narsarsukite.Sodic amphibole and pyroxenewere also involved in the reactions. The entry of Nb into the Na-Ti-silicaies can be modeledby MR3r(#+)-2. Fe3*also enteredthe mineralsthrough the model substitutionRt+68+n2+)-1, and, with fluorine, thrcugh n3*F(,aR4"O)-1.Neptunite was found to acceptNb, F and Fe3t in its structure.Crystal sorting of Ti-silicates, including an unidentified silicocarbonate,may have influenced the evolution of the magma.

Keywords:aenigmatite, astrophyllite, bafertisite, ilmenite, narsarsukite,neptunite, peralkaline granite complex, Strangelake, Quebec,Labrador.

SolvrN,rerne

Dans le granitehyperalcalin de StrangeLake, sur la frontibre entre le Qu6becet le Labrador,l'ilmdnite, la bafertisiteet les min6raux silicat6s de Ti temoignent de la cristallisation progressivedu magma et de r6actions avec le magma r6siduel. L'ilmdnite et I'aenigmatitesont des phasespr6coces qui ont progressivementc6d6 leur place d I'astrophyllite,la neptuniteet la narsarsukite.L'amphibole et le pyroxdnesodiques 6taient 6galement impliquds dansces rdactions.L'incorporation du Nb dans les silicates de Na et Ti peut 0tre expliqu6epar le couple MR3+(.d+)-2.De m€me, f incorporation du Fe3* se fait par une substitutionde type R;*(F*R2*)-I et, avecle F, par une substitutionde type R3rF(RaO)-t. La neptuniteincorpore Nb, F, et Fe3* danssa structurecristalline. l,e triage des silicatesde Ti a pu influencerI'evolution magmatique.

Mots-clCs:aenigmatite, astrophyllite, bafertisite, ilmenite, narsarsukite,nepfunite, granite hyperalcalin,Strange Lake, Qu6bec; Labrador.

hnr.orucrroN & Carmichael1969, Marsh 1975). The Tibearing mineralsin generalconcentrate the high-field-strength -bearing minerals are commonly among elementsin magmas(e.9., Green & Pearson1987), and the early-crystallizingphases in peralkalinerocks. thus their fractionationby crysta1sorting may strongly assemblageswith aenigmatiteor astrophyllite influence the trace-elementprofiles of derivative havebeen used to constraintoxygen fugacity (Nicholls magmaticliquids. Before Ti-minerals can be included in models of petrogenesis,systematic studies of their occurence, petrographyand chemistry are required. Here, we report on the Tibearing mineralsin the least- I Geological Survey of Canadacontribution number 67794. evolvedportion of the StrangeLake plutonic complex, ' Present address:SOQL'EM, 2600, boulevard Laurier, Quebec-Labrador.In common with many other Sainte-Foy,Quebec GlV 4M6. peralkaline rocks, a wide variety of Ti-bearing 780 TIIE CANADIAN MINERALOGIST

minerals are found: aenigmatite (Ang), astrophyllite condensed,where possible,down vectors of isovalent (Ast), bafertisite(Bft), ihnenite (Ilm), neptunite(Npr), substitution(e.g., combining Fe3*, Al, Cr, Ce,etc., as a and narsarsukite (Nrs). Other Tibearing minerals singlecomponent). tlat have been identified at Strange Lake include arfvedsonite (Arf1, (Ae), and Gpor-ocrcel SerrDlc pyrochlore, but theseminerals will not be considered in detail here. Three previously unknown phases The StrangeLake intrusive complex, located some encounteredalso have been analyzedby electron 250 km from Schefferville (Fig. 1), was first microprobe.Mineral symbols follow Kretz (1983). recognized in 1979 by geologists of the Ore Mineral compositionsare derivedfrom basic formulae Company of Canada. The post-tectonic nature of by the useof the vectormethod of Burt (1988)and are the peralkaline granite complex and its enclosed

STRANGE LAKE INTRUSIVE 56\ coMPt-Ex

FIc. l. Simplifiedgeological c).' map of the Strangel,ake intrusive body showing the distribution of the various Tibearing miner- als. The heavy dashed .A lines representfaults, and t:) the light solid lines, intru- I sive contacts. The rock I units are indicated by I a numbers: I country rock, I 2 early hypersolvus I granites, I 3 middle trans- I solvus granite, 4 late I subsolvus granite and I VL; pegmatite-aplite dykes. lo The distribution of the {v Tibearing minerals is 7 indicated by symbols. ivv Closed circles indicate vvv no Ti-bearing minerals observed;triangles repre- ,2v sentassemblages of astro- phyllite, aenigmatite, neptunite t ilmenite; squaresrepresena narsar- sukite or titanite. Ti.BEARING MINERALS. STRANGE INKE GRANTIE 781 rare-metalsdeposit were quickly recognized (Miller TABLE 1.ANALYTTCAL CONDMONS AND STANDARDS, 1986).The magmaticevolution preserved in the rocks ELECTRON-MICROPROBEANALYSES is from relatively high-temperaturehypersolvus units, GeologicalSuweyofCanada llarvaduoh/ersity through subsolws, rare-metalenriched phases, to low- (Ctawa, symbol O) (Catnbddge,lytrtbol I/) temperature,extremely enriched pegmatite-aplite Srandads D St@dards dykes. The Strange Lake pluton was described qusrE 0.02 €nsodite geologicallyby Zalacet al. (1984a,b), Currie (19857, Si Miller (1985, 1986, 1988, 1990), Birkett & Miller tt n$ile 0.04 run'le (1991),Pillet (1989)and Pillet et al. (1992,1993). Zr 0.2 zircon Detailedstudies include those of Jamboret al. (1987\ Sn ca$iit€rit€ o.2 cassitsite on armstrongite,Roelofsen-Ahl & Peterson(1989) on Nb o.2 NbrO: the crystal structureof gittinsite, Birkett el al. (1992) AI conmdum o.u2 lqratite on the Zr-bearingminerals, Nassif & Martin (1991, Fe nagn€tite 0.07 fayalite 1992) and Nassif (1993) on the .Salvi & rhodonite Williams-Jones (1990, 1991, 1992) studied fluid Mn rhodonite 0.05 inclusionsfrom the StrangeLake complex.A model Mg periclase 0.02 €nstatile for the chemical evolution of the magmas was Ca wollastonite 0.04 anoibile proposedby Boily & Williams-Jones(1994). Zn sptulerite 0.2 Z^O The geological map of the StrangeLake complex Ba sanbornite o.2 elsian (Fig. 1) is basedon field studiesand description of drill Na NaCl 0.03 albitr coresby Miller (1986).The earlyunits are dominantly KBr 0.05 microcline hypersolvus,with minor areasof transsolvusgranite. K On a microscopicscale, the feldsparsof theserocks are F liF 0.01 Fluor-botite perthite with local rims or interstitial patchesof albite IA faB6 0.2 notsough and K-. The temporally intermediate rocks occupy the northern and western portions of the Ce Pr, N4 and Eu w€re standardizedto fluoddes (4.g. CeF3) complex. Thesegranites are transsolvusto subsolvus, Snr, G4 Tb, Dy, Ho, Er, Yb, Lu and Y were individually *andardized to distinguishedby perthitephenocrysts in a two-feldspar metsls lanhgnides for Y (0.09) groundmassor by the presenceof two primary Typical limits ofdeteclion for *qo 0.2 to 0.3 €t(c€pt In atl Table "-" indicaresnot mslyse4 tt"d. not dd€cled. feldsparswithout perthitephenocrysts. The youngest Anab'tical condhions 15 kV l0 or 30 nA, dependingon the derm sought. rocks of the complex have extremely limited outcrop Daa reduotioq Ottawa, by a modified PAP program (Pouc,hou& Pichoir, and are known mostly from drill core. Geochemically, 1985); Ilanard by a Bence-Albee proceedure(Sandia laboraodes) nodi8ed byD. Lar€p. these granites show high concentrationsof rare D: est'rrratedlimit of ddgtion (weigh yo) elementssuch as Y, Nb, Zr, andBe (Miller 1988)and correspondinglyhigh concentrationsof minerals such as elpidite, pyrochlore and severalrare minerals of Y andBe. Thesegranites are all subsolvus. The distributionof samplesexamined is illustrated balanceand stoichiometry. The methodis explainedin in Figure 1. The latest-intrudedgranite and its derived detail for eachmineral. In Tables2 - 9, the symbol "-" pegmatite-aplite dykes (unit 4 in Fig. 1) were indicatesthat the elementwas not sought; the symbol extensively studied through exploration drilling and "n.d." indicates that the element was not detected. examinationof thin sections[see Birkett et al. (1992) Inferred concentrationsare presentedin parentheses for geologicalmaps and sections ofthe centralportion (i.e.,Fe3+,Li). The standardsused, estimated precision of the plutonl. Of the Ti-bearing minerals considered anddetection limits aregiven in Table 1. here, only amphibole, pyroxene, pyrochlore and titanite pseudomorphousafter a tabular precursor Pernocnepuv oF THETi-BEARING MI.{ERALS mineral have beenrecognized in the centralportion of the complex,and thus the detailsof sampledistribution The rocks describedhere are all granitic. Abundant are not reporoedin Figure 1. quartz, one or two feldspars,fluorite and pyrochlore are present in all samples examined. The earliest- Analytical methods crystallized Ti-bearing minerals are bafertisite, ilmenite, aenigmatite,and astrophyllite. These were Mineral compositions were determinedby wave- followed, in somecases through reaction, by neptunite, length-dispersionelectron-probe microanalysis using arfvedsonite, and aegirine. Narsarsukiteand titanite Cameca SX50 electron microprobes at Harvard pseudomorphousafter narsarsukiteformed under late University in Cambridge,and at the GeologicalSurvey igneousto subsolidusconditions (Fig. 2). In a few of Canadain Ottawa.Fe2+ and Fe3+ are calculatedfrom samples,Ti-bearing mineralswere not identified. Such total Fe by recalculation to accommodatecharge rocks have anomalouslyhigh amountsof fine-grained 782

Temporalrelations of the Ti-bearingminerals

Ilmenite Bafertisite Astrophyllite - Aenigmatite Neptunite Narsarsukite Arftedsonite Aegirine Titanite

Perthite 2-feldspars ------> Time ftc. 2. Temporalrelations among the Ti-bearingminerals at Strangel,ake.

dark amphibole or pyroxene, which are sufficiently feldspar, fluorite, zircon, vlasovite and quartz. abundantto incorporateall the availableTi in solid Commonly, the aenigmatiteshows ttte results of later solution. reactionsand is partially enclosedwithin amphibole Ilmenite forms equant, rounded grains invariably (Fig. 3D) or neptunite (Fig. O, or converted to armored in otler Ti-Fe-silicates. Ilmenite occurs astrophyllitealong grain marginsand cracks. surroundedby a rim of bafertisite, by astrophyllite Neptunite,a relativelycommon accessory, appears includedwithin aenigmatite,or simplyby aenigmatite. as red to red-orangeirregular or equantgrains. In rare In general,the ilmeniteand rim of Ti-Fe-silicateare cases, it occurs as subhedral to euhedral crystals themselvesenclosed in amphibole;relics.enclosed in Gig. D). In somecases, neptunite is rimmedor veined aenigmatiteare less common. In only one samplewas by arfuedsoniteor by astrophylliteor, locally, by ilmenite, rimmed by astrophyllite,found between aegirine. Neptunite in other cases rims or replaces amphiboleand feldspar;in one othersample, ilmenite aenigmatite(Fig.4C) and,locally, astrophyllite. In one occurswithin quartz. sample,neptunite forms equantgrains interstitialto Astrophyllite occurs in four principal habits at perthiteand thus may be in stablecoexistence with StrangeLake: small platesenclosed in feldspar,large nearbynarsarsukite and arfvedsonite. independentsubhedral to raggedcrystals (Fig. 3B), Narsarsukite arrd titanite pseudomorphicafter irregular corroded relics enclosedin amphibole narsarsukiteare found throughout the StrangeLake (Fig. 3A), and massesof crystals surroundingand pluton. High relief, second-orderbirefringence and a embayingaenigmatite or ilmenite.The occurrenceof strong tendencyto idiomorphismaid in identifling smallplates of astrophyllitewithin feldspar(Fig. 3C), narsarsukite.In the northernand centralportions of the associatedwith smallcrystals of arfvedsonite,indicates complex,the tabularpseudomorphs of titanite occcur the approximatelysimultaneous crystallization of these to the exclusionof the otherTi-rich accessoryphases. threeminerals. Narsarsukiteoccurs locally as poikilitic crystals,up to Aenigmatiteforms elongatecrystals, equant spongy severalmillimeters in maximum dimension"in the grainsor elongategrains cementing perthitic feldspar. southernportions of the pluton. It also forms early, Distinguishedby very deepred absorptionand marked equant grains interstitial to feldspars and quartz pleochroism,lamellar twinning in a few examples,and (Fig. 4B). h some samples,crystals of narsarsukite patchyzoning, aenigmatite is associatedwith perthitic (in placesnow replacedby titanite)occur within fine- Ti.BEARING MINERAI.S, STRANGET,AKE GRANTTE 783

Fro. 3. Textural relationsof astrophylliteand aenigmatite.A. Astrophyllite embayedand replacedby amphibole.Less obvious are dark relics of aenigmatitein the sameamphibole. Associated minerals are perthitic feldspar,quartz, and fluorite. Scale bar indicates500 pm, planelight. B. Astrophyllite in contactwith sodicpyroxene. Associated minerals are perthitic feldspar, quartz, sodic amphibole and fluorite. Scale bar 1 mm, plane light. C. Inclusions of equant amphibole and laths of astrophyllitein perthitic feldspar.The zonal distribution of the inclusionsindicates that they were included in the feldspar during its crystallization.Scale bar 500 pm, plane light. D. Relics of aenigmatitein sodic amphibole.Scale bar represents 500 pm, planelight. 784 T}IE CANADIAN MINERALOGIST

grained granitic inclusions (Fig. 5) and cross tlre narsarsukiteforms poikilitic grains cementingearlier- contactswith the host granite;these crystals may have formed mineralsof the rocks GrS.4A,) associatedwith formed later, in the subsolidus regime. Elsewhere, quartz, sodic amphibole,fluorite, hilairite, K-feldspar, especially in the southern portion of the complex, and albite. Theseoccurrences mav haveformed from a Ti-BEARINGMINERAIJ. STRANGEIAKE GRANTTE 785

Frc. 4. Textural relations of narsarsukiteand neptunite. A. Subhedral,poikilitic crystal of narsarsukitewith fine-grained, subhedralsodic amphibole.All of the narsarsukitein the imagehas tle sameoptical orientationand is interpretedas a single crystal. Associatedminerals are quartz, K-feldspar, albite, fluorite, and hilairite. Scale bar represents500 pm; crossed polarizers.B. Optically and chemicallyzoned crystal of narsarsukite,in optical continuity with the narsarsukiteat the lower ieft of the photograph.The crystal showsa core (yellow) separatedfrom a mantle Ged)by a zoneof micro-inclusions,and a thin rim (yellow). Associatedminerals are perttritic feldspar,quartz, and sodic pyroxene(below the narsarsukite),with a small core of sodic amphibole.Scale bar represents500 pm, crossedpolarizers. C. Colorlessnarsarsukite as a thin film surroundingneptunite. Included within the neptuniteare relics ofaenigmatitewith commonoptical orientation,small grains of astrophyllite and sodic amphibole.l,ocally, the neptuniteis rimmed by sodic amphibole(upper portion of the image). Associaterirninerals are quartz, fluorite and perthitic feldspar.Scale bar indicates 1 mm; plane light.D. Sodic amphibole (at extinction) is veinedand surroundedby neptunite.The sodicamphibole is alsolocally embayedby sodicpyroxene (lower portion of the image). Associatedminerals are perthitic feldspar, quaxt and fluorite. Scalebar indicates 1 mm, crossed polarizers.

residualmelt or evena postmagmaticfluid enrichedin occurs as equant $ains formed during the primary Ti, Na and F. Typically, thesecrystals of narsarsukite crystallizationof the rocks. In the dyke that forms the show anomalously low and relief. A principal mre-metals deposit at Strange Lake, the thin rim of narsarsukite, surrounding embayed primary crystals of narsarsukite (now replaced by earlier-formedTi-bearing minerals, is locally present titanite) share a flow alignment with other elongate (Frg. 4B). In the northern and central portions of the grains (albite, monazite, and one or more pluton, in the more evolved rocks, the narsarsukite, Zr-beaing minerals). Local partial replacement precursor to the tabular pseudomorphsof titanite, confirms that titanite is secondaryafter narsarsukite'

Flc. 5. Textural relationsof narsarsukite.A. Developmentof narsarsukiteporphyroblasts (ight-colored laths) in inclusionsof fine-grainedalkali granite.Similar porphyroblastsare also presentin the surroundingmedium-grained granite' Locally, the porpiyroblasts croJsthe contactso1 the inclusions.B. A poikilitic grain of narsarsukite(upper portion of the image' high ienifl. Wmin tle poikiloblast, tle sodic amphibolein the rock matrix has disappeared,as has most of the quartz, leaving feldsparand fluorite. Scalebar is 500 pm, planelight. 786 TTIE CANADIAN MINERALOGIST

CrutficAr Cowosmox or rnr 0.8 Ti-BEARTNGMnveRALs -o z Aenigmatite Aenigmatite ' 0.6 a c Aenigmatite (simplified formula NarFel+IiO, I [Si6Ot8]is a widespreadminor constituent of theleast- e evolvedrocks at Stranget ake. It is the most cornmon member of the aenigmatitegroup of generalformula o where-wA_ cationsinclude Na and Ca, 4?86T6C,20,''B o.2 cationsare,Fez+, Fer*, Mg, Mn, Al, andTi (among E \r" others),and ryZ cationsinclude Si, Al, B, and Be, as discussedby Burt (1994). Elecrron-microprobe 0.0 analyses of samples from Strange Lake (Table 2) 6.6 6.7 6.8 6.9 7.0 indicate solid solution toward wilkinsonire Tetravalentcations + 2 Nb (apfu) NarFefr+Fe]*SiuOro@uggan 1990) and only minor solid soluriontoward dorrite Ca2(Mg2Fe;+)(Al4SirO20 Ftc. 6. Infened proportions numbers of trivalent and (Coscaet al. 1988).Concentrations of M, Zr, Sn and tetravalentcations in aenigmatite(based on 20 atoms of Zn are-low, Calculation of Fe3+on the basis of oxygen)after the entry of niobium is accountedfor by the 20 oxygenequivalents and 12 cations,excluding Na, substitutionTir(NbFe3+)_1. The line of slope-2 represents yields good fits to the electron-microprobedata when the resultsof the ideal substitutionR+R2*(R3*)-2. the entry of.Nb is modeledby Tir[NbFe3+]_,.Other

substitutionsinvolving M also may model the data TABLB 2 AB{IOMATITE @MPOSITIONS. STRANOELAKE GRANIIE adequately,although the rangeofNb concentrationsis tv|o H O ooo not sufficientlylarge to test thesepossibilities. Other 01G16 016-t7 015-6-1 017-13 -lSxAll subsdrutionsinvolving Nb in minerals have been sio, 41 42-t7 42.47 r'0.@ 4t.K discussedby eernf & Ercit (1989).The distributions of Zrg2 0.08 0@ 0.09 !d !d Tio? 9.13 &99 927 8,v2 8J6 data points fit a substitutionmodeled by (.trF+R2+)R3+_2 s. 0.@ 0.08 0.@ 0.06 0.01 (Fig. 6) when the contents of Ca and Nb are Nbzo! 0.09 0.09 0.19 Ood Atzo: 0.36 0a 0.6 o,t1 0.m compensated.The excessofTi + 2M over I cationper @ao: 0.01 !d O.4l 20 oxygen atomsand Si less (Frg. Y:o. d dd than 6 atoms 7) €ezQ:) 000 106 0 indicate that incorporationof Nb and trivalent cations F€O Q12 39.43 4.23 3890 39.65 Ivtf 0.94 0.94 tr8 1.18 l.1l involveseveral sites in the mineral. Mso 0.01 0.03 0.01 0.03 0.m B80 0.@ 0.06 0.01 0.m !d CaO o2L O.t2 0.03 0.$ 0.01 7fi 0.@ 0.04 0.35 0,11 trd Na2O &03 8.06 738 6.8:' 6,X K.o 0.@ 0.01 0.03 0.04 nd t.l9 F nd 0.6 !d !dd Tolal 101.15 lm35 101J2 9934 98,31 -OEF 0 0.03 0 00 Sm 101.15 [email protected] 101J2 99,v .31 1.10 Aenigmatite . cad6 si 5.95 6.01 6.00 5.88 6.8 -o 7a 0.01 0.00 0.01 00 Z 1.05 Ti 0.97 0.96 0.98 og7 0,97 N Sn 0.m 0.01 0.0r 0.@ 0.m ao Nb 0,01 0.01 0.01 0,v2 0 + t. t AI 0.06 0.04 0.01 0.03 0.01 :: 1.00 aa - 0.m 0 0.02 Y -0 00 'o (Fe'1 0 00 023 0 Fe& 4:16 4:70 4,75 4:il 4.U 0.95 frl! 0.11 0.1t 0.15 0.15 0.14 . Olo Mg 0.m 0.0r 0.m 0.01 0.01 Ba 0.01 0.m 0.@ 0.00 0 Ca 0.03 0.o2 0,@ 0.0r 0.00 0.s 7a 0.01 0.00 0.04 o.m 0 5.70 5.80 5.90 6.00 Na 221 223 2-02 r.y2 1.95 0.00 0.@ 0.01 0.01 0 Si(aptu) F 0 0.04 0 00 Rc. 7. Proportionsof atoms (apfu) Electr@dqolElbe @bs of eignadte. Cati@ @ al@lared @ of Si uerszsTi + 2 Nb in a brsis of 20 oxyga ato6 ed 12 B atd T ads c dsssed io the aenigmatite(based on 20 atomsof oxygen).The ideal texl (FerOJ almla&d ftm stolclimetry. compositionof aenigmatiteis indicatedby the cross. Ti-BEARING MINERAI.S. STRANGEI-AKE GRANITE 787

TABLE 3. ASTROPHYLLITE AND NIOBOPI{YLLITE COMPOSITIONS wT.% 1 2 456789 5617-5 5617-7 5663-6 5654-3 5879-A9 H31-6 5860-2 Niol NioT sio, 35.84 35.92 36.73 35.93 35.69 34.93 36.42 33.63 33.49 Z;!O2 0.67 1.40 0.15 1.38 0.24 t.rI 1.51 0.24 nd Tio, 10.46 9.48 1l.99 9.15 11.32 t0.05 10.60 2.69 2.70 SnO, 0.17 0.27 nd 0.01 0.10 0.r8 nd 0.18 0.09 M2O5 1.76 2.m 0.18 3.47 0.37 t.2r 0.15 10.23 10.32 ArO, 0.34 0.18 0.40 o-.r, 0.18 0.26 0.07 r.20 t.40 c%o, nd nd 0.15 0.19 nd YrO, nd nd nd nd nd (FqoJ 7.26 8.96 1.90 14.M 2.40 1.28 5.94 1.47 l.4s FeO 26.97 24.85 33.13 19.U 30.60 32.62 29.14 25.28 24.87 MnO 1.82 1.96 1.37 1.78 2.47 2.31 0.93 8.81 8.66 Mgo 0.03 0.03 0.07 0.04 0.05 0.03 0.20 0.20 0.2r BaO 0.31 0.12 0.14 0.20 0.52 0.26 0.1i 2.12 nd CaO 0.18 0.20 0.31 0.75 0.38 0.28 0.16 0.93 0.65 Z;aO 0.16 0.21 0.10 0.21 0.65 0.55 0.11 0.13 0.28 NqO 3.65 3.66 3.54 3.r7 3.30 3.02 3.57 0.88 1.26 KrO 4.92 5.18 5.47 5.43 4.96 5.4s 5.16 1.87 2.24 F 1.13 0.91 r.43 1.38 0.93 0.78 1.52 nd nd Total 95.67 95.36 96.91 97.01 94.30 94.51 95.59 89.87 87.62 -O=F 0.48 0.38 0.60 0.58 0.39 0.33 0.64 0.00 0.00 Snm 95.19 94.97 96.31 96.43 93.91 94.18 94.9s 89.87 87.62 catrons si 7.84 7.86 7.99 7.71 7.98 7.90 8.00 7.99 8.02 Zr 0.07 0.15 0.02 0.14 0.03 0.72 0.16 0.09 0 Ti t.72 1.56 t.96 1.48 1.90 L7l t.75 0.48 0.48 Sn 0.02 0.03 0 0.00 0.01 0.02 0 0.01 0 ]\rb 0.r7 0.20 0.02 0.34 0.04 0.12 0.02 1.09 1.1i Al 0.09 0.05 0.07 0.02 0.33 0.39 :" :''o :'ou 00 0.01 0.02 0 Y. 00 000 (Fe'-) 1.20 1.48 0.31 2.27 0.40 0.22 0.98 0.26 0.26 Fel 4.94 +.)) 6.03 3.56 5.72 6.17 5.35 5.02 4.98 Mn 034 0.36 0.25 0.32 0.47 0.44 0.17 1.77 1.75 Mg 0.01 0.01 0.02 0.01 0.02 0.01 0.07 0.07 0.07 Ba 0.03 0.01 0.01 0.02 0.05 0.02 0.01 0.19 0 Ca 0.04 0.05 0.07 0.17 0.09 0.07 0.04 0.23 0.16 Zn 0.03 0.03 0.02 0.03 0.11 0.09 0.02 0.02 0.04 Na 1.55 l.) f 1.49 1.32 1.43 1.32 1.52 0.,10 0.58 K 1.37 1.45 1.52 1.49 1.42 1.57 r.45 0.s6 0.68 F 0.78 0.63 0.98 0,94 0.66 0.56 1.06 0 0

Elechon-microprobeanalyses of astrophyllite and niobophyllite (columns 8 & 9) calculatedon an anhydrousbasis of 28.5 oxygen atoms.

Astrophyllite Nb analogue of astrophyllite (but a phase that ls distinct from niobophyUite). The principal substitu- Astrophyllite, a silicate of simplified formula tions recorded from StrangeLake areTr (0.5 to 3 wt.Eo (Na,K)3FeTTirSis(O,OH)31,is a common accessory zro2), Nb (0.5 to 2 wt.Vo M2o5), and Al (0-5 to mineral in the least evolvedto moderatelyevolved 1.5 wt.VoAl2O3). rocks at StrangeLake. Following the terminology of Abdel-Rahman (1992) suggested that Nb enters Layne et al. (1982), the formula can be expressed the astrophyllite structure through the substitution as W3XjY2Zs41,where l4l includes the 10- to Nb5+ = Ti4* + vacancy. There are two mechanisms l3-coordinatedcations Na K, Ca andCs, X represents compatible with Abdel-Rahman's (1992) formulation: theeight-coordinated cations Fe2+, Mn, Mg, Zn andLi, lANb2Ge2+Ti2)-t and [W]Nb(NaTi)-1, where Na f representsthe octahedrallycoordinated cations Ti, includes Na, K, Cs, etc., and where [Xl indicates Zr, M, Sn, Fe3*, andZ, the tetrahedrallycoordinated a vacancy in the site of eight-coordinated cations, cationsSi, Al, andFe3*. Electron-probe microanalyses following Burt (1989). These substitutionsboth predict of astrophyllitefrom StrangeLake (Table 3) indicate a 1:l negative correlation between Nb and Ti in variable solid-solution toward the end members astrophyllite. The situation is complicated, however, kupletskite(Mn) and (Zr), andtoward a by the presence of other tetravalent cations that may 788 TIIE CANADIAN MINERALOGIST

1.6 1.4 Astrophyllite

'1.2 and :l o_ d 1.0 Niobophyllite E 0.8 :l E .9 0.6 z 4.4 0.2 'l o to 0.0 8.0 8.5 9.0 9.5 10.0 Tetravalentcations (apfu) Ftc. 8 hoporrions of tetravalentcations yersasNb atoms (basedon 28.5 oxygen atoms) in astrophylliteand niobophyllite.The line indicatesa slope of -O.5 equivalentto a substitution of the form Rj+(NbFe3+)_1.Symbols: x astrophyllite, this study, O: niobophyllite, this study, I Abdel-Rahman(1992), a Macdonald & Saunders (1973),n Nickel ar a/. (1964),A Marrin (1975),O Layne& Rucklidge(1982).

substitutefor Ti (e.9.,Z andSn). Finally, analysesof data. A straighdorwardsubstitution suggested for the astrophyllitecommonly report less than the ideal incorporationof Nb is NbR3+(R4+)_2.This substitution, 8 atomsper formula units of Si (apfu). Thus some common in the group, for example, also trivalent or tetravalentcations may be assignedto fill leadsto predictionsof the R3+of the mineral, and thus the requirementfor 8 Si. Consequently,we test the Nb leads to a model for ferric iron incorporation in substitutionin astrophylliteby examiningtle correla- astrophyllite. tion betweenthe sum of tetravalentcations (R4) and The substitutionNbR3+(JR{+)_, allows a lower limit Nb atoms (Fig. 8). Examinationof our data and other to be placedon the R3+conteni of asnophyllite.The publishedcompositions, either separately or combined, number of cations calculated after application of indicates that the correlation bewteenRa and M is the Nb model, however, should still approximatean near -O.5. Calculationswith various ferrous-feric astrophylliteformula in terms of the numbersof other ratios have only a minor effect on the calculated cations.Thus the formulashould yield Si = 8 or less, correlations, and cannot be an important factor in and,Rf* + 2 Nb = l0 or less.After modelingM in asrophyllite becauseall studies to date have shown astrophyllite, there commonly remains an excessof that iron in the mineral is dominantly Fe2+.Thus the atoms(in the total N* + 2 M), anda secondsubstitu- substitutionof Nb into astrophylliteis better modeled tion mustbe invoked.The substitutionn;+(R4R2+)_t is by M5* = 2N t otler atoms to maintain charge commonly computed to [mit the proportion of ff+ balance.There are no significant correlationsbetween cationsto a total basedon the mineral'sstoichiometry. the sumsof monovalentcations or tfie sumsof divalent cations and Nb in available compositions of Relations hip betvveenastrophyllite astrophyllite, but there is a negative correlation and niobophyllite betweenlevels of Si and Nb. If the differenceof total cations from the ideal 20 cations per 28.5 oxygen Niobophyllite, (K,Na)3@e2+,Mn)6(Nb,Ti)2Sis atomsis takenas an approximatemeasure of vacancies, (O,OH,D3r,was definedby Nickel et al. (1964) and no significant correlation exists between Nb hasbeen considered an end memberof a solid solution substitutionand vacancies.The presenceof excessH with astrophyllite (Nickel et al. 1,964,Macdonald & in interlayer sites cannot be testedwith the available Saunders1973, Abdel-Rahman 1992). The substitution Ti-BEARING MINERAIJ" STRANGELAKE GRANTTE 189 relating astrophyllite and niobophyllite can be TABIA 4. BAFBITTISIIB @MPCNInON!I, SIRANGE I.AKE @ANTTE expressedas [XlM2(TizF"2*)-r. No astrophyllite H H ooo0 analyzedto dateby Abdel-Rahman(1992), Macdonald NF5663-4 NFJ663-5 NF566-r8 NF5663-A B9-l t&-2 (1973), (1982) or in the sa 24t u33 aa8 .ll 2! 2143 & Saunders Layte et al. ztoz 0.08 0.19 0.12 0.12 d 0,12 present study shows a systematicdeficiency in R2* ffi" 16.80 15'84 14.41 15.08 m6 A,U S!O. !d !d 0.G 0.G 0.G 0r' cations that would indicate solid solution toward the Nhor 0rr 0.18 0.?5 0J0 ojl 0.88 niobophyllite compositionof Nickel et al. (1964). To ALOr 0.G 0.t9 08 0.46 0.42 Lqaot 9.6 - otE investigate these observationsfurther, new electron- G:O: !d l.7l 2gl 3.06 N40: - 0J0 probe microanalyses of "niobophyllite" from Seal sqor _nd oQo: - - 0.09 Lake, Labrador, were completed. Without a more Yros drddod definite formula for niobophyllite,Fe3+ in the resultsof (P%Or) 0 0 0000 FeO 2539 6.U x,l1 8a Aft 1030 the new miooprobe analysesof SealLake materialhas MrO 1.43 to tJ3 l.{0 0,92 0.65 present.These data, l'@ 0.@ 0.00 0.04 0.11 !d 0.02 beencalculated at5Vo oftotal iron BaO 28'47 a.8l 28.81 2A.1t 2321 8.r3 included in Table 3 and Figure 8, do not match well oo o,a, 0.04 0.06 0.06 0a 0.16 Zfi !d ltl 0!6 0.16 03! o,l4 with the single publishedcomposition of niobophyllite NLO 0.G 0.10 023 0.65 0.41 o.ilE by r;6 o.r3 0.15 0.16 r32 044 ojl and, furthermore,do not fall on the trend defined F r38 5.60 5.16 2l,9 223 1.96 astrophyllite compositions.The newly determined Total ltL19 ro1t5 10121 1U2.X ,n 98J7 compositionsofSeal Lake niobophyllite do not show a -OEF 227 2,K L17 1.09 0.95 0.83 S@ 1mJ2 9:t9 99.04 101.16 nat nJ4 deficiencyin R2+cations but are deficient in Na and K @d@ (Table3). The relationshipbetrveen Re andM Gig. 8) st z0l 2(E LA lgl 1ls2 924 h 0.m 0.01 0.v2, 0.01 0 0.m suggestsa range of Ti:M valuesrather than a simple T1 1.6 l.m 093 093 631 9J0 substitution. The deficiency in interlayer cations Sq 0 0 0.m 0m 0.4 0.o1 Nb 0.01 0,r 0G 0.01 0.10 0.o suggeststhat Nb may enterthis phaseby a substitution 0.01 o.0l o@ 0.03 024 02r la - 0.01 suchas [Ur]M(TiNa)-r. Anotherpossibility is to model Co 0 0.6 048 0.47 the incorporation of Nb in "niobophyllite' from Seal Nd Su :::f':: Lake by Ti3fFe2+M2l-1,as suggestedby Larsen et al. Gd - 0r0 Y 0000 (1992) for the entry of Nb in the mineral (Fr") 000000 (Na2Ti2Si2Oe).The data however,do not supportthe Fo& 1&) 1:19 1,80 2,m 4.(p 3.65 ldo 0.10 o,l0 0.13 0.10 0g 023 presenceof "excess" R2+ in this phase, and the M8 o 0 0.01 0.01 0 0l)l (ionic Ba 0.93 0.95 0.96 0n 49 4.6 substitutionwould require the entry of Fe2* Ca 0,0 0.m 0.0r 0.01 0.11 0.07 radius0.76 A) into a site normally occupiedby Ti4 b o 0 0.o 0.01 0'10 0.04 Na 0.01 o.a 0.04 0.r0 0J5 039 (ionic radius0.68 A). K 0.0t 0.@ 0.9, 0.16 0.q 023 The data available indicate that more than one t.4l 1.49 139 0.67 3.4 252 mechanismof Nb incorporationmay be involved El€dr@-DtgoFobe @lys of tslsdsire @d 8 bffdFtl&o @ (@ttss B9-f @d t{3F2). smdd tudilre of bafstirib @ @!@led to 9 oltga st@ €qd€&e' @d oI among minerals in the astrophyllite group, that he hftnisitr.llke phase,to it8 dy8a 8@ eqdwl€da. niobophyllite is not the only possibleNb analogueof astrophyllite,and that further examinationof the type material for niobophyllite and other membersof the astophyllitegroup is required. similar to bafertisite, but with higher Ti and Ce and lower Fe, hasbeen analyzed (Table 4). It alsooccurs as Bafe rti sit e, bafe rti sit e- like phase a rim around ilmenite grains, and is referred to as a bafertisite-like mineral becauseof the similarities in The occurrenceand chemistry of the rare mineral occurence,composition, and optical properties.This is bafertisite [BaFezTiO(Si2O7)(OH,F)2]and the not, however, the same phase as was analyzed by Mn-analoguehejtmanite have been reviewedrecently Mauger(1983). The low analyticaltotals suggestthat it by Vr6na et al. (1992). Other analytical data were may be hydrous. reportedfor bafertisite and an unidentified bafertisite- like phasefrom North Carolinaby Mauger(1983). At Ilmenite Strangel,akeo a phaseidentified as bafertisitefrom its composition occurs as a thin rim mantling grains of Ilnenite has been identified in the Strange Lake iknenite. Analytical data (Table 4) show substantial peralkaline granites as minute grains rimmed by concentrationsof the light rare-earthelements (up to bafertisite or a similar phase,or by astrophyllite,and 2 wt.VoCe2O3, not repofied in studies of bafertisite occludedin aenigmatiteor amphibole.Chemically, the from other localities), in addition to Nb concentrations ilmenite is rich in Nb andMn (Table5) andthus linked of up to A.5 wt.VoM2O5 (similar to earlier reports). to the compositionof the host granite' In general,there Spot analyses show that the rare earths are not is no correlation betweenlevels of Ti and Ba in our distributed evenly throughout the mineral. Data are analyticalresults, and the reportedBa in the ilmenite is not available for all the rare-earthelements. A phase thus not an analytical artifact. The association of 790 TTIE CANADIAN MINERALOGIST

TABLE '. ILMEMIE COMPOSMIONS. TABLE 6. NARSARSUKITE COMPOSITIONS SIRANGE LAKE GRANITE vt%oH wt oA o Core 1 Rim s6?R-, 56381 NF563$-A-7 NF5633-1 NF5879-A-2. 12 il sio, 0.o7 0.04 0.90 si02 61.47 60.97 61.34 61.65 6't.52 60.87 62.M 7rg2 d 0.1? Zfrz 0.54 1.23 2.77 1.86 0.92 2.21 1.03 TP? 51.67 s0.62 5050 rio t2.54 12.31 13.06 Q.7A t1.79 12.39 13.03 SrO2 trd d SnO, 0.t7 0.16 0.15 0.29 0.16 0.23 0.05 Mrot 0.66 l2t1 o.73 Nbro: 0.70 0.76 0.64 052 0.64 1.03 0.37 At o, 0.04 0.92 Al203 0.72 0.66 0.56 0.59 0.58 0.58 0.86 @ro: :'" 0.08 0.08 c9o, 0.04 0.24 nd 0.14 0.06 nd nd Yro3 nd &i YrO, 0.18 0.58 nd nd nd 0.29 nd (F%OJ 0J9 0 0 r ltvt 4.97 5.35 4.71 5.69 5.80 3.76 5.98 FeO 43.72 4Lt6 40.35 MnO l,tuo 2.92 2.91 5.17 Mgo nd 0.01 0.01 Mp 0.01 nd o.o, o.or o.ol o.o: BaO 0.21 nd BaO 0,42 1.30 0.16 0.16 0.37 0.42 0.85 Cao 0.6 : CaO nd 0.02 nd 0.01 0.03 nd 0.03 0.06 -ndnd 7N 0.15 0.49 ZnQ Na2O 0.04 nd Naro 15.39 14.93 14.81 15.13 14.96 15.09 14.59 Kao 0.01 0.r0 KrO 0.03 0.02 0.05 0.01 0.11 0.05 0.05 F trd : rd F t.71 1.72 1.62 1.65 r.5r 1.34 1.78 Totol 100,73 n.M 99.89 Atoms Total 98.67 99.m 99.88 100.43 98.46 98.29 100.69 si 0.m 0.@ 0,v2 -F4 0.72 9.72 0.68 0.69 0.64 0.56 0.75 Zt 0 0.00 Sm 97.95 98.n 99.20 99.74 97.83 97.72 99.94 0.98 0.99 a.v7 Sn 0 0 Nb 0.01 i.* 0.01 Atotns AI 0.00 0.@ si 4.02 4.00 3.99 3.99 4.05 4.m 4.00 C€ 0.@ :.00 0.00 Zr 0.02 0.04 0.09 0.06 0.03 0.07 0.03 Y 0 0 Ti a.o 0.6i 0.64 0.62 0.58 0.4 0.63 (Fel) 0.v2 0 0 Sn 0.01 0.01 0.00 0.01 0.01 0.01 0.00 F92' 9.92 4,92 0.86 Nb 0.02 o.a 0.02 0.02 0.02 0.03 0.01 IvIn 0.06 0.06 0.11 Al 0.06 0.05 0.M 0.05 0.05 0.05 Mg 0.47 0.00 0 Ce 0.00 0.01 0 Ba 0.00 0.00 0 0 0.m 0.0r Y Ca 0.01 0.02 0 0 0 0.01 0 0.m 0.m Fd. 0.2s 7^ 0.00 - 0.26 0.23 0.28 0.79 0.r9 0.29 0.01 Mn Na 0.00 0 K 0.00 0.00 Mgo 0.00 0.00 0.00 0.00 0.00 0.00 F 0 0 Ba 0.01 0 0.00 0.00 0.01 0.01 0.02 Ca0 0.00 0 0.00 0.00 0 0.00 Total 2.n ,.* 2.@ Zt Na 1.95 1.90 t.E7 1.90 t.9l 1.93 r.82 Rqr€s€nli[ive [email protected] eabses of ilmdte, K 0.00 0.00 0.00 0.00 0.01 0.00 0.00 calcolat€d@ a basis of thee ams of oxygeo ed mo cati@s. F 0.35 0.36 0.33 0.34 0.3r 0.28 0.36

ilmenite with bafertisitesuggests elevated Ba in the variation. In contrastto the findings of Wagner et aI. environmentof crysrallization.Ilmenite is a magmatic (1991)on narsarsukitefrom otherlocalities, that from phase that was in a reaction relationship with the StrangeLake doesnot display systematicvariation in residualliquid ascrystallization and cooling continued. tlte Ti content. The chemical zoning of Figure 9 is Marsh (1975) has describedilmenite rimmed bv re-emphasizedin Figure 10, where the Zr content is astrophyllitein syenite. comparedto the level of trivalent cationscorrected for Nb substitution. It is apparentthat the numbers of Narsarsukite trivalent cations entering the structureof the mineral varied systematically throughout its crystallization, Narsarsukitehas recently been studied and a first decreasingthen increasing.This slange may be modifiedformula suggestedby Wagneret al. (1991): due to variations in F activity rather than the avail- (Ti,Zr), Na2[ I_x)Fe3+] O 1_,FrS i4O I 0. (A-yz)H 20 . ability oftrivalent cations(see below). Narsarsukite at Strange Lake (Table 6) commoniy Mineralformulae were calculated on the basisof 11 displaysa chemicalzonation, revealed by variationsin (O + D, rather than on 7 cations as suggestedby the birefringenceof crystals (Fig. 4B). Traverses Wagner et al. (1991), becausethe Na site may not be indicate that the zonationis due to changesrn Zr con- completely filled, and calculations to a constanr centration, with antithetical variation in Fe (Fig. 9). number of cations will obscure site-filling relation- Minor but systematiczoning in Y also has been ships.The results of analysesof narsarsukite(with all documented,whereas Nb doesnot showregular spatial iron consideredas Fe3*)calculate to slightly more than Ti-BEARING MINERALS. STRANGEI.AKE GRANITE 791

TABLE 6. - Continued (which are calculatedas the difference in charge of Ca} from 2+). Analyticaldata from 5638- NF5633- NF5633- Nr5633- NF5633- {Na + K + Ba + 14 D-11 D.l5 D-17 D-18 this study and from Wagner et al. (1991) cornmonly atomsin the Si and Ti sio, 62.14 63.62 63.50 64.64 63.46 show a small excessnumbr of ZrO2 0.83 1.11 1.87 032 0.55 sites.This may alsobe an analyticalartifact, or it may Tio, 12.13 12.52 11.91 12.27 12.74 indicate that other atoms(such as Ti and Fer+or Fez+) SnO, 0.07 0.04 0.10 0.12 0.09 (Fe2+being much more N\Q, 0.56 0.64 0.43 0.25 0.32 also can occupy the Na sites Alo, 0.74 1.03 092 1,29 1.20 likely than the others). The presentdataset does not C%O, 0.08 0.14 0.22 0.02 0.19 resolve the possible entry of Fe2+in the narsarsukite YrO, :^^ structure,but doessupport the resultsof Wag$et et al. FqO, 5.82 5.86 5.57 5.53 ).EJ MnO - 0.09 0.03 0.01 nd (1991)that at leastthe large majority of theilon is Fer+. MgO 0.01 0.04 0.02 0.02 0.01 BaO 0.21 0.06 0.17 nd 0.22 CaO 0.01 0.03 0.03 0.02 0.01 Neptunite ZrO - 0.06 nd 0.04 nd Na,O 15.19 15.43 14.73 15.07 14.55 A study of the crystallographyof neptunite,ideally Kp nd 0.23 0.11 0.06 0.06 KNa2Li(Fe,Mg,Mn)rTrSirOro,has been carried out F 1.82 2.26 2.00 1.93 2.02 by Kunz et al. (1991), and the geologyof other occur- Total 99.61 103.16 10l.61 101.59 101.25 by Heirnich & (1963)and by -F=O 0.77 0.95 0.84 0.81 0.85 rencesreviewed Quon Sum 98.85 102.21 100.77 100.78 100.40 Lald & Nbee (1972). The compositionof nePtunite si 4.03 3.99 4.M 4.07 4.03 from StrangeLake (Table7) showslow concentrations b 0.03 0.03 0.06 0.01 0.o2 of Al, Sn, Zro Ca, Zn and lanthanides.Mineral Ti 0.59 0.59 0.57 0.58 0.61 formulae. calculated from results of electron- Sn 0.00 0.00 0.00 0.00 0.00 to 24 (O + F) equiva- Nb 0.02 0.02 0.01 0.01 0.01 microprobe analysesadjusted Al 0.06 0.08 0.07 0.10 0.09 lents, and with Li assumedtobe I apfu, are illustrated Ce 0.00 0.00 0.01 0 0.00 in Table7. Recalculationsto 16 cationsand to various Y. yield broadly comparable Fel 0.28 0.28 A.27 0.26 0.28 site-filling schemesall Mn 0 0.01 0.00 0.00 0 resultsin terms of calculatedFe2+'Fe3+ values. If all Fe Mg 0.00 0.00 0.00 0.00 0.00 is calculatedas Fe2*, an excessof cations results for Ba 0.01 0.00 0.00 0 0.01 cases.To model the substitutionsin neptunite, Ca 0.00 0.00 0.00 0.00 0.00 most Zn 0 0.00 0 0.00 0 the commonpresence of small amountsof Nb, and the 1.&2 1.84 1.79 Na l.9l' 1.88 positive correlation of F and R3+must be considered. K 0 0.02 0.01 0.01 0.01 The measuredcompositions can then be accom- F 0.37 0.45 0.40 0.38 0.41 modated bv three schemes of substitution: Electron-micmprob€ analyses of msarsukite. Analyses labelled n1.(NbR3.)_; R4o1n:*9_, and R4R2{R3*)-2. An fiom core to rim ae from the profile A B of Figre 58. All afremptto accommodateF throughR4+o2(R2+F2)-r did iron is reported as Fe3'. All malyss cported here were done in correlationswitl othercations, Ottawa. not produceconvincing and does not account for the positive correlation of F and Fe3+.Consequently, Fe2+:Fe3+ values were adjusted to minimize the difference between the the ideal5 cations,exclusive ofthe Na site,so thereis proposed substitutions and the proportions of R2+ thus no basisfor calculationswith someiron expressed versus N*. The results of the calculations are as Fe2*.Nb incorporationis modeledas Rj*61fUR31,. illustratedin Figures 14 and 15.The Fe2+:Fe3+value is Proportions of Ra and R3+ cations covary, with a closeto that calculatedfor 16 cations,or for 12 cations correlationof slopenear -l (Ftg. I 1). The relationships exclusiveof Li and the sum (Na + K + Ca + Ba). The of F with R3+and Re cations approximatelines of scatter(Figs. 14, 15) may result from the accumulation slope I and -1, respectively(Figs. 12, l3). The of analyticaluncertainties on the calculatedproportions substitutionscheme proposed by Wagneret al. (L991), of R3+.or from the effectsof other substitutionssuch as nl+O(RlD-I, thusseems dominant. However, itleaves [OF-2 or F"O2(R2*F)-1. Substantialscatter is evident much of the F unaccountedfor, with the majority of the in tht rehtionihip of calculated lth cations to F data points plotting abovethe line on Figure 12. This (Frg. 16). The good fits of the lines of Figures 14 may be an analytical artifact. Wagner et al. (199I) and 15 to the analyticaldata supportthe argumentthat attributedthis excessto the presenceof divalentcations the three schemesof substitutionconsidered here can assumed to enter the structure by a substitution account for the entry of "other" atoms into the nl+O2(R2+E)-,. Since the sum of cations is already structure. Since the electron microprobe cannot high, and recalculationwith more Fez+will lead to an monitor Li, and either excessor deficiency in Li is appilent increasein this sum, it is unlikely that this possible with compensationby Fe3* (cl Hawthorne schemeis significant. A moderatecorrelation exists et al. 1993), further manipulation of the data at betweenthe 'oexcess"F and vacanciesin the Na site this stage does not seem warranted.The remaining 792 TIIE CANADIAN MINERALOGIST 14 rioz 13 I 12 {'--V*---T 11

E eo I 3 5 * 2

A B FIc. 9. concentrationsof somemajor elements(in weight percentof the oxides)across the narsarsukitegrains along the profile of Figure 48.

Narsarsukiteprofile 2 o.s2 u, .E o.so (U E o.2s

0.5 -o z ' 0.4 t o.4 (t, J'ill'l'-. lr .o 0.9 n< g 0.3 (U xx r .--FEl- r ftr. C) It\- o *C O.2 -\ r "!" fr 0.2 \ -o .g 0.1 Narsarsukite Olo x 0.1 F Narsarsukite I t o AL 0.5 o.7 0.8 0.9 0 0.5 0.6 0.7 0.8 Ti+Zr+2Nb(aPfu) Ti+Zr+2Nb(aPfu) Frc. 1. of ft3*versu s Ti + Zr (apfu)(all corrected I Proportions Ti + Zx (corrected for Nb for narsarsukitebased on 1I (O + F). ftc. 13.Proportions of F atomsversrs substitution) basedon 1I (O + F). Theline indicates a slope of-l. Symbols:I compositions for Nb substitution)for narsarsukite of -1. Symbolsas noted in from StrangeLake, x: datareported by Wagneret al. Theline illustratesa slope (1991). Figure11.

anomalyin the neptunitecompositions concerns Mn, the proposedsubstitutions suggested here are new. which displays a negative correlation with Fe2* Becausepossible complications regarding filling of and a oositive correlationwith Fes*. The neqative the Si site are not addressedby this method, all correlationwith Fe2+is the result of competitio'nfor of the rY+ cations have been consideredtogether. the available sites in the neptunitestructure, but there A crystal-structurestudy of neptunitefrom peralkaline seems to be no a priori expectationof a positive granites will be required before the proposed correlation between Mn and Fer+. The data may formula can be rigorously tested. The proposed indicate removal of Fe2+from the system as other incorporation of F is the same as that proposedfor Fe2*-bearingminerals crystallized; this would leave narsarsukite by Wagner et al. (1991). A formula increasedFe3+ and Mn to enter the minerals. The for neptunitetiat accommodatesF, Nb, and 4'* .* nepfunitefrom San Benito County, Califomia (Kunz be *.itten KNa2Li(Fe2+,Mn,Mg)2-i{bJa3+,+z!+z et al. I99I\ containsnearlv all Fe as Fe2+"such that Ti?_2,_rzsi8o24-J:.

xrr rL 1.5 o.4 I I -o Neptunite I z g Xy o.g a :i , o I .F I rlr r fr o.2 I flo II E 0.5 llo 0.1 o Narsarsukite o r-;- 0.1 0.3 o,4 0.5 o.o 1 .3 1.4 1.5 1.6 1.7 1.8 1.9 2.O 2.1 - (aPfu) Trivalentcations Nb Divalentcations (apfu) Frc. 12. Proportions of F atoms versus R3+(corrected for Nb substitution) for narsarsukitebased on 11 (O + D. Frc. 14. Proportions of R3r (corrected for Nb and F There is an apparent,although relatively weak, positive substitutions)versas those of divalent cationsin neptunite corelationbetween the two. The line illustratesa slope of calculatedon a basisof24 (O + F). Theideal composition 1. The compositionsof ideal narsarsukiteplots at the of neptunite is indicated by the diamond. The line origil. Symbolsas noted Figue 11. illustratesa slopeof-2. 794 TTIECANADIAN MINERALOGIST

TABLE 7. NEPTUMTE COMPOSITIONS

vt.Va NF5638-9 015-A,4 015-3-13 002-6 017-5 0t7-18 NF5879-r1 NF5879-A-14 sio2 {l ,1 <1 << 50.64 5r.3E 51.17 50.96 50.l4 51.l3 ZrO, 0.01 nd 0.07 0.02 0.'t2 nd 0.08 0.01 Tio, r5.3E 14.75 14.71 15.99 14.60 13.51 14.00 13.58 SnO2 0.10 0.05 0.03 0.04 0.18 0.05 0.04 0.07 Nbro, 0.82 nd 0.10 0.25 0.32 0.M nd nd Aro, 0.05 0.19 0.40 0.13 0.09 0.07 0.10 0.10 cqo, 0.10 0.12 0.01 nd 0.16 nd 0.03 0.01 Y,o, nd nd nd nd nd nd nd nd (Fqo) 2.53 3.43 4.95 2.48 3.91 7.68 10.77 t-t) FeO 13.67 15.06 13.66 13.68 13.48 t2.49 9.47 12.24 MnO 0.30 0.46 0.60 0.50 0.70 0.58 1.05 1.02 Mgo 0.09 0.03 0.01 0.01 0.02 nd 0.05 0.09 BaO 0.05 nd nd 0.l8 0.23 0.16 0.11 0.03 CaO 0.03 nd nd nd nd nd 0.05 0.03 ZnO 0.24 0.05 0.15 0.26 0.01 0.09 0.29 0.31 (Liro) 1.60 1.61 r.6l l.61 1.60 l.6l 1.62 1.62 NarO 6.63 6.45 6.55 6.54 6.53 6.5s o.vJ 6.77 KrO 5.16 5.31 4.87 5.15 4.9'.7 4.89 4.U +.oz F nd 0.61 0.48 0.06 0.23 0.41 0.13 0.57 Toal 97.98 99.67 98.85 98.28 98,32 99.09 99.70 99.95 -O=F 0.00 0.26 0.20 0.03 0.10 0.t7 0.05 0.24 Sum 97.98 99.A 98.@ 98.26 98.23 98.92 99.64 99.71 Atoms Si 7.95 8.00 7.90 7.95 7.98 7.93 7.72 7.91 Zr 0.00 0 0.01 0.00 0.01 0 0.01 0.00 Ti 1.80 1.72 1.73 1.86 1.71 1.58 L,OL 1.58 Sn 0.01 0.00 0.00 0.00 0.01 0.00 0.@ 0.01 Nb 0.06 0 0.01 0.02 0.02 0.00 0 0 AI 0.01 0.04 0.07 0.02 0.02 0.01 0.02 0.02 0.01 0.01 0.00 0 0.01 0 0.00 0.00 Y 00 0000 0 0 (Fe1 0.30 0.lm 0.58 0.29 0.46 0.90 1.25 0.90 fe- 1.78 t.96 1.78 1.77 1.76 1.63 1.22 1.58 Mn 0.M 0.06 0.08 0.07 0.09 0.08 0.r4 0.13 Mg 0.02 0.01 0.00 0.00 0.01 0 0.01 0.02 Ba 0.00 0 0 0.01 0.01 0.01 0.01 0.00 Ca 0.01 0 0000 0.01 0.01 Zn 0.03 0.01 0.02 0.03 0.00 0.01 0.03 0.04 (Lt) 1.00 1.01 1.01 1.00 1.00 1.01 1.00 1,01 Na 2.00 1.94 1.98 1.96 1.97 1.98 2.07 L.V) K t.oz 1.05 0.97 1.02 0.99 0.97 0.95 0.91 F 0 0.30 4,24 0.03 0.11 0.20 0.06 0.28

Electron-microprobeanalyses ofnepunite calculatedon a basisof24 (O+F), I Li, and with Fe2', Fe! calculatedas discussedin the text.

Otherphases and Th (Table 9). Optically, the phase is isotropic (probably metamict given the U and Th contents) Petrographicobservations and electron-microprobe and resemblespyrochlore on cursory examination. analy$eshave led to the recognitionof two previously The absence of internal reflections in reflected unknown Ti-bearing phases.One phase has been light allows distinction from pyrochlore. Electron- identified as inclusions in narsarsukite(Table g, probe scans (Frg. 18) indicate the presence of C Fig. l7). This phasehas a high proportionof Zr, Ca and in the phase (cl Raudsepp 1995), but the concen- Na, with low or negligible concentrationsof Sn, Nb, tration and bonding cannot be ascertainedwith the Al, Fe, K and F. The low analyticaltotals suggestthat material presently available. Relationships of the phasemay be hydrous or contain additional light the unidentifiedphase to othersilicocarbonate minerals elements.Concentrations ofTi and? seempositively are unknown. Most silicocarbonateminerals also correlated. containH or B, or form in high-T, low-P environments The second,encountered in one sample(Fig. l7), (e.9., spurrite, tilleyite). It is unlikely that the has low levels of Si, Z, Ti and Fe, high levels unidentifiedphase shares common features with any of of Nb, Pb, and important concentrationsof U these. Ti-BEARING MINERAIJ" STRANGELAKE GRANTTE 795

2.5 Neptunite Olo 2.0 I

1.5 Divalentcations

T T r;f T-f - Nb 1.0 \T t Trivalentcations T +, -F \-+\-+ + 0.5 + tDlo + + 0.0 9.4 9.6 9.8 10.0 Tetravalentcations + 2 Nb + F (apfu) Rc. 15. A compositediagram illustrating neptunitecompo- sitionsbased on 24 (O + F). The abscissarepresents the TABLE & T,NIDENTIFIEDN-ZT-BBARING PHASE proportionoftetravalent cationscorrected for the substitu- STRANGEI.AKE MANIIE tionsofNb andF. Theproportion ofR3* (conectedfor Nb rtt- 70 NFs638-4 M563E-6 NF5638-7 NF5638-1E andF) andthe divalent cationsare plotted, as are reference sio2 50.6 53.82 $.Vl 59.41 linesof slopes-2 and+1. Idealneptunite is shownby the 7)Oz n.a, 8.41 1639 ll29 diamonds. Tio? 7.6 5.42 8.16 930 $il. 0.17 0.18 A.8 0.r2 M.ou 1.10 0J7 1.02 0.39 aaor 0.88 0.24 0.38 0.43 &zo. 0.74 0,29 0.33 0.16 Yzor !d L,79 nd nd FeO 1.88 0J0 0.80 2.fi LtuO 0.07 nd 0.04 0.06 Mso nd nd d 0.01 Bao 023 0.16 020 0.08 r.37 u.c CaO 2.90 2.61 3.96 Zrfr 0.01 0.03 0.03 0.o7 N%o 6,85 a31 0.65 5.14 KrO 018 0:16 1.39 0.05 0.60 0.4 Neptunite F 1.04 0.01 0.11 Total E5.v2 75.42 81.91 gr.w I -OEF 0.44 0.@ 0.05 02s Ssm 85.4E 15.42 81.86 9oJg I E 0.3 I L ! '= tr Atom ta si 1?J9 19.70 17.33 1E.63 a I Il k atu 1Jl 2.88 1.73 rt 2.r9 tr 0.2 ll t.s7 1.49 2.2L ' 0.92 Il ta S[ 0.cl 0.03 0.05 Nb 0.18 0.09 0.1? 0.06 036 0.10 0.16 0.16 0.1 t (Dto Ce 0.10 0.04 0.04 o.v2 j.-* Y 0 0.35 0.02 0 ' 024 0.6'l .lil.- t Pe2' 0J5 021 IvI[ 0.u) 0 0.01 0.02 0.0 Mg 0 00 0.01 nn 0.5 1.0 1.5 2.O Ba 0.03 0.gz 0.m 0.01 Ca 1.@ r.vz 153 0.6 Trivalentcations - Nb (apfu) Zn 0.@ 0.01 0.01 0.04 Na 0 0.45 Flc. 16. The proportion of F atoms verszs that of R3+ ( 0.13 036 0.@ o.a2 0.6() (correctedfor Nb substitution)in neptunite,calculated on F 0.01 0.r3 a basis of 24 (O + D. A weak positive corelationis Cari@sas €lolated to a basisof 48 O alons' all Fe 6 Fe?+. All evident. @lyss sse d@ bo@wa 796 T1IE CANADIAN MINERALOCIST

gW $Y?icrons FIc. 17. A. Unidentified Ti-Z-bearing phase.A back-scatteredelectron image illustrates the textures of the unidentified phase (hgh! in narsarsukitewhich, in tum, is surroundedby perthite with marginal albite (dark gray). B. Unidentified silico- carbonate(anow) in astrophyllitesurrounded by feldspar.

M ineral ass emhlage s and reaction relationships after initial consolidationof the granitesincludes: l) amphibole partially replaced by pyroxene (and With the exceptionof bafertisiteand the bafertisite- vice versa), 2) zircon rimmed by vlasovite or, much like phase,all of the Ti-bearing minerals and all of less commonly, by elpidite, and 3) vlasovite partia[y the mineral assemblagesreported here coexist with to completely replacedby catapleiite.These features quartz, fluorite, pyrochlore, and perthite or two occur locally even in the most primitive portions of feldspars. A Li-bearing mineral (polylithionite or the pluton. ln the more-evolved rocks, with higher neptunite)is presentin all the assemblages.At Strange concentrationsof volatiles, reactions were locally Lake, evidence of extensive reaction durine and intense, with amphibole or pyroxene replaced by Ti-BEARING MINERAIJ. STRANGELAKE GRANTTE 797

TABLE 9. UNIDENTTFIED1I-Nb-Pb.Si-C PIIASE. TABII 10. ASSBMBI.AGESAND SC{SI4ATIC REACIIONS STRANGEI.AT3 GRANIII AMONOSTTHE II-BEARING MINERAI.S, STRANGELAKE GRANNts Sio2vt% 19.15 ^O2 4.@ T10? 652 StableAss€mblagps Reasdoos SrO? o.fi TtOa 3.70 UO! lJ1 Ilm t B&(m) Nb?o5 19'44 N2O. 0.32 CraO3 2.4 Ilttr + Anc 0) Aig , Ast (conno) Ary + Arf Iln . Ast(m) Yrq d F€o 3.17 lv1@ 0.15 ArE + Aft(l) IIn , Ars0) Mgo !d Bd oc& o34 Ae +Ad ArS t Arf (m) Ao + Asi AoS i Ae(m) 7N 0.S rc U.49 NahO 0.06 Ast + Arf Arg i Npt (local) + 0.13 F o,42 Npt + Nr8 Npt Nrs 060I) EO Nr! +Ao Af t Npt (t6e) Total n.65 Nts + Ad Ast t Arf (cmno) geo -O-F 0,18 As + ArC 4 Nn(m) Nrs + Il€m Ast i Npt (ras) Sm n,47 Npt +Ad Ary t Ast + Ad(@) (@z) A8g { Ast + Ao 0@l)

Av@ge Butt of two mlyse$ (all Fe s Fez",@? by dftuq€ hm LN Vo\.

clay minerals or prehnite. Consequently,definition of major minerals. Suggestedreactions are based on assemblagesas opposed to coexistenceof minerals rimming or veining relationshipsand the presenceof requires a detailed examination of mineral textures. relics of one mineral in another(with constantoptical Deducedstable assemblages of precursorminerals and orientationof severalrelict mineral grains).Many early reactions amongstthe Ti-bearing minerals are listed assemblagesbecame unstable as the system evolved, in Table 10. Suggestedstable coexistence is basedon and were overprintedby later assemblages.Relations observationof minerals in contact without apparent of pyroxeneand amphibolegrains with the Ti-bearing reaction (especiallyalong planar boundaries),similar mineralsalso are complicated.As the mineral textures size-distributions,and textural relationshipswith other do not provide constraints on relative volumes of reactantsand products,meaningful balanced reactions among the phasescannot be recognized(cfi Gresens 1967). Nicholls & Carmichael (1969) recognized the ?. 20 'ho oxide field" in peralkaline liquids, and T L postulated reaction relationships among ilmenite, o )u, magnetite,aenigmatite, and pyroxenewith Na, Si and o O from the magma. The assemblagesobserved at t + StrangeLake indicatethat the early developmentof the -, rocks was at an apparentlymoderate oxygen fugaciry, c present o with the Fe dominantly as Fe2+, and with (Jt0 early-formed ilmenite present.At StrangeLake, and o ul probably in many other alkaline complexes,the o presenceof other anions, in particular F, may allow o. substantial Fe3+to be present without implying a a Thus, during crystallization g specific oxygen fugacity. 3 of the StrangeLake pluton, significant Fe3+ was o assemblageilmenite + U available in the melt, and the aenigmatite+ quartzwas stableat higher temperatures .41 .45 .46 .47 .48 (abovethe feldsparsolvus). At lower temperatures,the assemblagenarsarsukite + aegirine was appuently Sine0 stable (possibly with hematite) even at oxygen tugacitiesestimated by Salvi & Williams-Jones(L992) Ftc. 18. Spectrometerscans @C0 crystal) over the sur- to be 2 to 5 log units below the quartz - fayalite - roundingastrophyllite and the unidentified silicocarbonate oxygen buffer basedon the observationof mineral in the region of the carbon peak. The response magnetite from astrophyllite(A) is due to the carboncoating on the methane-bearingfluid inclusions.The presenceof the polishedthin section,whereas the more intensepeak and unidentified silicocarbonatemineral supportsthe low peak shift in B are due to the presenceof carbon in oxygenfugacity estimates of Salvi & Williams-Jones the mineral. (1992). 798 THE CANADIAN MINERALOGIST FeO

Tio2 F%os

Nrs Hom

ftc. 19. Deduced mineral comoatibilities illusuated in the tetrahedron Na - Fe2t - Fe3' - Ti. The assemblagesare (A) IIm + Arf + Ang + Ast, (B) Ad + Ang + Ast + Npt, (C) Arf + Ast + Npt + Ae, (D) Arf + Npt + Nrs + Ae, (E) Npt + Nrs + Hem + Ae, and (F) Arf + Npt + Ae + Hem. Mineral abbreviations are listed in the text.

The evolution of assemblagesof Ti-bearing neptunite) increasethe variance of the assemblages, mineralsat StrangeLake is illustrated schematicallyin so that four-phaseassociations such as illustratedare Figure 19. Hematite,albite and end-memberaegirine not rare. The earliest-formed Ti-bearing phase, are colinear in this projection, as are aegirine, ilmenite, was apparentlyjoined by aenigmatite+ narsarsukiteand hematite, although in nature, minor arfuedsonite.The ilmenitefrst becameunstable with elements such as Mn increase tfie variance of the the magma (and possibly with aenigmatite),and system. The compatibilities of Figure 19 are a bafertisitet astrophyllitereplaced it. Aenigmatitethen suggestedseries of univariant assemblages.Other becameunstable with the magmaand was replacedby elementssuch as Ca (amphibole)or Li (amphiboleand astrophyllite + arfuedsonite+ aegirine, by neptunite, Ti.BEARING MINERAIJ. STRANGEI.AKE GRANTTE 799 or by narsarsukite. As crystallization and cooling the chemicalvariations in the magmas,but this model continued, aegirine became stable relative to doesnot offer adequatemass-balance for somemajor arfuedsoniteand, in the final stagesof developmentof elementssuch as Fe, or for most trace elements.Boily the pluton, hematite formed. All of the assemblages & Williams-Jones(1994) used a combined least- shown in Figure 19 camot be formed from a single squares- Rayleigh fractionation model to produce a bulk composition,and the mineral assemblagesreflect more realistic estimateof massbalance. Both of these the magmaticdevelopment of the system.Assemblages studies, however, would have been improved if in Figure l9a to 19d were formed with perthite, early-crystallizingminslals such as aenigmatitewere whereas assemblagese and f formed with two included in the calculations, rather than relatively feldspars.The assemblagesof Figure 19a to e were late-crystallizing minerals such as arfvedsonite restrictedto the early granitesof Figure 2, whereasthe (Boily & Williams-Jones 1994). Phasesnot yet assemblageof Figure 19f formed in the middle-stage adequatelydescribed, such as the unidentified silico- and late granites. The sequential development of carbonateof Table 9, may well have influenced the mineralswith higherFe3+:Fe2+ values was a continuous magmatic evolution of the pluton, particularly process throughout crystallization on the scale of the trace-elementbudgets. individual samples and on the scale of the whole pluton. Although eventssuch as loss of a fluid phaseto CoNcLUsIoNs form the fluorite breccia in the ring-fractures are recorded at Strange Lake, there is no evidence for The entry of Nb into the Na-Ti-silicates at Strange abrupt changesin Fe3+:Fe2+values during cooling, as Lake can be approximatedby MR3+(ff)-1. The entry recordedin the Ti-bearine silicates.Instead. evolution of Fe3+into theseminerals can be successfullymodeled of Fe3+'Fe2+values was i continuousprocess, as can by substitutionssuch as *R2+(Rt+)-t. The composi- be seenin the shift of the phasecompatibilities away tional range of neptunite is extended tbrough its from the Ti-Fe2+ compositionspace toward the more incorporationof Nb, F and Fe3+.Unidentified phases, Fe3+-richcompositions in Figure19. including a silicocarbonate,crystallized early in the StrangeLake magma, and with other titanosilicates, DrscussloN may have influenced the subsequent chemical evolution of the system. Of the severalsubstitutions discussed by eemf & The reactions amongstthe Ti-silicates considered Ercit (1989), MR3+(&4+)_lcan accountfor a large here involved the residual magma or the immediate proportion of Nb in astrophyllite,and probably in the postmagmaticfluid. At the thin section scale of other minerals consideredas well. Substitutionssuch observationothe system involving the titanosilicates asR4tR2+(NbNa)_1 generally involve Ca; this and other wasopen, and without an additionalconstraint (volume schemescan in some casesbe eliminated becauseof relations or robust mass-balancecalculations), the the requirements imposed by observations of the actual reactions cannot be identified. The reactions correlationsof R+ and Nb. took placeat conditionsabove the feldsparsolvus until The relationshipsbetween oxygen fugacity and the the late-stage reactions involving narsarsukitetook ratio of ferrousto ferric iron in magmashave been little place. studied with other anions added to the experiments. The magmaticevolution at StrangeLake wastoward Mitchell & Platt (1978) and Mitchell (1990) have higher Fe3+:Fe2+ values, but no evidenceof any rapid discussedthe increasingratio offerric to ferrousiron in change imposed on the system is preservedin the mineralsof alkalinerocks with falling oxygenfugacity. Ti-silicates. Oxygen fugacity and Fe2+/Fe3+were Melt structure also influences the ratio of ferrous to decoupledat StrangeLake, most probably owing to ferric iron (Mysenet al. L980,1985, Mysen & Virgo the abundanceof F and the effectsof melt structure. 1989). In the Strange Lake magma, the elevated F content might have helped decoupleFe2+/Fe3+ from AcIG.IOWLEDGETIM.ITS oxygen fugacity, as revealed by 'Williams-Jonesthe fluid-inclusion studies of Salvi & (1992). Models We thank M. Van Baalenand D. Lange of Harvard requiring repeated fluctuations of oxygen fugacity University and G. Pringle of the GeologicalSurvey of during crystallization at Strange Lake (Pillet et al. Canada(GSC, Ottawa) for advice and assistancewith 1993)are not supportedby the progressionsof mineral electron-microprobeanalyses. G. Ansell, GSC, assemblages.Calculated constraints on oxygen provided a sample of niobophyllite from Seal Lake. fugacity using titanosilicates require correction for Ste\rart Fumefion took the photographfor Figure 5A'. incorporationofferric iron in coupledsubstitution with Discussion and reviews bv A.C. Roberts and W.D. Nb (c/. Nicholls& Carmichael1969, Marsh 1975). Sinclair(csc), P. dernf, Ii. Mirchell,R.F. Martin and Two models of the magmatic evolution of the an anonymousreviewer improved the presentationof StrangeLake pluton havebeen formulated. Pillet et al. ideas.W.E.T.Jr. acknowledgessupport by the Nafural (1992) consideredthat feldspar fractionation explains Sciencesand Engineering Research Council ofCanada. 800 THE CANADIAN M]NERALOGIST

REFERINcES HrrNnrcH,E.W. & QuoN,S.H. (1963):Neptunite from Seal Lake, Labrador.Can. Mineral. 7, 650-654. ABDEL-RArtoIAN,A. (1992): Mineral chemistry and para- genesisof astrophyllite from Egypt. Mineral. Mag 56, JAMBoR,J.L., Ronsnrs, A.C. & Gntce, J.D. (1987): t7-26. Armstrongite from the Strange[,ake alkalic complex on the Quebec-Labrador boundary, Canada. Powder BIRKETT,T.C. & Muen, R.R. (1991):Comment on "The Dffiaction2,2-4. role of hydrothermalprocesses in thegranite-hostedh,Y, REE depositat StrangeLake, Quebec/I-abrador:evidence Knarz, R. (1983):Symbols for rock-formingminerals. Ara from fluid inclusions"by S. Salvi and A.E. Williams- Mineral.68.277-279. Iones.Geochim. Cosmachim. Acta 55, 3443-3445. Kun4 M., ARMBRUSTER,T., Lecrn, G.A., ScHULiz,A.J., RoBERrs,A.C. & MannNo, A.N. Govrr-re, R.J., LorrERMosER,W. & AMTHAUER,G. (1992): Znconittm-bearingminerals of the StrangeLake (1991): Fe, Ti ordering and octahedraldistorsions in IntrusiveComplex, Quebec-Labrador. Can. M ineral. 30, acentric neptunite: temperature dependent X-ray and 19r-205. neuuon structure refinements and Mdssbauer spectroscopy.Phy s. Chem. M inerals 18, 199-213. BotLy, M. & Wtr-LrAMs-Jol.'rs,A.E. (1994): The role of magmatic and hydrothermal processesin the chemical evolution of the Strange Lake plutonic complex, Lanp, J. & Arssr, A.A. (1972):Chemical composition and physical, and structural properties of benitoite, Qu6bec-Labrador.Contrib. Mineral. Petrol. lIE,33-47 . optical, neptunite,and joaquinite. Arz. Mineral. 57, 85-102. BuRr, D.M. (1988):Vector representationof phyllosilicate compositions.1la (S.W.Bailey, ed.). Rev. Mineral. LARSEN,A.O., Raaue, G. & SAEBo,P.C. (1992): l,orenzenite t9,56r-599. from the Bratthagen syenite pegmatites, LAgendalen,Oslo region, . Norsk Geol. Tilsskr. (1989): Vector representationof tourmaline 72,38r-384. compositions.Am. Mineral. 74, 826-839. Lavxs, G.D., Rucrrncn, J.C. & Bnoors, C.K. (1982): (1994): Vector representationof some mineral Asuophyllite from Kangerdlugssuaq,East . compositionsin the aenigmatitegroup, with special M ineral. Mag. 45, 149-156. referenceto hgggvaite. Can. Mineral. 32, 449-457. MacooNelo, R. & SauNoeRs,M.J. (1973): Chemical denNf, P. & Encrr, T.S. (1989):Mineralogy ofniobium and variationsin mineralsof the astrophyllitegroup. Mineral. : crystal chemical relationships,paragenetic Mag.39,97-111. aspectsand their economicimplications. 1z Lanthanides, tantalumand niobium @. Miiller. P. Cemj & F. Saup6, eds.).SGA Spec.Publ. 7,27-79. SpringerVerlag,Berlin, Mansu, J.S. (1975): Aenigmatite stability in silica- Germany. undersaturatedrocks. Contrib. Mineral. Petrol. 50, r35-144. CoscA,M.A., Rousn,R.C. & EsspNr,E.J. (1988):Dorrite [Ca2(Mg2Fe;iXAl4Si2)O20],a new member of the MARTN, D. (1975): Snlies of Astrophyllite from Mont St. aenigmatitegroup from a pyrometamolphic melt-rock. Hilaire, Quebec. B.Sc. thesis, Carleton University, Am. M ineral. 73, 1440-1 448, Ottawa,Ontario.

Cunntp,K.L. (1985):An unusualperalkaline granite near Lac MAUcER,R.L. (1983): Bafertisite and an unidentified Brisson,Quebec-Labrador. Geol. Suw. Can., Pap.85-1"A, BaCaMnFeTisilicate from FountainQuaxry, Pitt County, 73-80. North Carolina.Southeastem Geology A, 13-20.

DuocAN,M.B. (1990):Wilkinsonite, Na2FeerFetrsi6o20, a MrLr-ER,R.R, (1985):Geology of the StrangeLake alkalic new member of the aenigmatite group from the complex and the associated Zr-Y-M-Be-REE WamrmbungleVolcano, New South Wales, Australia. mineralization.1n Granite-RelatedMineral Deposits; Am. M ineral. 75, 694-701. Geology,Petrogenesis and Tectonic Sening (R.P. Taylor & D.F. Strong, eAs.).Can. Inst. Mining Metall., Extended Gnssx,T.H. & Prensor, N.J. (1987):An experimentalstudy Abstr.,193-196. of Nb and Ta partitioning betweenTi-rich rninerals and silicate liquids as high pressure and temperature. Geochim.Cosmochim. Acta 51, 55-62. (1986): Geology of the Strange Lake alkalic complex and the associated Zr-Y-Nb-Be-REE GRrsENs,R.L. (1967):Composition - volumerelationships of mineralization. Newfoundland Dep. Mines, Mineral metasomatism.Chem. GeoI. 2. 47-65. DevelopmentDiv., CurrentRes., Rep.86-1, 1l-19.

HAWTHoRNE,F.C., UNcanrrrr, L., OBERI,R., Bo'rrAzzt,P.& (1988):Yttrium (Y) andother rare metals Ge, Nb, CZAMANSKE,G.K. (1993):Li: an imporuantcomponent of Ta, 7t) in Labrador.Newfoundland Dep. Mines, Mineral igneousalkali amphiboles.Azr. Mineral. 78, 733-745. DevelopmentDiv., CurrentRes., Rep. 88-1,229-245. TiBEARING MINERAI.S" STRANGELAKE GRAN]TE 801

(1990): The StrangeLake pegmatite-aplitehosted & -(1993): P6trologiedu granite rare-metaldeposit, Labrador.Newfoundland Dep. Mines peralcalin du lac Brisson, Labrador central, Nouveau- andEnergl, Geol.Surv. Branch, Rep.90-1,1,71,-182. Qu6bec. II. Min6ralogie et modalit6s de cristallisation. Can.J. Eanh 9ci.30,2423-2435. MrcHEt.l,, R.H. (1990): A review of the compositional '"AP" variation of amphibolesin alkaline plutonic complexes. PoucHou,J.L. & I\cuon, F. (1985): A@z)procedure Lithos26.135-156. for improved quartitative microanalysis.Microbeam AnaL20.104-106. & PLArr, G.R. (1978): Mafic mineralogy of ferroaugite syenite from the Coldwell alkaline complex, RAUDsEpp,M. (1995): Recentadvances in the electron-probe -65I. Ontario, Canada.J. Petrol. 19, 6n microanalysis of minerals for the light elemen.ts.Can Mineral. 33,203-218. MyssN,8.O., SeFEnr,F. & Vrnco, D. (1980):Structure and redox equilibria of iron-bearing silicate melts. Am. RoELoFsEN-AE,J.N. & PerensoN,R.C. (1989):Gittinsite, a Mineral.65. 867-884. modification of the thorweiiite structure. Can. Mineral. n.703-108. & Vrnco, D. (1989):Redox equilibria,structure, and properties of Fe-bearing aluminosilicate melts: relationships among temperature, composition and Sarvr, S. & WtruAMs-JoNFs,A.E. (1990): The role of oxygen fugacity in the systemNqO - Al2O3- SiO2- Fe hydrothermalprocesses in the granite-hostedZr, Y, REE - O. Am. Mineral.74, 58-76. depositat StrangeLake, Quebec/Labrador:evidence from fluid inclusions. Geochim. Cosmochim. Acta 54, NELMANN, E.-R. & SEmRr, F.A. 2403-2418. (1985):Redox equilibria and the strucfuralstates offemc and ferrous iron in melts in the system CaO - MgO - & - (1991):Reply to Commentby T.C. '"The Al2O3- SiO2 - Fe - O: relationshipsbetween redox Birkett and R.R. Miller on role of hydrothermal equilibria melt structme and liquidus phase equilibria. processesin the granite-hosted7'r, Y, REE deposit at Am. Mineral. 70. 317-331. Strange Lake, Quebec/Labrador:evidence from fluid inclusions".Geochim. Cosmochim. Acta 55,3447 -3449. NAssrF,G.J. (1993): The StrangeInfu Peralkaline Complex, Qudbec-Inbrador: the Hypersolvus- SubsolvusGranite & - (1992): Reduced orthomagmatic Transition and Feldspar Mineralogy. M.Sc. thesis, C-O-H-N-NaCI fluids in the Strange l,ake rare-metal McGill Univ., Montreal, Quebec. granitic complex, Quebec/Labftdor, Canada. Eur. J. Mineral. 4, 1155-1174. & Manrn, R.F. (1991):The hypersolwsgranite - subsolws granite transition at Strange Lake, VMNe, S., Rmnpn,M. & GuwEn, M.E. (1992): Hejtmanite, Quebec-l,abrador.Geol. Assoc. Can. - Mineral. Assoc. a manganese-dominantanalogue of bafertisite, a new Can.,Abstr. Program 16, A89. mineral.Eur. J. Mineral.4.35-43.

(1992): Feldspar & - mineralogyof the WAGNTER,C., PARoDI,G.C., SEMET,M., Ronrnr, J.-L., Strange Lake peralkaline complex, Quebec-Labrador. (1991):Crystal chemistry of - BERRAHMA,M. & Vpr-os,D. Geol.Assoc. Can. Mineral. Assoc.Can., Abstr. Program narsarsukite.Eur. J. Mineral.3, 575-585. 17.A83. S. Nrcr{ot-rs, J. & CARTwcHAEL,I.S.E. (1969): Peralkalineacid Zarec, I.S., Mnmn, R.R., BRKtrr, T.C. & Nams-, (1984a): liquids:a petrologicalstudy. Contrib. Mineral. Petrol.20, The StrangeLake deposit,Quebec-l,abrador. (abstr.). 268-294. Can.Inst. Mining Metall.,Bull.77(863),60

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-, CrENEvoy,M. & BErarcrn,M. (1992):P6trologie du granite peralcalin du lac Brisson, Labrador central, Nouveau-Qu6bec.I. Mode de miseen placeet 6volution Received August 6, 1995, revised manuscript accepted chimique.Can. J. Eanh Sci.29,353-372. April 5, 1996.