Canadian Mineralogist Vol. 23, pp. 577-582(1985)

THE RELATIVESTABILITV OF ELPIDITEAND VLASOVITE: A P_T INDICATORFOR PERALKALINEROCKS

KENNETH L. CURRIE AND EVA ZALESKI GeologicolSqney of Canada,601 Booth Street,Ottawa, Ontario KIA 0E8

ABSTRACT accessoryzircon. In peralkaline rocks, the ratio (Na + K)/Al excds 1, may be rare or absent, The univariant reaction Na2ZrSi6Otr.3H2O (elpi- andZr appearsin a bewilderingvariety of , dite; = 11ar7t5ino11(vlasovite) + 2 SiO2+ 3 H2O passes including in amphibolesand pyroxenes(up to seve- through the points 1000bars, 595 + 4'C and 2000 bars, ral percent ZrO). Among minerals that may appear &4 t 4"C. The reaction curve is unaffected by the presence as Zr-bearingphases in peralkalinerocks, vlasovite of excessNa in the vapor phase,but the substitution of Na2ZrSiaOlland elpidite Na2ZrSi6Orr.3HrOare of I N water HCI for decreasesthe stability field of elpidite specialinterest because for stoichiometriccomposi- by about 20'C. Elpidite is unstablerelative to keldyshite qtJartz+ Na2ZrSi2OTin highly chlorinated assemblages.Synthetic tions, elpidite:vlasovite +2 3 water. elpidite has smaller cell-dimensionsand a different space- Therefore, elpidite would be expectedin environ- group than natural elpidite, but syntietic vlasovite appears ments with relatively high activities of silica and essentiallyidentical to the natural . Elpidite forms water, and vlasovite in environments with relatively from hig[-temperature hydrothermal fluids, whereas low aclivities of silica and water. However, both vlasovite forms as a magmatic accessoryor by metamor- minerals, although never found together, apparently phism of elpidite. The more common occurrenceof elpi- occur in similar environments,namely highJevel dite, relative to vlasovite, suggeststhan an aqueousphase peralkaline ganites and peralkaline nepheline peralkaline granitic separatesfrom magma only when crys- relatively commonly in tallization is virtually complete. syenites. Elpidite occurs peralkaline , for example at Lac Brisson, Keywords: elpidite, vlasovite, reaction curve, pressure- Quebec(Zajac et al. 1984)and Mount Champlain, temperatureindicator, peralkalinegranite. New Brunswick(R.F. Martin, pers.courm. 1983)in Canada, and also in peralkaline syenitesat Mont Saint-Hilaire, (Chao 1967)and Lovozero, SoMMAIRE Quebec U.S.S.R.(Semenov 1967), as well asin maficqtrartz- (Kapustin 1966).Vlasovite has been (elpi- bearingfenites La r€action univariante Na2ZrSi6O15.3H2O peralkalinegranile dite) = yar2r5iao11 (vlasovite)+ 2 sio2 + 3 H2o est en reportedin blocks of high-level 6quilibre aux points 1000bars, 595 i 4'C et 2000 bars, found as inclusionsin trachyteon AscensionIsland 644 t 4oC. La courbede r6actionn'est pas affect6epar la (Fleet & Cann, 1967), and from metamorphosed pr6senced'un excbsde sodiumdans la phasevapeur, mais agpaitic rocks of amphibolite grade at Kipawa, Que- le champ de stabilitd de l'elpidite d€croit d'environ 20oC bec (Gittins et al. 1973),as well as from nepheline quand on remplaceI'eau par une solution de HCI (1N). syenitesof the Lovozero somplex (Semenov1967). L'elpidite estinstable vis-i-vis la keldyshite(Na2ZrSi2O?) The similarity of the paragenesessuggests that some dans les mdlangestrds riches en chlore, L'elpidite synth6- feature other than silica or water activity must con- tique possedeune maille plus petite que cellede I'elpidite mine- groupe trol the mutually exclusivecharacter of these naturelle, et un spatial diff6rent, mais la vlasovite pressure synthdtiqueresemble beaucoupau min6ral naturel. L'elpi- rals. If this controlling factor is or tempe- dite se forme d partir de solutions hydrothermales i haute rature, then the comparatively simple chemical temperature, tandis que la vlasovite provient d'une phase characterof the minerals (Semenov1967) suggests magmatiqueaccessoire, ou par metamorphismede I'elpi that their relations rnight give a useful P-T indica- dite. L'elpidite est plus rdpandueque la vlasovite, ce qui tor. In order to test this hypothesis,:m experimen- iait penserqu'une phaseaqueuse ne ses€pare des magrnas tal study was undeflaken to determine the relative granitiques hyperalcalins que lorsque la cristallisation tire stabilitiesof elpidite and vlasovite. i sa fin; EXPERIMENTAL METHOD Mots-c6s: elpidite, vlasovite,courbe de r6action, indica- teur de pressionet de temperature, hyperalcalin. Both elpidite and vlasovitecan be readily synthe- sized (Christophe-Michel-L5vy1961, Baussy et al. INTRoDUCTIoN 1974),but previous studies produced little useful information on the relativeor absolutestabilities of In most rocks, the molecular ration (Na + K)/Al the minerals.Since the natural paragenesessuggest is less than or equal to l, and Zr occurs mainly in that silica activity is not the major factor control- s77

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ling the relationsof the minerals,we worked mainly TABLE2. RESULTS0F HYoR0'ItlERl'lALEXPERIMENTS

with materialsof stoichiometricelpidite composition. (a) Flnid phe Fre watq We used different mixtures only to evaluate the Ru P(bars) T(c) Reactsts Produqts peralkalinity produce Na-Zr degreeof required to 5-t 2026 680 get vl + qtz silicatesrather than zircon in peralkalinecomposi- 7-2 m26 660 Bel vl + qtz 9-7 m26 650 gel vl r qtz tions. 54 2n26 AO gel el(+qiz) In all casesthe starting materialswere dried gels xt7 ?f26 635 *el et({itz) xl8 2n26 640 lel dl(+qtz) prepared from reagent-grade zirconyl chloride x20 2026 gr5 iel el+vl+qtz (ZrOCl.8 x21 2026 650 rel el(+qtz) H2O) as a sourceof Zr, sodium-stabilized xn 2026 648 tvl+gtz vl+qtz colloidal silica sol as a source of SiO2, and either xzt 2026 643 tvl+qtz el+vlrqtz x24 2026 638 *Yl{qtz reagent-gradeNaHCO3 or NaCl as a source of 64 l5L9 6140 tel Yl a qtz prepared u3 L5l9 6)0 gel vl + qtz sodium. Gels were by dissolving the 6-t l5l9 620 gel vl+(el) appropriateweight of zirconylchloride in 0.1 N HCI v2 L5l9 615 gel vl(+gtz + el) 8-l l'9 600 gel el(+vl + qtz) and adding the silica sol to it while stirring. For the 6-5 I5l9 600 gel el(+vl + qtz) initial experiments,weighed amounts of NaCl were xL2 l5l9 615 *eI el(rqtz) xl3 ljl9 620 rel dissolvedin this solution, and the materialeelled by xt4 lJl9 625 rel el{vl+qtz xt6 l'9 630 *el vI + qtz adding NH4OH. Hydrothermal experimentson this x26 l5t9 62t *vl+qtz el+vl+qtz material consistently produced keldyshite x27 1'9 62t rvl+qtz el+vl+qtz x29 t5l9 618 rvlrqtz e(+qtzJ Na2ZrSi2OTrather than elpidite or vlasovite. We )-6 tol, 600 gel vl(iqtz + el) prepared gel. t+4 l0r3 600 gel vl + qtz therefore a chloride-free The solution l8 t0l3 t80 gel e(+Stz) of zirconyl chloride and silica was gelledby adding ,7 tol, xo gel e(+qtz) u5 tol, 550 gel el(+vl + qtz) excessNH.OH. The gel was dried at 90oC for 12 54 tol Vto cel el(+Ctz) hours and fired at 900oCfor one hour, which quan- 34 t01, J00 tel e(rqtz) 44 l0l, 500 gel el(+gtz) titatively removed Cl by volatilization as NH4CI. ,2 l0l, 400 geI el(+gtz) u2 101, 400 tel el(rCtz) NaHCO, was then addedto the chloride-freemix, x5 l0l3 585 fel el and the mixture shakenin an agitator with plastic x7 l0l3 ,90 *el el( + qtz) x8 l0l3 595 el{Yl}qtz grinding balls for 30 minutes and heatedat 550oC x9 1013 59t *el vl + qtz for 4 hours to drive off COr. Gelswere made up so x30 101, 600 rvllqtz vl r qtz xrt 101, 59' rYllqtz el+vl{gtz that the calculated weight of the dried products xtt 101' 'EE rvl{qtz el(+qtz) 6-8 507 '80 6el vl r gtz(d) would be about 15-20 grams. The products were ,2 507 '80 gel el({qtz) rejectedif their weightdeparted from the calculated 9-t 507 560 gel e(rgtz) 507 %0 tel el(+qtz) weight by more than 0.02 grams. X-ray-diffraction 64 507 tt0 gel e(qtz) analysisof xl 507 546 *el el(*stz) the chloride-freestarting material showed xz 507 550 *el el weak linesof baddeleyite.Wet-chemical analysis of x3 507 554 *el el+yl+qtz x4 507 559 rel vl { qtz this material by S. Courville (Table 1) showedthat xt5 507 550 fvl+qtz it correspondedto the statedZr:Na:Si ratio within xu 507 557 rvl+qtz YI r qtz analytical error. (b) FluldphcelNNaoH The experimentswere conductedwith standard Blq P(bars) T(c) R€ctetg @ hydrothermaltechniques. About 0.2 gramsof start- 4-10 l0l3 600 get vl r qtz(el) ,-10 t0l3 550 gel el ing material were loadedinto thin-walled (0.1 mm) u9 101, 550 geI el gold tube, about 0.02 gramsof aqueousphase (dis- 3-9 l0l3 500 Eel el(+qtz) 4-7 1013 450 gel el(+qtz) tilled water, 1 N HCl, I N NaOH) added, and the ,7 t0L3 450 gel el(+qtz)

capsulewelded and weighed.Experiments were made (c) FluidpharelNHcl in Ren641 test-tubebombs with graphite or stain- R@ Pbas) 19) R@ctilts Products lesssteel filler-rods. Temperaturewas measuredby 94 2026 700 gel vl r qtz chromel-alumelthermocouple inserted into drilled 8-5 2026 660 gel e(+vl + qtz) 7-9 2026 6It0 gel el({vl r qtz) wellsin the bombs, and is believedto be maintained 7-7 2026 620 tel el(avl r qta within 2'C during experimenis.Prqssure was meas- X'E 2026 640 rel vl I qtz x19 2126 630 *el Yl + qtz ured on a 30-cm Heise bourdon gauge, and is x51 2026 625 *dl el+Yllgtz x40 2A26 620 reI el(+qtz) x4l 2026 640 * vl+qtz Yl + qtz xttz 2026 630 lvl+gtz vl + qtz x4? 2026 620 el TABLE 1. CHEMICAL COMPOSITIONOF STARTING MATERIALS 8-8 1013 60 gel vl(+el r qtz) 94 l0l3 640 gel Yl + qtz Veiftt Mol 9-1 l0l3 620 gel vl r qtz(+el) 7-5 l0l3 600 tel e(+qtz) SlOz 59,Ot% 6.006 x44 101, t90 *el vl r qtz Na?o 10.25 1.0t0 x45 1013 5t0 *el vl + qtz rel ZrO 2 20.17 1.@0 x46 l0l3 570 el(+qtz) Hz0 10.16 3.5t4 x47 1013 590 rvlrqtz vl + qtz 0.04 0.006 x48 101, 58 *vl{qtz vt + gtz x5t 101, t75 *vlrqlz el+vligtz S. CwiUe, salyst. Mol@lar propqtloB bced on 2k . 1.000 x49 1013 fvlrqtz el(+Stz)

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(d) Chlorlnated mlx, fluld phe Fre H2O boundary, a number of synthesisexperiments were Ru P(baF) 1(c) R€ctate Products made by running the starting mix at P-T for 168 l-l l0t3 500 Cl-8el kl i qtz hours @ig. l). Elpidite and vlasovitecan be readily L-3 l0t3 530 Cl€el kI { qtz synthesizedin neutral, alkaline or acid aqueousfluid l-4 l0l3 Yto Cl-gel kl + qtz t-7 l0l, ,70 Cl€el kI i qtz phases(Table 2). The equilibrium phase-boundary t-14 l0l3 5E0 cl-gel kI r qtz (Fie. l-16 l0l3 600 Cl-tel kl r qtz 2) was establishedby first converting the start- r-18 l0t3 620 Cl-gel kl + qtz ing material to elpidite (500" at I kilobar for 168 t-22 l0ll 660 Cl€el kl { qtz t-24 l0t3 700 Cl-gel vl4kllqtz hours) or to vlasovite+ quartz (650' at 500bars for t-26 t0l3 740 Ct-gel vl r qtz 168hours). Thesematerials were then usedas start- Synbols: v] vlasovlte, el elpidlte, kl keldyshlte,qtz quartz. ing materialsfor experimentsto establishthe reversed l',llnorand trace amunts (ln parentheses)my be retastable. equilibrium phase-boundary * denotesan equllibrlum experlmnt. The elpidite produced consistentlycoexists with a variable but small amount of quartz, suggesting eitherthat the mineral is slightly nonstoichiometric, believedaccurate to within 5 bars. At the end of an or tlat the material from which it crystallizeddeparts experiment the bombs were air-quenched.After sliehtly from elpidite cornposition.Since the start- quenchingthe capsuleswere weighed, slit with a ing mix containsNa2O, the solid phasewill depart razor, and the contentsmounted on glassslides for from elpidite stoichiometrybecause of solution in optical and X-ray examination. Only results from the aqueousphase. The appearanceofquartz rather capsules that exuded water on puncturing are than zircon in the products suggeststhat Zr must also reported in Table 2. Although elpidite can be opti- be quite solublein the aqueousphase. Watson (1979) cally recognized,we were unable to consistently concludedthat alkali zirconosilicate complexesplay recognizevlasovite optically, and the identifications a major role in the enhancedsolubilify of Zr andztr- given in Table 2 are all based on X-ray powder con in peralkalinemelts. His conclusionsmay also diffraction. Products of a few experimentswere also be applicableto the peralkaline aqueoussolutions analyzedby SEM by David Walker to check the of our experiments. Na:Zr ratio of syntheticelpidite relative to natural The X-ray diffraction powder-pattern of our syn- elpidite from Mont Saint-Hilaire. The ratio is essen- thetic vlasoviteagrees well with that in the ASTM tially identical in natural and artificial elpidite. file, and there appearsto be no differencebetween the natural and synthetic material. Although syn- ExPERIMENTALRESULTS thetic elpidite is easilyidentified on X-ray-diffraction record$,it exhibits either a broad or doublet peak In order to establish approximately the phase aI a d of 3.227A that is not mentionedin the ASTM

r elpidite o vlosovils+guorlz o elpidlfe+vlosovits+guortz

ao oo

v, L o tt

o aaa L '@t q o (L e(pidire v lqsovlle + aa guqrlz

Tetnperolure (oC) Ftc. l. Data on the synthesisof elpidite and vlasovitefrom gel of elpidite composi- tion. The curve dividing the fields of elpidite and vlasovite + quartz is taken from Figure 2. Excesswater or I N NaOH was added.

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TABLE3. INDETINGOF POI.IDER-DIFFRACTIONDATA FOR ELPIDITE

4/ea Svnthetlc elpidlte Natural elDldite

m d(A) I hk.l 20 d(A) I hkl t2.54 7.050 60 100 12.% 7"161 ,o t00 tt.6L 6.496 50 021 1t.44 6r5t0 50 021 17.t6 5.104 60 022 17.08 5.189 60 022 18.14 4.7Er 40 t2L 18.36 4.828 nl2l ",O,Otr"- 0lr* o t9.64 ,4.517 5 j/ 2t.52 4.125 40 122 21.22 4.102 o 22.)8 ?. 9 t0 02) a 22.t6 1.a67 n 13l* 3.662 5 040 o 74.8' t.575 n 0lr0 24.28 L 27.5t ,.217 50 042 27.!6 1.280 90 042 5 27.12 3.260 90 140 6 27.5E t.ztl ,0 140 tl 27.9t t.192 50 o24 o 28.t0 3.150 20 202 n.85 t.201 l0 202 o. 28.E6 t.09r 60 221 2t.51 3.lD 50 221 10.65 2.914 ,0 t42 t|.w 2.970 z0 142 31.6t 2.82,1 n 20t* 13.62 2.661 20 r4t ,2.t8 2.721 l0 143 )5.37 2.5t6 40 044 t4.52 2.597 l0 044 15.6 2.517 to 240 17.24 2.412 N 2q2 43.83 ?.46t 40 244 4r.0E 2.O9E m 244 Temperoture(oC) 45.12 l.U9 n 064 44.42 2.O)7 40 064 47.12 1.127 40 l6tr M.to 1.99 ,0 164 Frc. 2. Experimentaldata on the univariant reaction rr8.98 l.t't za 06r* : quartz water. the 52.48 1.742 m 26tl 5t.79 L.n4 40 264 elpidite vlasovite+ + Symbolsare 57.58 1.594 to 441 sameas in Figurel. Thearrows indicate starting assem- ,t.3t 1.579 40 441 blages,with right-pointingarrows indicating elpidite, * Indices markednith this symbolar€ not Pevrnlttedln the andleft-pointing arrows indicating vlasovite + quartz. structur€ for natural elpidite detenninedby Can1llo et al. Excesswater was added. (1973). Inderlngby J.L. ilanboron synthetic elpidlte prc- ducedin experlment4-4 and natursl elPidite from Lac Brlsson on the Quebec-Labradorborder.

powder-data file. A preliminary examination of our 29-1294 (synthetic elpidite) data and those of PDF TABLE4. CALC1JLATEDCELL-DIMENSIONS FOR ELPIDITE by J.L. Jambor strongly suggeststhat the indexing and calculated cell-dimensionsof synthetic elpidite Smtltetlc @ in the PDF arb in error. The indexing by Jambor is Ru 4-rt PDF29I294 Le Brlssm Mt. st-llilslre givenin Table 3, and the calculatedcell-dimensions a (A) 7.oq (0.012, 7,06 7.12 (o.o09l 7.lq material agreewell b 14.55 (0;021) 14.54 L4.67 (0.017t 14.68 in Table 4. The d valuesof our c r4.D $.oaal 14.21 14.67 (0.0261 14.65 with the PDF valuesfor synthetic elpidite, but all parameter$are significantly smaller than those for Data for synthetli elpidite calculaied for product of experlrent 4-4 and tai

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-( g / o o e7

elpldite

o L c, tt (D

J OE c' rooo! *d'ar/ U' o vlosovite IL f quortz

600

Temperofure (oC)

Ftc. 3. Experimentaldata on the relativestability of elpidite and vlasovite+ quartz in the presenceof I N HCl. Circles indicate products made from elpidite or vlasovite+ quartz stafring materials(same symbols as Fig. 2). Squaresindicate products made from gel. The broken line is the equilibrium curve from Figure 2. The solid line is the samecurve transposed20oC to lower temperature.Note the discrepancybetween synthesis and equilibrium experimentsat l0l3 bars.

lar water, not hydroxyl ion. The effect of other Iupr-rcarrous FoR PETRocENESIS moleculesin the water site may be a significant fac- tor affectingthe stability ofelpidite. Substitutionof The stability range of stoichiometricelpidite lies I N HCI for pure water raisesthe maximum tem- below the water-saturatedsolidus of granitic rocks, peratureat which elpidite appe€usin synthesisexperi- except at pressuresabove 2 kilobars. Since most ments by about 20oC (Fie. 3) but depressesthe known examplesof natural elpidite come from rela- equilibrium curve by about the sameamount. This tivelyhigh-level plutons, the experimentaldata imply depressioncould be qualitatively accountedfor by that elpidite developsat the hydrothermal stage,after depressionof the activity of water due to dilution solidification of the magma.Our experimentaldata with HCl. The discrepancyin behaviorbetween s1'n- agreewith observationsthat most natural elpidite thesisand equilibrium suggeststhat this dilution also occursin miarolitic cavitiesor vug-like masses.Our has significant kinetic effects. data are not directly applicable to the temperature Use of strongly chlorinatedmixes using NaCl as of formation of Ca-rich elpidite, which may possi- a source of Na rather than NaHCO, completely bly form at magmatic temperatures.Elpidite under- suppressedthe appearanceof elpidite in favor of went alteration, to hilaireite, gaidonnayite and keldyshite+ quafiz. Atransition from keldyshiter lemoyneiteat Mont Saint-Hilaire, and to gittinsite quartz to vlasovite occurs at some poorly defined CaZrSi2OTal Lac Brisson. These minerals must temperatureabove 700oC. Since keldyshite contains have stability fields at lower temperature than elpi- no site for chlorine, and can be synthesizedfrom dite. Our data imply that these stability fields lie anhydrousstarting materials @aussye/ aL ln 4), the below 400'C. appearanceof keldyshitein theseexperiments must Since vlasovite + quartz forms the high- be relatedto somecontrol of silica or water activity temperatureequivalent of elpidite, vlasovitemight exercisedby the Cl ion. The presenceof excessNa be expectedto appearas a magmatic accessoryphase in the fluid has no obvious effect on the stability rela- in elpidite-bearingperalkaline granites. Such an tions (Table l), but mixes with Na:Zr less tharr 2 occurrencehas neverbeen repofied. This apparent producezircon in addition to sodium zirconosilicates, anomaly can be explainedin severalways. Firstly, whereas mixes with Na:Zr less than about 1.3 vlasovitemay have simply been overlooked where produce only zircon. it occursin accessoryor trace amountsbecause it is

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difficult to recognizeoptically. We believethis expla- CeNtI-ro,E., RossI,G. & UNcensrrt' L. (1973): The 5E, nation to be un-likely.3""ondly, vlasovitemay hau. crystal-structureof elpidite. Amer- Mineral. been originally present, but irave since been con- 106-109' verted to elpidite. We are awareof no evidence,such tT3-i,.";tl%1"fi!331ffi";i"!,f$:"'^ilL"t#; ^ .rpiait.iseudomorphic artervlasovire, orelpidite such a with a vlasovitecore, which would support iiifiii", b-"JUi.. Can.Vnirai. g,iAiA-ZAl(absrr.). mechanism.We believethat the availableevidence stronglysuggests that vlasoviterarely or neveroccurs Cnnrsropn'-Mt4rpr-LEvv,M. (1961): Reproduction in elpidite-bearing granites. Low concentration and artificielle de quelquesmin€raux riches en ztconium high solubility of 2r n peralkaline melts (Watson (zircon, ,catapl6ite, elpi{ite); comparaison soc. tizs) coda retard nucleaiion of a Zr-rich phaseuntil avecleurs conditions naturellesde formation. MindraL Crist' Bull' 84' 265'269' the separation of * uq""ou; td; relatively rich frang' in Zr. The almost exclusivepresence of elpidite i" t'TJ;irro;* peralkalinegranites suggestsihat such a frie aque- f#),i;5tJt"'J;J,*:i#fift:::ffi1 ous phaseonly separatedat temperatureson or near lrtiiirit.- tntoe, 36, 233-241. the solidus. The rare occurrenceof vlasovite requires eitherunusuallyhighconcentrationsofZr inaper- GrrrrNs,J., GaspenntNr,E.L. & FrBer,S.G. (1973): alkalinemeltormetamorphismofanelpidite-bearing The occurrenceof vlasovite in Canada. Can. assemblage. Mineral,l2,2ll-214' The easysynthesis of Na-Zr silicates,their appar- (1966):A new occurrenceof elpidite ent independence of silica activity, and their KepusrtN,Yu. L. Dokl. Acad. Sci. USSR,Earth Sci. occurrencein peralkalinerocks suggest in the USSR. widespread Sect.l7l, 157-159. that they offer the possibility of a detailedsubdivi- sion of P-T-/(H2O) space.We intend to continue Sruerov, Ye, I. (1967):On varioussilicates of zirco- experimentalinvestigation of this subdivision. nium. /n Mineralogyof HydrothermalPegmatttes of Alkaline Massifs. Akad. Nauk SSSR' Inst. ACKNOWLEDGEMENTS Mineral. Geokhim.Kristallokhim. Redk. Elemen- tov, Moscow(in Russ.). We are indebted to J.L. Jambor, not only for powder patterns' but also for helpful WersoN, E.B. (1979): Zircon saturation in felsic indexing the applicationsto trace of elpidite. G.M. liquids: experimentalresults and discussionson the occurrence geochemistry.Contr. Mineral. Petrology70, powder pat- element LeCheminantassisted with the X-ray 407-419. terns. J. Gravesmade some initial experiments. Zerac, I.S., Mtt-Lsn,R., BInrcrr, T. & NarrBI-, S. REFERENCES (1984): The Strange Lake deposit, Quebeg- Labrador.Can. Iwt. Mining Metall.Bull.77 (862), Baussv, G., CARUBA,R., BAUMER,A. & Tunco, G. 60 (abstr.). (1974): Min6ralogie exp6rimentale dans le systEme ZrO2-SiO2-Na2O-H2O. Corr6lations p6trog€n6- Received December 17, 1984, revised manusoipt liques. Soc.frang. Mindral. Crist. Bull. 97,433-444. acceptedMaY 3, 1985.

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