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Home , Cummingtonite, Riebeckite

Conadian Mineralogist YoI.22, pp. 281-295(1984)

AMPHIBOLEAND PYROXENEDEVELOPMENT IN FENITEFROM CANTLEY, OUEBEC*

DONALD D. HOGARTH Ottawa-CarletonCentre for GeoscienceStudies, University of Ottowa,Ottawa, Ontorio KIN 6Ns PIERRE LAPOINTE Earth PhysicsBranch, Department of Energy,Mines and Resources,Ottawa, Ontario KIA 0Y3

ABSTRAcT l'h€denbergite,I'aegyrine tardive, le diopside.L'aegyrine tardivese d6veloppe lors dela croissancedes oxydes de fer Proterozoic fenites near Cantley, Quebec, formed from et de titane. Lespyriboles sodiques qui Cvoluentdans un biotite gneiss and hypersthene-augite gneiss by systbmeouvert tels ceux des f€nites de Cantley,definissent metasomatism possibly related to carbonatite, are descourbes dans les diaglammesde variation chimique; characterized by magnesio-, magnesio- par contre,ceux d'un systdmeclos ont tendancei segrou- and . The ratio Ca,/(Ca+Na+K) per, et ceuxqui proviennentde protolithes de composition decreasesfrom older to younger pyriboles. In maguesio- chimiquevariable montrent, ind6pendamment du systdme, arfvedsonite, the ratio Fe1/@e1+Mg) first increasesand une distributional6atoire. then decreases,but K remains constant with respectto Na and Ca. Magnesio-riebeckite,replacing or Mots-clds: f6nite, magndsio-arfvedsonite,magnCsio- hypersthene, shows a trend similar to that of magnesio- riebeickite,aegyrine, m€tasomatisme, variations chimi- arfvedsonite but is notably depleted in K and F. In ques,oxydation, graben Ottawa - Bonnechbre,Qu6bec. magnesio-arfvedsonite,and possibly magnesio-riebeckite, the-A sites are progressivelyfilled. Na- and Na- INTRoDUcToN , in the same hand specimen, are approximately coeval. Early aegirine substitutesfor the hedenbergiteend- The chemical trends illustrated by Na-amphibole member, and later aegirine, for tle diopside end-member. and Na-pyroxene from fenite have not been clearly Iate aegirineis contenporaneouswith major growth of @e, defined. Attempts have been made to outline these Ti) oxides. Na-pyriboles from open systems,such as those trendsin a generalway (e.9., Sutherland1969, Var- of the Cantley fenite, tend to define curves on chemical tiainen & Woolley 197Q,but thesewere not entfuely variation diagrams,whereas those from closedsystems tend to cluster; those formed in either syslem, but from pro- succe$sful,in part owing to lack of care in sample toliths of different chemical g6mpo5itions, give random selection and impure separates.In order to plots. define fenitic pyribole trends more precisely we will describethese from a small area that shows Keywords: fenite, magnesio-arfvedsonite, magnesio- minimal variation in the protolith. We will also com- riebeckite, aegirine, carbonatite, metasomatic rocks, pare these pyriboles with those of three other - chemical trends, oxidation, Cantley, Ottawa Bonne- nonigneousocclurences, each with a distinct origin. graben, chdre Quebec. In this paper thelermpyribo/e is usedto refer col- Soruuernr lectively to pyroxene and amphibole. An areanear Cantley, Quebec(Fig. l) wherefenite Les f6nites d'6ge protdrozoique de la rdgion de Cantley replacesvarious Precambrian rocks was chosen for (Qu6bec) ort 6t6 formees i partir d'un gneiss d biotite et this research.Occurrences were selectedfrom two hypersthdne- augite par un m6tasomatismequi serait reli6 metasomatized protoliths: biotite gneiss and d une carbonatite. Elles sont caract6ris€espar la pr6sence hypersthene-augitegneiss. Fenite, Mg-Fe-Na magrr6sio-arfvedsonite,magn€sio-riebeckite "the de et aegyrine. silicate zone" in Figures I and 2, is delineated by Dansles pyriboles, le rapport Ca,/(Ca+Na+K) ddcroftdes the presence, plus anciennes aux plus r6centes. Dans la magndsio- of Na-amphibole and Na-pyroxene arfvedsonite,le rapport Fe1/@e1+Mg) crolt d'abord et basedon field observations.Sample selection was puis diminue; par contre, le rapport K{Na + Ca) restecons- basedon representativemineral associationsand the tant. La magn6io-riebeckite,qui remplacesoit la cunming- suitability of grains for microprobe and petrographic tonite, soit I'hyperstlbne, secomporte commela magn&io- examination. arfvedsonite sauf appauvrissementnotable en K et F. Dans The fenites in this area were described briefly by la magn6io-arfuedsoniteet peut4tre la magn6io-riebeckite, Hogarth & Moore (1972)alid, Hogarth (1977).Fur- I'occupationdes sites.4 sefait de fagon croissante.L'am- ther details are to be found in the thesis of Lapointe phibole pyroxtne et le sodiquc d'un m0me€chantillon sont (1979)and the regionalreport of Hogarth (1981).The d peu prbs contemporains. L'aegyrine prdcoce remplace associatedoxides have been describedby Cockburn (1960. This researchis part of an ongoing study at *Publication 05-84 of tlte Ottawa-Carleton Centre for the University of Ottawa on the geology of the GeoscienceStudies. Gatineau-Lidwe district. 281

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PRECAMBRIAN .* FAULr ::...... ]:' F+l APPROXIMATEUMIT OF Mg-FE-NO-SIUCATEZONE E MENADIORITE SAMPLE LOCATIONS g MARBLE A CAJ-SIUCATE ROCK r Mg-Fe-No-stucATE RocK BIOT]TE GNEISS.MINoR HYPERSIHENE- O Mg-Fe-No-sruclirE RocK wrrH Fe-Ti-oxlDEs a AUGM GNEISS A OUARTZITE Ftc. l. Map showinglocation and geologyof study area(generalized after Hogarth l98l) and samplelocations. Limits of the Mg-Fe-Na zone mark the field-observed disappearanceof Na-amphibole and Na-pyroxene.

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mingtonite, saponite and biotite after hyperstene, and biotite after augite, chlorite after biotite, and sericite and scapolite after plagioclase. In addition, the monoclinic K-feldspar has inverted to microcline. Numerousbodie of fenite, tlte largest2500 m long and 150 m wide, are situated in a belt that approx- imately parallels the regional foliation. This belt at- tains a maximum thickness of 4 km near Cantley, whenceit can be traced northeasterlyfor 22kmto an occurrence near the Libwe River. The fenite replacesor transects all the above rock types and is superimposedon both the unaltered and retrograde minerals. A "silicate assemblage"characterizes most of the specimenslisted in Table l. It is composedof major amounts of Na-pyribole, lesseralbite and substan- tl ABJNDANTFE -Ti-OIIDE VEINS tial quantities of phlogopite. Associatedminerals are Mg-Fe -No-srLrcATE zoNE disseminatedhematite and minor but typical , M barite and apatite. It appearsas patches, dissemina- E BIOTITEGNEISS tions and cross-cutting veinlets. Indisputable l:F..'-----Tl -AJGITE Li;jjjill HYPEFIITHENE GNESS replacement-textures,such as aegirinepseudomorphs .f..* PRINCIPALVEINS (INCUNED, VEFNCAL) (and partial pseudomorphs) after biotite, were FOUANON ( INCUNED) observedin severalthin sections. Coarse-grainedoxides of iron and titanium (the ,t.i;: SllAMP "oxide assemblage")are present in cross-cutting Ftc.2. Detailedgeology of theHaycock Mine and vicini- veins and lensesof specularite-rutile-(a9., ty. Locationis givenby rectangleon Figure l. specimen 127, Table l), veinlets of specularite- calcite-barite, and strike -fillings of specularite-rutile-apatite (e.9., specimen002, Table 1). The surrounding rock is largely replacedwith the GsoLocv silicateassemblage. Cross-cutting lenses, the largest The map area lies on the western flank of an 3.5 m across,were testedfor iron ore in the 1870s almost isoclinal synform, overturnedtoward the east (the Haycock mine: Cirkel 1909).Commonly, the and plunging northward. Within this synform, the oxide veins and lensesare most abundant in the core principal rocks define a high-grade metamorphic of an occurrence; the comparatively oxide-free suite belonging to the Grenville Supergroup. The silicate assemblagecharacterizes the envelope @ig. ascendingsequence is graphitic marble and granite 2\. orthogneiss(left-hand side, Fig. l), a thin layer of Two Ca-Ba-R.EE carbonatites, associated with quartzite (omitted for simplicity), biotite gneissand fenite, crop out on the west side of the synform minor interlayered quartzofeldspathic and (north of Fig. l) and on the east side (northeast of hypersthene-augite gneisses(centre of area) and, Fig. 1), and are possiblythe sourceof metasomatic finally, a non-graphitic marble and metadiorite solutions that formed the fenites. With the excep- (right-hand side, Fig. l). Neither "glanite" (granite tion of three small dykes on the east flank to granodiorite) nor "metadiorite" ( diorite of the synform (3 km east of the c€ntreof Fig. l), to diorite) show cross-cuttingrelationships with sur- no alkaline intrusive rock is known in the immediate rounding rocks. They are concordanfly foliated near area. tleir margins and display an igneous texture (por- The age of the fenite can be tentatively placed in phyritic and ophitic, respectively)in their cores. All the interval 850 to 1050 Ma. The Cantley fenite rock types are cut by small dykes of granite postdates granite but probably is older pegmatite. Gneisses have attained the than the K/Ar ages determined from phlogopite , indicated by the associations separatedfrom fenite at the Haycock mine (980* 52 hypersthene + augite + andesine, hypersthene * Ma, M. Shafiqullah,pers. comm.; 862*31 Ma, almandine + andesine, hypersthene + K-feldspar Wanfesset al. 1974,p. 64, ageG.S.C. 72-88). and sillimanite + cordierite + K-feldspar. However, Northwest-, northeast- and east-west-striking retrograde activity has been extensive and is faults cut the metamorphic rocks, but their relation- characterized by such alteration products as cum- ship to granite pegmatite, syenite, carbonatite and

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TABLE1. IODAI. COITPOSIrION0F I'!NIj3 SPEcIMBlrs 00r. 002 009 041 062 1r3 LL4 126 127 176 229 248 250 263 296 300 305

Na-pjroxene 27.4 (I 40.8 1.6 r7.6 14.7 r.3.0 8.7 Tr 7.5 5.0 13.2 0.3 6.2 8.3 14.4 18.2 Na-anphlboLe I9.2 0 rJ.5 0 2.6 3.9 r.r..9 6.4 n 5.r- 7.3 L6.3 5.0 8.5 13.6 2r.9 2.7 Phl-ogoplte & blotlie 4.9 20 Tr 16.3 25.L r.3 8.4 r.6.7

Assenblage Ox Ct Ci Slt S11 S11 Si.l Ox S11 SlL Srl S11 S11 Sl.1 Sr1 Si].

9I oxlde; Ci sl.llcaie asssnblage < l- n f,ron oxide zon€; !l! stllcate assenbLage; Tr trace.

fenite is not definitely known. Possibly they ile part tion. Ferrousiron was determinedby titration (Jen of the Ottawa - Bonnechdregraben system,which 1973).Pyroxene in two other specimens(005 and has periodically been active since Helikian time 006)was handpickedand analyzedby E.L.P. Mer- (Hogarth & Moore 1972). cy. Separate005 camefrom a late calcite-pyroxene The Cantley area is on the north side of the Ot- veinlet cutting coarse-grainedoxides at the Haycock tawa - Bonnechdregraben; this structure haspossibly mine; separate 006 came from a calcite-py- beenimportant in localizingcarbonatite and fenite. roxene-rutile vein cutting fenite near Little Dam Alkalic activiry associatedwith the graben is general- Lake, approximately 13 km north-northeastof the ly Phanerozoic (Gittins et ol. 1967),but Proterozoic Haycock mine. repfesentativesare also known. Thus fenite near The secondauthor carried out Mdssbaueranalysis Meach Lake, Quebec, 15 km west of the present of pyriboles taken from approximately the same map-area,was datedat 910and 930Ma (phlogopite, location as specimen062 (Fig. l). K/Ar; Hogarth 1966)and silicocarbonatitenear the Ottawa River, 80 km northwestof the map area,at MrNgnelocv 1050Ma (zircon, U/Pb; Lumbers 1982). Generolfeatures Na- and Na-pyroxene are easily METHoDSoF INVESTIGATIoN distinguishedin the field. The pyroxene(aegirine) Pyribolesfrom 15 polishedthin sections(those of is yellow green, the Na-amphibolesare pale blue- Table l, excepting specimens001 and 009) were green (magnesio-arfvedsonite)or blue to violet analyzedby Hogarth at the Smithsonian Institution (magnesio-riebeckite).The minerals commonly "dif- with an ARL - SEMQ microprobe operating with fuse out" from veinlets or are restricted to certain a specimencurrent of 30 nA and an accelerating layers in the original rock. Some amphibolesare voltage of 15 kV. For unzonedgrains, averagesof ,but normally the grains are short to long several(up to 8) grains per sectionwere recorded; prismatic. Only in veinsthat cut the oxide assemblage for zoned grains, valuesfor the core and rim of a are relatively large crystalsof Na-pyroxene(up to grain were recorded separately.Data were corrected 2 mm across)found. by the methodsof Bence& Albee (1968)and Albee The paragenesiscan be studied readily in thin sec- & Ray (1970).Analytical data are believedto be ac- tion. In somesilicate assemblages,the earliestalkalic cluate to within 2Voof the value recordedfor ma- pyribole appearsto be a Na-amphibole, which grows jor oxides(SiOr, FeO1,MgO), 590 for NazO, l09o at the expenseof quartz (clusteredaround edgesand for minor oxides(TiO2, Al2O3, Cr2O3, MnO, CaO, interstitially), biotite (on the rims and along KrO) and 20s/of.or F. Pyriboles from specimens001 cleavages)and, more rarely, cummingtonite (on rims and 009 were analyzed for Lapointe by Tariq and in zoneswithin packets)and feldspar (ir- Ahmedali at McGill University with an Acton regular patches).This early-formed amphibole (Fig. microprobe, operatedat 15 kV and 30 nA. Data were 3) is commonly transectedor replacedby fine-grained reducedwith the EMPADR program (Rucklidge& pyroxene.In other cases(Fig. 4), the amphiboleap- Gasparrini 1969). pearsto postdatepyroxene. Rarely, early and late Amphibole from one specimen(017) was separated amphibolesoccur togetherin the samethin section. and then analyzed by Lapointe by atomic absorp- However, in the majority of specimensstudied,

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Amphibole Compositions of the amphibolesand their for- mulae are presentedin Table 2. The proportion of Fd* and Fe3* is calculatedon the basis of 13 oc- tahedral + tetrahedral ions and 46 charges. This calculation stipulates complete absenceof vacancies in the Ml, M2 and I4l structural positions. Amphiboles of three distinct types have been found in the silicateassemblage (IMA nomenclature; Leake 1978). Magnesio-arfvedsoniteis the most abundant, but some specimens(017,062) contain magnesio-riebeckite.Besides having less Na and more Fe3+, the latter is notably depletedin K and F. One specimen (250; Fig. 5) contains cum- mingtonite partly replaced by magnesio- FIc.3. Aegirine veinla (almost black) in microcline (grey- Q50b) riebeckite white) deflected and cutting through a subparallel, Q50a). fibrous aggregateof magnesio-arfvedsonite (medium Some grains are conspicuouslyzoned (Table 2), grey). Plane-polarizedlight, thin section ll4. with a narrow rim (r) grading into the main core- zone(c). Composition I l4r is from the inky blue tip of a taperedcrystal, I l4c representsits almost col- orlesscore. The rim is lower in Ca, but F doesnot vary. Amphibole 296 showsminor zoning in the same sense.Amphibole 062shows no evidenceof chemical zoning, but optical measurements(ZAc) suggestthat here too, the core is richer in Ca than the rim, although some other, undeterminedvariable may have influenced optical properties. is an important constituent of magnesio-arfvedsonite,reaching nearly 3VoK2O in specimen300. Whereasthis percentageis indeed unusual, elsewhere magnesio-arfvedsonitefrom fenite commonly exceeds2t/o K2O. Al is minor and cannot be correlated with Ca. Mn and Ti are in- significant (< 0.5090MnO and TiO).

Frc. 4.Veinletof (almostwhite) and magnesio-Pyroxene (grey) polygranular riebeckite transectinga clusterof Compositionsof pyroxeneare presented in Table (dark grey, photograph) aegirine right-handside of in proportion microcline-albite-phlogopiterock. Plane-polarized3. The of Fd+ to Fe3+ has been light, thin section062. calculated assuming4 cations with a total of 12 positive charges.Aegirine compositionspredominate but 263 and 305 extend into the field of aegirine- augite (Fe3* ( 0.8 ions per 6 oxygen atoms), pyroxeneand amphiboleseem roughly coeval.One accordingto the definition of Deer et al, (1978,p. mineral abuts against the other without obvious 483). However, in this paper we will refer to all our replacementor reaction relationship. specimensas aegirine, for convenience. A notable feature in several specimensis the As with amphiboles,some crystalsare distinctly preferenceof one mineral for a pafiicular host. The zoned. In Table 3, core compositionsare denoted Na-pyroxene preferentially replaces quartz, rarely by c and rim compositions,by r. In all cases,the core replacesfeldspar, and doesnot replaceactinolite or is richer in Ca than the rim, in agreementwith op- cummingtonite.An extremeexample, illustrated by tical properties(larger XAc, smallerbirefringence). specimen114, showsquartz and biotite + pefthite Ti and Al are irregularly distributed with respectto well segregatedinto alternating layers in a finely Ca; Mn is minor (< 0.20s/oMnO). laminated gneiss. Amphibole has preferentially replacedpart of the feldspar,whereas pyroxene has Chemical trends in the pyribole saite replaced the quartz. Possibly the control here is chemical, with K freely entering the structure of an The Cantley pyriboles define smooth curveson amphibole, but being excluded from that of a variation diagrams.Thus the 17 amphibole composi- pyroxene. tions can be fitted to two nearly parallel curves on

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1ABIA 2 . CSEI'ICAL Co}IPOSITIONOF AUPEMG

0.10 0.12 tr.a. 0.49 0.16 0.05 0.05 0.18 0.27 0.2L 0.09 0.29 0.11 0.16 o.r9 0.17 0.10 0.L0 0.44 0.115 l.lq 1.00 t.25 0.57 0.50 2.O5 r.60 r.31 0.08 O.29 0.46 L.29 7.r2 0.€6 1.20 FeAO3 5.89 5.7r 13.60 r4.4r u.25 10.49 13.53 10.86 10.59 12.39 rr.62 15.99 u.23 11.39 9.52 10.96 Fd q.96 5.6\ 8.211 6.q4 2.85 1.50 0.72 2,29 3.00 r.39 r.39 5.73 19.62 L.62 3.06 2.98 r.q3 U!0 a.a. O.1q 0.09 0.19 o,llt 0.115 0.x3 0.19 0.1e 0.!8 0.06 0.3r 0.23 0.10 0.15 0.24 lso L6.75 16.30 r0.04 10.99 t6.y L?.IL 16.80 16.5q 16.36 16.?2 r.7.07 U.5r 2r.39 16,54 15.92 15.82 U.58 r?.qt Cao o,52 0.3c 2.23 0.q2 l.l9 r.97 1.08 r..09 1.!0 1.9? 0.93 0.11 0.49 1.68 r.57 1.32 0.76 Na20 8.?r. 9.06 5.43 6.85 8.60 8.08 8.19 8.58 8.5r 7.45 8.61 ?.51 0.49 7.96 7.98 8.27 8.32 6.77 ry 2.41 2.38 0.28 0.3? r.50 1.64 r.50 2.ro 1.58 t.55 r.86 0.28 0.19 1.58 1.49 r.{8 2.911 F 0.7 3.3 2.6 2.9 2.q r.9 2.1 2.3 0.3 0.t 2.1 96.85 96.0r1 96.25 96.48 101.85 r00.69 mr.33 100.58 100.26r00.29 99.85 96.79 97.95 r00.59 r.00.02 99.93 99.? 99.64 0!l 0.3 1,4 t.t L.2 1.0 0.8 0.9 r.0 0.1 --i-Q3, 0.9 0.55 96.E6 96.04 96.25 En.i6 3p9.35-99,59 roo.r: 99.58 99.q6 99.39 98.85 96.69 97,9L 99.69 !e:ot IEES eo-.n 99.09

sl 8.r35 8.09? 8.055 7.99',t 7.792 7.843 ?.000 7.698 1.r\ 1.7fi 7.800 7.965 7.865 7.709 7.793 1.760 7.862 7.833 A1li 0.000 0.000 0.000 0.003 0.208 0.095 0.096 0.302 0.246 0.2r8 0.147 0.035 0.0?E 0.29r 0.207 0.240 0.138 0.167 8.rq 8.10 8.06 8.00 8.00 7,9\ 7.90 a.oo 8.oo 7.98 7.95 8.oo 7.94 8.00 8.00 8.00 8.00 8.00

0vl 0.0711 o.o71 0.196 0.169 0.000 0.000 0.000 0.040 0.020 0.000 0.000 0.015 0.000 0.003 0.010 0.016 0.00? 0.031 T1 0.011 0.0I3 0.05{ 0.017 0.005 0.005 0.019 0.029 0.022 o.oto 0.032 0.012 0.017 0.020 0.018 0.0t1 0.010 ro3{ 0.632 0.62L i6s 1.585 r.r94 t.112 7.432 L.L57 r.r27 r.313 1.242 1.752 L.e91 L.204 t.224 r.026 1.152 Fo2+ 0.59r 0.6E2 1.006 o.7E7 0.336 o.\77 0.084 0.272 0.355 0.16q 0.X65 0.698 0.365 0.356 0.172 0.r.66 u! 0.01? 0.011 0.023 0,049 0.054 0.016 0.023 0.014 0.022 0.007 0.038 0.027 0.022 0.018 0.029 0.018 u8 ii' 3.511 2.r06 2.394 3.U31 3.7L9 3.54 3.q97 3.q!? 3.510 3.61q 2.497 \.576 3.!?r 3.380 3.368 3.755 3.624 t 4.87 4.90 4.90 5.00 5.00 5.06 5.10 5.00 5.00 ,.02 5.0, 5.00 6.98 5.00 5.00 5.00 5.00 5.00

Ca 0.079 0.053 0.349 0.066 0.180 0.297 0.163 0.165 o,2r2 0.297 0.1q2 0.0u 0.0?5 0.253 0.240 0.?02 0.117 0.464 k 2.407 2.538 r.538 r.94r 2.352 2.20't 2.233 2.357 2.3p 2.035 2.371 2.LL9 0.86 2.L73 2.204 2.290 2.3tr r.E33 K 0.438 0.439 0.052 0.069 0.270 0.295 0.297 0.379 0.285 0.279 0.337 0.Or2 0.035 0.a84 o,27L 0,270 0.537 0.203 E 3.03 1.94 2.0E 2.80 2.80 2.68 2.90 2.93 2.61 2.85 2.r9 o.25 2.7L 2.7! 2.76 2.97 2.50

0.9 0.9 r.0 0.1 0.05 0.9 1.2 0.6

It@ oald@ rse rasolved ln fotmlee cslculatl@a, sc6pt tn 017 ed 250b. ALl @1yBes sr6 cenl.6il out by 6let!@ El'croplob€, *c6pt fo. @hlbole 017, rhich @s ealyzed by s@dald ch@i€L pr@edus. n.a. trot ealyzeal.

during growth, and the two curves of model I are, therefore, curvesof parageneticorder. According to model l, during mineral developmentvacant sites (n) are progressivelyfilled. In model 2, vacantsites in magnesio-arfvedsonitebecome filled but their pro- portion in magnesio-riebeckiteremains constant. In both amphibole and pyl'oxene,the four prin- cipal variables Fe, Mg, Ca and Na + K can be evaluatedon a Fef - Cat diagram [Fie. 7; Fel : l0OFe./(Fe + MB), Caf = l00Ca/(Ca * Na -r K)1. Early pyroxenecompositions, with high Cat, deviatefrom the dotted line (slopeCaflFet = - 1) but become coincident with it at lower Caf values. This can be explainedby oxidation of iron in high- Caf compositionsaccording to a hedenbergite- aegirinesubstitution (Ca + Fd+ - Na + Fe3*). FIc.5. Large,polygranular cluster of amphibole(centre of To explain the departure from a vertical line, we pro- photograph)in microcline.Cummingtonite (ight erey) posea concomitant diopside * aegirinesubstitution is replacedon theexterior of thecluster and along frac- (Ca + Mg - Na + Fd*). Thesesubstitutions pro- tures by magnesio-riebeckite(dark gey). Plane- ceeddown to about Caf = 10, at which point all polarizedlight, thin section250. the availableiron is completelyoxidized. From there, substitution is diopside - aegirine.The deviation from the diopside-aegirine line at high Caf can also a plot involving A ard B cations(ines I4A und MR, be explained in terms of vacant octahedral sites. Fig. 6), where /4 and B refer to the general formula However, we prefer the first alternative; it conforms for amphibole AB2C,TsO^(OH)2 (model l). with a major period of oxidation, as evident from As an alternative, model 2, magnesio-arfvedsonite the observations of the oxide assemblageby and magnesio-riebeckitecan be fitted (ess closely) Cockburn (1960 and with the chemical composition to winchite - magnesio-arfvedsoniteand winchite - of aegirine in similar depositselsewhere (see below). magnesio-riebeckitejoins, requiring substitutions of On the other hand, the plots of specimens005 and thetype n + Ca - Na t NaandCa + Mg * 006, analyzed wet-chemically, cannot be explained Na + Fe3*, respectively. Zonng relationships sug- in this manner. Caf is too high with respectto Fef , gestthat Na-amphibole becomesdepleted in and the ions Ca2* and Mg2* have not been

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!\Bf,B 3. CUF{ICAI COUPOSIIION OF PYBOXENE

sr02 52,67 53.10 5r.65 5r.69 52.57 53.88 52.99 52.56 52.7L 53.L9 52,79 1102 0.t8 0.13 0.042 0.068 0.05 0.o7 1.63 0.35 0.30 0.32 0.26 AbOe 2.9L r.98 3.r4 2.26 2.37 0.92 0.38 0.?t r.14 r.59 x.19 n.a. 0.06 !.a D.a. B.a. a.a. n.a. 0.03 tr.ar n.a. n.a. 9.06 30.16 31.05 3r.60 3L.92 29.70 29.55 30.?0 3r.33 3r.30 3r.65 F€O 0.34 0.9r 0.24 0.29 0.00 0.35 0.00 0.00 0.00 0.43 0.11 MnO q.a. 0.08 <0.002 <0.002 n.a. 0.05 0.05 0.09 0.1r. 0.12 0.08 lrrP o.25 0.u 0.03 0.10 0.24 2.2\ 1.46 1.17 L.23 0.?4 0.89 0.34 0.30 0.94 0.98 0.19 3.23 2.2O r.95 1.86 r.31 r.44 Na20 13.11 13,33 13.14 13.04 r4.l? 11.q3 t2.95 L2,97 13.10 13.00 12.87 ry 0.37 0.04 <0.02 <0.03 0.0r 0.03 0.04 o.o2 0.00 0.02 0.02 Bzo n.a. r.a. <0,05 <0.05 n.a. a.a. !.a. a.8. i.a. n.a. n.a. lotaL 162:23 166:8 r6o.-3d r66:If ror.52 lorled ror.25 r00.37 r01.?8 102.02 101.30

c

st 1.954 2.011 r.962 r.9?3 L.957 L,997 1.988 1.993 r.96? r.987 r.988 Al1! 0.936 0.000 0.038 0.027 0.043 0.003 0.012 0.00? 0.033 0.013 0.012 E 2.00 2.01 2.00 2.00 2.00 2.OO 2.OO 2.00 2.00 2.00 2.00 Alvl 0.092 0.088 0.103 0.0?5 0.061 0.037 0.005 0.025 0.01? 0.057 0.041 0.005 0.004 0.001 0.002 0.001 0.002 0.046 0.010 0.008 0.009 0.00? Cr 0.002 ---- 0.001 F€3+ 0.900 0.860 0.888 0.908 0.094 0.829 0.83q 0.076 ffi; il;; il;; F62+ 0.0r.1 0.029 0.008 0.009 0.000 0.011 0.000 0.000 0.000 0.014 0.003 u! 0.003 0.000 0.002 0.002 0.003 0.003 0.00t1 0.003 lrs 0.0:.4 0.010 0.002 0.016 0.013 0.124 0.082 0.066 0.068 0.041 0.050 E 1.02 1.00 1.00 1.00 0.97 1.00 0.9? 0.98 0.9E r..00 1.00 ca 0.014 0.012 0.038 0.040 0.008 0.128 0.088 0.0?9 0.074 0.052 0.058 NA 0.948 0.9?9 0.968 0.965 1.023 0.866 0.942 0.940 0.948 0.942 0.9110 r 0.0r8 0.002 0.000 0.000 0.000 0.001 0.002 0.001 0.000 0.001 0.001 E 0.98 0.99 1.01 r.00 1.03 1.00 r..03 t.02 1.02 1.00 1.00

S102 52.79 52.08 5r.93 52.7\ 52.89 52.\r 52.85 52.6L 52.\9 52.r' 53.L5 T102 0.32 0.42 0.51 0.11 0.46 0.39 0.u 0.3r 0.32 0.58 0.39 A1eo3 r.37 1.43 r.06 0.06 0.6't r.07 0.16 0.48 r..00 0.59 0.92 CrZO3 a.a. n.8. n.a. !.a. B.a. !.4. irar !.4. a.a. !.4. n.a. Fo203 29.1rr 30.87 29.81 32.7L 3r.34 3r.94 24.76 30.06 3L.5L 30.20 24.92 F€0 r.95 0.80 0.00 0.4r a23 0.00 4.811 0.06 0.89 r.35 2.9L Mtro 0.05 0.04 o.ro 0.06 0.10 0.08 0.ll 0.09 0.09 0.0E 0.18 ltgo 0.49 0.38 r.6q 0.25 1.51 r.07 2.56 0.93 0.89 0.54 3.20 cao 0.54 0.39 2.29 0.33 2.16 1.53 4.82 L.32 r.28 0.74 5.r.8 ll820 1.2.90 13.07 12.42 L3,32 L2.46 L2.85 10.24 L2.86 13.U 12.93 10.q4 Keo 0.0r 0.01 0.03 0.02 0.03 0.03 0.04 0.o2 0.02 0.02 0.02 f,eo !.4 B.a. a.a. n.a. n.a. n.a. n.a. !.a. __g:g: a.e. o.a. Total 99.56 99.\9 99.79 100.0:. 101.85 r01.37 100.49 98.7r1 r01.66 99.58 101.3r

4

sl 2.019 1.996 r.976 2.0L9 r.983 L.9',13 2.018 r.996 r.982 2.0L5 L.997 Ar iv 0.000 0.00q 0.0211 0.000 0.0r? 0.027 0.000 0.004 0.018 0.000 0.003 t 2.O2 2.OO 2.00 2.O2 2.00 2.00 2.O2 2.00 2.OO 2.02 2.00 alvl 0.062 0.061 0.021t 0.003 0.013 0.020 0.00? 0.017 0.027 0.02? 0.038 TI 0.009 0.012 0.015 0.003 0.013 0.011 0.003 0.009 0.009 0.017 0.011 Cr F63+ ;.;;; 0.890 0.E5ll 0.942 0.885 ;;;; ;;;; ;.;;; 0.895 0.872 0.?05 tr'e2+ 0.062 0.026 0.000 0.0r3 0.00? 0.000 0.155 0.002 0.000 0.043 0.092 MN 0.002 0.001 0.003 0.002 0.003 0.003 0.0011 0.003 0.003 0.003 0.006 !a 0.028 0.022 0.093 0.0111 0.084 0.060 0.146 0.053 0.050 0.030 0.u9 a 1.00 1.01 0.99 0.98 r..01 1.00 1.03 1.00 0.98 0.99 1.03 o.o?2 0.01.6 0.093 0.014 0.08? 0.052 0.r9? 0.054 0.052 0.030 0.209 lla o.957 0.9?r 0.9r5 0.989 0.906 0.938 0.?58 0.946 0.964 0.961 0.76r r 0.000 0.000 0.001 0.001 0.001 0.001 0.002 0.001 0.00r 0.001 0.001 E 0.98 0.99 l.0l 1.Q0 0.99 t.00 0.96 1.00 1.02 0.99 0.9',1

Im orld@ fGolved 1! lo@1a6 oaloqlailoDs, E:qepi t! 005 ed 006. All eslys@ by eleotroa DLorcprcbg doepi 005 ud 006 (rbloh rere @de by stedard oh@1q1 prooadFs). D.a. . loi @lya€d.

$ubstituted equally, as stipulated by the diopside - rutile) or, if is secondary, aegirine + one aegirine model. Ca-rich aegirine occurs in late or more primary oxides of Fe and Ti formed calcite-aegirine veinlets and perhaps formed under contemporaneously. different conditions from pyroxene compositions of Most magnesio-arfvedsonitecompositions define the main trend. a smooth curye on the left-hand side of Figure 7, Specimen127 contains a sharply terminated, zoned but the compositionsof three specimens(017, 062 euhedrd aegirine crystal, lying at the contast of two and 250) lie well beyond this line and can be fitted hematite grains containing oriented intergrowths of to a subsidiary, parallel, magnesio-riebeckitecurve. rutile. This suggeststhat aegirine + hematite (t We suggestthat magnesio-arfvedsoniteformed by

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MM{E|D - ARFVEDSONM o uAo{6lo - R|EBECKm VACANTSITESNAAB R, MONOVAI-ENTCATIONS IN A B B R" DIVALB{T CATIONS IN B MA MAGNESIO-ARFVEDSO{ITE TREND MR MAGNEIIO- RIEBECKITETREND MIGNESIO-ARFVEDSONITE_ WINCHlTE, MAGNESIO-RIEBECKITE_ WINg.IITE JOINS 30% t'

4 ENDMEMES:- 9 ,/a MAGNESIo.ARFVEDSoNm .-. /I/r MAGNESIo-RIEBECKITE \ ,?c RtenERm rT TREMoUTE tY, wtNcHm

i'.o\^- v

'-.o 5O% o R, FIc. 6. The Na-amphibolecompositions from Cantley plotted with respctto monovalentcations R' , divalent cations R"' and vacanciestr in the.4 and B positions of the formula AB2C5T8O22(OH,F)2,showing the two lineagesand trends of mineral development.

replacementof the dominant biotite gneiss,where with the core of an associatedzoned amphibole, but K and F were plentiful. In contrast, we believethat this is probably true to a first approximation only. magnesio-riebeckiteformed from a two-pyroxene Similarly, the pyribolescan be plotted on a Na - gneiss, which is particularly abundant in the areas Ca - K diagram (Fig. 8). Most tie lines that link pairs that furnished specimens017 and 062. Specimen250 of coexisting amphibole and pyroxene fan out from contains590 cummingtonite(Iable 3, composition magnesio-arfvedsoniteto aegirine.Throughout the 2500)pseudomorphous after hypersthene,as well as early and middle stages of magnesio-arfvedsonite rare, relict hypersthene.Magrresio-riebeckite appears development,corresponding to the lowest to in- to replace cummingtonite in preference to termediatecontent of Na (and, possibly, throughout hypersthene.Kushev (1960, 1961)and Lazarenko the whole episodeof magnesio-riebeckileformation), (1977) have shown that at Krivoi Rog, U.S.S.R., K remains approximately constant, but appears to magnesio-riebeckite,not magnesio-arfvedsonite,is increasein the late, or high-Na stage.No trends of derived from cummingtonite by alkali pyribole compositionsare evident along or acrossthe metasomatism. generalstrike or acrossthe main Haycock deposit Little can be said about the parageneticrelation- from which four pyribole specimens(001,002,062, ships of aegirine to magnesio-riebeckiteon the basis 009) were collected. of one specimen(062). Amphibole and pyroxeneare, apparently, not in contact and, therefore, textu(al NoNIcNEousArrert Pvntnor,ss evidenceis lacking. h.roxene compositionscan be linked to coexisting The Cantley pyriboles can be compared with magnesio-arfvedsonitewith a seriesof tie lines. Thus others from isochemically and metasomatically de- accordingto textural evidence,the three lowesttie- rived rocks usingthe following examples:(l) Meta- lines of Figure 7 may connect coeval pairs. In con- evapo"rite (isochemically derived rock), from the trast, a post-pyroxene amphibole characterizes Grabenbach - Grundlsee - Rigaus region, near specimen 263, and its tie line cannot link a pair in Salzburg,'Austria (Kirchner 1980),Q) fenite derived equilibrium. In constructing these tie lines the core from carbonotite (metasomaticrock), with paleoliths of zoned pyroxene was assumedto be in equilibrium of amphibolite and granite, from Sokli, Finland

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TIE UNE BETWEENCOREOF MAGilESIO-ARFVEDSO{TTE AND AEGIRINE trntr tr RIM xxl ,, n tr x CORE -RlEBecKrE TREND UNES OF PYRIBOLES ( APPROXIMATE,UNCERTAIN ) v iliAGNESIO- ARFVEDSoNITE = o MAGNESIO- RIEBECKITE Cd looCo(Co+No+K) o AEGIRINE Fer= tooFer/Fer + Mg)

FIc. 7. The Cantleypyriboles are plotted with respectto 100Cal(Ca + Na + K) ( = Cat) and 100per/Ger + Mg) ( = Fef), showingtie lines betweenassociated pairs (samethin section),lineages, and evolutionarytrends. Error bars indicate precisionof microprobe analyses.

(Vartiainen& Woolley 1976,Vartiainen 1980).Ad- noted in pyroxenesof "metasomatiles" of the Krivoi ditional data from other sourceswill be quoted on Rog (Nikol'skii 1961,Eliseev & Nikol'skii 1961)and captionsto the appropriatediagraurs. Q) Nonigneous in amphiboles from fenites around alkaline com- rock of disputedorigin, from Krivoi Rog, U.S.S.R. plexesof the Kola Peninsula(Sergeev 1967). These (Nikol'skii 1961,Kushev 1960, 1961, Polovko 1970). featuresconform with mineral zoning in the Cantley This may havebeen metasomatically derived by solu- pyriboles and suggestthat paragenetictrends should tions from granitic rock which replacedjaspilite (as be investigatedon diagramsof the type used here proposed by Eliseev & Nikol'skii 1961, Polovko (Figs. 6, 7 and 8). 1970),or formed through isochemicaltransforma- Fenitic amphiboles, especiallythose of Sokli, lack tions in an Fe- and Na-rich protolith (as proposed vacanciesin the /4 position, and the trend becomes by Aleksandrov 1962, 1963,Lazarenko 1977). linear along R' - R" @ig. 9). On the samediagram, Grains of fenitic pyroxene commonly show zon- the Salzburg amphibolescluster around Mr. The ing with a more augitic core and more aegirinic rim Krivoi Rog data-points are widely scattered,extend- (Sergeev1967, Sutherland 1969), indicating a pro- ing from closeto Ma (A + B* : 2.60) to beyond gressiveincrease in Na (and decreasein Cat) with ML wilh a clustering around Mn More significant mineral development. Similar zonation has been is their position on the Caf - Fef diagram(Fig. l0).

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Ftc.8. Na-Ca-K diagram of Cantley pyriboles, showing tie lines betweenassociated pairs, the three lineagesand evolutionary trends. Symbols as in Figure 7.

s FENITES FR(Iil SOI(LI, Flt{l-At{D r FENITES:U.S.S.R., AFRIO{ v MEIASONAITIEi: U.S.S.R. v iETA-EVAPORITES:SAL|ZBIFG, AUSTRIA OTHER SYMBOI.SAS IN FIG. 7

30% Rl

%a" v y v\

t\\

50% o R,

FIc.9. R'-R"-[ diagram (c/. Fig. 6) showingplots of Na-amphibolefrom depositsof three types: fenitesassociated with carbonatile (data from McKie 1956, Sutherland 1969, Vartiainen & Woolley 1976, Vartiainen 1980, Secher& Larsen 1980), "metasomatites" associatedwith CraniteKushev 1961,Glagolev 196Q, and meta-evaporitc (Kirchner 1980). The trends defined by the Cantley amphiboles have been added for comparison.

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o El AMPHIBOLES,PYROXENEI, FENITE: SOKLI N O rE " AFRICA, 40 SEDEN, GREEIU_AND,U.S.S.R. *'tob1lg.il**Es, "iErAsoiiAr:rrE": v v El" ,' v AMPHTBOLS,PYRO)(ENB, META-EVApORITS: V SALZBURG UMITINGTIE UNE: CANTLEY \v TRENDUNE: CANTLEY E UA MAGNEIIO-ARFVEDSONITE T'IR MAGNSIO-RIEBECKITE A6 AG AEGIRINE I 9r_ \ ! Co' \

v ;i\

ilE.\

t \; ooo \ tr "i v .t \ o tl g \.v I vv tr v I v

20 Fe'

Frc. 10. Cat - Fef diagram (cl, Fig. 7) for Na-pyriboles for the three types of occurrenceshown in Figure 9, with trend lines and limiting tie-lines of the Cantley plriboles added for comparison. Data from von Eckermann (1960, Sergeev (1967)and Kulakov et al. (1974)have been added to those used in Figure 9.

At high Caf, fenitic amphibolesplot close to the through variations in the composition of the Cantleymagnesio-riebeckite trend, but depart from paleosome(cummingtonite-). this curve at low Caf, whencethey becomeenrich- On the Na-Ca-K diagram (Fie. 1l), the majority ed in Fe. A similar trend can be seenin , of compositionsof amphibolefrom Sokli definesa whereFet is increasedas Caf is depletedin the ap- linear trend betweenthe Cantley magnesio-riebeckite proximateratio l:l (owingto complexreplacements line (upper trend) and the Cantley magnesio- involving Fd*, Fe3+,,rAl, Ti, Mg, Ca and Na). arfvedsoniteline (lower trend). The other plots of The Salzburg pyroxenes plot close to magnesio- fenitic amphiboleare dispersed.The Salzburgdata- riebeckite.Pyroxene compositions from the Krivoi points cluster around the Na apex and are K- Rog rocks cluster around pure aegirine, but the plots depleted; the Krivoi Rog data-points are widely of associatedamphiboles show wide scatter.Accor- dispersedbut show a tendencyto depletion in K. ding to Kushev (1960) and Pavlenko (1959), the Tie lines betweenassociated pyroxene and am- general trend, from early to late stages of phibole in fenites intersect each other and intersect metasomatism,is one of continuousaddition of Fe tie lines linking pyriboles of the Cantley fenites. For to the amphibole, leading from magnesio- simplicity, they have been omitted from the riebeckite, to riebeckite but irregularities appear diagrams.Unfortunately, it is impossibleto define

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q FEl,,llTES:SOKLI r u AFRICA,GREENLAND, U.S.S.R. .,MTTASOI,ATITES": v U.S.S.R. v MEIA-EVAFORITES:SAIIBIRG

UMITING AMPHIBOLE-PYROXENETIE UNE: CANTLEY TREND LINE: CANTLEY TREND UNE: SOKU

or

q Co

FIG.ll. Na - Ca - K diagram (cl. Fig. 8) for Na-(Mg-)amphibolefrom the three types of occurrenceshown in Figure 9, with trend lines and limiting tieJines defined by the Cantley pyriboles added for comparison.

,tssociatedamphibole - pyroxenepairs at Krivoi Rog of both alteredgranite and amphibolite.Vartiainen and Salzburg from the published data. Also not & Woolley (1976)contended that location of a fenitic shownon our diagramsis Al, which is notably high pyribole with respectto a large carbonatite intrusion in the Salzburgpyriboles, intermediatein the Sokli (a T-Xcontrol) is alsoimportant, and that, at Sokli, pyriboles, low in the Cantley pyriboles, and extreme- pyriboles from fenite close to the carbonatite are ly variable in the Krivoi Rog pyriboles. higher in Ca than those from fenite further away. Pyriboles in meta-evaporiteare chemicallydistinct This effect is impossibleto evaluatefor specimens from those in fenite. The former cluster on varia- from Cantley,where large bodies of carbonatiteare tion diagrams, as would be expectedin a closed absent. system.On the other hand, pyriboles from fenite The Krivoi Rog rocks, with pyribolesof dubious tend to follow smooth curves on these diagrams, parentage, do not fit either metasomatic or which seemsnatural for an open systemwith con- isochemicalmodels of origin. Specimenswere de- tinuous readjustmentof compositionof the starting rived from an €ueaof considerablesize (a strip 40 material to changing P-T-X conditions. The km long, l-3 km wide); variations in the protolith chemical composition of the starting material is also are known to occur (Nikol'skii & Eliseev 1961)' important, so that pyribolesfrom both metasomatic which would account for the scatter in variation rocks and meta-evaporiteswill vary somewhatfrom diagramsusing either model. one occurrenceto the next and evenwithin an in- dividual occurrence.These controls explain the well- OxtettoN defined chemicaltrends of fenitic pyriboles in the Cantley region outlined in Figure l, a small areawith The degreeof oxidation of pyriboles can be ex- minor variations in the protoliths. Violations of these pressedin terms of Fe3*/(Fd* + Fd+) or oxidation controls may partly account for the scatter of ratio (O.R.); this function canbe plotted againstCaf pyribole compositions at Sokli, where fenite consists as in Figure 12. Our amphibolecompositions (Fd*

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a CANTLEY o SOKLI () ! AFR|CATU.S.S.R.! SWEDEN AI$PHIB0LB: SOKLI

- -.---> APPROXIMATEFENITIC PYROXENE TRENDUNE ' PYROXENESFROM CANTLEY _____a . POSSTBLETREND UNE FOR 6qr AMPHIBOLE,SOKU

\n \t _;;d***_-p9?_\ \----.\\. \\ r\\\ t\\ \ o4r\ Fr \\

oa 27d, 60 80 loo o. R.

Frc. 12. Cat - O.R. diagram tO.R. : 100Fe3+,/(Fd+ + Fe3+)l showingapproximate oxidation trend of pyroxene compositionsfrom carbonatite-linkedfenites, a possibletrend of the Cantley pyroxenesand the field of Sokli (Finland) amphiboles. Compositional data for pyroxene from von Eckermann (1966),McKie (1966),Sergeev (196?, Sutherland (1969),Kulakov et al. (1974),Vartiainen & Woolley (1976),and Table 3 (this paper); data for Sokli amphiboles from Vartiainen & Woolley (1976).

and Fe3* calculated)give scatteredoxidation ratios suggestedthrough the Sokli amphibole field. (not plotted) but valuesare consistentlylower than Progressiveoxidation is also suggestedin the those of pyroxene.Amphibole and pyroxenefrom Cantley pyroxenebut with a different trend. Early the Krivoi Rog region (Fd+ and Fe3* determined pyroxene underwent intense oxidation, becoming chemically)also give scatteredplots. All but one of completelyoxidized at about Caf 10.This oxidation the pyribole compositionsfrom ihe Salzburgmeta- conforms with the occurrenceof partially martrtized evaporites (Kirchner 1980) are derived from magnetite associatedwith pyriboles of the in- microprobe analyses.For simplicity, we plot com- termediatestage (e.g., specimen Ml). Hematiteis the positions of fenitic pyroxeneand of amphibole from only iron oxide associatedwith pyribolesof the late Sokli and comparetheir trends with plots of O.R. stage(e.g., specimen009). calculatedfor pyroxenecompositions from Cantley A check on the oxidation ratio was made by (Fre. l2). M6ssbaueranalysis for a samplecollected close to Fenitic pyroxenesfrom Finland (Sokli), Sweden the sourceof specimen062 (adit portal, Haycock (Alnd) and variouslocalities in U.S.S.R. and Africa mine). Measuredand calculatedO.R. valuesare in show a trend of gradual oxidation from early (high good agreement:O.R. of pyroxeneby Mdssbauer Caf) aegirine-augiteto later aegirine. A trend is also spectroscopy - 100, by calculation from the

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analytical data 100; O.R. of amphibole by AlrrseNonov, I.V. (1962): metasomatism oc- Mdssbauerspectroscopy 68.0, by calculation from curring in the Krivoi Rog area. .lz Tr. Shestogo the analytical data 66.8. Soveshch.po Eksperim.i Tekhn. Mineral. i Parogr. (A.I. Tsvetkov,ed.), Akod. Nauk S.S.S.R.,Inst. CoNcr-usroNs Khirn. Silikatov 1961,61-66(in Russ.). Chemical compositions of pyriboles from Cantley (1963):Sodic metasomatism in the Krivoi Rog are similar to those of Sokli and other occurrences arer,.In GeokhimiyaShchelochnogo Metasomatoza where fenites have been derived from carbonatite. (V.V. Shcherbina,ed.). Akad. Nauk S,S,S,R,,Inst. Differences in mineral chemistry and mineral Geokhim.Anal. Khim. 1963,74-l5l (in Russ.). development can possibly be explained in terms of (1968):Empirical conec- variations in host rock and different physimchemical BeNcn,A.E. & Ar.nrn,A.L. tion factorsfor the elegtronmicroanalysis of silicates conditions of mineral formation. The Cantley and oxides.J. Geol, 76.382403. pyribole suite occurs in a particular biotite gneiss horizon and, therefore, the host rock is composi- CrnrEl, F. (1909):Report on the iron ore deposits tionally rather uniform. Less common hypersthene alongthe Ottawa(Quebec side) and GatineauRivers. + diopside + plagioclasegneiss appears to give rise CanadaMines Br., Publ,23, to magnesio-riebeckite instead of magnesio- arfvedsonite. CocruunN,c.H. (1966): Geology of the Haycock We proposethat Na, K, Mg and, perhaps,other Mine, GatineauArea, Quebec.B.Sc. thesis, Univ. elements, were introduced by carbonatites near Ottawa, 0ttawa, Ontario. - Cantley, on the north side of the Ottawa Bon- Dren, W.A., Hown, R.A. & Zussuer, J. (1978): nechdregraben, under conditions of waning thermal Rock-FormingMinerals. 24, Single-ChainSilicates. activity, near the closeof Grenvillian metamorphism Longmans,Green and Co., London. (ca. 950Ma b.p.). The resultingfenitization wasac- companiedby progressiveoxidation. We further sug- vouEcrpnvasx,H. (1960: The pyroxenesof theAlnci gestthat the calcium-depletiontrend in pyribolescor- carbonatite(sdvite) and of the surroundingfenites. responds to deposition during falling temperature, Mineral. Soc.India, IMA vol., 126-139. as proposedfor similar changesin pyribolesin fenites Eusnrv, N.A. Nrror,sru, A.P. (1961):Types of derivedfrom carbonatitesin the Kola Peninsulaby & metasomatites,their relation, and genesis.Tr. Lab, Sergeev(1967). Geol. Dokembriya, Akad. Naak S.S.S..R.13, 172-197(in Russ.). ACKNowLEDGEMENTS Yom, D. (1967):The The authors an NSERC grant Grrrws, J., MacNTyRE,R.M. & acknowledge agesof carbonatitecomplexes in easternCanada. (A2122), which defrayed researchcosts. The final Can.J. Earth Sci,4,651-655. work was done at the SmithsonianInstitution and the U.S. GeologicalSurvey (Reston, Va.) by Hogarth Gracomv, A.A. (1966):Metamorphism of Precam- while on sabbaticalleave. Mdssbauer analyses were brian Rocks of the Kursk Magnetic Anomaly. made under the supervisionof Michael Townsend Petrographyand Mechanismsof Metamorphismof at the Mines Branch (now CANMET), Ottawa and Iron Formation and Certain Other Precombrian aegirinespecimens C[)5 and @6 were separatedat the Rocks of the Ancient Slicein the lron Ore Region Universityof Ottawa by Ann Hobart Kasowski.We of the Kursk Magnetic Anomaly. Izd. Nauka, (in thank the following persons for reviewing the Moscow Russ.). manuscriptand providing helpful commentsfor its Hocenrn, D.D. (1966):Irtrusive carbonaterock near improvement: Daniel Appleman (SmithsonianIn- Ottawa, Canada.Mineral. Soc.India, IMA vol., stitution), Michael Fleischer, E-ar Zen and Jane 45-53. Hammarstrom (J.S. Geological Survey), John Moore, (Carleton University), Ralph Kretz (Univer- (1977): Iron-alkali mineralization near Cantley, sity of Ottawa) and two anonymous referees. Quebec. Geol. Assoc. Can. - Mineral, Assoc. Can. Diagramswere'drawn and photomicrographstaken Program Abstr. 21 25, by Edward Hearn (University of Ottawa) and the (198 G6ologie partie ouest de la rdgion manuscriptwas typed by Carole Brown and Kathy - l): de la de Mizistdre de l'4nergie et des ressources Ledger. Quinnville. du Qutbec, Rapport intdrimoire DPV-816. REFERENcES & Moonr, J.M. (1972):Excursion stops in Alnnn, A.L. & Rav, L. (1970):Correction factors for Precambrian rocks. 6. The Haycock property. ln electronprobe microanalysis of silicates,oxides, car- Geology of the National Capital area. (D.M. Baird, bonates,phosphates and sulfates. Anal. Chem.42, ed.\.24th Int. Geol. Congr. (Montreal), Guidebook 1408-t4t4. to Excursions E.23-B27.

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JeN,Lo-SuN (1973): The determinationof iron(Il) in & Elrsrrv, N.A. (1961):General information silicaterocks and minerals.Anal. Chim, Acta 66, on metasomatitesof the Krivoi Rog ore belt. Zr. 315-318. Lab. Geol.Dokembriya, Akad. Nauk S.S.S.R.13, 18-25(in Russ.). KrncuNnn,E.C. (1980): Natriumamphiboleund Natriumpyroxene als Mineralneubildungenin PewrNro, A.S. (1959):Peculiarities of metasomatism Sedimentenund basischenVulkaniten aus dem Per- in a region of northern Krivoi Rog are,a.Izvest. moskyth der Nordlichen Kalkapen. Geol. Akad. Nauk S.S.S.R., Ser. Geol. 1959 (no. l), Bundesanst(Ilein) Verh,, 249-279. 8l-l0l (in Russ.). Porovro, N.I. (1970): Material Balance During the Kularov, A.N., Eworrvov, M.D. & BuI-arrr,A.G. Formotion (1974): penin- of Alkaline Metasomatitesof theKrivoi Mineralveins in fenitesof the Tur,ii RogJaspilite Zonq.Izd. NaukovaDumka, Kiev (in sula in the Murmansk regtron.Zap. Vses.Mineral. Russ.). Obshchest.103, 179-191(in Russ.). RucrLrnor,J.C. & Gespenr.rul,E.L. (1969):Specifica- KusHnv,V.G. (1960):Alkaline amphibolesof Krivoi tions of a computerprogram for processingelectron Rog. Tr. Lab. Geol. Dokembrtya, Akad. Nauk microprobeanalytical data: EMPADRYII. Dep. S.S.S.fi. ll, 218-291(in Russ.). Geol., Univ. Toronto, Toronto, Ont.

- (196t):Alkaline amphibolesin the Krivoi Rog Srcurn, K. & LanssN,L.M. (1980): Geology and metasomatites,Tr. Lab. Geol.Dokernbriya, Akad. mineralogy of the Sarfart0q carbonatite complex, Naafr S.S.S.R.13, 4y'.-it (in Russ.). southernwest Greenland. Lithos 13, 199-212. Srncrrv, A.S. (1967):Fenite Complexes Ultrabasic Laporvrr (1979): of P. Fenitization around Hematite Oc- and Alkalic Roc&.Leningrad State University, Len- cuftencesat theHaycock Mine, Hull and Templeton ingrad (in Russ.). Townships,Quebec, M.Sc. thesis,Univ. Ottawa,Ot- tawa, Ontario. SurHnnlaNo,D.S. (1969): Sodic amphibolesand pyroxenes from fenites in east Afica. Contr. Lezenewxo,E,K, (1977):Mineraloglt of theKrivoi Rog Mineral, Petrology U, lt4-135. Basin. Naukova Dumka, Kiev (in Russ., Eng. summ.). VenrnulrcN,H. (1980):The petrography,mineralogy and petrochemistryof the Sokli carbonatitemassif, LEar

McKn, D. (1960: Fenitization..I/,Carbonatites (O.F. WarLess,R.K., SrnvrNs,R.D., Lecnatcr, C.R. & Tuttle & J. Gittins,eds.). John Wiley & Sons,New Dnlauo, R.N. (1974): Age determinationsand York. geologicalstudies. K-Ar isotopicages, Report ll. Geol. Sum. Can, Pap. 13-2, Nrol'sru, A.P. (1961): and aegirine-augites in the Krivoi Rog metasomatites.fr. Lab. Geol. Dokembriya,Akad. Nauk S.S.S.R.13,2644 (in ReceivedFebruary 21, 1983,revised manuscrtpt ac- Russ.). ceptedAugust 16, 1983.

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