Insights into the evolution of an alkaline magmatic system: An in situ trace element study of

21 Pages·2017·9.86 MB·English

by  Anikó Batki

Lithos300–301(2018)51–71
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Lithos
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Insights into the evolution of an alkaline magmatic system: An in situ
trace element study of clinopyroxenes from the Ditrău Alkaline
Massif, Romania
AnikóBatkia,b,⁎,1,ElemérPál-Molnára,b,1,M.ÉvaJankovicsa,b,AndrewC.Kerrc,BalázsKissa,b,GregorMarkld,
AdriánHeinczb,SzabolcsHarangia
aMTA-ELTEVolcanologyResearchGroup,PázmányPétersétány1/C,H-1117Budapest,Hungary
b‘Vulcano’PetrologyandGeochemistryResearchGroup,DepartmentofMineralogy,GeochemistryandPetrology,UniversityofSzeged,EgyetemStreet2,H-6722Szeged,Hungary
cSchoolofEarthandOceanSciences,CardiffUniversity,MainBuilding,CardiffCF103AT,UnitedKingdom
dFachbereichGeowissenschaften,UniversitätTübingen,Wilhelmstrasse56,D-72074Tübingen,Germany
a r t i c l e i n f o a b s t r a c t
Articlehistory: Clinopyroxeneisamajorconstituentinmostigneousrocktypes(hornblendite,diorite,syenite,nephelinesye-
Received7August2017 nite,camptonite,tinguaiteandijolite)oftheDitrăuAlkalineMassif,EasternCarpathians,Romania.Phenocryst
Accepted28November2017 andantecrystpopulationshavebeendistinguishedbasedonmineralzoningpatternsandgeochemicalcharacter-
Availableonline5December2017 istics.Majorandtraceelementcompositionsofclinopyroxenesreflectthreedominantpyroxenetypesincluding
primitivehigh-CrFe-diopside,intermediateNa-diopside-hedenbergiteandevolvedhigh-Zraegirine-augite.
Keywords:
Clinopyroxenesrecordtwomajormagmasourcesaswellasdistinctmagmaevolutiontrends.Theprimitive
Clinopyroxene
diopsidepopulationisderivedfromanearlycamptoniticmagmarelatedtobasaniticparentalmelts,whilstthe
Alkalineigneouscomplex
LA-ICP-MS intermediatediopside-hedenbergitecrystalsrepresentaNa-,Nb-andZr-richmagmasourcerecognisedforthe
Zoningpatterns firsttimeintheDitrăumagmaticsystem.Thismagmafractionatedtowardsijoliticandlaterphonoliticcomposi-
Antecrystrecycling tions.Fieldobservations,petrographyandclinopyroxene-meltequilibriumcalculationsrevealmagmarecharge
Magmarecharge andmingling,pyroxenerecycling,fractionalcrystallisationandaccumulation.Repeatedrechargeeventsofthe
twoprincipalmagmasresultedinmultipleinteractionsbetweenmoreprimitiveandmorefractionatedco-
existingmagmabatches.Magmaminglingoccurredbetweenmaficandfelsicmagmasbyinjectionofijolitic
magmaintofissures(dykes)containingphonolitic(tinguaite)magma.Thisstudyshowsthatantecrystrecycling,
alsodescribedforthefirsttimeinDitrău,isasignificantprocessduringmagmarechargeanddemonstratesthat
incorporatedcrystalscancruciallyaffectthehostmagmacompositionandsowhole-rockchemicaldatashould
beinterpretedwithgreatcare.
©2017ElsevierB.V.Allrightsreserved.
1.Introduction The textural, zoning and compositional characteristics of
clinopyroxeneinpetrologicallyandgeochemicallydiversevolcanicand
Open- and closed-system magma chamber processes such as plutonicrockshavebeenextensivelystudiedoverthepast40years
magma mixing, mingling, recharge, crystal mush remobilisation, (e.g., Dobosi et al., 1991; Dobosi and Fodor, 1992; Duda and
crystallisation and assimilation significantly affect the evolution of Schmincke, 1985; Gernon et al., 2016; Jankovics et al., 2012, 2016;
differentmagmasinthelithosphereaswellastheirvolcanicactivity.In- Marksetal.,2004;Nakagawaetal.,2002;Neumannetal.,1999;Shane
vestigationofexhumedmagmareservoirs,i.e.,plutonicsystems,can etal.,2008;Strecketal.,2002;Stronciketal.,2009;Ubideetal.,2014a,
significantlycontributetoourunderstandingthesemagmaticprocesses 2014b;Wass,1979;WinpennyandMaclennan,2011).Thesedetailed
(e.g., Barbarin and Didier, 1992; Baxter and Feely, 2002; Frost and mineral-scalestudieshaveinferredtheoriginofdifferentclinopyroxene
Mahood,1987;Kerretal.,1999;Maetal.,2017;Micheletal.,2016; populations,fromopen-andclosed-systempetrogeneticprocessesoper-
Weidendorferetal.,2014). atinginsubvolcanicmagmastoragesystemstotheevolutionandascent
historiesofdifferentmagmas(replenishment,magmamixing,mingling,
xenocrystincorporation,fractionalcrystallisationandcontamination).
⁎ Correspondingauthorat:MTA-ELTEVolcanologyResearchGroup,PázmányPéter Basedontheseresults,clinopyroxeneisconsideredasasignificantpetro-
sétány1/C,H-1117Budapest,Hungary.
geneticindicatorthatcanbeeffectivelyusedtounraveltheevolutionof
E-mailaddress:[email protected](A.Batki).
1 Thefirsttwoauthorshavecontributedequallytothiswork. magmaticsystems.
https://doi.org/10.1016/j.lithos.2017.11.029
0024-4937/©2017ElsevierB.V.Allrightsreserved.
52 A.Batkietal./Lithos300–301(2018)51–71
ThepetrogenesisoftheDitrăuAlkalineMassifhasbeeninthefocus andhavebeendatedat232–216Maand217–196Ma,respectively.
ofmanystudiesinthelast150years(e.g.,Batkietal.,2014;Codarcea AgeshavebeenobtainedbyK–Aronhornblende,biotite,nepheline
et al., 1957; Dallmeyer et al., 1997; Fall et al., 2007; Kräutner and andfeldsparseparates(Pál-MolnárandÁrva-Sós,1995),andamid-to
Bindea, 1998; Morogan et al., 2000; Pál-Molnár, 2000, 2010b; late-Triassicageoftheearlycomponentswaslaterconfirmedbyaddi-
Pál-Molnáretal.,2015b;Pál-MolnárandÁrva-Sós,1995;Streckeisen, tional40Ar/39Arhornblendeagesof231Maand227Maforgabbro
1954,1960;StreckeisenandHunziker,1974).However,becauseofthe anddiorite,respectively(Dallmeyeretal.,1997).AU–Pbzirconageof
widerangeoflithologiesandcomplexfieldrelationships,contrasting 229.6±1.7Mahasbeenreportedforthesyenites(Panăetal.,2000).
modelsfortheoriginandmagmaticevolutionofthemassifhavebeen Amantleoriginforthemaficandultramaficbodieswasinferredby
proposed.Sincemostofitsrocktypescontainclinopyroxene,aninte- KräutnerandBindea(1998)andbyMoroganetal.(2000).Morogan
gratedtexturalandgeochemicalstudyofthismineralphaseservesas et al. (2000) suggestedthat the massif wasformed from primitive
ausefultooltounravelthesuccessionandinteractionsofmagmasas basaniticmagmasthatresultedfromsmall-fractionasthenospheric
wellasthedeep-seatedpetrogeneticprocessesintheDitrăuplutonic melts,followedbyprogressiveevolutiontophonoliticresidues.Theyat-
system. tributedanimportantroletoassimilationandfractionation,inconjunc-
Inthisstudy,wepresentthetexturalvarietiesandanewmajorand tionwiththemixingoffelsicandbasaniticmelts.Thehornblenditesare
traceelementgeochemicaldatasetofdiverseclinopyroxenecrystals interpreted as gravitational cumulates on a magma chamber floor
fromsevenrelatedrocktypesofthealkalineigneoussuiteoftheDitrău (Pál-Molnár,2000,2010b;Pál-Molnáretal.,2015b)orasdisrupted
plutonic system. Textural and zoning characteristics are combined bodiesofformerside-wallcumulates(Moroganetal.,2000).Modelling
with chemical compositions to identify distinct phenocryst and suggeststhatcamptonitedykeshavebeengeneratedby1–4%partial
antecryst populations. We use in-situ LA-ICP-MS data to carry out meltingofanenriched,amphibole-bearinggarnetlherzolitemantle
clinopyroxene-meltequilibriumcalculationsinordertorevealthedom- source.Thesedykesrepresenttheonlyprimitivemaficmeltknownin
inantopen-andclosed-systemmagmachamberprocesses.Additional- themassifandthereforehavebeeninterpretedastheparentalmelts
ly,anewmagmasourcehasbeendiscoveredintheDitrăumagmatic ofthewholeigneouscomplex(Batkietal.,2014).
systemandfurthergeneticrelationshipsbetweenthestudiedalkaline
igneousrockshavebeenidentified. 3.Fieldrelationsandsamples
2.Geologicalsetting Hornblenditecumulatesareenclosedingabbroic–dioriticrocksas
lenticularorblock-shapedbodiesfromafewcentimetrestoahundred
TheDitrăuAlkalineMassifisaMesozoicigneouscomplexlocatedin metresormoreinsize.Thecumulatesspanawiderangeofcomposi-
theEasternCarpathians,Romania(Fig.1a).Themassifoutcropsimme- tionsbutpredominantlyconsistofolivineand/orclinopyroxenetoes-
diatelyeastoftheCălimani–Gurghiu–HarghitaNeogene–Quaternary sentiallymono-mineralichornblendite.Acompleteigneousrockseries
volcanicchain(Fig.1b)andispartlycoveredbyandesiticpyroclasticde- fromhornblenditetogabbro,diorite,monzodiorite,monzonite,quartz
positsandlavasaswellasbyPliocene–Pleistocenesediments(Codarcea monzonite,syenite,quartzsyeniteandgranitecanbeobservedfrom
etal.,1957;Pál-Molnár,2010a).Theigneouscomplexwasformeddur- thenorth-westtothenorth-eastpartofthemassif(Pál-Molnáretal.,
inganextensionalphaseoftheAlpineorogenyrelatedtoariftedconti- 2015b)(Fig.1c).
nentalmarginadjacenttoTethys.Theintrusionsareinferredtohave Syenites show mingling features with dioritic/gabbroic rocks
been related to the opening events of the Meliata–Hallstatt ocean (describedas“Ditroessexite”byStreckeisen,1960)(Fig.2a).Nepheline
(Hoecketal.,2009)whereriftingisproposedtohavecommencedin syenitesarethemostabundantrocksofthemassifandpredominatein
thePelsonianSubstage(MiddleTriassic)(Kozur,1991). theeasternpartandformlargebodiesanddykes.
The basement of the Eastern Carpathians is composed of Raretinguaites,whicharepetrogeneticallyrelatedtonephelinesye-
NeoproterozoictoearlyPaleozoicperi-Gondwananterranesthatwere nites(Streckeisen,1954)formthindykescrosscuttingthegranites,sye-
variablyaffectedbytheVariscanorogeny,andsoissimilartoother nitesandnephelinesyenites.Additionally,small,discrete,rounded,
basementterrainsofEurope(Balintonietal.,2014).TheDitrăuAlkaline ijoliticenclavesoccurwithinsomeofthetinguaitedykesindicating
MassiflieswithintheDaciaMega-Unit(MedianDacides;Săndulescu, mingling (mechanical interaction) of co-existing mafic and felsic
1984)oftheAlpine–Carpathian–Dinaricregion(Fig.1a)andintrudes magmasbeforesolidification(e.g.,BarbarinandDidier,1992;Ubide
the Variscan metamorphic rocks that form the Alpine nappes in etal.,2014c).Theglobulartolenticulardarkgreyijoliteenclaveswith
theEasternCarpathians.TheAlpinenappesfromthebottomtothe sharpmarginsvaryindiameterfrom1to9cm(Fig.2b).
topare:theBucovinian,theSubbucovinianandtheInfrabucovinian Representative samples of rocks containing clinopyroxenes
Nappes. These nappes were thrust over each other during the i.e., hornblendite cumulates, diorites, syenites, nepheline syenites,
Cretaceous (Austrian tectogenesis), and have an eastern vergence. camptonitesandtinguaitedykesincludingijoliteenclaveswerecollect-
Structurally,theDitrăuAlkalineMassifisthepartofthelowermost edfromdistinctpartsoftheDitrăuAlkalineMassif(PietrărieideSus,
BucovinianNappe,andisindirectcontactwithfourofitsPre-AlpineOr- TarniţadeJos,Teasc,Jolotca,CreangaMare,DitrăuandCetăţiiCreeks)
dovicianGondwananterranes(metamorphicunits)(BretilaTerrane, (Table 1, Fig. 1c). Hornblendite cumulate, nepheline syenite,
Tulgheş Terrane, Negrişoara Terrane and Rebra Terrane; Balintoni camptonite, tinguaiteandsomeof the ijolitesamples have formed
etal.,2014). partofpreviouspetrologicalandmineralogicalstudies(Batkietal.,
Themassifconsistsofaseriesofultramaficandmaficcumulates 2004, 2012a, 2012b, 2014; Batki and Pál-Molnár, 2011; Fall et al.,
gradingtointermediateandfelsicrocksfromwesttoeast(Pál-Molnár, 2007;Pál-Molnár,2000,2010b;Pál-Molnáretal.,2015b).
2000;Pál-Molnáretal.,2015a,2015b).Hornblendite,gabbroanddiorite
arethedominantrock-typesinthenorth-andcentral-westpartofthe 4.Petrographyandwholerockgeochemistry
igneouscomplex;monzonite,syenite,quartzsyeniteandgraniteextend
fromthenorthtothesouth-east,whilstnephelinesyeniteisconcentrat- 4.1.Hornblenditecumulate
edinalargeareaofthecentralandeasternpartofthemassif(Fig.1c).
Thewhole massif is cutby numerousdykesincluding camptonites, Hornblendite cumulates have been recently described by Pál-
tinguaites,alkalifeldsparsyenitesandnephelinesyenites. Molnár(2010b)andPál-Molnáretal.(2015a,2015b).Accordingto
TheultramaficrocksrepresenttheoldestpartoftheMassifandwere thesestudies,twocumulatetypescanberecognised:poikiliticolivine-
emplacedfrom237to216Ma,althoughtheiragesoverlapthatofthe bearinghornblenditecumulate,andpyroxene-richhornblenditecumu-
gabbros(234Ma).Thenephelinesyenitesandgranitesareyounger, late.Therocksaredarkgrey,coarse-grained,inequigranularanddisplay
A.Batkietal./Lithos300–301(2018)51–71 53
Fig.1.(A)LocationoftheDitrăuAlkalineMassifinthestructuralsystemoftheAlpineCarpathian–Dinaricregion(Pál-Molnár,2010a).(B)AlpinestructuralunitsoftheEasternCarpathians
(Săndulescuetal.,1981,modified).(C)SchematicgeologicalmapoftheDitrăuAlkalineMassif(Pál-Molnáretal.,2015b)showingsamplelocations.
orthocumulateandmesocumulatetextures.Poikiliticolivine-bearing 10vol%),upto16vol%clinopyroxene,~5vol%plagioclase,~5vol%ap-
cumulates consist of up to 30 modal% olivine and 23% cumulus atite,~3vol%titanite,and~3vol%magnetite.Amphiboleoikocrystsen-
clinopyroxene enclosed by intercumulus amphibole oikocrysts. closesmallclinopyroxeneswithsizesofaround450μm(Fig.2binPál-
Pyroxene-richcumulatescomprisinganearlymonomineralicassem- Molnáretal.,2015b).Brown-coloured,euhedraltosubhedral,cumulus
blage of up to 90 vol% amphibole accompanied by biotite (up to clinopyroxeneisalsopresent(Fig.3a).
54 A.Batkietal./Lithos300–301(2018)51–71
Fig.2.Fieldrelationsindicatingminglingfeaturesbetweenco-existingmagmasintheDitrăuAlkalineMassif.(A)DioriteenclavesenclosedinsyeniteatJolotcaCreek.(B)Fine-grained
ijoliteenclavesintinguaitedykesatCreangaMareCreek.
Olivine-bearingcumulatesarethemostprimitiveamongtheDitrău rarely,clinopyroxene.Accessoryminerals(~5vol%)includezircon,
mafic-ultramaficcumulateserieswithMgOcontentsof16–17wt%and apatite, magnetite, titanite and rutile. The subhedral, commonly
thehighestNiandCrconcentrations(b390ppmandb509ppm,respec- cracked,1–5mmsizedamphiboleoccursasmaficcrystalclotsenclosing
tively).Theyarealsotheleastenrichedinrareearthelement(REE)and anhedral clinopyroxene crystals, biotite, magnetite and titanite.
havepositivePb,HfandTiandnegativeZrandYanomaliesonprimitive (Fig.3c).
mantle-normaliseddiagrams.Pyroxene-richcumulateshavehighalkali, Thestudiedsyeniteisalkalineandperaluminouswithanagpaitic
TiO ,P O andFeOTcontentsandhighSr,Ba,Zr,NbandYconcentra- indexof0.64,slightlySi-undersaturatedwith3.4%nephelineinthe
2 2 5
tions(Table2).Chondrite-normalisedREEpatternshavenoEuanomaly norm,anddoesnotcontainnormativequartzorleucite.Sodiumandpo-
andareenrichedinLREE,whilstprimitivemantle-normalisedpatterns tassiumconcentrationsarehighandnearlyequal(6.1wt%Na Oand
2
havenegativeP,Ti,UandK(Pál-Molnáretal.,2015b). 6.2wt%K O;Table2).ThesyeniteisrelativelyenrichedinZr,Nb,Sr,
2
Ba,LaandCe.Chondrite-normalisedREEpatternsareenrichedinLREE
andshowaslightdepletioninMREE.
4.2.Diorite
Thestudieddioriteisdark-to-lightgreycoloured,medium-grained
4.4.Nephelinesyenite
withgranulartexture,andiscomposedofamphibole(44vol%),biotite
(11vol%),plagioclase(35vol%),subordinateclinopyroxene(4vol%),
The white to reddish nepheline syenite is coarse- to medium-
apatite,magnetite,andtitanite.Anhedralclinopyroxeneissurrounded grained.Itconsistsoflargecrystalsof40–55vol%feldspar(orthoclase,
byeuhedralamphibolecrystals(250–3000μmsized)andsubhedralbi- microclineandsubordinatealbite)and10–35vol%nepheline(upto
otite(upto7.5mm)(Fig.3b). 25mmand15mm,respectively),subordinatebiotite(2–10vol%)and
Thedioriteismoderatelyevolved(mg#0.4)andiscompositionally clinopyroxene(2–7vol%),amphibole(2–5vol%),late-stagehydrother-
similartotheDitrăucamptonites(Table2).Itplotsinthebasaniticfield malcalcite+cancrinite+sodalite+analcimeand3–5vol%accessory
oftheTASdiagram(notshown)withSiO contentsof43wt%andtotal
2 zircon,monazite,apatite,titanite,magnetiteandilmenite(Fig.3d).
alkalis(Na2O+K2O)of5.4wt%.TheTiO2contentishigh(4wt%)andis TheDitrăunephelinesyenitesarecharacterisedasperaluminous
acommonfeatureoftheDitrăumaficrocks,alongwithhighNb,Zr,Sr,
andmiaskiticrocks(agpaiticindexvariesfrom0.8to1.0)andtwodif-
BaandLREEenrichment.
ferentgeochemicalcompositionsareobserved(Table2).Generally,
nephelinesyenite-IhashigherAl O contents(21–24wt%)andalkalis
2 3
4.3.Syenite (14–16wt%Na O+K O)butlowerREEconcentrationswithasignifi-
2 2
cantnegativeSm anomaly than thatof nephelinesyenite-II(Al O
2 3
Thegreyishpinkcolouredsyeniteisinequigranularandmedium- b21 wt%andNa O+K Ob13.5wt%).Chondrite-normalisedREE
2 2
to fine-grained. It consists of amphibole (2 vol%), biotite (1 vol%), patternsofbothtypesareU-shapedwithamarkeddepletioninMREE
potassiumfeldspar(80vol%),subordinateplagioclase(11vol%),and typicalofphonoliticcompositionsbutMREEdepletionofnepheline
Table1
MineralassemblageoftheinvestigatedsamplesfromtheDitrăuAlkalineMassif,Romania.
Phase Rocktype Phenocrystsa(ph) Groundmassminerals(gr), Accessoryminerals Secondaryminerals Samples
cumulusminerals(c) intercumulusminerals(ic)
Cumulate Ol-bearingHornblendite Cpx,ol(c) Amph(ic) Ap,mag Srp,mag VRG23
Cumulate Pyroxene-richHornblendite Cpx,amph(c) Bt,pl(ic) Ap,ttn,mag Act,chl,ep VRG6706
Intrusive Diorite Cpx,amph,bt(ph) – Ap,ttn,mag Act,chl,ser VRG6567
Intrusive Syenite Cpx,amph,bt,pl,kfs(ph) – Zrn,ap,ttn,mag,rt Chl,mag,hem,ilm,ep,ms,cal VRG7420
Intrusive Nephelinesyenite Aeg,ne,kfs,ab,bt(ph) – Zrn,ap,ttn,mag,ilm Ms,anl,sdl,ccn,mag VRG6727
Dyke Camptonite Cpx(ph) Amph,bt,pl(gr);ocelluscal Ap,ttn,mag Act,chl,mag VRG7292,VRG7294
Dyke Tinguaite Cpx(ph) Aeg,ne,ab,kfs,ccn(gr) Zrn,ap,ttn,fl Bt,ser,mag VRG7306,VRG7338
Enclave Ijolite Cpx(ph) Aeg,ccn,kfs(gr) Ap,ttn Bt,mag VRG7338,VRG7480
Cpx,clinopyroxene;ol,olivine;amph,amphibole;bt,biotite;pl,plagioclase;kfs,K-feldspar;aeg,aegirine;ne,nepheline;ab,albite;ccn,cancrinite;ap,apatite;mag,magnetite;ttn,titanite;
zrn,zircon;rt,rutile;ilm,ilmenite;fl,fluorite;srp,serpentine;act,actinolite;chl,chlorite;ep,epidote;ser,sericite;hem,hematite;ms,muscovite;cal,calcite;anl,analcime;sdl,sodalite.
a Theterm“phenocrysts”isusedhereinageneralsenseregardlessoftheirorigin.
A.Batkietal./Lithos300–301(2018)51–71 55
Fig.3.CharacteristicpetrographicfeaturesofthestudiedigneousrockscontainingclinopyroxeneintheDitrăuAlkalineMassif.(A)Browncumulusdiopsideinpyroxene-richhornblendite
cumulateVRG6706,1N.(B)Green,anhedralclinopyroxenecrystalextensivelydecomposedtochloriteandactinoliteindioriteVRG6567,1N.(C)Hornblendecrystalclotenclosinggreen,
anhedralclinopyroxenecrystalsandcrystalrelicts,biotite,magnetiteandtitaniteinsyeniteVRG7420,1N.(D)Darkgreen,subhedralaegirine-augiteshowingirregularzoningwith
magnetite+albite+biotitecoronainnephelinesyeniteVRG6727,1N.(E)Palebrown,subhedraldiopsidecrystalsinocellarcamptonitedykeVRG7292,1N.(F)Contactbetween
ijoliteenclaveandthehosttinguaitedykeVRG7338,1N.(G)Fe-diopsidecrystalsovergrownbyaegirine-augitegroundmassmicrolitesintinguaitedykeVRG7306,1N.(H)Green,
euhedralandskeletalclinopyroxenetogetherwithbrown,subhedraldiopside,biotiteaggregates,ocelliandfeldsparxenocrystinijoliteenclaveVRG7338,1N.Mineralabbreviations
areafterKretz(1983).
56 A.Batkietal./Lithos300–301(2018)51–71
Table2
Whole-rockmajor(wt%)andtraceelement(ppm)compositionsofthestudiedigneousrocks,DitrăuAlkalineMassif,Romania.
Location PietrărieideSus PietrărieideSus Teasc DitrăuCreek TeascCreek JolotcaCreek CreangaMare CreangaMare Cetăţii
Creek Creek Creek Creek Creek Creeks
Sample VRG6706 VRG6774 VRG7420 VRG7506 VRG7507 VRG7292 VRG7306 VRG7338 VRG7480
Rock Px-rich Diorite Syenite Nepheline Nepheline Camptonite Tinguaitedyke Ijoliteenclave Ijolite
type Hornblendite syenite-I syenite-II dyke enclave
Pál-Molnáretal. Batkietal.
(2015b) (2014)
SiO2 32.36 43.53 60.54 57.89 55.44 45.22 57.50 49.02 45.51
TiO2 5.25 3.96 0.62 0.17 1.34 2.08 0.50 1.33 2.13
Al2O3 9.88 14.50 19.13 21.69 18.06 12.52 21.81 18.85 16.13
FeOt 20.73 14.42 3.03 3.31 5.23 10.47 3.99 6.13 8.48
MnO 0.26 0.26 0.08 0.06 0.20 0.16 0.16 0.19 0.26
MgO 9.06 5.15 0.49 0.01 1.24 10.01 0.96 3.03 5.08
CaO 13.55 10.98 2.08 0.22 3.67 8.85 2.15 4.42 5.82
Na2O 1.77 3.54 6.12 9.32 6.48 3.01 9.38 8.17 5.75
K2O 1.38 1.87 6.20 5.91 5.52 2.36 5.47 4.72 5.89
P2O5 2.72 1.46 0.11 n.d. 0.22 0.26 0.08 0.35 0.42
LOI 2.60 n.a. 1.30 1.30 2.30 n.a. n.a. 3.20 4.10
Total 99.56 99.67 99.70 99.88 99.70 94.93 102.00 99.41 99.57
mg# 0.53 0.41 0.26 0.00 0.32 0.70 0.32 0.50 0.54
Be n.d. 1.86 n.d. n.d. 1 1.20 4.96 12 19
Sc 24 10 1 n.d. 2 17 1.71 6 11
V 356 223 28 43 68 150 29 102 125
Cr n.d. 4.04 n.d. n.d. n.d. 277 20 89 103
Co 63 32 2.10 0.80 7.80 45 6.84 19 25
Ni 28 20 0.30 n.d. n.d. 214 15 46 83
Cu 58 81 0.70 n.a. n.a. 49 16 4.10 4.40
Zn 142 149 52 n.a. n.a. 104 124 132 335
Sr 778 1246 610 421 855 695 411 1200 676
Ba 418 616 899 192 767 597 221 1244 582
Rb 29 80 117 114 168 184 467 310 505
Pb 2.60 n.a. 2.40 n.a. n.a. n.a. n.a. 17 7.10
Th 2.70 n.a. 9.60 8.30 8.90 n.a. n.a. 28 41.80
U 1.00 n.a. 3.20 21.70 1.60 n.a. n.a. 8.00 8.20
Zr 160 343 493 60 362 168 602 484 534
Nb 48 185 86 37.60 155 53 104 126 212
Ta 3.20 n.a. 5.10 0.90 6.30 n.a. n.a. 3.30 4.50
Y 36 41 14.80 1.20 22 14.70 12.90 22 31
Hf 4.90 12.66 8.90 0.80 8.50 8.00 7.21 8.80 7.80
Mo 1.40 3.86 2.00 n.a. n.a. 7.80 2.13 0.40 0.40
S n.a. 837 n.a. n.a. n.a. 595 135 n.a. n.a.
La 71 113 62 7.80 107 32 81 102 133
Ce 155 229 101 8.70 171 55 114 138 148
Pr 20 n.a. 9.66 0.70 14.18 n.a. n.a. 12.36 13
Nd 88 91 33 2.00 42 22 19 40 41
Sm 17.30 17.50 4.34 0.20 6.18 4.80 4.29 5.87 6.37
Eu 5.18 4.80 1.32 0.14 1.82 1.50 1.03 1.67 2.09
Gd 15 n.a. 3.37 0.21 5.13 n.a. n.a. 4.58 6.22
Tb 1.94 n.a. 0.51 0.03 0.72 n.a. n.a. 0.66 0.89
Dy 8.89 9.76 2.66 0.18 3.80 4.00 2.39 3.72 5.01
Ho 1.36 n.a. 0.52 0.03 0.76 n.a. n.a. 0.68 0.92
Er 3.07 n.a. 1.37 0.13 1.90 n.a. 3.20 1.83 2.68
Tm 0.38 n.a. 0.21 0.03 0.29 n.a. n.a. 0.32 0.38
Yb 2.21 4.46 1.36 0.20 1.91 2.20 1.99 1.88 2.46
Lu 0.31 n.a. 0.23 0.02 0.30 n.a. n.a. 0.29 0.27
FeOtastotaliron;mg#=Mg/(Mg+Fe2+),Fe2+calculatedaccordingtoIrvineandBaragar(1971);n.a.=notanalysed;n.d.=notdetected.
syenite-Iismorepronounced.Bothtypesofnephelinesyeniteshave subordinateannite,anhedralplagioclase,accessoryacicularapatite,
pronouncedpositiveSrandZr-HfanomaliesandlackEuanomalieson opaquemineralsandtitanite(Fig.3e).
primitivemantle-normalisedplots. TheDitrăucamptonitesarebasaniticandtrachy-basalticincomposi-
tionandSi-undersaturatedwitholivineandnephelineinthenorms.
4.5.Camptonite Thesamplesarehighinalkalis(Na O/K O=1–3)andtitanium(upto
2 2
4wt%TiO ).Mg#variesfrom0.44to0.70andpositivelycorrelates
2
CamptonitedykeswerepreviouslyinvestigatedbyBatkietal.(2004, withCrandNiabundances(Table2).High143Nd/144Ndratios,high
2014).Basedontheirresultstheclinopyroxene-bearingcamptonite fieldstrengthelement(HFSE;suchasZr,HfandNb),largeionlithophile
dykes are fine grained with a hypocrystalline porphyritic and element(LILE;likeRb,BaandSr)andLREEconcentrationsarecharac-
panidiomorphictexture.Majormineralsareclinopyroxene,amphibole, teristic. Chondrite-normalised REE patterns lack Eu anomalies and
biotiteandplagioclase.Texturally,subhedraltoanhedralclinopyroxene showsignificantfractionationofHREE(La/Yb=15–38)(Batkietal.,
crystals (ca. 1–10 vol%) are set in a groundmass of kaersutite, 2004,2014).
A.Batkietal./Lithos300–301(2018)51–71 57
4.6.Tinguaite University,UK.Allmeasurementswerecarriedoutusingspotanalysis
andThermoElementalPlasmaLabtime-resolvedanalysismode.The
AsnotedbyBatkiandPál-Molnár(2011)tinguaitedykesarefine laser beam diameter was 40 μm, with a frequency of 10 Hz and a
grained with a porphyritic and sugary texture. The rocks possess powerof~5Jcm−2.Ablationswerecarriedoutunderapureheliumat-
clinopyroxenecrystals(upto5vol%)embeddedinaholocrystallineto mosphere.Acquisitionslasted50s,includinga20-sgasblankpriorto
hypocrystallinegroundmasswherealkalifeldsparrandomlycrosses laser ablation and a 10-s washout at the end. BIR-1, BIR-2, BHVO,
nephelinegivingaradialappearance(Fig.3f,g).Thegroundmassalso BHVO-2,BCRandBCR2standardswereusedasexternalstandards(see
includesbiotitemicrocrystsandinterstitialcancrinitewithaccessory OnlineAppendix).CaandSiconcentrationswereusedasinternalstan-
zircon,titaniteandmagnetite.Secondarybiotitealsooccurstogether dardstocorrectconcentrationvalues.CaandSiconcentrationswere
withsubordinatechlorite,epidote,magnetiteandcalcite,seldomclearly quantitativelymeasuredpriortoLA-ICP-MSusingEPM.Gasblanksub-
reflectingtheshapeofclinopyroxenecrystals. tractionandinternalstandardcorrectionswereperformedusingThermo
TheDitrăutinguaitesaremoderatelytostronglysilica-undersaturated Plasmalabsoftware.
(Ne=7–25)intermediaterocks(54–58wt%SiO )andarephonoliticin
2
composition.Theyhaveperalkalinetoperaluminouscharacteristicsand 6.Clinopyroxenetextureandzoning
areenrichedinalkalis,Zr,Nb,Rb,Ba,SrandLREE(Table2).Chondrite-
normalisedREEpatternsareconvex-downwardswithmarkedenrich- ClinopyroxenecrystalsinthedifferentDitrăurocksshowdiverse
mentinLREEandslightenrichmentinHREE(La/Yb=24–40)(Batki texturalandzoningfeatures(Figs.3and4)andthissectiondescribes
andPál-Molnár,2011). clinopyroxenecharacteristicsfromeachstudiedrocktype.
Inthepoikiliticolivine-bearingcumulates,clinopyroxenemicrocrysts
4.7.Ijolite areeuhedral-subhedral,unzoned,browncolouredand150–600μm
sized(Fig.2binPál-Molnáretal.,2015b).Brownclinopyroxenecrystals
Ijoliteenclavesareholocrystallinetohypocrystallinewithporphyritic inthepyroxene-richcumulatesarerarelyzoned,euhedraltosubhedral
textures.Majormineralsaresimilartotinguaites,however,maficmin- inshapeandoccurasmacrocrystsupto4mminsize(Fig.3a)(Pál-
eralsdominateoverfeldsparsandfeldspathoids.Palebrownandgreen Molnáretal.,2015b).
clinopyroxenecrystals(upto15vol%)aresetinaveryfinegrained Thedioriteclinopyroxenecrystalsaregreen,upto2.7mminsize,
groundmasscomposedofmostlyaegirine-augiteneedlesandsmallbio- haveananhedralshapeandarepartlydecomposedtochloriteandac-
titegrainsof10–80μmwithinterstitialalkalifeldsparandcancrinite tinolite.Theyusually containapatite,magnetite,titaniteandhorn-
(Fig.3h).Accessorymineralsincludetitanite,apatiteandmagnetite.A blendeinclusions(Fig.3b).
characteristicfeatureoftheijoliteenclavesisthepresenceofabundant Clinopyroxenecrystals(660–800μm)andcrystalrelicts(80–150
sphericalorellipsoidalleucocraticglobules,0.2–2.0mminsize.Theycon- μm)insyenitearegreen,anhedralandpartlydecomposedtosecondary
tainalkalifeldsparandcancrinite±albite(Batkietal.,2012a,2012b). amphibole.Alltheclinopyroxenecrystalsareenclosedbysubhedral
Theijoliteenclavesarenepheliniticincomposition(45–49wt%SiO hornblendegrainsandoccurtogetherascrystalclotswithirregular
2
and11–13wt%Na O+K O;Table2).Theyhavemetaluminousto boundaries(Fig.3c).
2 2
peraluminouscharacteristicsandarehighinTh,U,Nb,Zr,Rb,Ba,Sr Inthenephelinesyenite,clinopyroxeneispresentasdarkgreen,
andLREE.TheCr(48–116ppm)andNi(57–80ppm)concentrations subhedral,elongatedaegirineandaegirine-augiteshowingirregular
arehighercomparedtootherijolitesworldwide(e.g.,3–8ppmCrand zoningcommonlysurroundedbyamagnetite+albite+biotitecorona.
b50–70ppmNi,FlohrandRoss,1989;9ppmCrand33–48ppmNi, Aegirineneedlescanreach6mminsize(Fig.3d).
WittkeandHolm,1996).Chondrite-normalisedREEpatternsareslop- The pale brown clinopyroxene crystals in camptonites are
ingwithmarkedenrichmentinLREEandslightdepletioninMREE subhedral,unzonedand0.6-to2.4-mm-diametersized(Fig.3e).They
resultinginaconvex-downwardsshape. varyinabundanceandgenerallyhavebeenreplacedbyanassemblage
oftremolitetoactinolite,andbiotite(Fig.3ainBatkietal.,2014).
5.Analyticalmethods Inthetinguaitedykes,threeclinopyroxenepopulationsarepresent:
1)palegreen-yellowishgreencrystals(300–700μm),2)palebrown-
Electron microprobe analyses (EMPA) were carried out on 20 beigemacro-andmicrocrysts(0.3–1.2mm)and3)greengroundmass
clinopyroxenecrystalsfrom7polishedthinsection(30μm)witha microlitesof20–200μmsize.Greencrystalsaresubhedralandshow
JEOL 8900 electron microprobe operated in wavelength-dispersive multiple zoning with an anhedral corroded core surrounded by a
modeattheFachbereichGeowissenschaften,UniversitätTübingen, growthzoneandarimwhichusuallyconsistsofsmallclinopyroxene
Germany,usingabeamcurrentof15nA,anaccelerationvoltageof grainssimilartothoseofthegreengroundmassmicrolites(Figs.3f
15kV,andadefocusedbeamdiameterof10μmandattheInstituteof and 4a, b). Pale brown clinopyroxene macro- and microcrysts are
GeologicalSciences,UniversityofBern,Switzerland,usingaCameca subhedralandnormalzonedwithanunzoned,slightlyroundedcore
SX-50electronmicroprobeinwavelength-dispersivemodeoperated overgrownbyarimconsistingofsmallcrystalslikethoseofthegreen
at an acceleration voltage of 15 kV and a beam current of 20 nA. groundmassmicrolites(Figs.3gand4c).
Countingtimeswere16sforpeakand8sforbackgroundmeasure- The ijolite enclaves consist of green clinopyroxene crystals
ments.AdditionalEMPAon7clinopyroxenecrystalsfrom2polished (70–1700μm)thatarezoned,euhedraltosubhedral,oftenskeletal
thinsectionswereperformedattheInstituteforGeologicalandGeo- enclosingthegroundmassandalsoenclosetitaniteandF-apatitegrains
chemicalResearch,ResearchCentreforAstronomyandEarthSciences, (Fig.4d).Palebrownclinopyroxenecrystalcores(50–1200μm)show
Hungarian Academy of Sciences, Budapest, Hungary, using a JEOL oscillatoryorsectorzoning.Theyaresubhedralwithslightlyresorbed
Superprobe733operatedatanaccelerationvoltageof20kVanda cores reflecting partial dissolution and are overgrown by a later
beamcurrentof15nA.Standardsusedwerebothnaturalandsynthetic aegirine-augiterim(Fig.4e,f).
mineralphases.TherawdatawereprocessedusingtheJEOLintegrated
ZAFcorrection(Armstrong,1991)andonlinePAPCamecaSoftware. 7.Clinopyroxenecompositions
Traceandrareearthelementconcentrationsinclinopyroxeneswere
determinedbylaser-ablationinductivelycoupledplasmamassspec- 7.1.Majorelements
trometry(LA-ICP-MS)usingthesame30μm-thickpolishedsections
asfortheEMPAandaNewWaveResearchUP213Nd-YAG213nm Representativemajorelementanalysesoftheclinopyroxenepopu-
UVlasersystemcoupledtoaThermoXSeries2ICP-MSsystematCardiff lationscanbefoundinTable3andthecompletedatasetisgivenin
58 A.Batkietal./Lithos300–301(2018)51–71
Fig.4.BSEimagesofdetailedtexturalandzoningcharacteristicsoftheDitrăutinguaiteandijoliteclinopyroxenecrystalsshowingtheanalysedlaserspots.(AandB)Multiple-zonedgreen
clinopyroxenecrystalswithanhedral,roundedcores,growthreversezonesandovergrowthrimssimilartothegroundmassmicrolitesintinguaiteVRG7338andVRG7306.(C)Unzoned,
subhedraldiopsideclotovergrownbyaegirine-augiteintinguaiteVRG7306.(D)Green,euhedralandskeletalclinopyroxenephenocrystenclosingtitaniteandF-apatiteinijoliteVRG7338
(notethesamemineralassemblagesintheskeletalpartsofthecrystalandthegroundmass).(EandF)Brown,subhedralpyroxenecrystalswithsectorandoscillatoryzoningshowing
resorbedcoresandovergrowthaegirine-augiteriminijoliteVRG7338.
SupplementaryTableI.Inthepyroxenequadrilateral(Morimotoetal., Indioriteandsyenite,greenclinopyroxenecrystalsshowanincrease
1989)theyrangeincompositionfromdiopsidetoaegirine-augite.The inAeg-contents(upto14mol%and43mol%,respectively)without
clinopyroxene compositional trends observed in the different rock any significant enrichment of the Hd component (Hd b 29 mol%,
typesareshowninFig.5. mg# =0.74–0.84,mg# =0.69–0.79)comparedtohorn-
diorite syenite
Themostprimitive,diopside-richpyroxeneisfoundincamptonite blenditediopsides.Intermediatecompositionsarealsorepresentedby
(Di77–93,Hd1–19,mg#=Mg/(Mg+Fe2+)=0.81–0.99),inolivine- greenclinopyroxenesfromthetinguaitedykesandassociatedijoliteen-
bearinghornblendite(Di72–81,Hd13–25,mg#=0.75–0.86;Pál-Molnár claves.Intinguaite,greencrystalcoreshavehedenbergiteandaegirine
etal.,2015b)andinijoliteasresorbedcores(Di80–94,Hd1–15,mg#= contents of Hd20–32Aeg12–15 (mg# = 0.65–0.78), whilst in ijolite,
0.84–0.99) (Fig. 4e, f). In tinguaite, the growth zones around the green crystal cores span a wider compositional range (mg# =
anhedralgreencrystalcores(Fig.4a,b)alsohaveahighDicomponent 0.55–0.81)startingwithhighHdupto40mol%and10–23mol%Aeg.
(Di mg#=0.82–0.83).Clinopyroxeneinpyroxene-richhornblendite Asimilarlybroadcompositionalrangeiscoveredbytheijolitepyrox-
78,
islessprimitivewithhigherinHd-contents(Di67–78,Hd15–26,mg#= enerimswheregreencrystalrims(Hd23–31Aeg28–51,mg#=0.40–64)
0.74–0.84), and overlaps the compositional range of camptonite andovergrowthrimsonbrownresorbedcores(Hd12–28Aeg35–55,
crystals. mg# = 0.53–0.78) clearly overlap. Tinguaite pyroxene rims are
Table3
Representativemajorelementcompositions(wt%)oftheclinopyroxenepopulations,DitrăuAlkalineMassif,Romania.
Sample VRG6567 VRG7420 VRG6727 VRG7294 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338 VRG7338
Rock Diorite Syenite Nepheline Camptonite Tinguaite Tinguaite Tinguaite Tinguaite Ijolite Ijoliteenclave Ijoliteenclave Ijoliteenclave Ijoliteenclave Ijolite Ijolite
type syenite dyke dyke dyke dyke dyke enclave enclave enclave
Spot Bn518/24 Bp22 Bn21 Tü22 Up30 Tü51 Tü54 Tü57 Tü28 Tü31 Tü29 Bp15 Bp2 Tü90 Bp33
Cpx Antecryst Antecryst Phenocr. Phenocr. Matrix Crystalrim Antecrystcore Antecryst Phenocr.core Phenocr.core Phenocr.rim Antecrystrim Antecrystcore Matrix Ocellus
crystal microlite (cpx2) (cpx2) growthz. (cpx1) (cpx1) (cpx1) (cpx5) (cpx6) microlite microlite
A
(cpx2) .B
a
Type TypeII TypeII TypeIII TypeI TypeIII TypeIII TypeII TypeI TypeII TypeII TypeIII TypeIII TypeI TypeIII TypeIII tki
e
t
Mineral Na-Fe- Na-Fe- Aegirine- Fe-diopside Aegirine- Aegirine- Na-Fe- Fe-diopside Na-Mg Na-Fe- Aegirine- Aegirine- Cr-Fe-diopside Aegirine- Aegirine- al.
SiO2 d50io.2p0side d50io.5p0side a5u0g.8it4e 48.01 a5u2g.1it2e a5u3g.0it8e d48io.0p8side 45.58 H49d.20 d47io.8p3side a5u2g.9it1e a5u2g.4it9e 48.07 a5u3g.5it1e a5u1g.8it5e /Lithos
TiO2 0.59 1.12 0.19 2.28 0.15 0.79 1.85 3.36 1.08 1.45 0.27 0.17 1.66 1.36 0.97 30
Al2O3 2.82 2.81 1.57 7.44 1.92 1.70 5.78 8.37 4.64 5.74 1.67 1.10 6.28 1.86 1.32 0–
CFer2OOt3 n10.a..99 n11.a..69 n24.a..71 n6..6a.3 025.0.225 2n2.a..59 n11.a..50 n7..5a.9 n14.a..09 n12.a..55 n17.a..96 01.90.008 05..6988 n20.a..33 02.02.229 301(2
MnO 0.43 0.90 1.23 0.12 0.62 1.81 0.42 0.11 0.72 0.51 0.91 0.52 0.37 0.42 0.25 0
1
MgO 11.08 10.02 1.04 13.86 1.39 1.90 9.51 12.15 7.89 8.69 5.58 5.66 14.18 3.53 4.40 8)
ZrO2 n.a. n.a. n.a. 0.00 n.a. 0.67 0.05 0.02 0.08 0.13 0.25 n.a. n.a. 0.17 n.a. 51
CaO 22.12 20.97 3.35 21.60 3.49 7.53 19.59 22.01 19.39 19.94 12.07 14.84 23.11 8.06 11.82 7–
1
Na2O 1.75 1.73 11.55 0.60 11.52 9.19 1.61 0.67 2.12 1.71 6.61 5.64 0.23 9.17 7.59
K2O 0.02 0.00 0.00 0.03 0.00 0.02 0.00 0.00 0.00 0.02 0.01 n.a. n.a. 0.04 n.a.
Total 100.00 99.74 94.48 100.57 96.47 99.28 98.38 99.86 99.20 98.57 98.23 99.50 100.56 98.45 98.71
Mg# 0.84 0.70 0.99 0.86 0.63 0.33 0.65 0.83 0.58 0.63 0.60 0.59 0.91 0.53 0.64
Di 70 59 6 82 8 10 56 78 47 53 30 33 88 19 26
Hd 15 28 4 14 7 26 32 17 37 33 23 25 10 18 16
Aeg 14 13 90 5 85 64 12 6 16 14 47 42 2 63 58
FeOtastotaliron;Phenocr.=phenocryst;Na-MgHd=Na-Mg-hedenbergite;growthz.=growthzone;sectorz.=sectorzone;n.a.=notanalysed.
5
9
60 A.Batkietal./Lithos300–301(2018)51–71
Fig.5.CompositionalvariationsoftheDitrăuclinopyroxenesintermsofDi–Hd–Aegendmembermol%.Intherighttriangleclinopyroxenetrendsfromotheralkalinecomplexesareshown
forcomparison:(1)Murun,Siberia(MitchellandVladykin,1996),(2)Lovozero,KolaPeninsula(KorobeinikovandLaajoki,1994),(3)Fen,Norway,acmitictrend(Mitchell,1980),(4)Alnö
Island,Sweden,sodictrend(HodeVuorinenetal.,2005),(5)EasternUganda(TaylorandKing,1967),(6)SouthQôroq,SouthGreenland(Stephenson,1972),(7)Ilímaussaq,SouthGreen-
land(Larsen,1976).
higherbothinHd(Hd26–37,mg#=0.19–48)andAegcomponents 7.2.Traceelements
(45–64mol%).ContinuousAegenrichmentcanbeobservedfromijolite
pyroxene rims through ijolite ocelli (Aeg43–59) and groundmass The different clinopyroxene populations, macrocryst, micro-
microlites (Aeg61–63), tinguaite pyroxene rims to tinguaite matrix phenocrystandcrystalcoresintheDitrăurockshavebeenanalysed
microlites(Aeg69–85)andnephelinesyenitephenocrystcompositions. fortraceelements.However,overgrowthmantlesandrims,aswellas
Nepheline syenite contains the most evolved clinopyroxene with groundmassmicrolites,weretoosmalltogetreliabledatasetsbyspot
76–90mol%Aeg. analyses.TheanalysesaresummarizedinTable4andinSupplementary
Comparedwithtrendsfromotheralkalinesuites(Fig.5),theDitrău TableII.Rareearthelement(REE)andtraceelementpatternsarenor-
pyroxenesarecompositionallysimilartotheLovozero(Korobeinikov malisedtochondriticvaluesofMcDonoughandSun(1995).
and Laajoki, 1994), Alnö (Hode Vuorinen et al., 2005) and Uganda Di-richpyroxenesincamptonite,olivine-bearinghornblenditeand
(TylerandKing,1967)trendsinthattheystartwithahighDi-content ijolitedisplayvariableCrconcentrationsandcanreachexceptionally
andshowaslightinitialincreaseofFe2+duringfractionationbefore high values up to 5540 ppm (Batki et al., 2014), 5360 ppm and
trendingtowardsAeg.Ijolitepyroxenesalsodisplaysimilaritieswith 5290ppm,respectively.Inijolite,someoftheovergrowthrimswhich
theFenacmitictrend(Mitchell,1980)indicatinganotableincreasein areveryclosetothepalebrown,resorbedcrystalmargin(b1847ppm
Na+withinindividualgrains. Cr)andocelligroundmassmicrolite(b1505ppmCr)alsohavehighCr
Di-richpyroxenesincamptonite,ijoliteandtinguaitearealsohighin contents.AlltheotherpyroxeneshavelowCrvalues(b90ppm).Zrcon-
TiO (upto3.3wt%,2.3wt%and3.5wt%respectively)andAl O (upto centrationsinpyroxenesincreasefromprimitivediopsidetothemost
2 2 3
7.9wt%,6.8wt%and8.6wt%respectively),whilstnephelinesyenite evolvedaegirine-augitereaching6260ppminnephelinesyenitephe-
aegirine-augite(TiO b0.8wt%;Al O b2.5wt%)andtinguaiteground- nocryst.Generally,theincreaseinAegcomponentaccompaniedbyan
2 2 3
massmicrolite(TiO b0.2wt%;Al O b2.2wt%)arepoorintheseele- increaseinZrisalreadyknownfromotheralkalinecomplexes(e.g.
2 2 3
ments(Fig.6).Allrimandgroundmasscompositionsinijoliteand Larsen,1976;Mannetal.,2006;Nielsen,1979).
rimsintinguaitehavelowandfairlyconstantAl O butvariableTiO NormalisedREEconcentrationsforDi-richpyroxenesincamptonite
2 3 2
contents.Greencrystalsinijoliteandtinguaite,andtheotherpyroxenes andijoliteare2and2.5to40and60timesenrichedrelativetochondrit-
inhornblendite,dioriteandsyeniteshowvariableconcentrationsboth icvalues,respectively(Fig.7a).Althoughresorbedcrystalsinijoliteare
inTiO andAl O (Fig.6).PlotsofSiO andAl O againstMg#clearlyre- slightlymoreenrichedinREEthancamptonitemacrocrysts,theirpat-
2 2 3 2 2 3
vealtwovariationtrendsinclinopyroxenecompositions.Ontheone ternsclearlyoverlap.La /Yb valuesspananarrowrangebetween0.5
N N
hand,SiO inbrown-colouredpyroxenesincreaseswithdecreasing and0.6(camptonitemacrocrysts)andbetween0.6and0.9(ijolitere-
2
Mg#fromcamptoniteandijolitetohornblenditecumulatecrystals, sorbedcrystals).TheREEcontentsoftinguaitebrownpyroxenecrystals
whilstAl O decreases.Ontheotherhand,thegreenpyroxenerims are5to70timesthoseofchondritewhilsthornblenditecumuluscrys-
2 3
andgroundmassmicrolitesinijoliteandtinguaiteshowincreasing talsareupto100timesenrichedrelativetochondriticvalues(Fig.7b).
SiO anddecreasingAl O withdecreasingMg#.Dioriteandsyenitepy- Tinguaitebrownpyroxeneandhornblenditepyroxenecrystalshave
2 2 3
roxenesrepresentadistinctgroupbetweenthetwovariationtrends La /Yb ratiosof0.8to1.0and0.7to1.0,respectively.Normalised
N N
withmid-rangeSiO andlowAl O contents(Fig.6). REEpatternsoftinguaitebrownpyroxenecrystalsarefairlyparallelto
2 2 3