Major element geochemistry of Neoproterozoic succes- sions ofVaranger Peninsula, North Norway, and Sredni and Rybachi Peninsulas, Northwest Kola, Russia:

ANDREIV.SOCHAVA&ANNASIEDLECKA NGU-BULL 432, 19 97 - PAGE 77

Major element geochemistry of Neoproterozoic succes- sions ofVaranger Peninsula, North Norway, and Sredni and Rybachi Peninsulas, Northwest Kola, Russia:

provenance patterns and basin evolution

ANDREIV.SOCHAVA^t &ANNASIEDLECKA

Sochava,A.V.&Siedlecka,A.1997:Major elemen t geochem istry of Neoprote rozoic successions of Varang er Peni nsu la,NorthNorway,and Sredni andRybachi Penin su las,Northwest Kola,Russia: prov enance patterns and basin evolution.Norgesgeologiskeundersokelse Bulletin432,77-93.

Majoreleme nt analysesof 46 1 samp lesofNeop rote rozoicsedi me nta ry rock s wereclassifi edbyusing petroc hemi cal plot s andstat isti cally treatedinclust er analyses.In general,thestudiedsiliciclast ic rocksrep resenttwomajor associ- atio ns.Thefirstcontain s arko ses to quartz aren ite s withpredomin antl yillit icshales; it includesthemajorityof the st udied formatio nsand may be interpreted asa productof denudationoftheconti nentalcrust.The second associa- tion co m p rises greywackesand lithic arenitesassociatedwithshales whichcontainsome chlori te and Na-feldspars.

Thechemistr y suggests that therewas acontribution from abasic,Na-rich crustor volcanic so urce.

The geochemistry isinaccordwithinterpretationsofsedime nt aryenvironm entsand basindevelop m ent basedon ot her meth od s.Italso indicate sa temp or arily cold and dryclimate whichiscomp atible wit h sedimentaryfaciesana- lysis and thefactthatthere was no con ti nenta l veg etatio n. Formationswhichare rep resented byinterbedd ed vari e- gatedsiliciclas ticand carb onatero cks andexhibi t traces ofevaporites constit ut e ano the rimporta nt climat ic indi ca- tor.

Andreiv.Sochava:Instituteof Precambrian Geologyand Geochronology,RussianAcademy ofSciences,Makarova emb.Z, St.Petersburg,Russia.

Anna Siedlecka,Norges geologiskeundersekelse,PostBox3006-Lade,7002 Trondheim,Norway.

Introduction and scope

The Neoproterozoic (Up per Riphean and Vendian)succes- sions of the Varanger,Rybachi and Sredni Peninsulas have been studied in the early nineties in a joint Norwegian- Russian project.St rat ig raphiccorrelati on,thenature and de- velopment of sedimenta rybasins and theirsubsequent de- formation were themain objectives of the project and re- sultsofmuch ofthisresearchwerepublished in aGeolog ical SurveyofNorw aySpecialPublicat ion (Rober ts&Nordgu len, eds.1995).

The VarangerPeninsulaandthe adjacent Rybachi-Sredni Peninsu lasof NW Russia(Fig.1)areimportantareas for un- derstand ing the Neoprot erozoic geology of the northern FennoscandianShieldfor severalreasons.These areasare in- terpret ed asthe northw esternmost partoftheTiman -Kanin - Varang er Belt and arethebest exposed,and perhaps the most thoroughly studied, segment of this elongate tectonic structure.A lithostratigraphy is well establishedand suppor- ted by a fairly wellknown time-stratigraphybased onvari- oustechniques (see e.g.Siedlecka 1995a).Correlation bet- ween the segmentsof the st rat ig rap hic record has recently been out lined (Sied leckaet al 1995a,1995b,Sochava1995) (Fig. 2).Environ me nts of depo sit ion based on sed im enta ry facies analysis in the various format ion s are fairly well

known.This

is particularly true for the Varanger Peninsula.

tDeceased2lst.July1997

New research has also improvedour understanding of the nature of the sedimentary environments in which the Neoproterozoicsuccessionsof Rybachi and Sredniwere ac- cumulated(Sied lecka 1995b).The geologicalhistory of this area may therefore provide a useful reference frame for the wholeof theTiman -Varang er Belt,providing that also its bedrockgeochemis try is studied to someextent.

While there are geochem ical data available from the RybachiandSredni Peninsulas, relatively little atte nti on has been paid to the importance of geoche mistry of the Neoproterozoic rocks of the Varang erPeninsula,for an un- derstandingof the palaeotectonic setting,nature of the prov- enance area(s)and the processes behind theformation of the stratig raphicsuccessions .Some geochemical data from theRybachi-Sredni areas have been published in Russian, wit h only two recent contributions in English (Siedlecka 1995a, Sochava 1995). On Varanger, wit h one exception (Siedlecka 1995a).geochemi caldata were non-existent. For thisreason, themajority of theNeoprot erozoi cfor mation s on Varanger Penin sulahavenow been sampled and sofar analysedjustformaj or eleme nts.The results havebeen stat- isticallytreated along with the available analysesfrom the Rybachi-Sredni successions, and these are discussed joi ntly inthis paper.Thegeologyof the discussed areas is shown in Fig. 1,and Iithostratigraphies and correlation in Fig.2 .

NGU-BULL 432 , 19 9 7- PAGE78 ANDREI V.SOCHAVA&ANNASIEDLECKA

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Ourobjectivesare asfo llo w s:(1)topresent, for the first time, compreh en siv emajor eleme ntanalyti caldataon the Neo proterozoicsuccessionsofthe VarangerPeninsu la;(2) to compare these compositions with tho se of the Rybach i- Sredn i area;(3)to evaluate the useful ness of major elem ent co m positio nfo rabetterunder stan di ng of thenature ofthe provenanceareaand basindevelopment; and(4)to provi de a reference frame forfurther interpret at ion ofthedevelo p- mentoftheTim an-V arang erBeltin Neoproterozoictim e.

Geo log ical framework

Neoproterozoic successio ns of the coastal area s of East Fin nm ark (No rway) and nort he rn coastal Ko la Peninsula (Russia) occurin five separate regions(Fig.1B):

(1) Barents SeaRegion(BSRJ,northeasternVaranger Peninsu la;

(2) Tanafjor de n-Varan ger fj o rdenRegion andGaissa Nap pe Complex(TVR),so uthweste rn Varang er Peninsu la;

(3) Ryb ach iPeninsul a(RP);

(4) Sredn iPen insu la(SP);and

(5) Kildin Island (KI),notinclud edinthis study,acor rela- tive succession to that onSred ni.

The Neoproterozoi c stra tigra phic succ essio ns preserved in these areasare separate d fro m eachot he reith erby fault li- nes,e.g.theTro llfj orden-Ko m agelvaFault Zone (TKFZ)and Sred ni-Rybach iFaultZo ne(SRFZJ,or geo g rap h ically(Fig. 1).

Alo ng strike theyexhibit similar itie sin overall facies deve- lop ment and thick nesse swhile across the majorfaults, i.e.

across regional depositio nalstrike,the y aretotallydifferent.

Arift basin witha precu rsorfault tothe TKFZ andSRFZ asthe riftmargi n-forming str uct u rehasbeen suggest ed asthesite ofaccumulatio n ofthesesuccessions:basinal (alsoreferre d toas mio geocl in al oralloch thono us)north eastofthe fault, andpericratonic (autochtho no us)so uth w est of the margina l escarpm ent (Siedlecka 1975, 1985, Sied lecka & Robert s 199 5).

The BarentsSeaRegio n comprises the most com plete basinal succession,consisting of two groupsseparat ed from eachother byamaj o r angular unconform it y andhaving a maximu m thick n ess up to 15 km.The lower,Barent s Sea

ANDREIV.SOCHAVA

s

^{ANNA SIEDLECKA NGU-BULL432, 1997- PAGE 79}

Group is a c.9000 m-thickcontinuous successioncommen- cing withasubmarineturbiditesystem and terminat ingwith fluvial and coastaldeposits.The upper, Lokvikfjelle t Group is a c.6000 m-thicksuccession of predominantly shallow-marine sedimentaryrocks(Levell 1978).The Rybachi segment ofthe basinal succession consists of the cAOOO m-thick Rybach- inskaya Supergroup,whichis comparable to and suggested

to be stratigraphical lycorrelativewit h the lowermostpart of the Barents SeaGroup in the BSR(the KongsfjordFormation (Fig. 2) (Siedlecka et al. 1995a).Both units represent sub- marine turbidite systems. The substratum of the basinal successions is nowhere exposedand its nature may only be interpreted from the petrographical and geochemical composition of the Neoproterozoicsedimentaryrocks.

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NGU-BU L L432.1997 - PAGE80 ANDREIV.SOCHAVA& ANNASIEDLECKA

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ANDREJV. SOCHAVA&ANNA SJEDLECKA

Bycontrast, the pericraton ic successionsrest unconfor- mably on the older Precambrian crystalline substratum, partsof whichconstituted the obviousprovenance area or areas(Sied lecka 1995a).They consist mainly of fluvial,coas- tal,shallow-marine and deltaicdepositswhich, on Varanger Peninsula andfurt her to thewest,include theVarangerian glacial record.The pericratonicsuccessions are characteri- sed by several unconformities;themostpronounced ofthe- se arethe pre-Ekkereya and pre-Smalfjord unconfor mities onVaranger, and the pre-Volokovaya unconformit y on the SredniPeni nsula (Fig.2).lnspite ofthegeographicalproxi- mity between theTVRand the SP (and Kildi n Island). a st raig htforward Iit host rati g raphic correlatio nis not possi- ble.Stratig raphic correlat ionalong strike and acrossthe marginalfaultzoneisthereforebasedon the integ ration of a variet y of featu res and meth ods,primarily microfossils, st romatolites, radio metr ic ages and field evide nce (see Sied lecka 1995for references).The importance of unconfor- mitiescannot be assessed too lightly,particularlythe'mis- sing link' pre-Ekkereya unconformity in the Lille Molvik- Trollfjordenarea(Rice 1994) (Fig.1C).

Material and analytical methods

Major elementcompositionsof 461 samples of theUpper Proterozoic sandstones, siltstones,clayey shales and carbo- nate rocksfrom the Varanger (23 1 samples)and Rybachi and Sredn i (230 sample s) Peninsulas are included in this stu dy. FromVaranger, sandstones are represented by 129 sample s,siltst ones by 40, clayey shales by 46 andcarbonate rocksby 16sampl es.Thefollow in g collections ofsamples wereused:

Varanger Peninsula: (1) 188 samples collect ed by A.Sochavaundertheguidanceof A.5iedl ecka, analysed by using convent ionalwet chemic alanalyses;(2) 34 sam ples from the Kongsfjordand Berlevaq Format io ns; and 9sam- plesfromtheNyborg andGol neselvaFormation s, all collec- ted byA.5ied lecka and analysed by the XRF meth od.

Rybachi-Sredn i Peninsulas: 216 samples collecte d by A.5ochava and 14 by A.Siedleckaon Rybachi-Sredni,all ana- lysed by the XRF technique .

The analyses of the 188 samples collected on the VarangerPeninsulaconstitutethe coreof thiscontribution.

The analyt ical data have been listed in an unpublished report(Sied lecka1996). Resultsofanalysesof the samples collected previously byA.Siedlecka have been repor t ed in Siedlecka (1995a). The average major element composi- tions of the main rock-types from the format io ns on Rybachiand Srednihave been presented in Sochava(1995).

The individ ual analysesfrom these areas have not been published.

The mean compositions of the sam ples from variou s formations on Varanger Peninsula are shown inTables 1 and 2,and of allsamples used in the cluster diagrams in

T able 3.

NGU-BULL 43 2 ,199 7 - PAGE 81

Major element geochemistry:

classification plots and cluster dendrograms

Sandstones were categorised by adopting the chemical classification diagram of Pettijohn etal.(1987). This classifi- cation has the advantage of defining the petrographic names of differenttypes of sandstone.We usethese names later inthis paper while describing and discussingthe che- mical characteris ticsofthe analysed rocks.

The distribution pattern which emerges from the plots (Fig.3)show sthatthe sandsto nesrangeinchemical (i.e.min- eralogical) mat uri ty from greywackesor arkosesto quartz arenites.Thesandstonesof the Barents Sea Group (plot A) seem to showatrendof increasingmat urit y upwards inthe st ratigra phicsectionand,atthe sametime,a disti nct decrea- se in relative sodium content. Sandsto nes of the Sandfj ord enFormati on of thel.ekvikfj elletGrou p exhibit the highest maturity in theBSR,while theBerlevaqFormation, which is thrusted upon the l.ekvikfj ellet Group,is compara- blein chemical signat ure to the KongsfjordFormation.The Tanafjorden Group comprises sandstones of moderate to high maturity,whilethe Vestertana Groupin its lowerpart is dominated by immat ure sandstones,especially the grey- wackes of the Nyborg Formation(plot B).Sandstones of the Vadse Group show a clearbimodalityin maturitywitha pre- dominanceof subarkoses(plot C),whilethe Srednisuccessi- on contains sandstones which exhib itaconsiderablescatter (plot D).There is,however,a distinc t trend in the lower Kildinskaya Group,from arkosesinthe Pyaryajarvinskaya to quartz arenites inthePalvinskayaFormat io n.There is alsoa second diff erent trend from the lit hic arenites of the Poropelonskaya to the K-enriched arkoses of the Zemle- pakht inskayaFor mation .Plot Eshows theimmatu renature ofsandstones of the Rybachinskaya Supergrou p,compara- ble to that of the Berlevaq, Kongsfjord and Nyb org Formations (plot A).Interpretat io ns of these distribution patt erns are presented later,alongwit ha geochemica lsub- divisionof the rocks asindicatedby cluster dendrograms.

Clayeyshaleswereclassifiedinternaryplot s devised by Golovenok(1977)(Fig. 4).The plots show that the shales fall mainly within or closeto the illitefield. Some fairly clearde- partures from this pattern wererevealedin the Batsfjordand Tyvjofjellet Formations in the upper Barents Sea Group,in the Tsypnavolokskaya Format ion on Rybachi and in the Karujarvinskayaon Sredn i (Fig. 4).These deviations are ana- lysedlater along with sandstones,with the cluster dendro- grams, anddiscussedin a wider stratigraphiccontext.

The above classificationsof sandstones and shales are based on the use ofratios of onlythree or four elements.This means that the majority of theanalyticaldataandinforma- tionprovidedby abou t10 majorelements are notincluded.In orderto fillthisgapwetreatedour databy applyinga statis- ticalcluste r programme.Clust er analysisapplied togeoch e- micaldatais basedoncomplete major elementinformat ion and provides atoolfor groupingtogether closelyassociated

NGU -BULL432, 1 9 9 7 - PAGE 82 ANDREIV.SOCHAVA

s

^{ANNASIEDLECKA}

rocksasreflectedby theirchem icalcomposit ion.

The analysedrocks clustertogethe r into severaldistinct groups onthe basis of their relativelyclose similarityin com- positi on (Figs.5 - 7).Adecreasing degree of similarity is shown bythe ste pwise higher levelwithin group distance

shown bythe dendrograms.

Several characteristicsof the studied rocksemerge from an analysisof the clusterdendrograms(Figs.5 - 7).The most conspicuous is the clustering of sandstones (Fig. 5).

Therefore,our analysisof the clustering patterns startswit h

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•

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1.0 0.9 0.8 1.0 0.9 0.8

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Fig.4.Neoproterozoicclayey shales ofthe Varanger,RybachiandSredniPeninsulason the diagrams AIP3/ (AI20 3+MgO +K2)vs.K20(AI203+MgO+K20) (Golovenok 1977).

ANDREIV.SOCHAVA&ANNA SIEDLECKA

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NGU-BULL 432,1997- PAGE83

WITHIN GROUP DISTANCE (Inunites of qUBs i·Eu c lideandist anc e )

1

Lithi c arenites 4 greywa c ke s&arkose s 5 Greywa ckes

2

NGU-B U L L 432,1997 - PAG E84

that of the sandsto nes and issupplementedwith thecluster- ingpatterns ofassociated siltstonesand clayeyshales.

The maj ority of sand stonesof the analysedformati ons fall into the supergroup 1,groups 1-3(Fig. 5.).They represent sandstones ranging from quartzarenites to arkoses,arechar- acterised by usually high Si02,predo m inance of K20over Na20,Fe203 over FeO,fairly highTi02andmostly low MgO.

The second superg roup, groups 4 -6,has com paredwit h the first supergroup, a significant ly lowerSi02 content ,higher Na,O,AI,03T and MgO.Itconsi stsprimarily of greywackes.

The patt erns for siltstone sand clayey shales exhibit more scatter and are clusteringintoeleven and seven groups,re- spectively.Interest ing ly, a combi ned approach to the sand - sto nes,siltstonesandclayey shales asthey occurin thest rati-

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ANDREIV.SOCHAVA& ANNA SIEDLECKA

graphic successionsshows bothsome strikingsimilariti esas wellas some anomalies wheresimil arit ies could normally be expecte d.Thelatter deservespecialattention .Thisispart icu- larly trueforthe sand stonegroups 2 and3.Althoughthereis an overalepattern of clustering ofthe formations from the basinal realm separately from those of the pericratonic realm,there are also several examples of both realms being representedin one clustergroup. For convenience,in the ana- lysis whichfollows they are labelled(b) and(p). respectively.

The Kongsfjord(bl, Berlevag (bl and Nyborg(pl Formations, and the Rybachinskaya Group(bl The Kong sfjo rd greywackes occur mostly in group 5while those in the Berlevaq Formation and the Rybachinskaya Group distinguish them selves by having maximum values

WITHIN GROUPDISTANCE

0.03 0.06 0.09 0.12 0.15 0.18 0.21

ANDREIV.SOCHAVA&ANNASIEDLECKA

for Na20,CaOandAI20 3and cluster toget her intogroup 6 (Fig.5).Silt st o nes associated with greywackes(Fig.6,part s of group s10 and11)exhib it veryhig h AI203conte nt s.The maj- orit yof theclayey shales cluster in group 1(Fig.7)and are charact eri sedby maximum conte nts of Nap and MgO,high FeOand CaO,low K20 anda sig nificant predom inance of FeO over Fe203'These characterist ics do not deviate much fromtho se of the greyw ackes withwhich theshalesare as- sociate d.How ever, in theKongsfjo rdFormat ion abimodality in the shale co mposit io n is registered(Fig.7).lnfact,the maj- ority of Kongsfjordshales cluster in group 7 comprising illitic shales with high A120 3,FeO and K20 contents. Asimilarbi- modal distribution may be traced for the shales of the Nyborg Fo rm ation (Fig.7,groups 2 and 4).The shales of group 4have a com positio n contrastin g wit h therem ain der of theform ation by having min im alcontents of AI203and Na20,maximalMgO content and relativelyhigh K20 .These characte ristics arenotdiscernibl e on the classificat io ndia- gramm e,Fig 3. Inadd it io n,shalesofthe Nybor g Fo rm at ion

Fig.7. Cluster dendrogramfor clayey shales.

NGU-BULL 432,19 9 7 - PAGE 85

are usually redand showa predominanceofFe203over FeO.

They can beinterpreted asilli t icwit h somechlorite admix- ture, and are similar to the shales of the Karuj arvinskaya, Tyvjofj ell et andBatsfjord Formationsin term s of theirhig h MgO content. Shaleswith a highadmixtureof dolo mit icce- ment and dolo m it es are also present in the Nyb o rg Formati o n(Table1).

The Sandfjorden Formation (b}, the Tanafjorden Group(p },and the Veinesbot n(p},Ekke raya(p}, Stappogiedde(p},Pyrayarj arvinskaya(p} and Palvinskaya(p}Formation s

Sandstonesof theseunits are characterised by the highest contents of Si02,low co nt ent s ofall other elements and a pred o m inance of K20over Na20(Fig.5,group1).

TheVagg eFo rm at iondiffers from the remaining form at i- ons of theTanafjord enGrou p by bot hthepresence ofarko- ses withahighconte nt of K20 andoflit hicarenite with a predomina nce of Na20 over K20 (Fig. 3B,Tab le 1).On the

WITHINGROUP DISTANCE

0.03 0.06 0.09 0.12 0.15 0.18 0.21

I I I I I I r

NGU- B U L L 432, 1 9 9 7-PAGE 86 ANDREIV.SOCHAVA&ANNASIEDLECKA

5andstones

Formation BerlevAg Kongsfjord BAsn",ringen Batsfjord Tyvjofjellet 5a ndfjorde n Veinesbotn Klubbna sen Fugleberget

Numb.of samples,---- 7 - ^{26 8 1 7 9 5 - 4 8}

5i02 79.14 7.13 76.10 6.53 74.67 3.45 80.84 77.37 5.07 93.95 1.63 97.38 1.37 82.82 7.13 82.82 2.13

Ti02 0.59 0.50 0.80 0.29 0.82 0.26 0.54 0.64 0.21 0.16 0.18 0.03 0.00 0.49 0.15 0.99 0.14

AI20, 8.25 2.66 9.71 3.00 10.14 1.87 6.64 7.26 2.47 2.45 0.67 0.70 0.44 7.01 2.73 6.00 0.57

Fe20, 2.79· 1.05 5.04· 1.66 1.05 0.66 1.03 2.12 1.20 0.12 0.16 0.31 0.27 0.21 0.23 0.87 0.54

FeO 3.24 0.68 3.05 0.52 0.24 0.45 0.28 0.07 0.13 2.68 1.55 1.82 0.32

MnO 0.07 0.04 0.06 0.02 0.06 0.02 0.01 0.03 0.03 0.01 0.00 0.01 0.00 0.01 0.00 0.03 0.03

MgO 0.79 0.23 1.65 0.60 1.65 0.28 1.91 1.86 0.59 0.27 0.15 0.03 0.02 0.88 0.62 0.80 0.27

CaO 1.89 1.40 1.05 0.68 0.67 0.35 0.27 2.01 1.30 0.35 0.08 0.10 0.10 0.30 0.03 0.84 0.53

Nap 2.52 1.09 2.06 0.60 2.00 0.62 0.53 0.61 0.19 0.09 0.11 0.01 0.00 1.05 0.37 0.72 0.08

K20 1.12 0.64 1.37 0.79 2.71 0.68 2.52 3.49 1.03 1.08 0.46 0.39 0.31 2.65 0.71 2.84 0.30

Pps 0.07 0.05 0.13 0.04 0.12 0.03 0.11 0.10 0.04 0.02 0.01 0.03 0.00 0.12 0.04 0.13 0.02

LOI 2.06 1.16 2.02 0.66 2.79 0.50 2.25 3.50 1.08 0.75 0.20 0.23 0.06 1.47 0.84 1.75 0.80

Tot al 99.29 99.99 99.92 99.70 99.51 99.70 99.29 99.69 99.61

5andstones

Formation Golneselva Ekke roya Gronneset 5tangenes Dakkovarre Gamasfjellet Vag ge Hanqteceerro Smalfjord : "

Numb.of_{sa m pl ~}_ 3 - - - 1 - 4 1 5 4 3 ^- 3 3

5i02 90.44 5.74 92.65 87.81 8.28 95.18 93.58 3.36 97.58 0.20 80.43 9.86 95.97 2.13 82.26 2.20

Ti0 2 0.15 0.08 0.03 0.22 0.20 0.04 0.07 0.06 0.03 0.00 0.34 0.10 0.05 0.05 0.42 0.06

AI20, 4.38 2.70 1.75 6.37 4.73 1.35 2.49 1.61 0.79 0.67 5.82 4.55 1.46 0.99 7.30 1.17

Fe 20, 1.13· 0.23 1.04 0.31 0.35 0.94 0.35 0.30 0.01 0.00 5.66 5.12 0.01 0.00 0.78 0.16

FeO 0.80 0.23 0.17 0.10 0.35 0.40 0.10 0.00 1.49 1.04 0.10 0.00 1.79 0.21

MnO 0.02 0.00 0.09 0.01 0.00 0.03 0.02 0.00 0.01 0.00 0.07 0.07 0.01 0.00 0.02 0.00

MgO 0.21 0.09 0.49 0.20 0.19 0.05 0.17 0.13 0.04 0.00 0.47 0.25 0.08 0.07 0.98 0.11

CaO 0.03 0.03 0.97 0.16 0.03 0.05 0.16 0.09 0.14 000 0.14 0.00 0.14 0.12 0.32 0.08

Nap 0.60 0.28 0.10 0.83 0.60 0.39 0.32 0.13 0.02 0.00 0.41 0.35 0.09 0.07 1.26 0.17

K20 1.87 1.10 0.30 2.67 1.99 0.42 1.28 0.71 0.16 0.10 1.23 1.58 0.60 0.49 2.51 0.47

Pps 0.04 0.03 0.02 0.02 0.02 0.02 0.04 0.05 0.01 0.00 0.05 0.00 0.03 0.00 0.09 0.00

LOI 0.44 0.48 1.32 1.14 0.62 0.85 0.85 0.38 0.54 0.16 2.10 0.61 0.55 0.20 2.09 0.24

Total 98.19 99.56 99.97 99.42 99.68 99.43 98.21 99.09 99.82

d C b be

dlarn kt ite s 5 d

Fe total as Fe203

an stones aronate- anng san stones

Formation Nyborg Mortensnes·· 5tappogedde Basnc.eringen BAtsfjord Tyvjofjelle t Fug le berget Dakkova rre Gra sda le n Numb.ofsamples . 9

-

1 4 1 8 1 1 1 1

5i0 2 72.02 3.04 71.22 89.08 6.61 63.95 66.55 10.61 78.00 64.52 77.21 59.17

Ti02 0.80 0.09 0.48 0.18 0.12 1.23 0.41 0.14 0.51 0.99 0.06 0.02

AI20, 11.47 1.32 9.78 3.60 1.33 6.75 6.11 2.18 4.82 6.73 1.43 0.49

Fep, 5.24· 0.75 0.95 0.46 0.58 0.61 0.64 0.50 0.59 1.99 2.6 1 0.01

FeO 2.27 0.39 0.26 3.35 1.72 1.27 0.90 1.91 6.76 0.10

MnO 0.08 0.01 0.07 0.03 0.00 0.43 0.09 0.04 0.09 0.25 0.58 0.01

MgO 2.17 0.42 2.42 0.69 0.90 5.14 3.82 2.55 2.89 3.72 1.99 9.19

CaO 0.57 0.25 2.22 1.0 1 1.74 5.70 7.35 3.15 3.80 5.91 0.42 11.68

Nap 3.24 0.79 2.00 1.0 1 0.52 1.40 0.60 0.26 0.60 0.82 0.13 0.18

Kp 1.16 0.60 2.46 0.99 0.42 1.17 2.58 0.72 2.34 3.15 0.70 0.14

P20 S 0.09 0.21 0.09 0.03 0.02 0.48 0.07 0.02 0.06 020 0.11 0.01

LOI 2.66 1.40 5.77 2.34 2.47 9.78 10.06 3.74 5.80 9.79 7.27 18.78

Tot a l 99.50 99.73 99.81 99.99 100.00 100.40 99.98 99.27 99.78

.. ...

5iltstones

Formation Kongsfjord BAsn",ringen BAtsfjord Tyvjofje lle t 5andfjorden Klubbna se n Ekkero ya 5tangenes Dakkovarre

Numb.ofsa mp le s. 4 2 3 1 1 3 3 2 2

- -

5i02 71.27 2.03 67.18 59.77 9.33 59.89 77.20 63.38 4.67 73.99 2.07 68.09 70.07

Ti0 2 0.79 0.07 1.04 0.67 0.15 0.81 1.33 0.8 2 0.14 0.49 0.20 0.64 0.69

AI2O, 12.51 2.43 14.33 11.53 2.40 13.69 8.37 12.65 2.00 12.39 1.64 12.38 14.58

Fe20, 0.78 0.31 0.47 3.24 1.62 4.49 0.76 0.84 0.48 1.91 0.38 2.97 1.05

FeO 3.59 0.61 5.85 1.77 0.68 1.90 5.02 5.78 0.60 1.86 0.36 3.89 2.33

MnO 0.05 0.03 0.09 OOn 0.05 0.04 0.04 0.16 0.24 0.06 0.04 0.11 0.02

MgO 1.77 0.29 2.43 5.49 2.81 5.23 1.27 3.08 0.89 1.19 0.13 1.50 1.17

CaO 1.40 0.75 0.55 4.20 4.17 2.22 0.28 1.93 2.60 0.22 0.17 0.35 0.21

Nap 2.43 0.65 1.69 0.35 0.16 1.08 0.06 1.91 0.08 1.22 0.27 2.19 1.83

K20 2.08 1.07 2.94 4.27 1.01 5.38 3.08 3.41 0.49 3.73 0.45 3.34 4.72

P20S 0.09 0.07 0.18 0.16 0.04 0.16 0.08 0.21 0.03 0.08 0.03 0.07 0.07

LOI 3.48 0.23 2.63 8.63 6.77 5.80 2.88 5.69 3.65 2.63 0.21 4.53 3.06

Tota l 100.24 99.38 100.14 100.69 100.37 99.86 99.77 100.06 99.80

5iltstones

Formation Vagg,,---- Grasdalen Smalfjord'" Nyborg 5tappog iedde

Numb.of sam ple s. 2 2- 5 - ^{1 5}

5i02 73.33 64.43 68.86 4.71 75.58 68.59 2.06

Ti0 2 0.52 0.67 0.55 0.11 0.49 0.67 0.05

Alp, 13.06 13.48 11.97 2.00 9.39 12.87 0.63

Fe p, 1.67 1.17 1.29 0.31 0.48 1.75 0.37

FeO 1.68 2.82 2.58 1.64 2.87 3.33 0.30

MnO 0.02 0.0 1 0.04 0.00 0.05 0.11 0.03

MgO 0.69 5.72 2.58 0.57 1.49 1.67 0.56

CaO 0.2 1 1.25 1.47 0.42 0.70 1.14 0.45

Nap 1.24 2.10 1.70 0.68 1.80 2.51 0.34

K20 4.35 2.84 3.18 1.47 3.08 2.68 0.55

Pps 0.06 0.11 0.12 0.00 0.10 0.12 0.00

LOI 2.55 5.23 5.08 0.78 2.98 4.43 0.60

Total 99.38 99.83 99.42 99.0 1 99.87

Carbonate-bea rinosiltstones Tyvjofjeller Grasdale n 5malfjord· ·

-

2 1 1

50.92 55.10 65.86

0.54 0.67 0.54

7.91 12.86 10.59

2.00 1.37 1.03

1.51 1.67 2.39

0.14 0.06 0.06

8.18 5.60 3.07

9.34 5.84 3.20

0.39 1.60 1.60

3.11 3.87 4.00

0.09 0.17 0.13

15.70 11.18 7.40

99.83 99.99 99.87

Tabl e1.Meancom posit io nof UpperProterozoic sandsto nesandsiltsto nesofthe Varanger Peni nsula (leftvalues-averages;rightvalues-standard deviati on s) (162samples)

ANDREIV. SOCHAVA&ANNA SIEDLECKA

clusterdendrogram,thelith ic arenite is similar to the sand- sto nes of the Zemlepak ht inskaya and Basnceringen Formati on s (Fig.5).

Siltstones showsimilar charact eristicsto the sandst ones;

they are Si02- rich,and low in AlP 3and Na20, and thereis some variabilityin MgOconten t.Themajor it yof theclayey shalesassociatedwith these sandstonesandsiltsto nesareil- liticincomposit ion andexhibit high, orthe very highestre- gistered K20 cont entsand high A1203.On thedendr ogram (Fig.7)theycluster mainl y ingroups3 and 6,prim arily be- cause of the differe ncesin thecont ent s of CaO and MnO (Iow in group 3) andof Ti02,Fe203(hig h ingroup 6),Si02 and CaO (minima l in group 6).Shales of the Sandfjorden Formati on have the high estmean conte nt of K20 and lo- west Na20 in the st udied set and plot in thefield of illitic shales(Table1,Fig.4).On thecluster dendrogra m, two sha- les of this formati onforma separategroup6characterised byhigh A1203,Ti02,Fe203andespeciallyK20 (Fig.8,Tabl e5).

These shales have the high est mean content s of LOI and showatendencyto swellingsimilar tothat seen ink-be nto- nitic clays.

The sing lesample of siltsto ne,as wit h the shales, has highTi02and hasthelow estmeancont ent ofNa20 in the st udiedset(Table1).

TheStapp og ieddeForm ation has a comp lex major ele- ment geochem istry.The sandsto nesrange from fine-grai- ned to coarse-grainedsuba rkosesandsublit hicarenites(Fig.

3).Thesandst ones have approx imate ly the same mean con- tent s of Na20andK20 wit hapredo minance of theformerin one of the samples,and they resemblesome of the samples from the Stangenes and Kuyakanskaya Form ation s.

Silt ston es are distingui shedbythehigh est Na20 meancon- tentin thesetand showa similarityto some(the mostpoly- mictic) of the siltsto nesin the Pyaryaj arvinskayaFormati on (Ta ble1,Fig.7).Shales haverelativelylowAI203andK20 con- tent s and areinclud ed in group 1on the clusterdiag ram (Fig.8).They are composi ti onally similar to shales of the TsypnavolokskayaForm ation and thereis alsosomesimilari- ty to shales of the Rybachinskaya Supergroup and the Porop elon skaya and Kongsfjo rd Form at ion s.The presence ofred beds in theSta ppog iedde Form ati on is reflecte d in thepredo minance of Fe203overFeO in the composit io nsof sandstonesand shales (Table1).

The Basnceringen(b), Batsfjord(b) and

Tyvjofjellet(b) Formations, the bulk of the Vads0 Group(p), the Vagge(p), Smalfjord(p) and

Mortensnes(p) Formations and the

Poropelonskaya(p),Zemlepakhtinskaya(p), Karuyarvinskaya(p) and Kuyakanskaya(p) Formations

Groups 2 and 3 on the clusterdendrogram for sand stones embracesubarkosesto arkoses,subordinate sublit hicareni- tes,and have atransit ional position between group1onone

side and groups 4 to 6 on the other

(Fig. 5).

The sandston es

NGU-BULL432,1 99 7 - PAGE 87

clusteringingroups2and3 arefrompart s ofthestratigrap- hic sect io ns in both basinaland pericratonic realm s.When analysing grou ps2and3 of the sandsto nedendrogram in combination wit h the stra ti graphic posit ion of the samples, it appears thattheyrefl ect, at leastpartl y, a distinc tgeoche- micalchange(1)upwards in theBasnceringenFormation,(2) fromtheKlubbn asentotheFugleberget Format ion and(3) from the Porop elonskaya to the Zemlepakhtinskaya Form ati on. The sandsto nes of the low er Basnceringe n Formation ,for example,representgreywackessimilar totho- se of the Kongsfjord Form ation.High er up,however,the Basnceringen sandsto nesare geochem icallydifferent:they havehigh er K20 and Si02conten tsand also higher MgO, Fe203T and Ti02.The more K-Fe-andCa-rlchvarietiesshow an aff inity wit h the sandsto nesof the overlying Batsfj ord and Tyvjofj elletForm atio ns,andthis same feature applies to the siltsto nesand clayey shales.Ontheot herhand,thegrey- wacke-akinsandstonesof theBasnceringenForm ation may be geochemically loosely compared to those of the Klubbnasen Form ati on, and those wit h Kp>Na20 and Fe203>FeOtotheFuglebergetFormation.The sandstonesof thelatt erhavethehigh estTi02cont ent inthe stu died set, presumably caused by a concentration of heavy minerals - prob ably tit anom agnet it e, ilmenit e and leucoxene. Silt- sto nesof thisform ation also havehighTi02contents (Table 1),and there is also some similarity to sandsto nesof the Tyvjofj ellet and Puma nskaya Formati on s. Shales of the FuglebergetFormati on, on the ot her hand,aredistingu ished bythe highe st mean conte ntsof A1203,Ti0 2,Fe203and P20_S and one of the high est K20 conte nts in the st udied set (Table2).Thenot abl e predominanceof Fe203over FeO dis- tingui shes these shales from those in the under lying Klubbnasen Form ation.

The Porop elon skaya sandsto nesshow a very scatte red patte rnofthe major eleme ntcompos it ions,whileshalesare illit ic wit haNa-feld spar admixt urecomparable to theGroup 1 shales of the Kongsfjord Form ati on (Fig. 7). The Basnee rinq en suba rkosesshow an affinity wit h bot h the Zemlepakhti nskayaand the Kuyakanskaya Formati ons (Figs.

3 and 5, groups2 and 3).Shalesof the overlyin g Zemle- pakht inskaya, on the ot her hand, areakin to those of the Batsfjord-Tyvjo fje llet Form ation s in terms of K20>Napand Fe203>FeO. Inaddi tio n, the Klubbnasensandsto nes,are si- milartoboth the Basnceringenand the Zem lepak ht inskaya (and the Smalfjo rd) Formati on s with a disti nct predo mi- nance of FeOoverFe203.On the cluste rdendrogram they appea r in groups2to4,rangingfrom arkoses togreywackes (Figs.3 and 5).Anoth er featureofinterest isthe fairly high contentsofP20_Sin shales oftheFugleberge t Formati on and in the siltstones of the Zemlepak htins kaya,whichare also comparable on ot her geochemica l and sedimen to log ical grounds (cf.Sochava199 5, Siedleckaet al. 1995a).

Dolomite-ceme nted sandsto ne wit h intraformational clastsof sandsto ne fromthe lowerpart of the Basnceringe n Form ation have relat ively

high

cont ent s of Ti02,MnOand

NGU- B U L L432,1997 - PAGE 88

P₂0_S (Table 1).Phosphate-bearing sandstoneshave been describ ed from this stratigraphicunit(Neg rutsa et al. 1995).

A high Ti0₂ conte nt in siltstones of the BasnCEringen Formation may reflect a concentration of heavy mineral s.

Sandstones and siltstones wit h high cont ents ofTi0₂ are known also from the ZemlepakhtinskayaFormation of the SredniPeninsula(Negrutsa1971).

Arkosesandlit hic arenitesof theBatsfjo rdandTyvjofjellet Formation s clusterin group 4.Those which have aconsid e- rableamount of carbo nate cement areexcluded from the cluster dendrogram.The predominance of Fe_{20 3} in the sandstones,silt stones andshalesreflect thepresence of red beds.Shales andsilt stones usuallycontain anadm ixt ure of carbonate(high MgOand CaO)andarecomp arableto those of the Karuyarvin skaya Formation (Fig. 7, group 4).

Carbonate rocks (Batsfj ord Formation:3 samplesof dolo- mite,onelimestoneand onedolomitic limestone)are usually represented by inter bedded thin layersof fine-grained car- bonateandsiltst one and have a relatively highad mix tu reof silica(Table 1).

Geological significance of the major element geochemistry: source areas, tectonics and palaeogeography

Thecluster dendrograms,and particularlytheoneforsand- stones(Fig.5),will againbe astart ing pointin the discussion whichfollows.Thetwo supergroupsemerging on thisden- drogram reflect (alongwith the st atisti cal data on dend ro- grams for silt stonesandshales)thepresence of twomajor associatio nsof rocks.

Thefirst association may beinte rpreted asaproduct of denudati on of the continental crust.It is mostlyrepresented by sediments occurring in the succession softhe perlcrato - nic areas of therift basin(TVR and SP).The second associa- tion has a different geochemical signature, characteristic for the basinalsuccession s(part s of theBSR and RP).Rocks of some form ations,however,plot both in the first and inthe second association ,and obviously groups3 and 4 of the sandst ones representan intermediateor 't ransiti onal' major element geochem istry,which appearsto have some strati- graphicimpo rt ance.Therefore,further on,we use the term transitional because itreflects betterthe stratig raphiccon- text s andis explai nedby changes ofenvironmen ts of depo- sition and provenance areas with time. The arkosic BasnCEring enFormation,forexampl e, is alarge progradatio- nal slope-prodelta-de lta plain succession (Sied lecka &

Edwards 1980, Siedlecka etal1989) wit ha swichfromare- trogradational Kongsfjord- lowermo st BasnCE ringen deve- lopmen t toa progradational trend higher up. Therefore,de- pend ing from which part oftheBasneerinq en Formation,lo- werorupper,the samplesweretaken,they willshowsimila- ritieseither to the Klub bnasen,considered to represent a prodelta, asthe lowe r Basneerinqen does,or e.g. to the Zemlepakhtinskaya and Fugleberget Formation s,both of

ANDREIV.SOCHAVA & ANNA SIEDLECKA

whichareinterpreted as deltafront and braided fluvial plain sedimen ts(Banks et al. 1971,Siedleckaetal.1995a)as with theupperBasnCEring enFormation.

The geochemi calchanges also suggestthe possibilityof a change in composition of the provenance area, which might have resulted eitherfrom a deeperlevel of erosion,a change of direction of palaeocurrents, i.e. directionof mate- rial supply,which might have been caused by a tectonic event and development of an unconformity.Interestingly, theunits wit h thetransitional major element geochemist ry wit hin separatesuccessions (Poropelonskaya-Zemlepakh- tinskaya,Klubbnasen-Fugleberget,the BasnCEringenForma- tion andthe uppermostBargout naya Group(comparable to the lower BasnCEringen Formation))appear to have a similar stratigraph icposition (see Fig.2).This in turnsuggests that perhaps therewas just one particulartectonic eventin the hinterland that led to changes in palaeogeography and, consequent ly,influenced the distribution of the activated sourceareas and intensifiedthe sediment supply.

Quartz arenites,abundantin the first association (group 1 in Fig.5),may reflect botha deepweath ering of sourceare- asand degradat ionof the landscape,andthe import ant role ofaeolian orwave breaker processesin rewo rkingthe clastic mate rial prior to the Neoproterozoic sedimentation .The quartz arenite-rich formations,Le.theHanqleceerro,Gamas- fjellet,and parts of Gronn eset and Veinesbotn,were acc- umulated eitheras coastal sandsandshelf blanketoras flu- vial mature sands and reflect, ingeneral terms,a tecton ic stability,peneplained landscape and along-lasti ng rewor k- ing of the sediment.

Interpretation of the majorelementgeochem istryofthe EkkeroyaFormat io n remainsuncertai n.The singlesample of fine-grained sandstone with quartz overgrowt h cement plotson the boundarybetweenquartzarenitesand sublith- ic arenites (Fig.3).Siltstones haverelativelyhigh Si0₂con- tents and are similar to the siltstones of the Dakkovarre, Vaggeand Nyborg Formations(Table1,Fig.7).Mappingand scdimentolog icaland biostratigr aphicresearchhave show n that the formationchanges laterally in thickness andlit holo- gy,that it accumulated in several different environments and that itis separated from the subjacent and overlyingfor- mationsby unconformities (Johnson 1978,Vidal 1981) (Fig.

2).Itmay therefore be assumed that somereliefrejuvenati- on and a period of bothintensifiedand diversesedimentati- on took placebefore a majo rregression and prior to accu- mulationoftheTanafjorden Group.

Quart z arenitesand arkoses are associatedwithunusual- ly K₂0-rich clayeyshales(the mean composition in several formations is >6 % wit h a maximum of c.7.4% in the FuglebergetFormation,seeTable 2).A possibleexp lanation for this specificfeatureis the absenceofvascularvegetation onthePrecambrian continents.This was the mainreason for the difference inweat hering in the Precambrian,compared to youngerperiods,particularly the substantially lower mo- bilityofpotassiumin theweatheringcrustswhich promoted