Petrology and metallogeny associated with the Tryvann Granite Complex, Oslo Region

Petrology and metallogeny associated with the Tryvann Granite Complex, Oslo Region

ODD NILSEN

Nilsen ,O.1992: Petrology and metallogeny associatedwiththeTryvannGranite Complex,Oslo Region. Nor.geol.unaers.Bull.423,1-18.

The Tryvann Granite Comple x (TGC) comprises four separat e intrusive bodi es within theOslo Graben.Itconstitutesadifferentiated suiteof young (240- 245Ma) alkalinequartzsyenitesand granitesderived from a strongly fractionated,hydrous residual meltwhichwas emplaced during the collapse of the Brerum Cauldron.The emplacement occurred contemporaneously with the formation of the ring-dyke complex. Intramagmatic vein-type molybdenite ,pyrite and Fe-o xide mineralizations occur associatedwith a widespr eadalbitichydrothermal alterationconfinedchiefly tofracture zones within the TGCcomplex. On a regional scale,thegeological patte rn,asrevealed bygravimetr icanomalies ,and the spatial metamorphicand rnetasomati calteration patternsadja- cent to the southern part of the Brerum Cauldron,indicate the existenc e of a(partly) hidden, NE-SW trending ,elongated plutonic complex to which the TGC may berelated.This complex apparently follows a centralvolcani caxis which constitutesapos sible plutonic linkbetween the Brerum and NittedalCauldrons of the OsloGraben.

O.Ni/sen,Institutt for Geologi,Universitetet i Oslo ,0316 05/0 3,Norway.

Introduction

The Oslo Paleorift constitutes a well documen- ted continental riftsystem of Permo-Carbonife- rous age. On land, the Oslo Rift forms a major graben structure - the Oslo Graben (Ramberg 1976) - which has been extensive- ly studied for more than a century.Geophysi- cal data have shown that the rift continues to the SSW into the Skagerrak sea, where it is bounded by Mid to Late Precambrian gneisses and migmatites (Ro et al. 1990).Comprehensi- ve summaries of the Oslo Rift geology have been presented by Oftedahl (1960, 1980), Ramberg (1976),Dons & Larsen (1978),Neu- mann & Ramberg (1978) and Neumann (1990).

The Oslo Graben has been subdivided into two major graben segments,termed the Vest- fold Graben (southern) and the Akershus Gra- ben (northern).Within the graben the Precam- brian basement is overlain by pre-rift Cambro- Silurian metasediments, which are folded in the central and northern part of the Oslo Regi- on. They are inconformably overlain by a thin horizon of predominantly continental, Upper Carboniferous metasediments. However, Per- mian volcanites, metasediments and plutonic rocks make up the main lithologies of the Oslo Graben.

The Oslo Rift was magmatically active for more than 60 million years.Magmatism began at about 300 Ma (Late Carboniferous),and the rift went through several intrusive and vol- canic periods up to about 240 Ma (Sundvoll et aI.1990). The tectonomagmatic evolution of the Oslo Rift has been subdivided into diffe- rent stages by Ramberg & Larsen (1978), Larsen & Sundvoll (1982) and Sundvoll et al.

(1990). After initial fissure eruptions of plateau lavas of basaltic and intermediate, trachytic composition, a period of central volcano activi- ty associated with cauldron collapses and ring- dyke formation took place. This central vol- cano stage seems to have continued into the main intrusive period with the emplacement of large batholiths of monzonite (Iarvikite), syenite and granite.The petrogenesis of these rocks has recently been extensively studied by Neumann (1978,1980,1988), Neumann et al.(1988) and Rasmussen et al.(1988).

Within the Oslo Graben magmatic rocks, chiefly of the alkaline kindred, cover more than 75%of the area.Along with the petrologi- cal and geochemical research, the metalloge- netic aspects of hydrothermal, late- and post- magmaticprocesses associatedwith the mag- maticactivityhave been investigated.Compre-

2 Odd Ni/sen GU.BULL.423.1992

10

I

1111111111111111111 1111111111 LEGEND:

Perm ian pluton ic rocks Permian volcanicrock s Cambro - Silurian me t a se dimen t s Precambrian gneisses

~

D IIJ

I

Fig.1:Key mapof theOslodistrictwith maingeologicalelements.From aterstad&Dons (1978).Insetmap(A):The Oslo Rift withgraben faults (stippled lines) and Permian igneous rocks (inblack).

hensive accounts of the geological evolution and metallogeny of the Oslo Paleorift have recently been presen ted by Vokes (1973, 1988),Ihlen(1978,1986),Ihlen & Vokes (1978) and Bjerlykke et al.(1990),and intramagmatic and related exocontact deposits of molyb- denite have been described as an important class of hydrothermal ore deposits in the OsloGraben (Geyti &SchOnwandt 1979,Ihlen et al.1982, Schonwandt & Petersen 1983,Pe- dersen 1986). The molybden ite deposits are related to highly differe ntiated extrusive and intrusive graniticrocks,temporallyand spatial- ly associatedwith the caldera formations and batholithemplacementsduringdifferentstages in the tectonomagmaticevolution of the Oslo Rift.

Biotite granites are the major host for the

intramagmatic Mo-depositswhichinclude both vein- and stockwork-type mineralization. Ba- sed on their petrography and field and age relationsh ips, the biotite granites (BG) of the Oslo Graben have been classified by Gaut (1981)into two major groups (BG1 and BG2).

BG1comprisethe older (270-260 Ma)subset- vus granites which occur as large batholithic bodies emplaced during the early batholith stage(e.g.theFinnemarkaand Drammengra- nites)(Fig.1). The BG2 granites are younger

(250-240 Ma),hypersolvus alkali-felds par gra-

niteswhichingeneralform smaller,stock-like bodies. They probably evolved as late-stage differentiation products of syenites, to which they have transitionalcontacts (e.g.in Hurdal) (Pedersen 1986).

Both types occur in the central and north-

NGU·BULL. 423.1992 Petrologyand metaffogeny 3

GEOLOGICA L MAPOf THE SOUTHERNOSLO NORDMARKREGION

o

-

Explosion breccio

Rhyoliticandtrachyticfelsite s

Gro nite- &sye ni te porphyry (Ring -dykecomp lex)

Alkal i-feld spargra nite

Alko li- feldsp'"

quartz sye nite

TRYVANN GRANITE COMPLEX

G

C7\l ~

o

Alkali-feldsparsvenite[Nc rdmcrkite ]&

syenite(G refse n-syenite]

Coarse-gra ined monzodiori te

(Kjelso sil e)

Fine-gra ined mo nzodiorite [A ke r i te]

Trochytic (rho mb - porphyr y)loves&

basol ts

Combro- Silurion me tas ed im en ts Majorfault

Fig.2:Geological map of the southernOslo Nordmark region.

tram wa y O.N.19 9 1

4 Odd Nilsen

ern part of the Oslo Grabe n and, together withalkali-feldsparsyenites andalkaligranites (ekerite), constitute mostof the plutonicrocks in the Nordmarka-Hurda len Syenite Complex of the Akershus Graben Segment (Ramberg 1976).In the Oslo distric t this plutonic comp- lex borders the Cambro-Silurian metasedi- mentsof thelowland ofBcerumand Oslo and the Bcerum Cauldron(Fig.1). Geological maps of the area under considerat ion at 1:50 000 scale have been compiled by Holtedahl &

Dons (1952) and Naterstad et al.(1990).

Between the lakes Bogstadvann and Mari- dalsvan n four separate granite bodies intrude the different syenitic rocks of the Nordmarka - HurdalenSyeniteCom plex(Fig.2).The Tryvann granite is the largest of these; and together withthe intrusionsatSkadalen,Aklungen and Hammeren itforms theTryvannGraniteComp- lex (TGC), as revealed by the common field relations,petro logyand geochemicalcomposi- tion of these four bodies.

The aim ofthispaper isto reviewthepetro- logyand geochemistryofthe TGC,with particu- lar reference to the associated late- to post- magmatichydrothe rmal oremineralization.The tectonomagmaticrelationshipof the TGCwith the BcerumCauldron will be discussed.Some preliminary ideas on the association betw een the TGCandadjace ntore mineralizationsasso- ciated with the late-m agmatic episo des in the development of the Oslo Rift have previously been presented by Nilsen (1990).

Geological setting

The Tryvanngraniteconstitutes the majorgra- niticbodyof theTGC,coveringappro ximately 10km²of thehillTryvannsheqdaand the west- ern hillsidedown to lake Bogstadvann (Fig.2).

The petrog raphy ofthisgranite has previously been presented bySeether (1962),Gaut (1981) and Petersen (1983), but no comprehensive geochemical accounts have yet been publish- ed. However, the Rb-S r age determination of the graniteat 241±3 Ma by Sundvoll (1978), Sundvoll & Larsen (1990) and Sundvoll et al.(1990) has shown that the Tryvann granite represents one of the young est magmatic rocks sofarreported from theigneou scomp- lexes of the Oslo Rift.

GU.BULL.23.1992

TheTryvann graniteconstitutes a composite stock-shaped intrusion situated close to the eastern boundary of the Bcerum Cauldron . It includes an eastern segment of medium- to fine-grained, partly porphyritic, alkali-feldspar quartz syenite,and a western segment of fine- grained, granophyric, alkali-feldspar granite of a greyish-pinkcolour. Inthe fieldthe bounda- ry between the two lithologies is transitional over a distance of approximately 100 m.The Skadalen, Aklungen and Hammeren Granites are satellite intrusions to the main Tryvann granite body.They are allfine-grained,grano- phyric, alkali-feldspar granites with irregular contacts.

The Tryvann granitehasanimportantspati- al and tectonomagmatic relationship with the Bcerum Cauldron (Figs.1 & 3). The geology of the Bcerum Cauldron has previous ly been described by Holtedahl (1943),Seether (1945, 1962)and Oftedahl (1952,1953,1978).Ithas a semi-ellipticoutline,measuringc.8.5 x10 km, and constitutes one of the best preserved cauldron structuresof theOslo Rift.Itiscom- posed of members of theyounger lava series of the Oslo region which, in a pre-cauldron stage.were intersected byfine- and medium- grained monzodiorites (akerite), syenitic plu- tons and dykes,as wellas hypabyssalporphy- ritic rhyolitic and syeniticfelsites (e.g.the Lat- hus porphyry (Oftedahl 1946,1957), and the Serked alporphyry(Holtedahl1943)).Subsequ- ent igneous activity led to the formation of numerous igneous breccia vents, ignimbrites and volcaniclast icmetasediments.To the west the cauldron borders the lava seriesat Kolsas and Krokskogen;to the nort h and to the east the various monzonitic and syenitic pluton ic complexesof the Nordmarka-Hurda lenSyenite Complex;and to the souththe Cambro -Siluri- an metasediments of the Oslo region.

The cauldron subsidence took place along a nearly vertical, cylindrical fault zone, less than 1OOmin width.Oftedahl (1953)has estima- ted a vertical subsidence of 600-700m in the southern part and approximately1500minthe nort hern segment of the cauldron.

Along the cauldron bound ary a prominent ring-dyke is exposed. The ring -dyke ha s a thickne ss of 20-100m and branches out as a concentricring-dyke complex in the Serkeda- len area to the north of the cauldron where individual dykes may attain thicknesses of several hundred metres. The ring-dyke comp- lex has steeplydippingboundaries against the

NGU. BULL423.1992 Petrolog yand metallogeny 5

o

.

THEBk RUM CAULDRON

~ Syenitesand

~ monzodiorite

Univ,ofOslo

/

..

):~

COMPLEX VC o>' Q".~ ^Explosionbreccic ')1

~o·.,!.a. ~~

~ Cambro-Silurionmetc-. ~a'?

L...D

limestone ~oo.

....

r - I Rhyolitic and

L - J ^{lra chytic}

felsites

o

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Fig.3:Geological mapoftheBcerumCauldron.Mod ified fromHolted ahl&Dons(1952)and Naterstad etal.(1990).

adjacent wall rocks that are commonly breccia- ted.The dyke rocks appear undeformed and seem to have been emplaced after the subsi- dence of the cauldron block, and accordingly represent the last stage of igneous activity associated with the main subsidence of the Brerum Cauldro n (Srether 1945).

The ring dyke is basically developed as gra- nophyric quartz porphyries ,syeniteporphyries and microgranites.Animportant feature of the Tryvann gran ite are its spatial and temporal relationshipswith the ring-d yke syste mof the Brerum Cauldron whichcan be studied in the Ringeriksflaka area to the west of lake Try- vann (Fig.2). Here the alkali-feldspar gran ite protrudes from the mainTryvann granite body and continuesas a partofthe ring-dyke,sepa- rating thealkali-feldspar quartz syenite inthe east from the subsided raft of the olderGref- sen syenitewithinthe cauldron.The fieldrelati- ons reveal clearly that the emplacement of Tryvann granite took place after the subsiden- ce of the Brerum Cauldron,but contemporane- ouslywiththeformationof the ring-dykecornp-

lex along the main cauldron fault zone.Thisis in accordance with earlier assumptions by Srether (1945),Smithson (1961) and Petersen (1983) which have recently been supported by a Rb-Sr age of 243±3 Ma for the ring-dyke (Sundvoll et aI.1990).

The contacts of the TGC withthe enclosing syenites within and outside the cauldron are sharp and subvertical,often following the pro- minent fracture pattern of the area. The con- tacts to the surrounding pluton ic rocks are in generalcharacterized by sub-parallelapophy- ses and veins of porphyric aplites, 1-20 cm in thickness,protruding from the main granitic intrusions.

The pluton ic rocks intruded by the TGC comp risea complexof alkali-feldsparsyenites (nordmarkite),syenites (Grefsen syenite),fine- tomedium-grained monzodiorites(akerite), and coarse-grained monzodiorites(kjelsasite),The Grefsen syenite is an ordinary syenite, which is commonly developed as a plagioclase- phyr ic variety. It has been intruded by the Tryvann and skacaren granites , while the

6 Odd itsen GU-BULL423.1992

Alkali-feldspar quartz syenite

%p 35

i

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o 01' ⁰

e' •••

o ••

0;/"

A

Fig.4:Moda lcomposrnonof the Tryvann Granite Comp- lex.including datafrom Gaut (1981).Field sofclassificati- on: 2:Atkan-tetd spar granite 3:Granite 6: Alkah-Ields par quartzsvenue7:Quartz syernte.

o

The alkali-feldspa r quartz syenite whichoccu- pies theeastern part of theTryvanngraniteis a greyish-pink, commonly porphyritic, fine- grai!1ed rock with a subhedral,granular textu- re.PerthiticK-feldspar,quartz andalbite cons- titute more than 95 vol% of the rock. Brow n biotite, partly chloritized, occurs in minor amounts « 3 vol%), along with accessory apatite,rutile,zircon,f1uorite,sphene,magneti- te, hematite, pyrite and ilmenite. Scattered xenocr ysts of a greenish-grey amphibole with strongly abraded grain boundaries occur in some syenite varieties, presumably derived from the enclosing Grefsen syenite.

Phenocrysts01perthitic K-Ieldsparoccur in

general asscattered,randomlyoriented,sub- hedraltablets,2-7mmacross and withayellow- ish-grey colour in a fine-grained (0.2-1mm) granular matrix. The K-feldspar is developed as a braid- or patch-perthite,commonly sho- wing a distinct Carlsbad-twinning. Albite oc- curs as subhedral separate grains in the ma- trix, but mainly occurs as cores within, or mantles around, the turbid zoned K-teldspar

Petrography of the Tryva nn Granite Comp lex

Aklungen and Hammeren bodies of the TGC intru de aphyricand comm onlyaegirine-bearing alkali-feldspa r syenites (nordrnarkite). Due to the indistinct field relationships between the two syenite types,noatte mpt hasbeenmade in this study to distinguish betwee n them in the field.In theOslo-Nittedaldistrict,the field relationships sugges t thatthe Grefsensysnites are olderthan the alkali-feldsparsyenites,and this has been supp orted by the recent Rb-Sr datings ,e.g. ± 255Ma and :!: 250 Mafor the Grefsen syenites andalkali-feldspar syenites , respectively (Sundvoll et aI.1990).

Diabase dykes,0.5-1.5m in thickness,tran- sect theTGCand theBcerum Cauldronbounda- ry in a few places. Their petrography has been presented by Scether(1947) and Huseby (1971). They are regarded as the youngest magmaticrocks of theregionand are control- led by the prominent N-S fracture system of the area.

To the south of the TGC and the Nord- marka-HurdalenSyeniteComplextheHo/men- Daga/i exptosion-breccie transects the Cam- bro-Silurian horntels sequence in the area between Holmenkollen and unernasen (Figs.

1,2 &3).Thebrecciahasbrieflybeenprese n-

ted by Holteda hl (1943,p.50) and Scether (1962,p.94), and bears an interesting relation- ship to theTGC as itis compose d of various angular andsub-rounded fragmentsof hydro- thermally altered and unaltered varietiesof fi- ne-grained,granitic rock s,resemblingthe diffe- rent lithologies of the TGC together with a varietyof fragmentsofdiffe rentlithologiesfrom the Cambro-Silurian sequence, Preca mbrian gneisses and igneous rocks from the Nord- marka-Hurdalen Syenite complex. The rock- flour matrixconsists ofCambro -Silurian shale andlimestone closeto thecontactandof tuffa- ceousigneousmaterialelsewhere.The formati- on of the breccia-pipe probably signifies the last magmaticeventassociated with the deve- lopment of the TGC and will be considered later.

NG U·BULL42 3.199 2

grains and phenoc rysts . Quartz form s an- hedral interstitial grains, 0.2-0.6mm across and, less commonly,micrograph ic intergrowths with the K-fe ldspars. In the field the general porphyric texture and the low quartz content (15-20 vol.%) distinguish the alkali-feldspar quartz syenitefrom the alkali-feldspar granite, but transitional varieties are common in the border zone betweenthem.Dark brown bioti- te occurs as scattered, random ly oriented, single flakes, 0.3-1mm in length, commonly associated with aggregates of fine-gra ined magnetite,apatite,rutile and sphene.The bioti- teis commonly replaced by a darkgreenchlo- rite alongcleavage planesandgrainboundari- es.Sphene generallyoccurs as euhedral gra- ins, commonly replacing magnetite and fine- grained aggregates of rutile. Zirco n is afairly common accessory mineral, and occur s as single, euhedral prisms, less than 0.3mm across.

Alkali-feldspar granite

Thealkali-feldspa rgranitediffe rs petro graphi- cally from the alkali-feldspar quartz syenite by its generalaphyric texture and higher qu- artz content (25-30 vol.%).Towards the wes- tern margin of the Tryvann granite miarolitic cavities, 2-10mm across, are commonly pre- sent,but no particular lateral or verticalcompo- sitiona lzoningis observedin the granitebody.

The granite has a granophyric texture with

Petrologyand metallogeny 7

an average grain size of between 0.1 and 1mm. The granophyric texture is defined by subhedral grains of quartz enclosing K-feld- sparinamicrographicpattern.Themineralogi- cal com position does not differ significantly from that of the alkali-feldspar quartz syeni- tes. However, the Skadalen, Aklungen and Hammeren granites are significant ly depleted in biotiteand magnetite in comparisonwiththe Tryvann granite. In places, arfvedsonite may occur as the predominant dark mineralconsti- tuent in amounts of less than 3 vol.% within the Skadalenand Hammeren granites,thereby indicating a gradation to peralkaline (ekeritic) varieties.

AlbitereplacesturbidK-feldsparsin the alka- li-feldspar granites to various degrees, and transitions to greyish-wh itealbite granites are frequentlyobserved.Therole of hydrothermal alteration resulting in albitization of the TGC and surro unding rocks will be discussed in a later paragraph.

Modal analyses have been performed on 23 samples from the TGC (Table 1) and are prese nted in a Strecke isen diagram together with 6 analyses of the Tryvann granite from Gaut(1981)(Fig.4). Most samplesclusterin the alkali-feldspargranite field of thediagram,but the more albitic varietiesgradeinto the grani- te field.Dueto the generalporphyritictexture, onlyalimitednumber of alkali-feldspar quartz syeniteswere found suitable for modalanaly- ses. However, these samples fall well within the alkali-feldspar quartz syenite field of the diagram.

Table1:Modal cornposmonof theTryvann Granite Complex.

ALKA LI·FELDSPA RGRANITE

ALKA LI ·FELDSPAR QUA RT Z SYENITE

SAM PLE NO. 28 33 36 50 64 93 107 109 113 134 138

'"

MINERAL MINERA L

(vol.% ) (vol.%)

AIMe 7.0 4.5 30 3.5 4.9 34 7.3 48 85 12.0 92 4.1 00 38 11.7 92 Alblte 4.8 11.7 81 7.5 7.7 9.8 6.1 Quartz 29.0 30.0 31.5 33.0 33.1 20.4 24.7 32.' 18,4 30.7 23 3 2i.3 27.9 308 37.4 284 Quartz 21.8 182 7.9 26.3 11.7 17.4 17.5 Alkallfsp. 62.0 645 63.0 630 61.1 70.8 642 61.0 700 51.5 65.1 723 693 61.2 48.4 59.5 AJkahfsp. 69.0 64.8 76 8 63.6 721 68.9 70.0 B.atJ18'CtlJorrte 1.0 05 0.5 0.1 2.6 18 0.3 07 0.5 0.7 0.1 BlOtltel Ch lo nle 2.5 1.7 2.1 06 1.5 1.3 2.2

Artvedsorute 43 33 Amphl~e 1.8 3.4 0.6 1.1

Apatite Apatit e

Bunte Rutlle

Zircon Zircon

Fluors pa r x Fluorspar

Carbon ate 1.1 , Carbon ate 1.5 0.8 1.6 1.0 1.3

Magnetite 0.5 05 0.5 1.2 1.1 1.1 06 35 1.8 1.3 1.5 05 1.0 2.6 Magnetite 0.3 1.7 1.8 0.8 1.5 0.7 0.7

Hematrte 1.0 Hemaute

Pyrite 1.0 20

SUM 98.' 99.6 99.3 98.8 995 99.7 98.9

SUM 100.01000 100.0100.0 99.7 99.5 991 996 102.597.7 994 995 994 996 99.6 99.7

It:Accessory constituent. SampleIocalttJes aOOtxx116S- 2:ROOklelva(top).vceseneonen^{Tryvann.3:AOdkleiva(middle),}Vak-sank olle n -Tryvan n.4;R0dkleiva (bo tt om), VoksenkOllen-Tryva nn.7:WylJerl0ypattoo),Rlngenks flaka•Tryvann.28:N.Stramsbra ten.Sar xedalen-Tryvann.33:Busstoc,Bogstad.Sark ec alen -Rlng-dyke.36:Hythbakke n.S.Tryv ann- Tryv aM.50:PrestenJ(jhaug en.W.Tryva nn • Tryvann.64:Footpatn Bomv81en-Frog ners,;eua-Skadal.

93:Heftyebakken.SETryva nn•SkAdal.107;W.St.Aklungen •Aklungen.109:W.LAklungen• Aldunge n.113:E.Maneskinnsleypa.vettekcnen. Aklunge n.134:Hammeren•Hammeren.138:Skjervenm arx a•Hammer an.141:Skjerv enSawmill-Hammer en.39:Tryvannsklelv a.!OP.40:Tryva nn tower.41:Gretrumskleive ne.47:Skogen stereo.53:Plnslehog da.55:N.Heqqenunet.58:Tryvann.

8 Odd ilsen

The ring-dyke complex

The petrography of the ring-dyke complex of theBcerumCauldro n has previouslybeenpre- sented by Scether (1945) from the southern part of the cauldron.Ingeneral,thering dyke is developed as a fine-grained, pinkish-grey quartz-syenite porphyry. Randomly oriented phenocrysts of subnec ratalkali feldspar, 1-5 mm across, occur scattered in a very fine- grained, partly granophyric grou ndmass of quartz and alkalifeldspar with albitein minor amounts.Rounded phenoc rystsofquartz,less than 1mm across,mayoccur in places.Bioti- te,sphene,zircon,rutile,fluor ite,apatite,hema- tite and pyrite are accessory constituents.In the southern part of theBrerum cauldro nscat- tered xenoliths,1-10 cm across, occur in the ring-dyke. They are composed of porphyritic basaltsand various rhomb-por phyrylithologies from the central igneous complexes of the cauldron.

Ana lytical proced ures and result s

Thirty-two chemicalanalyseshavebeenperfor- med on the different lithologies of the TGC and the Brerum Cauldron ring-dyke complex (Tables 2 & 3). Major and minor elements weredeterminedbyX-ray fluorescence (XRF) analyses on a Philips instrument,using fused pellets made from rock powder mixed 1:9 with LiB.O,. The trace elements (Mo,Nb,Zr,Y, Sr,Rb,Ce and Ba) were analyzed on pressed

12 L

~ L ^{0 e}

o+ Peraluminous _{0· ' ,}

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0j l.O

L

Peralkaline

I

a l

i

r _I

09 1.0 U 1.2

AI,OJ/ (Na, O+K,ol

Fig.5:AI,O,I( a,O +K,O)versusAI,O,/( a,O+ K,O + CaO) of theTryvann Grarnte Complex.Field boundaries accor- ding to snanc(Carrrucnael et aI.1974).Oxidevaluesare in molecular proportions. Legend: Circ les with dot - Alkali- feldspar quartz syernte: Open circles - Ring-dyke: Filled Circl es-Alka li-fe ldsparqr arute.

GU·BULL423.1992

A b !

^\

Fig.6:O-Or -A b relationsfor theTryvan nGranite Complex. Cotecttc lines with thermal minima (x)are shown for ditte- rent volat ile contents afte r Tuttle & Bowe n (1958) and Manmng(1981):a:1xoar.4.3%Hp b:3 xoar.8%H,Oc:

1 Kbar.l~oF c:1 xoar.2%F.Symbo lsasin Figs.5&7.

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Fig.7:Harkerdiagrams showing major and minor OXides from samples rom the TryvannGranite Comp lex and the B<erumCauldr onring dykecomplex.Allfigures areweigh per centvalues

NGU·BUL L.42 3.19 9 2 Petrologyand metallogeny 9

Table2:Chemica lanalysesand CIPWnormsof theTryva nnGra niteComple xand theB<erum Cauldr onringdyke.Allvalues are In wl.% exceptfor traceelement s,which are in ppm.

ALKAll-FELOSPAAGRANITE ALKALI·FELDSPAR

QUARTZSYENITE RING-DYKE

SAMPLENO. 28 36 64 93 107 109 113 '34 138 141 '0 41 53 58 50 L07 Ll1 l37 L38

00, 74.35 77.18 76.50 72.50 71.25 73.10 73.'6 ^{71.88 74.36 76,02} 76.85 76.32 6834 73,84 6687 69.72 7108 75,46 71.17 7602 76.20 75.68 TiO, 026 0.12 009 035 0.36 020 029 033 0.28 0.14 0.17 020 0.49 029 0.63 0.52 0.15 023 0.38 0.15 0.14 0.15 AJP, 13.81 13.02 12.21 14.n 14.51 11.39 13.713 13.91 13,46 12.68 12.35 12.78 16.20 1"67 16,07 15.83 1304 13.64 15.95 13.01 12.98 13.56 Fe,O; 1.41 1.20 1.35 2.69 3.44 2.81 1.96 2.10 1." 2.06 1.98 2.27 2.46 1.76 2.98 2.61 1.50 1.74 1.92 1.30 1.18 1.30 MnO 0.05 0.05 005 0.12 0.21 0.27 0.14 0.12 0.12 0.13 0.17 0.17 0.10 0.05 0.11 008 0.05 0.11 0.12 003 0.02 0.04 MgO 0.24 0.13 0.12 035 0.34 0.27 0.05 0.19 0.10 008 0.09 004 043 027 0.60 0.49 0.06 0.12 0.26 0.16 0.14 0.21 CaO 022 0.03 0.10 0.33 0.18 0.12 0.00 0.21 022 0.05 0.02 0.00 0.58 0.28 0.95 062 0.06 0.39 0.44 0.00 0.00 0.00 NaJO '.00 4.17 3.86 4.79 4.81 3.50 4.37 '.02 ^4.32 '33 3.98 4.44 633 4.14 '83 '.65 3.86 4.15 4.75 3.92 '06 3.79 K,O '03 4.28 '.00 ^{4.22 4.89} 386 '90 5.03 4.93 4.22 398 366 4.80 4.85 4.98 4.76 4,41 4.18 633 '09 '50 '63 P,OI 003 0.01 002 0.07 0.07 0.03 0.02 0.03 0.03 0.02 002 0.02 0.11 0.04 0.15 0.12 0.03 0.03 0.04 0.02 0.02 0.03 S 0.11 001 001 0.26 0.01 0.08 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.00 0.04 0.01 0.01 LOI 0.41 0.16 0.23 0.67 0.27 2.91 0.24 058 0.49 0.45 0.26 0.18 0.39 0.42 026 0.38 02' 1.08 0.52 0.19 0.20 0.26 SUM 99.72100.3698.5410 1.12 100.34 98.54 98.90 98.45100.20 100.19 99.88100.09 99.24 '00.6298.43 99.79 100.49101.13 100.8898.93 99.46 99.68

Mo 11 13 9 19 21 0 2 6 6 '3 8 0 9 12

•

Nb 84 94 141 89 17' 218 '9' 160 158 241 162 217

..

Z, 244 169 209 312 560 714 621 '14 383 '69 '02 619 39' 214 '68 371 169 '00 634 204 201 199

Y '6 31 29 36 102 13' 55 96 82 109 55 82 58 50 66 57 22 56 81 36 36 35

S,_{ae 2'}31_{3 228}8 ₂₆₉6 ₁₈14_{8 211}'2 ₂₃₉14 _20'19 ₂₃₃20 ₂₂₅31 5

•

29' 230 191 180 227 14' 163 220 186 140 145 211 203

Ce 183 81 14 143 368 160 17' 219 209 113 116 138 161 '66 145 151 82 129 220 93 81 86

Ba 157 79 0 411 41. 132 123 92 175 20 10 26 667 275 720 726 58 148 168 83 '6 58

Clpw·NOAM C1PW-NOAM

SAMPLENO. 28 36 64 93 107 109 113 134 138 14. '0 41 53 58 50 L07 Lll l37 L38

0 32.12 36.29 39.10 27.39 23.37 39.09 29.36 29.13 29.97 3461 38.48 36'8 17.65 30.65 17.58 22.92 37.67 34.43 21.89 37.86 35.'6 35.86 0, 28.78 25.28 24.08 24.87 28.98 23.90 29.40 30.42 29.27 25.04 23.65 21.69 28.75 28.65 30.04 28.39 26.03 24.73 31.44 24.51 2683 27.57 AI 34.06 35.19 33.20 40.34 40.67 30.96 37.46 3414 36.64 36.72 33.79 37.59 45.61 34.9' ^41.62 39.67 32.56 36.08 40,03 33.57 34.59 32.24 An 0.90 0.08 0.37 1.18 0.44 0.'2 0.00 1.17 0.90 0.12 0.00 0.00 2.19 1.13 3,81 2.31 0.01 1.74 1.92 0.00 0.00 0.00 C 1.67 1.48 1.41 1.87 1.13 1.36 1.27 1.45 0.68 0.94 1.49 1.51 1.45 0.18 1.38 2.19 1.86 1.64 1.64 2.15 1.43 2.32

o 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.65 0.41 0.00 0.53 Wo 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 H, 0.60 0.32 0.33 0.87 0.85 0.89 0.13 0.49 025 0.31 0.36 2.00 1.09 0,67 1.53 1.23 0.15 030 0.00 0.00 0.35 0.00 M' 0.52 1.01 1.28 1.22 3.17 2.59 1.63 1.61 1.50 1.93 1.85 2.18 1.44 1.11 1.61 1.43 1.25 1.49 1.27 0" 085 1.01 Hm 0.55 0.70 0.00 0.89 0.03 000 0.15 0.27 0.18 0.00 0.00 0.00 0.61 0.37 0.84 0.70 0.10 0.09 0.35 0.24 0.18 0.14

,

""

SUM 99.98100.62 99.99 99.95 99.51 99.84 99.98100.01100.0 1 100.01100.0110 1.85 100.0198.36100.01100.0499.90100.01100.0099.98 99.98 99.11

oTotalFeasFe,O, Samplelocalitiesand bones•2:Aookleiva(lop).VoksenkOllen.Tryvann.4:A0(lkleiva(bOttom).VoksenkOllen.Tryvann.28:N.stromSbr.alen.Serkedalen.Tryvaoo.36:

N.Hytlibakken.S.Tryvann.Tryvann.64;Footpalh Bomveien·Frognerscetra.sk.adal.93:Heftyebakken.SETryvann. Sk-'dal.107:W.St.Ak:ungen,Aklungen.109:W.L Ak1ungen.Aklungen.113:E.M.aneskinnsl"ypa.vertakouen.Aklungen.134:Hammeren.Hammeren.138:Skjervenmarka.Hammeren 141:skjervensag.Hammeren.40:

Tryvanntower. 47;skogen station.53:PinSlehegda.58:Tryvann.50:Presterudhaugen.W.Tryvann.7:0sterb (87J4f10).l07:NWPlpenhus.s0fk edalen.Lll:NWPipen- huS.Ser1l.edalen.l31:Road S.ly$8dammene.S0fkeda'en.138:Gran.S0rkedalen.

Table3:Chemic alanalyses of hydro therm allyalte redvarieties(A)oftheTryvann GraniteComplex .enclosing syenites and theBrer um Cauldronring dyke With theiradj acent.unaltered protores (U).Allvaluesare inwt.%.except fortrace elements.

which areinppm.

ALKALI·FELDS P AR GRANITE RING· DYKE GREFSEN·SYEN'TE

SAMPLE NO. U A U A U A U A U A U A U A U A

64 65 109 108 141 142 2 A2 4 A4 7 1 48 49 132 133

SiOI ^71.25 55.27 71.88 75.49 76.32 75.34 74.35 69.75 77.18 78.44 75.'6 73.56 66.70 62.79 64.09 71.91

TiOI ^{0.36 0.38 0.33 0.28 0.20 0.21 0.26 0.30 0.12} 0.11 0.23 0.24 0.48 0.63 0.73 0.59

AIIOI 14.51 13.95 13.91 13.3 1 12.78 12.59 13.81 14.98 13.02 12.7' 13.64 13.31 16.84 16.59 16.92 16.49

FeIO" ^3.44 3.9' 2.10 2.00 2.27 2.20 1.41 353 1.20 1.04 1.74 1.87 2.86 3.32 3.14 0.77

MnO 0.21 3.44 0.12 0.15 0.17 0.08 0.05 002 0.05 0.38 0.11 0.10 0.14 0.69 0.17 0.03

MgO 0.34 0.04 0.19 0.21 0.04 0.11 0.24 013 0.13 0.13 0.12 0.14 0.50 0.60 0.66 0.16

CaO 0.18 0.70 0.27 0.04 0.00 0.00 0.22 0.00 0.03 0.00 0.39 0.39 0.80 1.62 0.59 0.02

NalO 4.81 7.94 4.02 7.49 4.44 6.96 4.00 832 4.17 6.60 4.15 4.16 5.59 9.24 5.88 9.14

K,D '.89 0.28 5.03 0.07 3.66 0.02 4.83 016 4.28 0.05 4.18 4.26 5.44 0.13 5.07 0.06

P,O, 0.07 0.10 0.03 0.03 0.02 0.02 0.03 0.03 om ^{0.01 0.03 0.04 0.09 0.15 0.16 0.03}

S 0.01 1.31 0.01 om om ^{0.01 0.11 0.98 0.0 1 0.00 0.00 0.44 0.18 0.08 0.02 0.01}

LOt, 0.27 2.45 0.56 0.22 0.18 0.26 0.41 1.54 0.16 0.36 1.08 0.90 0.34 2.08 0.36 0.45

SUM 100.34 89.80 98.45 99.30 100.09 97.80 99.72 99.74 100.36 99.83 101.13 99 .4 1 99.96 97.92 97.79 99.66

Mo 21

•

Nb 17' 119 160 169 217 203 84 105 94 103 157 153 100 76 95 177

Z, _{560 438 414 437 619 554 244 283 169 156 400 392 691 575 500 857}

Y 102 40 96 93 82 66 45 32 31 20 56 57 97 66 74 49

Sf 42 1093 20 13 5 8 31 13 8 11 27 40 62 149 201 11

Rb 211 16 233 4 191 3 243 5 228 2 186 207 122 5 113 4

Co 368 280 219 179 138 99 183 91 81 66 129 127 372 230 245 107

Ba 474 39000 92 43 25 19 157 19 79 10 148 215 396 161 2380 57

• TotalFeasFe~O, Samplepairsandlocalities - 64/65 :Frog nerscetra.109/108:W.L.Aklung en.1411142:Skjervensawmill .Hammeren.2fA2:A0Clk~iva(top)•

vckseokcaen.4iA4:ROOkle;ve(bottom).Voksenkolle n.711:05te'As.48149:Skoge n.1321133:S.S.Aklung en.