Bergvesenet Postboks3021, 7002 Trondheim Rapportarkivet

Bergvesenet rapport nr Intern Journal nr Internt arkiv nr Rapport lokalisering Gradering BV469 Trondheim Apen

Kommer fra ..arkiv Ekstern rapport nr Oversendt fra Fortrolig pga Fortrolig fra dato: Falconbridge Sul 211-72-22 Sulfidmalm A/S

Tittel Peninsula,

Forfatter Dato Bedrift H A Rosenqvist 1972 Sulfidmalm A/S

KommuneFylke Bergdistrikt 1: 50 000 karlblad1: 250 000 kartblad Lyngen TromsøTroms 16343 16344 16334 15342 15R31.Tromsø

Fagområde Dokument type Forekomster Geologi Rapport

Råstofftype Emneord Malm/metall Ni Co Cu S

Samrnendrag Dette er en oppsummering av tilgjengelig informasjon om Lyngengabbroen fra før "Operasjon Phoenix" startet i 1973. FCi nALCONBRIDGE •IKKELVERK A/S

A/S SULFIDDIALM

PROJECT 905-22

'ENIESNLA,

cy 1973

by

n. A. ROSENQVIST LYNGENPENINSULA,TROMS.

INTRODUCTION.

The Lyngenpeninsula,locatedsome 30 km E of Tromsø in N. , is largelybuilt up by one of the biggest gabbro massifs of the country. Falconbridge'sinterestin the Lyngen gabbro and its Ni-Cu potentialwas initiatedby G. P. Mitchell as far back as in 1962, i.e. the year A/S Sulfidmalmwas formed. A 3 week reconnaissanceof part of the area was taken without encouragement. In 1963 S. N. Charterissuggested a full assessmentof the area (2 month's field program) but his proposalwas precludedby budget limitations that year. A 5-day reconnaissancein the area was taken on Sulfid- malm's behalf by T. Birkeland (Univ.of Tromsø) in 1972. His work showed the existenceof sulphide"enriched" layerswithin the gabbro complex,the sampledones being however of low content. The Lyngen area is includedin the plans for the helicopter supportedprogram 22-PHOENIX1973,whereby a full assess- ment (by prospecting)of its sulphidepotentialis planned to be made. This report is intendedto summarizeour presentknowledgeof the area.

GEOGRAPHY.

The Lyngenhalvøya(69° 30' 14/20°E) is a 85 km long, 15 km wide N-S elongatedpeninsulabounded by Lyngenfjord (E), (W) and Balsfjord (SW). It is characterized by rough mountaineoustopography,the highest,peaks reachingattitudeswell above 1.500 m a.s.l. Motor roads run along the fjords around the peninsula,the NE part being an exception. The municipalcenter of the area, ,can be reachedby car from Tromsø in 1-2 hours.

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Lyngen area is coveredby good four-colour1:50.000topo map sheets. These are based on aerial photographsapprox. 1:40.000dated 1953-54.

GEOLOGY.

The dominantfeatureof the Lyngen area is the central core og layred gabbro,being exposed over approximately 400 km'. The coastalareas of the peninsulaare built up by Cambro-Silurianmetamorphicrocks (largelymetasedi- mentary),tectonicallyseparatedfrom the interiorgabbro. The geologyof the Lyngen area, as presentedby Randall (1971),is shown in figs. 1 and 2.

(1) IGNEOUS ROCKS (Fig. 2) a) Lyngen gabbro: This is a layeredhypersthenegabbro strikingapproximatelyparallelto the peninsula and dipping to the west. The layeringappearsas variationin mineral compositionas well as grain size. Individuallayers,varying in width from 1-2 cm to severalhundred meters,have been observedfor severalkilometersstrike length. The gabbro is foliatedparallel to the layering. Scatteredbut uncertain observationsof rythmic layeringsuggests a bottom directiontowards East. The internalstructureof the layered gabbro has not been investigated. It is only describedas complex due to thrusting faultingand folding.

The Lyngen gabbro is reportedas extensivelysaussuritised and uralitised. The originalcompositionaccordingto Randall (1971)was that of a hypersthenegabbro character- izedby bytoronite,hypersthene(En 70) and clinopyroxene. Munday (1970),who worked in the northernmostparts of the peninsula,reportedfresh gabbroprincipallyconsisting of plagioclase(An 78), diopsid,olivine,hyperstheneand magnetite.

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The abbro is a small mass, forming a prominentpeak 10 km S of Lyngseidet. The gabbro shows similaralterationto that of the main Lyngen gabbro,but they differ from each other in contactrelationships. The Furuflatengabbro has developeda metamorphiccontact aureole (garnets associatedwith poikioblastichornblende)whereasthe contactsof the Lyngen gabbro are tectonic.

Several Ultramaficbodies, emplacedwithin the Lyngen gabbro,have been mapped (Fig. 2). These are dunites - pyroxenites,being exposed as elongatedmasses 1/4 - 2 km in length. In a considerableportion of the Lyngen gabbro, the ultramaficsare located close to the eastern contact. They could be interpretedas early differentiates of the main gabbro,however tectonic contactshave been observedand in some instancesfresh ultramaficsare surroundedby stronglyaltered gabbro. Birkeland (1972) suggeststhe possibilityof ultramaficintrusionsalong thrtustplanes.The main ore mineral of the ultramafics is magnetiteoften with a small core of cromite (Randall 1971).

At the northerntip of the peninsulaoccuresminor bodies of a stronglyalteredhornblende- clinozoisite- oligoclase rock. These extensivelyshearedbodies are interpretedby Randall as originallytroctolites.

A number of se entinitesare located along the major dislocation,which forms the W boundaryof the metasedi- mentary VardtindFormation. In the south these are small (100-200m long) bodies but in the north a dike like serpentiniteof severalkm's length occure. The northern serpentiniteis characterizedby large magnetiteoctahedia and alterationto talc and carbonate.

Severalsmall bodies of olivine-enstatite-dolomiterocks, named sagvandites,occure within the metasedimentary Lyngseidetgroup. An igneous as well as metamorphic (metasomatismof limestone)origin for the sagvandites has been suggestedin the literature.

• / 4 -4-

g) Meta-doleritedikes occure within the metasedimentary Ullsfjordgroup as shown on fig. 2.

COUNTRYROCKS (Fig. 1)

The gabbro core of Lyngen peninsulais surroundedby largely sedimentarymetamorphicrocks. Their general trend is sub-parallelboth to the gabbro outcrop and the fiords.

- The countryrocks W of the gabbro all belong to the greenschistmetamorphicfacies and consistof quartz- feldspar-micaschists,quartzite,pure and impure (sandy)limestones,conglomeratesand chloriticphyllites. The phyllitesof the VardtindGroup is found adjacent to the gabbro and has a faultedrelationto the other rock groups (cf. 1 e).

- East of the gabbro amphibolites,graphiticphyllites, feldsphatisedquartz-garnet-micaschists and limestone have been mapped. The metamorphicgrade varies from greenschist(phyllites)to high amphibolitefacies (schists). Chemicalevidenceand field resemblencewith sheared gabbro suggeststhe possibilityof an igneousparentage for the amphibolitesof the Kjosen Formation(Randall 1971).

STRUCTURE.

All the contactsof the Lyngen gabbro are describedto be of tectonicorigin and there is no evidenceof a metamorphicameole. In the west a steep westerly dipping fault marks the border. The eastern contact is sheared and of less clear character. Possiblyit representsa thrust plane. It is consideredthat the Lyngen gabbrohas been thrust, from the west, to its presentposition.

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Randall (1971)identifiedthree main fold episodesin the Lyngen area:

F1 Some evidenceof this can be seen in most of the metamorphicgroups,but it is dominantin the Lyngs- eidet Group where a NW lineationis developed parallelto fold axes.

F2 The second folding is visible as both major and minor folds and is responsiblefor the main distri- bution of rock groups. The 8xial planes and cleavage have a consistentstrike (15 ) but may vary markedly in dip. It is thought that the thrustingfrom the west which controlsthe boundariesof the Vardtind formation,the Lyngen gabbro and to a large extent the internalstructureof the gabbro,was associated with this deformation.

F3 The third deformationproduceda strong almost verticalcleavageof similar strike to that of F2 and some minor upright folds.

As mentionedabove the internalstructureof the gabbro core is describedas complex. Fig. 3 shows a simplified profile over the gabbro as mapped by Birkelandin 1972. The gabbro is here folded in angular folds with N-S to NE-SW trending and moderatelyto low dipping axes. This means that approximatelythe same levels of the gabbro are exposedboth in E and W.

(4) GRAVITY.

A gravityprofileby Chroston (1972) across the Lyngen peninsulahas revealed a positive 16 mgal anomaly associatedwith the gabbro (Fig. 4). Interpretationof the anomalysuggeststhat the gabbro is essentiallywedge- shapedwith the maximum thickness1.5 km occurringat the western contact(Fig. 5). This shape is consistentwith the hypothesisthat the gabbrohas been thrust in from the west.

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Worth noting in fig. 5 are the gravity low Z and adjacenthigh Y. FollowingChroston(1972)a possible interpretationfor Z is faultingor thrustingof lower density rocks into the gabbro. The positionof such a fractureapproximatelycoincideswith the line of ultramaficbodies, describedabove (1 c). It may be argued,says Chroston,that in fact the important feature is the complementarypositiveanomalyY and that this is due to the higher density of the ultramafics. However their extent as indicatedby their surface outcropwould not be sufficientto cause the anomaly.

RECONNAISSANCEPROSPECTING.

1962: Some 3 weeks in the area were spent by Per Lund, NGU- geologist. His main task was to prospectthe ultramafic bodies, shown on the 1:1 milj. geologicalmap of Norway i.e. a very limitednumber c4/theultramaficsnow known to exist. Lunds investigationswere discouragingand no sulphidemineralizationwas reported. Lund also mapped out the gabbro contactsin the vicinity of Kjosenfjordand some scatteredportions in the south.

1972: A brief reconnaissance(5 days) by T. Birkeland (Univ. of Tromsø), coveringa considerablearea N and S of Kjosen- fjord,was taken this summer. Rusty layers, of 10-100 m width, were commonlyobservedin the gabbro. The most prominentrust localitiesare marked on a 1:50.000map togetherwith sample localities. Rustinessis caused by sulphidedisseminationevenly dispersedthrough out the layer. Concentrationswere nowhere observed. Due to severe topographysamplingwas restrictedto local talus and in some instancescompletely. Three mineralized rock sampleshave been assayed:

Ni Co Cu

TB Lyngen 3 B 0,15 <0,01 0,05 0,65 %

tt fl It 0,07 fl 0,18 0,60 "

tt fl 5 B <0,05 <0,05 0,62 "

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REFERENCES.

REITAN (1960) Kviteberg,NGU 212 a pp 63-65.

LUND (1962) Rapport,Dagbok, Bergartsliste Lyngen,Troms. Sulfidmalmfile.

MUNDAY (1970) The Geology of the northernpart of the Lyngen peninsula,Troms, Norway. Unpubl.PhD-thesis,Univ. Newcastle upon Tyne.

RANDALL (1971) An outlineof the Geology of the Lyngen peninsula,Troms, Norway. NGU 269 pp 68-71. The Igneous rocks of the Lyngen peninsula,Torms, Norway. NGU 269 pp 143-146.

CHROSTON (1972) A gravityprofile across Lyngenhalv- øya, Troms, northernNorway. NGT Vol. 52 pp 295-303.

BIRKELAND(1972) Orienteringom Lyngen gabbroen Sulfidmalmfiles. Lyngen,field report Sulfidmalmfiles.

BAND (1972) Discussionswith T. Birkeland,memo Sulfidmalmfile.

ENCL. Fig. 1-5. , 69

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Eig. I. Geological sketch map of the Lyngen peninsula.

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144

YNOSPUVA 5 . GABBRO 4.15 ULTRAMAFIC5 ENPLACED IN GABBRO

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GEOLOGICALSKETCHMAPSHOWING THE DISTRIBUTIONOFTHE MAIN IGNEOUS ROCKSOF THE LYNGEN PENINSULA

the distributionof the niain igneousrocksof the Pig.1- Geokigicalskerchntap showing Lyngenpeninsula.The atea nonh of the line /1-11is based on unpublisbedwork by R. J.C kfunday.

TNLL (Clies) 12km

Simplified profile E-W through the Lyngengabbro along Stor - tinddalen - Russedalen.

a Ira. A 0 ( ) 298 P. N. CHROSTON (ct 2)

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Bougueranomaly profile and sketchgeology acrossLyngenhalvoya.

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Fig. 5. Computed model for the residual anomaly based on regional gradient A. A/S SULFIDMALM

INTER-OFFICE MEMORANDUM

Date: 19th February,1973

To: FalconbridgeNikkelverkA/Ss/ cc: M. Clarke, D. R. Lochhead, R. B. Band, H. A. Rosenqvist

From : B. Gammon

Subjea:

905-22 L n en Peninsula Troms (Re ort No. 211-72-22).

Please find attachedRosenqvist'ssummaryof available informationon the Lyngen gabbro area which will be coveredby "OperationPhoenix"in 1973. This major basic body (400 sq.kms.)is almost completelyuninvesti- gated in its interiorportionsdue to severe topography which has hindered access.

rn 22FEB1973 1-1

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