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	INDUSTRIMINERALDATABASEN
	Forekomstområde 1849 - 359
	(Sist oppdatert 14.jun.2006)

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Beskrivelse

The rocks of the Linnajavri area is built up of the Caledonian Nappe sequence thrusted onto Precambrian granitic basement as shown in Fig. 1. The geology of the area is dominated by tectonic nappes and flakes of rocks separated by a net of tectonic melange zones. In the Linnajavri area the relatively flat-lying Caledonian nappes constitutes two open syn-form structures with weakly dipping to undulating axes towards east. The granitic basement is found to the west and to the east a large area of Caledonian rocks are found. The tectonic mélanges consist of crushed wall rocks, and are preferably developed where blocks of ultramafics and soapstone are involved, i.e. within the ophiolite fragments, also occur in the sediments. The Caledonian rocks consist mainly of sediments with minor volcanics. Included in the sequence is also ophiolite fragments. The sediments are metamorphosed to mica schist, garnet(-amphibole) mica schist (sometimes carbonate bearing) and marbles (partly calcitic (color banded) and partly dolomitic). Quatzitic layers are also included in the mica schists. Amphibolite layers in the sediments of both volcanic and intrusive origin (sills) are found. The whole sequence is intruded by small trondhjemite bodies and layers. Especially within the marble unit in the anti-form structure at Cohkuljavri in between the two mentioned syn-forms (Fig. 1) the trondhjemite constitutes up to 50 % of the marble unit. The ophiolite fragments occur in two different nappes. The most complete section is found at Ridoalggicohkka (Southern area), and includes the ultramafics, pillow lava, gabbro, amphibolite and conglomeratic weathering products with well-rounded pebbles from these rocks. Well-preserved pillows are found in the not so strongly influenced block of rocks between mélange zones. Only one dyke has so far been registered intersecting the pillow lave. However, no detailed investigation for dykes within the mafic rocks have been undertaken. Within the geographically Northern area ophiolite fragments are found and in the same nappe as at Ridoalggicohkka but in a different lithological setting (Fig. 1). The major ophiolite fragments in the Northern area are in different nappe and is more tectonically fragmented than it is at Ridoalggicohkka (Fig. 1). The roks suite includes the ultramafics and dark medium-grained amphibolites. At Njaskasvarri a body of leucogabbro and graphite-bearing schist is occurring (Fig. 1). Ultramafic scree material and conglomerate are also found in the Northern area with weakly rounded pebbles of soapstone. The utramafic rocks at Ridoalggicohkka and in the Northern area are similar: dunite and peridotite. Only in one ultramafic body, the Njaskasvarri 985 body, a clear cumulate sequence is found. The dunitic bodies are normally the most fine-grained and the peridotite coarser grained. The ultramafics locally contain pods of chromite, which has survived in the alteration process to serpentinite and to soapstone. The gabbro bodies are normally medium grained. The suite of rocks of the ophiolite fragment has been exposed for weathering and the source rock for conglomerates and grits deposited. The conglomeratic rocks vary a lot in composition. At the southern side of Gaskavarri a conglomeratic breccia with pebbles of barely rounded soapstone are found. The conglomerate at Ridoalggicohkka has well-rounded pebbles in most cases with onionskin structure. They vary from serpentinite conglomerate, green conglomerate with large amounts of mafic material and epidote, to more gray conglomerates with micaceous matrix. The type of conglomerate varies from monomict (serpentinite conglomerate) to polymict. Mostly the conglomerates are matrix supported with transgressions to grit and coarse grained sediment. There is repeated change in composition of the conglomerate beds with thickness of each bed down to half a meter. Alteration of the rocks in the ophiolite fragments is extensive. In the pillow at Ridoalggicohkka solutions introduced sulphur and magnesium have flowed through vents (hot spots). The solutions caused sulphide impregnation and in the aureole (1 meter thick) around the vent growth of flaky talc. Along shear zones in the amphibolites within the Ridoalggicohkka syn-form it has been introduced magnesium and talc growth can bee seen as half centimeter unorientated flaky crystals. Late hydrothermal activity in the ophiolitic rocks has bleached the rocks around veinlets wherein quartz, carbonate and chlorite are deposited. Silification along thin veins in the conglomeratic rock is also common. Soapstone alteration with introduction of CO2 in the process is of varying degree in the different bodies from limited to extensive, in some places up to 100 % (Klebervann deposit). Alteration took place from cracks, joints and breccia zones in the ultramafics. In several places the primary magmatic textures can be seen inherited from the dunite or peridotite. At one locality (Kleberflåget deposit) the alteration process was taken further with in excess CO2 contribution and the soapstone broke down to listvenite, a rock consisting of magnesite-dolomite and quartz. The larger part of the ultramafics are altered, and only to a small extend unaltered dunite and peridotite is found. Most of the ultramafics are serpentinites, some of them with a sharp green color. Hydrothermal activity has been pervasive for the whole nappe sequence of the area. Numerous small near vertical quartz-rich pegmatitic veins intersect the sediments preferably in a N-S orientation or parallel to the schistosity. The emplacement of the rocks in the Linnajavri area: The ultramafics are regarded as ophiolite fragments, with serpentinite and soapstone alteration that has taken place at an early oceanic stage. Later the ophiolite, more precisely its oceanic crust + mantle precusor, was obducted , exposed for weathering, then strongly eroded and dismembered. Finally the fragmented remains of the ophiolite were incorporated into Caledonian nappes being thrusted onto the Precambrian granitic basement of continent Baltica. The geology of the area is dominated by tectonic nappes and flakes of rocks separated by a net of tectonic melange zones. In the Linnajavri area the relatively flat-lying Caledonian nappes constitutes the eastern part in two open syn-form structures with the granitic basement to the west. The soapestone bodies of the Linnajavri area. The Linnajavri soapstone deposits were discovered late summer 2000 based on an idée by L.P.Nilsson and I.Lindahl. There is no sign of previous activity or exploitation of the deposits. In the national database two dimension stone deposits of serpentinite were registered when the investigation of the area started in 2001. The soapstone deposits of the Linnajavri area, with a significant reserve for soapstone as dimension stone and for talc floatation are marked with number from 1 to 23 at Fig. 1. An overview of the same 23 deposits in the Linnajavri area is given in Table 1 with estimated reserves listed. Table 1: Estimated reserves of soapstone in the different bodies. Mill. The Northern area (9): tons. Brief comments 1. Boarta, lens 2 0.25 Talc rich with a thin serp. lid on top. 2. Klebervann 1.7 100 % altered to soapstone 3. Njaskavarri 985 0.5 The end of a layered ultramafic lens 4. Kvitfjell NV 2.9 Serp. inclusions in the soapstone. 5. Kvitfjell SØ 1.0 Serp. inclusions in the soapstone. 6. Cohkul 6.0 Large flatlying lens. Small outcrop 7. Kleberlia (Diagonalgangen) 1.33 Part of ultramafic lens 8. Helikoptergangen 0.38 Intersecting altered breccia zone 9. Grensegangen 1.5 Intersecting altered breccia zone The Southern area (14): Brief comments 10. Kleberflåget 50.0 Huge. Top of serpentinite. 11. Vakkerdalen 3.0 Soapestone enveloping serpentinite 12. Hatten 2.0 Soapestone enveloping serpentinite 13. Klebergryta nedre 2.5 Soapestone enveloping serpentinite 14. Klebergryta øvre 8.0 Complex alteration pattern 15. Nåva 1.0 Talc rich soapstone. Underground 16. Kleberbotn 0.2 100 % altered to soapstone 17. Kleberbreen 7.0 Intersecting altered breccia zone 18. Ridoalggicohkka 1248 10.0 Large. 100 % altered to soapstone. Including "Raskleberen" 19. Ridoalggicohkka 1192 V 1.5 Western part of ultramafic lens 20. Ridoalggicohkka 1192 Ø 2.5 Eastern part of ultramafic lens 21. Langkleberen 7.0 100 % altered to soapstone 22. Langkleberdalen 2.5 Connecting two ultramafic lenses 23. Bananvann S 4.0 Complex alteration pattern The deposits that are altered to a more or less to 100 % soapstone are: Boarta (lens 2), Klebervann, Kleberflåget, Nåva, Kleberbotn, Ridoalggicohkka 1248 and Langkleberen. The deposits for dimension stone or small-scale mining for talc based on size and quality are: Boarta (lens 2), Njaskasvarri 985, Helikoptergangen and Kleberbotn. The deposits for mainly or exclusively underground mining and talc floatation are: Cohkul, Vakkerdalen, Hatten and Nåva. The estimation of the reserves is based on the detailed geology of each body of ultramafics with pattern of soapstone alteration, structure of wall rocks of the ultramafics and geology of the area. The reserves are estimated down to only around 50 metres. The most significant additional resources are in the Southern area with a series of ultramafics on a distinct level, and where there most likely occur ultramafic bodies with soapstone alteration at this level in the shallow open syn-form. Mineralogy and mineral chemistry The soapstone from the Linnajavri area is of the same type as known from other areas in the Caledonides where soapstone is a result from alteration of ultramafic rocks. The soapstone is a talc-carbonate rock. Talc from altered ultramafics to a certain extent inherit the trace element chemistry of the unaltered rock. The carbonate forms during introduction of the CO2, giving magnesite and some dolomite with some iron substituting in the carbonate lattice (breunnerite). In addition chlorite of varying composition normally occur in the soapstone of Linnajavri. In the soapstone from Linnajavri sulfides are extremely rare. The dominating opaque mineral are spinel, mostly magnetite and ferro-chromite.

Beliggenhet

The Linnajavri area close to the Swedish border in Hamarøy Municipality in Nordland County became easier accessible when the area was exploited for hydroelectric power production during the early 1980ies. Study of old published and unpublished geological data, reading lines and between lines led in 2000 to the discovery of the pervasive alteration of the ultramafic rocks in the Linnajavri area to soapstone. The study of the area was initiated by the landowner (Statskog) and NGU. Statskog has during the investigation period from 2000 to 2006, together with two industrial mineral companies, contributed with 50% of the funding of the project. During the years 2001-2005 detailed mapping of the ultramafics and to a certain degree the neighbouring rocks has been undertaken. Extensive sampling and study of the rocks have been done. The soapstone has been evaluated as a source for dimension stone and has to a certain extend been characterized as a source for talc flotation. The distance from the central part of the deposit area and the deep-water harbour at Leirfjord is c. 35 kilometres, with 26 km of existing road, and 8-10 km with no road. The deposits are located in a mountainous area 500-1200 m.a.s.l. No signs of previous exploitation of the soapstone have been recognized. Parts of the deposit area will be subjected to special environment regulations.

Litteraturfortegnelser:

Fra NGU's Referansearkiv.:

Brattli, B.; Prestvik, T. , 1987

	Linnajavri. Berggrunnskart; Linnajavri; 22303; 1:50 000; sort/hvitt;

;Norges geologiske undersøkelse;KART

Foslie, S. , 1936

	Tårstad kisfelt.

;Norges geologiske undersøkelse;FAGRAPPORT;Bergarkivet; No.BA 680;3 sider

	Abstrakt:
	Rapporten beskriver feltet, og det anbefales at A/S Bjørkåsen gruber blir forespurt om de har intresse av feltet, og kan foreta de nødvendige undersøkelser.

Foslie, Steinar , 1942

	Hellemobotn og Linnajavrre. Geologisk beskrivelse til kartbladene.

;Norges geologiske undersøkelse;KARTBESKRIVELSE; TIDSSKRIFTARTIKKEL;NGU; No.150;1-119 + p sider

Abstrakt:

The situation of the maps is shown on p. 6. They form the southern continuation of the map Tysfjord, recently described by the author (NGU no. 149). The petrology and chemistry of the rocks are reserved for a special paper. The main part of the district is highland with an average elevation of 6-700 m above sea level, as shown on the hypsographic curves, fig. 13. It has been completely glaciated and almost deprived of dÅbris and glacial drift. The highland is cut abruptly by the fjords, which penetrate nearly to the watershed, leaving only a narrow strip of land draining westwards to the Atlantic. Norway has here its narrowest part, the distance from the head of Hellemofjord to the frontier amounting to only 6.3 km. The extreme westerly position of the watershed is a main geomorphological feature of the district. A consequence of this are also the numerous ice-dammed lakes, which have existed here in late glacial time. Their situation is shown on fig. 2. Several of them are smaller local lakes west of the watershed. The main ice lakes were dammed against the Scandinavian watershed, and only a small part of them have therefore covered Norwegian territory. From north to south they are: Suorke Lake, which drained through Tappa Korso (Rieppi) to Mannfjord, Store Lule Lake to Hellemofjord, and Salojaure Lake to Sørfolla.

Lindahl, Ingvar; Nilsson, Lars Petter , 2001

	Kartlegging av talk/klebersteins-forekomstene i Linnajavri-området i Hamarøy, Nordland

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.2001.112;91 sider

Lindahl, Ingvar; Nilsson, Lars Petter , 2002

	Oppfølgende feltundersøkelser av talk- og klebersteinsforekomster i området Boarta-Gaskavarri (Linnajavri Nordområde), Hamarøy kommune, Nordland

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.2002.090;53 sider

Abstrakt:

Mandatet for sommerens feltarbeid var å vurdere klebersteinens tonnasje og kvalitet i Nordområdet, som råstoff for nedmalt talk. Rapporten beskriver resultatene fra feltundersøkelsene med fokus på tonnasjebeskrivelse. En hel rekke nye små klebersteinslinser og tilknyttede bergarter ble kartlagt i detalj, men det ble ikke oppdaget noen store nye forekomster. Vi regner nå med å ha kartlagt i overflaten alle vesentlige klebersteinsforekomster innenfor det vi her benevner som Linnajavri Nordområde, dvs den 10 km lange strekningen fra fjellsletten Boarta i NV fram til riksgrensen på fjellryggen Gaskavarre i SØ. Vi regner videre med å ha kartlagt de aller fleste smålinsene av kleberstein i Nordområdet. Det er ingen klare geologiske eller geofysiske indikasjoner på at noen av disse kan ha et mulig økonomisk potensiale på dypet, men det er mulig at helikoptergeofysikken er for grovmasket og flylinjene ugunstig orientert når det gjelder å fange opp anomaliene som ultramafittene gir. Til sammen 10 av forekomstene ble målt opp ved hjelp av laser, kompass, barometer og GPS. Det er utarbeidet kart over disse forekomstene (horisontalprojeksjon) med utregnet areal samt struktur-observasjoner. Tonnasjeestimater er også beregnet. Til sammen 6 av de 10 oppmålte forekomstene er så store ( 1 mill. tonn ) at de kan være av interesse for industrien. Mange av tonnasjeestimatene er likevel så usikre at geofysiske bakkemålinger med påfølgende modellberegninger bør gjøres. Dette kan være gunstige grunnlagsdata fofør man starter planleggingen av diamantboringer. Det gjelder i særdeleshet den antatt største forekomsten, linsen Cohkul-1, som har et relativt lite utgående i dagen, men har en tilknyttet helikoptermålt magnetisk anomali som indikerer at kroppen er stor på dypet. Til sammen 12 helt friske prøver á ca. 100 kg ble tatt ut med motorsag for videre kvalitetstester (oppredningsforsøk) ved SI

Nilsson, Lars Petter; Lindahl, Ingvar; Gautneb, Håvard , 2003

	Mineralkarakterisering av talk/kleberstein fra Linnajavri-området, Hamarøy kommune, Nordland

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.2003.027;17+193 sider

Abstrakt:

Rapporten gir en oppsummering av det arbeidet som er utført på mineralkarakterisering av talk/kleberstein innsamlet under feltarbeidet i 2000-2002. Resultatene er framstilt som en katalog for de fagfolkene som skal videreføre forsøk med oppredning av kleberstein fra Linnajavri-området. Rapporten gir en komplett oversikt over det prøvematerialet som er innsamlet, resultatene fra utførte hvithetsmålinger og kjemiske analyser av hoved- og sporelementer. Videre er det gjort semi-kvantitative mineralbestemmelser med XRD og mineralkjemiske analyser på SEM. Det er gjennomført en beregning av talkinnholdet i klebersteinern basert på kjemiske analyser og mineralogiske undersøkelser (SEM analyser og digital billedbehandling). Identifisering av mineralene og bestemmelse ac kornstørrelse er gjort med undersøkelser i gjennomfallende og reflektert lys. Det er gjort digital billedbehandling av slipbilder for å bestemme mengde opakmineraler (oksider) og deres kornstørrelsesfordeling.

Skilbrei, Jan Reidar; Nilsson, Lars Petter; Lindahl, Ingvar , 2003

	Magnetisk modellberegning av talk/klebersteinsforekomst ved Cohkul (Linnajavri Nordområde), Hamarøy kommune, Nordland

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.2003.044;17 sider

Abstrakt:

En hel rekke melangesoner og tulknyttede ultramafiske linser med klebersteinsforekomster er tidligere kartlagt innenfor det som er benevnt Linnajavri Nordområde, dvs. den 10 km lange strekningen fra fjellsletten Boarta i NV fram til riksgrensen på fjellgryggen Gaskavarre i SØ. Det er gjort magnetiske modellberegninger av den antatt største ultramafittkroppen , linsen Cohkul-1 (jfr. Lindahl og Nilsson, 2002) som har et relativt lite utgående i dagen, men som har en tilknyttet stor helikoptermålt magnetisk anomali. De flymagnetiske måleprofilene er plottet oppå topografiske og geologiske kart ( fra Lindahl og Nilsson, 2002). In-situ magnetiske målinger viser at det bare er ultramafitten som er magnetisk. Det er gjort magnetiske modellberegninger over utgående av ultramafittlinsen ved Cohkul. Det er modellert på et utplukk fra det magnetiske griddet (med programvare for 2 1/2D modellering), og på flylinjeprofiler (3D modellering). Modellformen framstår som en tykk og noe vridd diskos. Ellers minner formen om mange av de utgående linsene som er kartlagt. Dyprekkevidden kan være 300 til 500 m. Modellberegninger er sensitive for modellert dyp til topp av det magnetiske legemet. Følsomheten er relativt mye mindre for dypet til bunn av legemet. Det bør tas prøver for petrofysiske undersøkelser fra ultramafitten. Dette vil redusere usikkerheten ved modellberegningene. helikoptergeofysikken er generelt for grovmasket og flylinjene ugunstig orientert når det gjelder å fange opp anomaliene som de minstre ultramafittene gir. Det anbefales magnetiske bakkemålinger over ultramafitten ved Cohkul. Bakkemålingene bør legges over utgående. Da vil en få et sikrere grunnlag for å modellere dyp og fall til kroppen mot nordøst. Kart over magnetfeltet med foreslåtte bakkeprofiler er vist på en figur.

Lindahl, Ingvar ; Nilsson, Lars Petter , 2005

	Klebersteinsforekomstene i Linnajavri-området, Hamarøy kommune, Nordland. Statusrapport april 2005

;Norges geologiske undersøkelse;RAPPORT;NGU-rapport; No.2005.034;35 s. + 22 sider

Abstrakt:

NGU og Statskog har i felleskap påvist og kartlagt Norges største klebersteinsforekomster i Linnajavriområdet i Hamarøy kommune i perioden 2001-2004. Ressursene er meget store med et tjuetalls forekomster på mer enn 1 mill. tonn hver. De totale ressursene som regnes er meget store med et tjuetalls forekomster på mer enn 1 mill. tonn hver. De totale ressursene som regnes som påvist er til sammen på ca. 100 mill. tonn kleberstein hvorav mer enn 80% i den sørlige delen av området (i teksten benevnt som Sør-området). Klebersteinen som i gjennomsnitt holder ca. 50% talk har et økonomisk potensiale både som råstoff til talkproduksjon og som i gjennomsnitt holder ca. 50% talk har et økonomisk potensiale både som råstoff til talkproduksjon og som naturstein. Forekomstene representerer utvilsomt en viktig nasjonal ressurs.

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