TALK

Det er foretatt kjerneboring og geofysiske undersøkelser av klebersteinsfore- komster rundt et gammelt brudd ved Klungen gård, Melhus. Klebersteinsforekomsten ligger som en plateformet kropp omtrent parallelt med terrengoverflaten. Totalt anslår vi mektigheten av tilgjengelig kleberstein til å ligge mellom 7 og 20 meter. En granittgang skjærer på skrå oppover i kleber- steinssonen og sperrer for drift på de dypere deler av klebersteinen i om- rådets nordøstlige deler. Forekomsten viser interne vekslinger mellom karbonat- rik, myk og karbonatfattig, hard kleberstein, hvorav førstnevnte totalt utgjør ca. 70%. Store deler av forekomsten er relativt forskifret, og det foreligger en viss fare for at dette virker negativt på blokkstørrelse og bearbeidings- egenskaper. Lømasseoverdekningen i området er tolket ut ifra borhull og geo- radar. Det ble påvist en gammelø skrottipp opp til 9 meter mektig øst for bruddet, og vi kan med rimelig stor sikkerhet spore konturene av et gjenfylt, gammelt brudd i sydøst. Videre ser vi fra undersøkelsene at vi jevnt over har mindre enn 4 meters overdekning på flaten vest for hovedbruddet og i området rundt borhull 6 og 9. Disse områdene vil uten tvil være de best tilgjengelige for bruddrift.

Chemical characterisation of flotation test material have been carried out on commision for Norwegian Talc AS. Comments on the chemistry with respect to the mineralogical content and to content of toxic elements are made.

(Forkortet) Rapporten oppsummerer resultater fra befaring av ofiolittfragmenter i Snåsa og Lierne i månedsskiftet juni-juli samt en kort oppfølgingtur i oktober 1999. Etter undersøkelse av en hel rekke ofiolittfragmenter står vi igjen med to som det er klart verd å følge opp med hensyn til mineralressurs-potensialet nemlig Raudfjellet i Snåsa og FJellraudberget i Lierne.

I forbindelse med kartlegging av talkforekomster har NGU utført magnetiske målinger over Kvanndalen-forekomsten. Tidligere geofysiske helikoptermålinger har vist at metoden er velegnet for påvisning av ultramafitt i dette området. Hensikten med bakkemålingene var å se om det var sammenheng mellom tre tidligere påviste blotninger av ultramafitt. De tre kartlagte kroppene ga klare magnetiske anomalier. De magnetiske målingene har vist at det er ingen sammenheng mellom dem, og at forekomsten av ultramafitt i dette området består av tre separate og klart avgrensede kropper.

XRF-analyses of products from beneficiation tests of Nakkan talc, made by OMYA GMBH, is described. The results are compared with earlier test-results from Nakkan and from the mine. The mineralogical compositions have been estimated from the chemical data. The purest talc products contain around 96-97% talc and, in addition, minor amounts of chlorite and carbonate. The carbonate-product "Mag 2" contains around 80% carbonate, 15% talc and 5% chlorite. Based on XRF analyses, the Ni content in the talc products is around 0,16%, which is comparable to earlier studies of Nakkan products, but lower than in products from the mine which contain around 0,24%. If similar procedures have been followed in the benefication process, a general lower content of Ni in the talc lattice from the Nakkan deposit compared to the mine is indicated. Instead, more Ni is bound in sulphides and spinels. Although not encountered earlier in the Altermark talc by the present author, possible trace amounts of As are weakly indicated. Since important trace elements occur in very small amounts or below the detection level by XRF, it is recommended to apply other analytical methods (ICP-AES, AAS, LECO) with lower detections levels to achieve more correct numbers.

Fortrolig til 01.01.2002. A Reconnaissance study of talc has been carried out in selected parts of the Norfjord area. In the area between Norfjord and Hornindalsvannet a considerable number of ultramafic lenses occur along a certain level in the host rock. The ultramafites are highly schistose and consist primarily of serpentine. Talc-carbonate rocks/soapstone occur along the margins. Based on our field visit, the talc-carbonate rocks appeared to be intimately interlayered with the host serpentinite, such that large, homogeneous, high-quality volumes of pure rocks were not proven. For this reason, whiteness-values are rather low (53-71%). Despite the negative results, it is still possible that some of the larger ultramafic lenses in the area carry more pure talc-carbonate rocks. South of Norfjord, in the vicinity of Davik, talc-carbonate rocks occur at the margins of three closely associated ultramafic lenses termed "Storekleberen and "Sørekleberen". The deposits have been studied by Fure (1996). A commented summary of his investigation is given in this report.

Det har blitt utført permroll separasjon og hvithetsmåling av rågods, magnetisk og umagnetisk fraksjon på talkrik kleber fra Grunnes, Nyeng, Steien og Brokskardet kleberforekomster i Troms. Disse er de mest talkrike forekomstene som er kjent i fylket. Alle forekomstene er små og svært overdekket. Grensene mot sidebergartene er ikke blottet og noen intern sonering kan heller ikke studeres. Prøvene ble knust til kornstørrelse mellom 0.1 til 0.25 mm. Det var kun prøvene fra Steien og Brokskardet som ga noen umagnetisk fraksjon etter permroll separasjon. Høyeste målte hvithet var på 71.0%R457 fra umagnetisk fraksjon Steien. Det er derfor klart at ingen av forekomstene har hvithetstall som ligger i nærheten av interessante verdier for bruk av talk som fyllstoff.

As a part of the development of the Nakkan deposit in Altermark a study focused on mineralogy has been carried out. Detailed field inspections of drill cores from 1997 and 1998 are described. The inspection shows that zones contaminated by amphibole are very few and small. XRD, XRF and microscopic analyses were carried out from selected samples from the 1997-drill cores. Microprobe analyses have been carried out on selected samples from the talc mine, Store Esjeklumpen and the Nakkan deposits, with specific attention to the Ni-content in the talc-lattice. From this study it seems clear that there are large variations in the NI-content in the talc-lattice. From this study it seems clear that the magnetite content is much lower than previously indicated by the method based on removal of magnetic matter. From the XRF-chemical analyses, a method is described and used to estimate the mineral content of the samples. No clear differences are found regarding the content of talc, breunnerite and chlorite. But unfortunately, very few samples from the mine have been investigated, and more samples are urgently needed in order to make reliable conclusions.

The chemistry of products from benefication tests of Altermark talc made by Pluss-Staufer AG is described. The earlier conclusions that the ore is very pure when it comes to elements with potential risks to health have been confirmed, although minor amounts of Cr and Ni are present. Of major importance is the composition of talc-products from the Nakkan deposits, which is currently being investigated, and the current mine as well as their relationship to chemical composition of the crude ore. Pluss Stauffer has succeeded in making pure talc-products of high quality of the Altermark talc. Some slightly different results were obtained from the Nakkan ore, with respect to recovery and whiteness, which were also element characteristics of products, but with some small variations in the content of Ni and Cr. The content of Ni and Cr are lowest in the Nakkan product. Estimation of mineralogy from the chemical data, indicate that the amount of talc in the best products reaches around 95%, the remainder being carbonates and chlorite. In the present report a model is presented which explains the variations in the Ni and Cr contents in relation to the grade of talc-carbonate alteration. With progressive alteration of serpentinite to talc-carbonate the magnetite and Ni-bearing sulphides disappear. The Fe from magnetite moves into carbonate, talc and chlorite, while Ni from the sulphides moves into talc, and to a limited extent, into carbonate. Chromium, which is abundant in magnetite, moves primarily into chlorite, but to a much more limited extent also into talc.