Litteraturfortegnelser: |
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Karlsen, Tor Arne; Nilsson, Lars Petter , 2000 |
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;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.99.135;146 sider |
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Abstrakt: |
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Information about talc and soapstone deposits registered in NGU's different databases and various available literature have been collected and described in the present report. Around 400 deposits/occurrences are known, but the detail of the available information varies widely. By reading old field-books as well as old manuscripts, maps, etc. dating as far back as A.D.1758, quite a lot of data has been found. The result of the work shows that most described talc in Norway is of ultramafic origin and is associated with serpentinites. The most common mineral association is talc + breunnerite. Different talc-provinces can be defined from the registered and non-registered data, the most important being Nord-Gudbrandsdalen, Altermark and Stølsheimen. While Altermark and Stølsheimen have been investgated in some detail with respect to talc as an industrial mineral, the Nord-Gudbrandsdalen talc province has been investigated both for milling talc and for soapstone use as dimension stone. Deposits that are probably extensive, but have so far not been investigated in detail, include the Lesjehorrungane deposits in the Nord-Gudbrandsdalen region and the Raudfjellet deposit in Nord-Trøndelag. The fractionated metakomatiites (pale green talc-chlorite rocks) of the southern part of the Palaeo-proterozoic Karasjok Greenstone Belt in Finnmark, Northern Norway, possibly represents, by far, the largest accumulations of talc in Norway. These rocks are recently mapped, for the first time, but other critical information is, however, very scarce. |
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Spalteganger i Sør-Varanger. |
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;Norsk geologisk forening;TIDSSKRIFTARTIKKEL;Norsk geologisk tidsskrift; Olaf Holtedahl på 60-årsdagen 24. juni 1945.; No.25 (1-4);127-146 sider |
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Abstrakt: |
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The coastal districts of Sør-Varanger, Petsamo, and Murmansk are intersected by dark dykes. Two main directions are much in evidence, i.e. approximately N 25 W and N 25 E. Dykes in a third direction, N 80 W, are also encountered, but to a far lesser extent. Only dykes the widths of which are more tham 10 m are shown on the map. Maximum width 80 m. The dip is verticaL or very steep. Younger than the dykes are tectonic lines, along which horizontal dislocations have occurred. A block structure is thus developed, and always the northernmost block is seen to have moved towards the north. The terrain is built up of various pre-Cambrian gneisses, mostly striking N 40 W. Petrographically the dykes are divided into four groups. I. Diabases, the principal minerals being plagioclase (composition: core 55 An, rim about 35 An) and diopsidic pyroxene. II. Spessarites (=altered diabases), mineral constituents being now plagioclase (core 55 An, rim 25 An) and green hornblende, secondary from pyroxene, and also some quartz. III. Oceanitic dykes: plagioclase (core labradoritic), diopsidic pyroxene, olivine (with about 15 per cent of fayalite). IV. Quartz diorites, with plagioclase (core 15-20 An, rim 8 An), green hornblende, quartz. The mineral contents might indicate that groups I and III are Younger than groups II and IV. Observations from the intersections of the dykes only in a few cases give positive informations as to the relative ages of the dykes. However, one dyke, a variant of group III, is younger than another dyke, the type of which, unfortunately, is unknown. Furthermore, a variant of group I is younger than a dyke of group II. The object of this paper is to show the interesting map pattern formed by the dykes, and to point out the tectonic problems relating to the directions of the dykes and the younger tectonic lines. |
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