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	Occurence 0 - 000 FEIL
	(Object Id: ) (Last updated: 14.10.2020)

Mineralization

	Era:	Proterozoic	Period:
	Genesis:	Regional metamorphic	Form:	Lens
	Main texture:	Banded	Min. distribution:

Main grain size:

Fine grained (< 1 mm)

	Strike/Dip:		Direction:
			Plunge:

Stratigraphic classification of host rock

Era:

Period:

	Province:
	Geotec.unit:
	Tectonic complex:
	Igneous complex:

Group:

Formation:

Information(s) in free text format

Free text

The kyanite quartzite of Tverrådalen is situated about 8 km beeline and 12 km by road SE of the community centre Skei at the innermost part of Øvstebødalen. The valley is here called Tverrådalen. The kyanite quartzite occurs at the southern steep slope at the altitude 300 m a.s.l. and 100 m above the river Tverråa. The outcrop extends 10 x 5 m. The deposit was studied in detail by Wanvik (1998). Two core drill holes, 9 and 5 m in depth, were performed. The thickness of the kyanite quartzite lens dipping 85° southward is 5.5 m. The deposit is situated in the border area between the basal, autochthonous Proterozoic gneiss units and the allochthon Caledonian nappe rocks that extends from the Trondheim region along Surnadal and further westwards to the Molde area. Detailed mapping of the area was carried out by Tørudbakken (1982). The kyanite quartzite lens is associated with small amphibolite lenses with a thickness of 5 to 50 m. Both units are hosted in granitic gneiss of Middle Proterozoic age (0.9-1.6 billion years). The thrust zone of the Caledonian nappes is about 1 km north of the deposit. The average composition of 11 samples from the kyanite quartzite of Tverrådalen is 65 wt.% quartz, 31 wt.% kyanite, 3-5 wt.% muscovite and 0.5 wt.% rutile wherby the quartz content varies between 75 and 55 wt.% and the kyanite content between 20 and 44 wt% (Wanvik 1998). SiO2 varies between 68 and 83 wt.% and Al2O3 between 13 and 31 wt.%. The average crystal size of quartz is 0.318 mm (n=200). Kyanite plates are about 800 µm in length and contain common inclusion of quartz. Occasionally, kyanite is overgrown by retrograde muscovite along micro-shear zones. About 10% of the kyanite crystals are completely sericitised. Quartz of the Tverrådalen deposit has an average Ti content of 10.6 ppm. Al varies between 14.0 and 18.5 ppm. Li, Be, B, Mn, K, Ca and Fe are generally below the limit of detection. The average Ge concentration is 0.43 ppm.

Photo(s) from the Deposit area:

Photo no. 1 showing Outcrop of the Tverrådalenl kyanite quartzite" Photo no. 2 showing Section of the Tverrådalen kyanite quartzite" Photo no. 3 showing Micrograph of kyanite quartzite"

Bibliography:

From NGU's Reference Archive:

Tørudbakken, Bjørn O , 1982

	En geologisk undersøkelse i nordre Trollheim ved Surnadal, med hovedvekt på sammenhengen mellom strukturer, metamorfe og aldersforhold.

;UiO Geologisk fellesråd;AVHANDLING

Wanvik, Jan Egil , 1998

	Kyanite investigations in Tverrådalen, Surnadal

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.98.080;23 pages

	Abstract:
	A kyanite-quartzite south-east of Skei in Surnadal has been investigated by field sampling and core drilling with Pack Sack equipment. The 5-6 m thick layer, identified only in a single outcrop, has an average kyanite content of 30% according to analyses of the drill cores. The deposit has a near vertical plunge and the lateral extension is unknown, due to lack of outcrops.

Müller, Axel ; Wanvik, Jan Egil ; Kronz, Andreas , 2005

	Norwegian kyanite quartzites - potential resources of high purity quartz?

;Norges geologiske undersøkelse;RAPPORT;NGU-rapport; No.2005.039;70 s. pages

	Abstract:
	Forkortet: This study represents an evaluation of Norwegian kyanite quartzite occurrences as potential deposits of high purity quartz raw material. Kyanite quartzites are rare fine-grained with 70 to 85 vol. % quartz and > 15 vol. % kyanite (Al2SiO5) which occur in Proterozoic supracrustal rock units. Kyanite quartzites form stratiform lens-shaped bodies, which can extend several kilometers.

Fieldsamples

	Sample No.	Sample type	Miscellanrous
	DH1 0-3.5m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-poor kyanite quartzite No. of registrated oxide analyses = 1
	DH1 3.5-4.8m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	DH2 0-1.1m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	DH2 1.1-3.5m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	DH2 3.5-5.5m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	DH2 5.5-9.1m	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	1907401	Bedrock	Sampler: Muller/...Stored: NGU Comment: Kyanite-poor kyanite quartzite No. of registrated element analyses = 1 No. of registrated mineral analyses = 3 No. of registrated oxide analyses = 1
	5	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	6	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	7	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-poor kyanite quartzite No. of registrated oxide analyses = 1
	8	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-rich kyanite quartzite No. of registrated oxide analyses = 1
	9	Bedrock	Sampler: Wanvik/...Stored: NGU Comment: Kyanite-poor kyanite quartzite No. of registrated oxide analyses = 1

NB! All analyse values are shown at the end of the printout.:

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The fact sheet was created on 06.05.2024

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