English version
	MALMDATABASEN
	Forekomstområde 1664 - 021
	(Sist oppdatert 05.jul.2023)

Betydning

Offentlig:

(No data)

Economical:

Lite viktig , (Confirmed 03.jul.2023 by Jan Sverre Sandstad)

Mineralization

	Era:	Paleozoic	Period:	Ordovician
	Dating:		Method:
	Genesis:	Vulkeks	Form:
	Main texture:		Min. distribution:	Massiv

Main grain size:

Main alteration:

	Strike/Dip:		Direction:
			Plunge:

Stratigraphic classification of host rock

Era:

Paleozoic

Period:

Ordovician

	Province:	Caledonides
	Geotec.unit:	Trondheim Nappe Complex
	Tectonic complex:	Gula Complex
	Igneous complex:

Group:

Gula

Formation:

Mineralogy

	Relationship	Mineral	Amount
	Gangue mineral	Quartz	Major mineral (>10%)
	Gangue mineral	Biotite	Subordinate mineral (1-10%)
	Ore mineral	Magnetite	Major mineral (>10%)

Lithology:

	Relationship	Rock	Origin
	Host rock	Båndet kvartsitt	Sedimentary Original rock :Exhalite
			Metamorphic facies :Greenschist

Opplysning(er) i fritekstformat

Fri tekst

Bjørnmyrgruva ligger i glissen granskog rett vest for ei myr i svært overdekket området ca. 150 m vest for gammelveien over Strandfjellet. Gruva ble drevet på ren magnetittmalm på 1820-tallet av Mostadmark jernverk. Den består av en vannfylt, tilnærmet trekantformet synk med lengste sider 4x6 m. Massiv magnetitt finnes i i fast fjell eller som en større blokk sørøst i synken. På tippen dominerer båndet kvartsittisk bergart i tillegg til finkornet, massiv magnetitt. Det er trolig at mineraliseringen er av samme type som ved Røsbekken som ligger 1,5 km lengre sør.

Bibliography:

From NGU's Reference Archive:

Torske, Tore , 1965

	Geology of the Mostadmarka and Selbustrand area, Trøndelag.

;Norges geologiske undersøkelse;TIDSSKRIFTARTIKKEL;NGU; No.232;1-83 + ka pages

Abstract:

The bedrock of the area consists of metamorphic epiclastic, volcanic, and intrusive rocks of assumed Lower Ordovician age, assigned to, and lithologically matching the rocks of, the Røros, Støren and Lower Hovin Groups of the Trondheim Region. A detailed petrographic description of the rock varieties is given. The metamorphic grade of all rocks corresponds to the Greenschist Facies. - Small ore deposits occur in connection with the volcanic rocks. They comprise pyrite-pyrrhotite ores of the Leksdal Type, mixed pyrite-magnetite ores, and iron oxide ores. - Lithological variations of the sedimentary rocks is tentatively correlated with events during the early periods of the Caledonian Orogeny. - The volcanism within the area seems to have started with a phase of explosive activity, followed by extrusion (mostly submarine) of copious amounts of spilitic lavas; towards the end of the main period of volcanism a new episode of explosive activity has produced what is called the upper pyroclastic horizon, comprising rocks ranging from coarse volcanic breccia to finegrained tuffs. - The intrusive rocks consist mainly of saussurite gabbros and quartz keratophyres. The latter are thought to be intrusive rather than effusive, and evidence is offered to support this. In some places the character of pyroclastic material points to a quartz keratophyre parentage. Thus, quartz keratophyres may have occurred both as intrusive and volcanic rocks.

Fieldsamples

	Sample No.	Sample type	Miscellanrous
	Bjørnmyrgruva-1	Dump	Sampler :J.S.Sandstad/...Stored :Løkken/...Size(kg) :2 Kommentar :Massiv, finkornet magnetitt med feltspat/apatitt? årer No. of registrated element analyses = 1 No. of registrated oxide analyses = 1

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

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Analyse Results

from

Forekomstområde 1664 - 021 Bjørnmyrgruva

Element analyses

( *=parts pr. million, #=parts pr.billion, Negative values means below detection limit value.)

Sample No.	Sample Type	Cu*	Zn*	Pb*	Co*	Ni*	Ag*	Au#
Bjørnmyrgruva-1	Dump	253	102	7	238	141	-.1	44.5

------------------

Sample No.	As*	Cd*	Ba*	Mo*	Sn*	Sb*	Bi*	Se*	Ga*
Bjørnmyrgruva-1	18	-.1	7896	2.50	-1	1	-0	-0.50	5.40

------------------

Sample No.	S%	V*	Fe%	Th*	U*	W*	Rb*	Sr*	Y*
Bjørnmyrgruva-1	.20	372	35.86	-0.20	0.80	-1	2.6	450.2	25.1

------------------

Sample No.	Zr*	Nb*	Ta*	Cs*	La*	Ce*	Pr*	Nd*	Sm*
Bjørnmyrgruva-1	26	0.90	-0.10	0.40	7.70	13.50	2.12	10.50	3.09

------------------

Sample No.	Eu*	Gd*	Tb*	Dy*	Ho*	Er*	Tm*	Yb*	Lu*
Bjørnmyrgruva-1	1.10	4.24	0.75	5.16	1.11	3.37	0.54	3.59	0.59

------------------

Sample No.	Be*	P*	Hf*	Hg*	Tl*
Bjørnmyrgruva-1	2	698	0.60	-0	-0

Oxide analyses

( All values are in % )

Sample No.	Sample Type	SiO2	Al2O3	TiO2	Fe2O3	MnO	MgO	CaO
Bjørnmyrgruva-1	Dump	19.09	4.21	0.34	51.27	13.79	0.58	2.78

------------------

Sample No.	Na2O	K2O	P2O5	Sum
Bjørnmyrgruva-1	0.51	0.03	0.16	93.00

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Faktaarket ble generert 13.06.2026

Spørsmål eller kommentarer vedrørende faktaarket kan mailes til: ressursdatabaser@ngu.no

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