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THE ORE DATABASE
Deposit Area 1640 - 042
(Last updated 27.okt.2023)

Name of Deposit Area : Lomtjønna
(Object Id : 1640,042,00,00)
Location
County : Sør-Trøndelag (16) Municipality : Røros (1640)
Map 1:50000: Røros (1720-3) Map 1:250000: Røros
Marking point: Longitude: 11.2606350 Latitude: 62.5550100
EU89-UTM Zone 32 (Coordinates IS confirmed)
X-coord: 616229 m. Y-coord: 6938046 m.
Commodity
Main Type: Base metals (Cu,Zn,Pb,Fe sulphides, As,Sb,Bi,Sn) Sub Type: Sulphides
Element(s): Kis
Production
Activity: Mining Reserves:
Prod. method: Open pit and underground mining Production:
Prod. status: Disused, closed Volume of dump: 200 m3

Importance
Public: Little Importance (reg. 18.02.2015)
Economical: Minor interest , (Confirmed 19.okt.2001 by Terje Bjerkgård)

Products
Element/product Crude ore grade or quality
CU
KIS

Operations
From - To Activity Comments
Test mining
1997 - 1997 Sampling Company/Institution :NGU

Mineralization
Era: Paleozoic Period: Ordovician
Dating: Method:
Genesis: Volcex Form:
Main texture: Banded Min. distribution: Disseminated (<20 % ore minerals)
Main grain size: Fine grained (< 1 mm) Main alteration: Chloritisation
Strike/Dip: Direction:
Plunge:
Stratigraphic classification of host rock
Era: Paleozoic Period: Ordovician
Province: Caledonides
Geotec.unit: Røros Nappe Complex
Tectonic complex:
Igneous complex:
Group: Aursund Group Formation:

Mineralogy
Relationship Mineral Amount
Gangue mineral Chlorite Major mineral (>10%)
Gangue mineral Muscovite Major mineral (>10%)
Gangue mineral Quartz Subordinate mineral (1-10%)
Gangue mineral Garnet Subordinate mineral (1-10%)
Gangue mineral Amphibole Subordinate mineral (1-10%)
Ore mineral Pyrrhotite Major mineral (>10%)
Ore mineral Chalcopyrite Major mineral (>10%)
Ore mineral Pyrite Subordinate mineral (1-10%)
Ore mineral Magnetite Subordinate mineral (1-10%)

Lithology:
Relationship Rock Origin
Wall rock Semipelitic muscovite schist Sedimentary
Original rock :Greywacke
Metamorphic facies :Greenschist
Wall rock Metagabbro Intrusive
Original rock :Gabbro
Metamorphic facies :Greenschist

Structures
Location: Type: Orientation(360 gr.): Relation to min.:
Wall rock Foliation Strike/Dip :220 / 46
Wall rock Fold axis Dir./Plunge :258 / 21

Information(s) in free text format
Free text
Lomtjønna gruve ligger i tett skog i østvendt li ca. 600 m nordøst for Lomtjønna. Gruva består av en dagskjæring mot nordvest i en skrent ca. 5 m lang og 2-3 m dyp som fører inn til en vannfylt synk ca. 4 x 2.5 m i omriss. Forekomsten ligger på kontakten mellom semipelittisk muskovittskifer og en større kropp med metagabbro. Kontakten mellom bergartene er skarp. Mineraliseringen er tilknyttet skifrig og vesentlig biotitt-klorittomvandlet gabbro. Stedvis opptrer hyppig euhedral granat (2-3 mm) og 3-4 mm amfibolnåler. Mineraliseringen består hovedsaklig av mm til dm-tykke bånd med kobberkis og magnetkis, vesentlig i form av svake impregnasjoner, men også enkelte massive bånd. Ellers opptrer stedvis spredte < 1 mm pyrittkuber og < 1mm magnetitt-oktahedre.

Fieldsamples
Sample No. Sample type Miscellanrous
Lomtjønna-1 Dump
Sampler :T. Bjerkgård
No. of registrated element analyses = 1
ST0171.01 Dump
Sampler :Terje Bjerkgård/Leif Furuhaug/...Stored :Løkken/...Size(kg) :2
Comment :Semimassive bands (< 2 mm) of chalcopyrite and pyrrhotite in schistose amphibole-chlorite schist.
No. of registrated element analyses = 1
ST0171.02 Dump
Sampler :Terje Bjerkgård/Leif Furuhaug/...Stored :Løkken/...Size(kg) :2
Comment :Schistose metagabbro with very weak impregnation of pyrrhotite and chalcopyrite, occuring in mm-sized streaks.
No. of registrated element analyses = 1
ST0171.03 Dump
Sampler :Terje Bjerkgård/Leif Furuhaug/...Stored :Løkken/...Size(kg) :2
Comment :Amphibole-garnet-biotite-chlorite schist with weak impregnation as streaks of pyrrhotite, lesser chalcopyrite, scattered pyrite cubes and octahedrons of magnetite.
No. of registrated element analyses = 1
399706 Dump
Sampler :MINDEX ASA
No. of registrated element analyses = 1
NB! All analyse values are shown at the end of the printout.:

Name of Locality : Skjerp
(Object Id : 1640,042,01,00)
Location
County : Sør-Trøndelag (16) Municipality : Røros (1640)
Map 1:50000: Røros (1720-3) Map 1:250000: Røros
Marking point: Longitude: 11.2610790 Latitude: 62.5554830
EU89-UTM Zone 32 (Coordinates IS confirmed)
X-coord: 616250 m. Y-coord: 6938100 m.
Commodity
Main Type: Base metals (Cu,Zn,Pb,Fe sulphides, As,Sb,Bi,Sn) Sub Type: Sulphides
Element(s): Kis


Analyse Results
from
Deposit Area 1640 - 042 Lomtjønna

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#
Lomtjønna-1 Dump 61800 4830 9 280 68 13.2 426.0
ST0171.01 Dump 44732 4951 -3 311 82 9.5 446.0
ST0171.02 Dump 1146 164 3 59 19 -.3 1.0
ST0171.03 Dump 644 250 -3 46 40 -.3 2.0
399706 Dump 11000 919 23 97 37 1.2 283.0
------------------
Sample No. Pt# Pd# As* Cd* Ba* Mo* Sn* Sb* Bi*
Lomtjønna-1 2.5 .5 2 17.6 90 18.80 7 0 13
ST0171.01 2.0 -1.0 -2 21.8 38 10.00 -3 47
ST0171.02 -1.0 1.0 4 .6 -1 -1.00 4 -3
ST0171.03 3.0 2.0 3 1.1 203 -1.00 -3 3
399706 117 2.4 63 8.00 3 3
------------------
Sample No. Se* Ga* Ge* In* S% V* Cr* Mn* Fe%
Lomtjønna-1 116.00 11.05 0.49 5.47 10.00 81 46 2990 23.40
ST0171.01 13.00 70 56 904 22.69
ST0171.02 2.03 109 1 688 8.09
ST0171.03 .76 213 75 1256 12.53
399706 67 268 1272 12.10
------------------
Sample No. Th* U* W* Rb* Sr* Y* Zr* Nb* Ta*
Lomtjønna-1 3.19 1.00 0 22.7 38.9 10.4 15 3.10 0.25
ST0171.01 6.00 -8.00 -2 5.0
ST0171.02 -2.00 -8.00 -2 10.0
ST0171.03 3.00 -8.00 2 3.0
399706 8.0
------------------
Sample No. Cs* La* Ce* B* Li* Be* Sc* Ti* Te*
Lomtjønna-1 2.19 9.20 20.50 9 0 11.20 1547 12.95
ST0171.01 4.00 -3
ST0171.02 1.00 -3
ST0171.03 1.00 -3
399706 5.00 899
------------------
Sample No. Hf* Re* Tl*
Lomtjønna-1 0.40 0 1
ST0171.01
ST0171.02
ST0171.03
399706

The fact sheet was created on 19.05.2024
Questions or comments regarding the fact sheet can be emailed to:
ressursdatabaser@ngu.no
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