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THE ORE DATABASE
Occurence 4203 - 013 Klodeborg
(Object Id: 5210)
(Last updated: 29.11.2001)
Location
County: Agder Municipality: Arendal (4203)
Map 1:50000: Arendal (1611-4) Map 1:250000: Arendal
Coordinate system: EU89-UTM Zone 32
East: 483865 m. North: 6478910 m.
Longitude: 8.7235490 Latitude: 58.4505840
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Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Importance
Raw material meaning: Little Importance (reg. 18.02.2015)

Resources and production
Activity: Mining Reserves:
Operating method: Open pit and underground mining Historical production: 450 thousand tons


Products
Element/product Crude ore grade or quality Reg. date
Fe 50 % 29.11.2001

Operations
From - To Activity Comments
1620 - 1799 Regular production Company/Institution :Different iron works
In this period the mines were worked periodically by different small iron works including Moss, Fossum, Bærum, Næs and Fritzøe jernverker.
1800 - 1867 Regular production Company/Institution :Fritzøe jernverk
1868 - 1916 Regular production Company/Institution :Næs Jernverk
1870 - 1916 Regular production Company/Institution :Næs jernverk

Mineralization
Era: Proterozoic Period: Mesoproterozoic
Genesis: Skarn formation Form: Plate
Main texture: Massive Min. distribution: Massive (>50 % ore minerals)
Main grain size: Fine grained (< 1 mm) Main alteration: Skarn formation
Strike/Dip: 55 / 70 Direction: 190
Plunge: 45
Stratigraphic classification of host rock
Era: Proterozoic Period: Mesoproterozoic
Province: South Norwegian Basement Province
Geotec.unit: Bamble Complex
Tectonic complex:
Igneous complex:
Group: Formation:

Mineralogy
Relationship Mineral Amount
Gangue mineral Garnet Major mineral (>10%)
Gangue mineral Calcite Major mineral (>10%)
Gangue mineral Diopside Major mineral (>10%)
Gangue mineral Biotite Subordinate mineral (1-10%)
Gangue mineral Hornblende Subordinate mineral (1-10%)
Gangue mineral Scapolite Subordinate mineral (1-10%)
Gangue mineral Spinel Accessory mineral (<1%)
Ore mineral Magnetite Major mineral (>10%)
Ore mineral Pyrite Accessory mineral (<1%)

Lithology:
Relationship Rock Origin
Host rock Marble Sedimentary
Original rock :Limestone
Metamorphic facies :Granulite
Wall rock Migmatitic micaceous gneis Sedimentary
Original rock :Greywacke
Metamorphic facies :Granulite
Wall rock Banded calc-silicate gneisses Sedimentary
Original rock :Marl
Metamorphic facies :Granulite
Wall rock Granitic pegmatite Intrusive
Original rock :Granite pegmatite
Metamorphic facies :Amphibolite
Wall rock Charnockite Intrusive
Original rock :Hypersthene granodiorite
Metamorphic facies :Granulite
Wall rock Fine-grained felsic gneiss Extrusive
Original rock :Rhyolite
Metamorphic facies :Granulite
Wall rock Amphibolite Extrusive
Original rock :Basalt
Metamorphic facies :Granulite
Wall rock Quartz dioritic orthogneiss Intrusive
Original rock :Quartz diorite
Metamorphic facies :Granulite

Structures
Location: Type: Orientation(360 gr.): Relation to min.:
Host rock Fold axis Dir./Plunge :163 / 60 Post-mineralisation ;...Effect :Modifies
Wall rock Mineral banding Strike/Dip :49 / 80 Pre-mineralisation ;...Effect :Modifies
Wall rock Mineral banding Strike/Dip :58 / 67 Pre-mineralisation ;...Effect :Modifies

Information(s) in free text format
Free text
The gneiss complex in the Klodeborg mining field comprises a strongly folded sequence of alternating units of amphibolites, fine-grained felsic gneisses (meta-volcanites?), migmatitic micaceous gneisses, calc-silicate gneisses and diopside-garnet-scapolite skarns. The two latter contain occasionally subordinate marble units. The sequence is partly truncated by a complex of quartz-dioritic to granodioritic orthogneisses and charnockites as well as by late, weakly deformed granitic pegmatite dykes. A number of individual mines and prospects were worked for semi-massive to massive magnetite ores occurring as concordant to sub-concordant zones in the skarns and locally in the calc-silicate gneisses. The ore zones is composed of fine-grained magnetite intergrown with diopside, calcite, garnet, hornblende, biotite and spinell. The ores carry only accessory amounts of sulphides, mainly pyrite. The ore grades were in the range 40-50 % Fe, 1.5-2.2 % Mn, 0.15 % Ti, 0.01-0.,03 5 P, 0.02-0.05 % S, 0.2-0.3 % Zn. The ores are particularly high in manganese compared with other skarn iron ores in the Arendal district. Most of the ore production in the mining field came from the Klodeborg ore zone which can be followed continuously over a distance of about 375 m. It strikes NE-SW and dips 50°-75° SE. The dip of the ore zone becomes gradually steeper with depth. The ore zone show a pinch and swell structure and forms a S-shaped fold structure in its middle part (Jordet mine). Both the ore bodies and the late folds plunge 45°-60° towards SSW-SSE. The individual mines which is up to ? 300 m deep (mine?), is located in fold hinges (Western Kjenli and Jordet mines) and swells with a thickness of 5-16m. The most important mines, mentioned in order from northeast towards southwest, are the Northern Klodeborg, the Southern Klodeborg, Jordet, Eastern Kjenli and Western Kjenli mines. The Evens mine is situated in a separate ore zone representing a disconnected member of the Klodeborg zone further southwest. Foss and Kjenliås mines is situated in the northwestern part of the ore field.

Bibliography:
From NGU's Reference Archive:
Vogt, J.H.L. , 1908
De gamle norske jernverk
;Norges geologiske undersøkelse;TIDSSKRIFTARTIKKEL;NGU; No.46;83 pages
Abstract:
Diese Abhandlung bespricht die früheren norwegischen, mit Holzkohle betrieben Eisenwerke.

Vogt, J.H.L. , 1910
Norges jernmalmforekomster
;Norges geologiske undersøkelse;TIDSSKRIFTARTIKKEL;NGU; No.51;225 pages
Abstract:
Magmatische Ausscheidungen (I-VI).

Vogt, J.H.L. , 1918
Jernmalm og jernverk. Særlig om elektrisk jernmalm-smelting.
;Norges geologiske undersøkelse;TIDSSKRIFTARTIKKEL;NGU; No.85;181 pages

Bugge, Jens A.W. , 1960
Description of mines and deposits. Skarn iron ore deposits in the Arendal district.
;Norges geologiske undersøkelse;EKSKURSJONSGUIDE; TIDSSKRIFTARTIKKEL;NGU; No.212m;26-38 pages

References not to be found in NGU's Reference Archive.:
Langberg, C.A.: Myntmester Casper Herman Langbergs manuskript om Jernverkene. Norges geologiske undersøkelse.

The fact sheet was created on 02.05.2024
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