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	THE ORE DATABASE
	Occurence 5605 - 023 Gjeddevann
	(Object Id: 914) (Last updated: 01.03.2005)

Operations

	From - To	Activity	Comments
	1993	Geology	Company/Institution :NGU
	1995 - 1996	Geophysics	Company/Institution :NGU
	1996	Core drilling	Company/Institution :NGU

Mineralization

	Era:	Proterozoic	Period:	Paleoproterozoic
	Genesis:	Shear zone formation	Form:	Plate
	Main texture:	Fracture filling	Min. distribution:	Disseminated (<20 % ore minerals)

Main grain size:

Fine grained (< 1 mm)

Main alteration:

	Strike/Dip:		Direction:
			Plunge:

Stratigraphic classification of host rock

Era:

Proterozoic

Period:

Paleoproterozoic

	Province:	Troms-Finnmark Basement Province
	Geotec.unit:	Polmak-Pasvik Greenstone Belt
	Tectonic complex:	South Pechenga
	Igneous complex:

Group:

Langvann Group

Formation:

Mineralogy

	Relationship	Mineral	Amount
	Gangue mineral	Quartz	Major mineral (>10%)
	Gangue mineral	Actinolite	Subordinate mineral (1-10%)
	Gangue mineral	Plagioclase	Subordinate mineral (1-10%)
	Gangue mineral	Graphite	Subordinate mineral (1-10%)
	Gangue mineral	Calcite	Subordinate mineral (1-10%)
	Ore mineral	Arsenopyrite	Major mineral (>10%)
	Ore mineral	Pyrite	Major mineral (>10%)
	Ore mineral	Gold	Major mineral (>10%)
	Ore mineral	Chalcopyrite	Subordinate mineral (1-10%)
	Ore mineral	Magnetite	Subordinate mineral (1-10%)
	Ore mineral	Pyrrhotite	Subordinate mineral (1-10%)

Information(s) in free text format

Free text

In 1993 gold-bearing quartzite boulders assumed to represent true outcrops were discovered by NGU during regional geological investigations of the Paleoproterozoic Pasvik-Polmak Greenstone Belt (Melezhik, 1995). The discovery point is located on the southern shore of a small shallow lake which Melezhik (1995) termed Gjedde or Pike Lake since his discovery of arsenopyrite-rick quartz boulders was the result of an attempt to stone a big pike. However, on a recently published orienteering map the lake is designated Lake Støvlevann (1:15 000, "Sukkeråsen", I.L. Pasvik-Hauk/Sandnes I.L., 1995). Core drilling in 1996 including 12 DDH with a total length of 600 m over a strike length of 350 m, showed that the mineralised outcrops at the shore of the lake actually represent large blocks of the underlying bedrocks. The gold mineralisation is therefore totally covered by blocky till. Based on the results of magnetic and electromagnetic (IP, SP, VLF) ground-surveys it can be concluded that the mineralisation gives no clear response. Detailed geochemical surveys of tills and top-soils in the area around the lake gave only weak anomalies in the mineralised area, except for the area west of the lake where mineralised bedrocks subsequently have been found by drilling by Scannor. The Gjeddevann gold occurrence is located to the lower peripheral part of the South Pasvik Thrust Zone, a regional thrust zone along the upper margin of the Pasvik Greenstone Belt. The gold mineralisation is hosted by a strongly sheared and imbricated volcanic sequence with planar structures striking E-W and dipping 30°-45° south. The host rocks comprise various phyllonitic biotite-, hornblende- and/or chlorite-rich schists as well as amphibolites and thin tectonic lenses of fine-grained quartzites (£ 5m). The sequence has been affected by three regional scale deformational events (D1-D3). Progressive N-S shortening with associated folding and thrusting occurred during the D1 and D2 events, when the sequence was infiltrated by large volumes of hydrothermal fluids as indicated by the high density of discordant and foliation-concordant quartz±calcite veins/stringers as well as widespread silicification. Native gold and arsenopyrite were probably precipitated during the end of the D2 event and preferentially as dissemination both in the schists adjacent to concordant quartz veins and along their margins. Native gold forms 1-100mm grains, occurring mainly as inclusions and micro-veinlets in cataclastic arsenopyrite and more rarely as isolated grains interstitial to arsenopyrite, pyrrhotite and/or gangue minerals. High gold concentrations (>1g/t) are invariably restricted to areas containing visible arsenopyrite, which means the westernmost 50m of the drilled area, i.e. in DDH 2, 3, 4, 5, 8 and 9. All of these drill holes, except for DDH 4 and 8 (not analysed), contain 1m-sections with average grades in the range 1.3-6.3 g/t Au. Although the gold mineralisation is hosted by a number of different lithologies, the highest gold grades are encountered in the main grunerite quartzite of DDH 2 with a maximum of 14.7 g/t Au over 0.25m. This quartzite carries three 1m-sections averaging 2.9, 6.0 and 6.3 g/t Au or combined, 2.5 g/t Au over 3.25m. The gold grades and the length of mineralised sections are either too low or too short to be of any economic significance. However, the gold mineralisation may represent the eastern peripheral part of a auriferous hydrothermal system which may have its centre further west along strike.

Bibliography:

From NGU's Reference Archive:

Melezhik, Victor A. , 1995

	The Gjedde Lake gold occurrence in Pasvik

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.95.079;25 pages

Abstract:

The Gjedde Lake gold occurrence was found in the Pasvik Valley during field work in the summer of 1993. The area is poorly exposed and this hampered the investigation. The gold mineralisation is related to the upper section of the Early Proterozoic Petsamo Supergroup. The host rocks are represented by cherty quartzites, considered as chemical sediments related to submarine exhalations. The gold mineralistion is assosiated with the sulphide facies of the cherty quartzites, while the oxidised magnetite-bearing sulphide-free rocks do not contain any gold. The highest gold content is ca. 10 ppm. Detailed mapping of discovery site outcrops and limited sampling have been done. Further investigations are recommended, including ground geophysical survey (IP) and mapping of boulders and outcrops within an area of 0.5 km². Some trenching and core drilling are needed in this poorly exposed terrain.

Lauritsen, Torleif , 1996

	Ground VLF and magnetic surveys at the Gjedde Lake in Pasvik, Sør-Varanger, Finnmark, 1996

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.96.085;7 pages

Ihlen, Peter; Often, Morten; Braathen, Alvar , 1996

	Core drilling at Gjedde Lake and regional structural geological investigations in Pasvik, North Norway

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.96.145;68 pages

Finne, Tor Erik , 1997

	Evaluation of detailed C-horizon sampling as prospecting methods at Gjedde Lake gold mineralisation

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.97.172;52 pages

Braathen, Alvar , 1997

	Results from a structural study in Pasvik, North Norway

;Norges geologiske undersøkelse;FAGRAPPORT;NGU-rapport; No.97.018;31 pages

Abstract:

This report describes results from structural investigations undertaken in Pasvik in l996. The Early Proterozoic rocks of the Pasvik (Petsamo) and Kobbefoss Groups, and Archaean gneisses were deformed during three ductile to semiductile stages, designated D1, D2 and D3. Typical structures such as foliation, cleavage, lineations and folds support the structural sub- division, and place constraints on the structural position of the Gjedde Lake gold occurrence.

Fieldsamples

	Sample No.	Sample type	Miscellanrous
	SP-30	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	SP-33	Bedrock	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	93/1	Bedrock	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	93/3	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	93/4	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	93/5	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing grunerite quartzite No. of registrated element analyses = 1
	93/6	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1
	93/6-1	Block	Sampler: Melezhik, V. Comment: Sulphide-bearing cherty quartzite No. of registrated element analyses = 1

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

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Analyse Results

from

Deposit Area 5605 - 023 Gjeddevann

Element analyses

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

Sample No.	Sample Type	Au#	As*	S%	V*	Cr*	Rb*	Sr*
SP-30	Block	9630.0	8	.66	28	10
SP-33	Bedrock	440.0	31500	.44	11	17	55.0	11.0
93/1	Bedrock	4740.0	13	1.18	17	16
93/3	Block	1250.0		.87	13
93/4	Block	1200.0	48	.59	9	7
93/5	Block	1000.0		.08	13	11
93/6	Block	4490.0	5842	.09	26
93/6-1	Block	9100.0	15	.85	21	6

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The fact sheet was created on 30.04.2024

Questions or comments regarding the fact sheet can be emailed to: ressursdatabaser@ngu.no

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