|
|
|||||||||||||||||||||||
|
||||||||||||||||||||||||
Theme Magazines and Fact Sheets
EXPLORATION AND MINING IN GREENLANDGreenland Mineral Resources
Fact Sheet No. 8
Download pdf-file go_fs08.pdf (~250 kbyte). Requires pdf-reader, Acrobat GSview or similar
The gold potential of the Taartoq area is apparent
and significant, judged from several showings
hosted in different parageneses and associations.
Since the discovery of the main gold occurrence in
the area in 1971, a number of companies have
devoted substantial resources to assessing the ore
potential. GEUS has included the area in regional
survey projects since the 1950s. The Taartoq gold
field is so far representing the only South Green-
land Archaean hosted gold mineralisation with
average gold grades of 815 g/t, reaching up to a
maximum of 50 g/t gold.
and significant, judged from several showings
hosted in different parageneses and associations.
Since the discovery of the main gold occurrence in
the area in 1971, a number of companies have
devoted substantial resources to assessing the ore
potential. GEUS has included the area in regional
survey projects since the 1950s. The Taartoq gold
field is so far representing the only South Green-
land Archaean hosted gold mineralisation with
average gold grades of 815 g/t, reaching up to a
maximum of 50 g/t gold.
Geological setting
The Taartoq area, located in the heart of South West
Greenland, is considered as the Archaean foreland com-
posed of high-grade gneisses and greenstones (the
`Tartoq Group'). The environments for gold deposition
are sequences of volcano-sedimentary supracrustal
rocks, which rest unconformably upon the Archaean
gneisses of low to medium metamorphic grade.
Greenland, is considered as the Archaean foreland com-
posed of high-grade gneisses and greenstones (the
`Tartoq Group'). The environments for gold deposition
are sequences of volcano-sedimentary supracrustal
rocks, which rest unconformably upon the Archaean
gneisses of low to medium metamorphic grade.
The metavolcanics and metasediments are several kilo-
metres thick and are observed as dark green and rusty
greenstone layers. The Sermiligaarsuk fjord displays
several outcrops of `Tartoq Group' rocks and gold
showings.
metres thick and are observed as dark green and rusty
greenstone layers. The Sermiligaarsuk fjord displays
several outcrops of `Tartoq Group' rocks and gold
showings.
The basement gneiss has ages ranging from 2980-3500
Ma, and Taartoq greenstones are assumed to be late
Archaean, deposited between 2500 and 3000 Ma.
Ma, and Taartoq greenstones are assumed to be late
Archaean, deposited between 2500 and 3000 Ma.
The northern area (Iterlak) forms a tectonic enclave of
greenstones within the basement. The main part of the
eastern and south-eastern area is composed of monoto-
nous greenstones. A characteristic feature of the Iterlak
sequence is the abundance of acid meta-tuffs, mostly
sericite schists.
greenstones within the basement. The main part of the
eastern and south-eastern area is composed of monoto-
nous greenstones. A characteristic feature of the Iterlak
sequence is the abundance of acid meta-tuffs, mostly
sericite schists.
The southern area (Nuuluk) includes a prominent zone
of high-strain rocks - the Nuuluk Linear Belt. The belt is
400 x 4000 m, and is characterised by nearly parallel
structures and numerous thrusts. This sequence is com-
posed of mixed layers of brown weathered carbonate
schist, nodular greenschists and highly sheared volcano-
chemical sediments including iron oxide schists,graphitic
shales and sericite schists.
of high-strain rocks - the Nuuluk Linear Belt. The belt is
400 x 4000 m, and is characterised by nearly parallel
structures and numerous thrusts. This sequence is com-
posed of mixed layers of brown weathered carbonate
schist, nodular greenschists and highly sheared volcano-
chemical sediments including iron oxide schists,graphitic
shales and sericite schists.
Gold occurrences
Several gold occurrences are located within the Taartoq
metavolcanics reaching up to 50 g/t gold (over 0.6 m).
Gold occurs in pyritiferous quartz lenses and veins in
carbonatised shear zones, in pyrite-arsenopyrite-quartz
layers with gold grades around 815 g/t, and low grade
gold associated with banded iron formations. Other
types, only located in the southern area, involve copper
bearing parageneses with chalcopyrite, tennantite, and
chalcocite in concordant veins and lenses (grades up to
8 g/t gold). Locally, pyritic schists with varying graphite
content carry spahlerite and increased gold values of
2.5 g/t (and up to 6.7 % zinc).
metavolcanics reaching up to 50 g/t gold (over 0.6 m).
Gold occurs in pyritiferous quartz lenses and veins in
carbonatised shear zones, in pyrite-arsenopyrite-quartz
layers with gold grades around 815 g/t, and low grade
gold associated with banded iron formations. Other
types, only located in the southern area, involve copper
bearing parageneses with chalcopyrite, tennantite, and
chalcocite in concordant veins and lenses (grades up to
8 g/t gold). Locally, pyritic schists with varying graphite
content carry spahlerite and increased gold values of
2.5 g/t (and up to 6.7 % zinc).
Gold mineralisation is above all confined to linear belts
and carbonate-rich zones. The gold is some times visible
as discrete droplets within the sulphides on the micro
scale as well as in non-sulphide associations.
and carbonate-rich zones. The gold is some times visible
as discrete droplets within the sulphides on the micro
scale as well as in non-sulphide associations.
Gold is thought to have been introduced into the Taar-
toq greenstones during the formation of stratiform
exhalites with massive-sulphide and chert as sulphide
facies BIF. Regional metamorphism resulted in recrystalli-
sation and segregation of the chert into compact bodies
of quartz and residual massive-sulphide. Subsequent
episodes of shearing and intensive carbonate alteration
along the shear zones lead to the liberation and precipi-
tation of gold.
toq greenstones during the formation of stratiform
exhalites with massive-sulphide and chert as sulphide
facies BIF. Regional metamorphism resulted in recrystalli-
sation and segregation of the chert into compact bodies
of quartz and residual massive-sulphide. Subsequent
episodes of shearing and intensive carbonate alteration
along the shear zones lead to the liberation and precipi-
tation of gold.
The ratio between the content of gold and silver (true
fineness) has been calculated for some of sulphide para-
geneses in the Nuuluk area. It is noticeable that the
gold fineness decreases from layers with arsenopyrite-
pyrite (990) towards the tennantite (720) and the chal-
copyrite (500) lenses, thus pointing to a trend in mobili-
fineness) has been calculated for some of sulphide para-
geneses in the Nuuluk area. It is noticeable that the
gold fineness decreases from layers with arsenopyrite-
pyrite (990) towards the tennantite (720) and the chal-
copyrite (500) lenses, thus pointing to a trend in mobili-
The Taartoq gold field,
South West Greenland
Nuuluk gold locality within the greenstone of the `Tartoq Group'
south of the fjord Sermiligaarsuk, South-West Greenland.
south of the fjord Sermiligaarsuk, South-West Greenland.
sation of the silver during later diagenesis and
hydrothermal processes.
hydrothermal processes.
The gold occurrences in the Taartoq greenstones
are assumed to be deposited between 25003000
Ma, and are the only known Archaean gold miner-
alisation in South Greenland.
are assumed to be deposited between 25003000
Ma, and are the only known Archaean gold miner-
alisation in South Greenland.
Gold exploration
An extensive exploration activity has been carried
out in the 1000 km
out in the 1000 km
2
area, including several drill
programmes and geophysical surveying. Renzy
Mines Ltd, Cominco Ltd, GREENEX A/S and NU-
NAOIL A/S carried out most of the exploration
projects from the 1970s to the 1990s, whereas
GEUS has conducted general and specialised sur-
vey work since the 1950s.
Mines Ltd, Cominco Ltd, GREENEX A/S and NU-
NAOIL A/S carried out most of the exploration
projects from the 1970s to the 1990s, whereas
GEUS has conducted general and specialised sur-
vey work since the 1950s.
Among the geophysical exploration results is a re-
markable feature of the Nuuluk area with a signifi-
cant VLF anomaly in the Western Carbonate Zone.
Pyritic schists with graphite and banded sphalerite
are observed in both the northern and southern
portion of the zone. The geophysical anomaly sug-
gests a large conductive zone, which could be
equivalent to a sulphide body in excess of 20 mil-
lion tons of zinc ore. Limited follow-up of the
anomaly located graphite rich layers as conductors
only.
markable feature of the Nuuluk area with a signifi-
cant VLF anomaly in the Western Carbonate Zone.
Pyritic schists with graphite and banded sphalerite
are observed in both the northern and southern
portion of the zone. The geophysical anomaly sug-
gests a large conductive zone, which could be
equivalent to a sulphide body in excess of 20 mil-
lion tons of zinc ore. Limited follow-up of the
anomaly located graphite rich layers as conductors
only.
Short hole drillings (Winkie) were initially carried
out in 1982, with 23 holes totalling 460 m. Later,
the two most impressive occurrences in the
Nuuluk and the Iterlak areas have been core
out in 1982, with 23 holes totalling 460 m. Later,
the two most impressive occurrences in the
Nuuluk and the Iterlak areas have been core
drilled. Work to drill 13 holes
totalling 1364 m down to a
maximum of 120 m was car-
ried out in 1993.
Regional geochemical map-
ping and study of the
pathfinder As outline the field
with a gold potential.
Additionally, elevated Zn val-
ues in stream sediments char-
acterise the area where the
gold mineralised Archaean
greenstones are observed.
totalling 1364 m down to a
maximum of 120 m was car-
ried out in 1993.
Regional geochemical map-
ping and study of the
pathfinder As outline the field
with a gold potential.
Additionally, elevated Zn val-
ues in stream sediments char-
acterise the area where the
gold mineralised Archaean
greenstones are observed.
Concluding remarks
Gold occurrences in South
Greenland are demonstrated
to be located within the
Archaean `Tartoq Group'
rocks, similar to major gold
camps in `old' greenstone
Greenland are demonstrated
to be located within the
Archaean `Tartoq Group'
rocks, similar to major gold
camps in `old' greenstone
belts throughout the World. During exploration
activity in the 1980s and the 1990s, knowledge
about the gold field was increased and refined
since the discovery in 1971, and, consequently, the
potential for locating viable gold deposits here has
improved.
activity in the 1980s and the 1990s, knowledge
about the gold field was increased and refined
since the discovery in 1971, and, consequently, the
potential for locating viable gold deposits here has
improved.
Geological Survey of Denmark
and Greenland (GEUS)
Øster Voldgade 10
DK-1350 Copenhagen K
Denmark
Tel: (+45) 38 14 20 00
Fax.: (+45) 38 14 20 50
E-mail: geus@geus.dk
Internet: www.geus.dk
Bureau of Minerals and Petroleum
(BMP)
Government of Greenland
P.O. Box 930
DK-3900 Nuuk
Greenland
Tel: (+299) 34 68 00
Fax.: (+299) 32 43 02
E-mail: bmp@gh.gl
Internet: www.bmp.gl
Greenland Mineral Resources
Author:
K.Secher
Editor: K.Secher
Layout: GEUS, Grafisk
© GEUS 2004
ISSN: 1602-8171
Key references
Appel, P. W. U. and K. Secher (1984): On a gold mineralization
in the Precambrian Tartoq Group, SW Greenland. Journal
of the Geological Society, London,
141
: 273278.
Evans, D.M. & King, A.R. 1993: Sediment and shear-hosted
gold mineralization of the Tartoq Group supracrustals, south-
west Greenland, Precambrian Research
62
, 6182.
Nutman, A. P. and Kalsbeek, F. (1994a): A minimum age of
2944 ± 7 Ma for the Tartoq Group, South-West Greenland.
Rapport Grønlands Geologiske Undersøgelse,
161
: 3538.
Schjøth, F., Garde. A.A., Jørgensen, M.S., Lind, M., Moberg, E.,
Nielsen, T.F.D., Rasmussen, T.M., Secher, K., Steenfelt, A.,
Stendal, H.,Thorning, L. & Tukiainen. T. 2000: Mineral
resource potential of South Greenland, Danmarks og
Grønlands Geologiske Undersøgelse Rapport
2000/57
, 36
pp, CD-Rom included.
Secher, K., & Kalvig, P. 1987: Reconnaissance for noble and
base metal mineralisation within the Precambrian supracrustal
sequences in the Ivigtut-Kobberminebugt region, South-
West Greenland. Rapport Grønlands Geologiske
Undersøgelse
135
, 52-59.
Steenfelt, A. 2000: Geochemical signatures of gold provinces
in South Greenland. Transactions Institution of Minig and
Metallurgy, section B, Applied Earth Science
109
, B14B22.
Steenfelt, A. 2001: Geochemical atlas of Greenland West and
South Greenland, Danmarks og Grønlands Geologiske
Undersøgelse Rapport
2001/46
, 40 pp. (CD-ROM included).
Stendal, H. (ed.) 2000: Exploration in Greenland: discoveries of
the 1990s. Transactions of the Institution of Mining and
Metallurgy, section B, Applied Earth Science
109
, B1B66.
Metavolcanic rocks mixed with metasediments, belonging to the Tartoq Group
Amphibolite, marker horizons in gneiss
Mica schist (garnet, cordierite, silimanite bearing)
Gneiss, mainly granodioritic or quartz dioritic; biotitic, hornblenditic, muscovite-bearing, with agmatites
and enclaves of Tartoq Group greenschists
Gneiss with abundant gabbro-anorthositic enclaves. The matrix is mainly granodioritic to quartz dioritic
Granite (sensu lato), foilated biotitic, with enclaves of mica schist; with amphibolitic enclaves
Last modified: April 17, 2005
|
