|
|
|||||||||||||||||||||||
|
||||||||||||||||||||||||
Theme Magazines and Fact Sheets
EXPLORATION AND MINING IN GREENLANDGreenland Mineral Resources
Fact Sheet No. 17
Download pdf-file go_fs17.pdf (~0.5 mb). Requires pdf-reader, Acrobat GSview or similar
The intracratonic Thule Basin straddles northern
Baffin Bay and has its largest part submerged. The
most extensive onshore exposures are on the
Greenland side. The basin is one of several Pro-
terozoic depocentres on the northern rim of the
North American craton with comparable develop-
ment histories: thick sandstone and basalt units in
lower levels, often with red beds, are succeeded
by carbonate/shale-dominated sequences. Two of
these basins are the Athabasca Basin of northern
Saskatchewan and the Borden Basin of northern
Baffin Island, both known for their economic min-
eralisation, U and Pb-Zn, respectively.
Baffin Bay and has its largest part submerged. The
most extensive onshore exposures are on the
Greenland side. The basin is one of several Pro-
terozoic depocentres on the northern rim of the
North American craton with comparable develop-
ment histories: thick sandstone and basalt units in
lower levels, often with red beds, are succeeded
by carbonate/shale-dominated sequences. Two of
these basins are the Athabasca Basin of northern
Saskatchewan and the Borden Basin of northern
Baffin Island, both known for their economic min-
eralisation, U and Pb-Zn, respectively.
Geology and mineralisation
The Thule Basin was mapped in the 1970s. It has seen
little commercial exploration but in Greenland intermit-
tent economic reconnaissance was performed 200107
by GEUS. The bedrock of the Thule region is dominated
by two Precambrian provinces: a high-grade Archaean
Palaeoproterozoic crystalline shield overlain by the
unmetamorphosed Mesoproterozoic?Neoproterozoic
strata of the Thule Basin (Thule Supergroup). The pro-
found unconformity between these two provinces is
well preserved through the region. To the north, the
Super-group is disconformably overlain by the Lower
Palaeozoic Franklinian Basin. The Thule Supergroup is a
68 km thick multicoloured, continental to shallow
marine se quence with one main interval of terrestrial
basaltic rocks. Basic sills are common at several levels.
The strata are little deformed occurring as shallow-dip-
ping packages in fault blocks.
Five groups are recognised:
little commercial exploration but in Greenland intermit-
tent economic reconnaissance was performed 200107
by GEUS. The bedrock of the Thule region is dominated
by two Precambrian provinces: a high-grade Archaean
Palaeoproterozoic crystalline shield overlain by the
unmetamorphosed Mesoproterozoic?Neoproterozoic
strata of the Thule Basin (Thule Supergroup). The pro-
found unconformity between these two provinces is
well preserved through the region. To the north, the
Super-group is disconformably overlain by the Lower
Palaeozoic Franklinian Basin. The Thule Supergroup is a
68 km thick multicoloured, continental to shallow
marine se quence with one main interval of terrestrial
basaltic rocks. Basic sills are common at several levels.
The strata are little deformed occurring as shallow-dip-
ping packages in fault blocks.
Five groups are recognised:
Smith Sound Group.
This group is up to 700 m thick
and represents the northern basin margin sequence.
It is composed of varicoloured sandstones and shales,
including red beds, with subordinate stromatolitic
carbonates.
It is composed of varicoloured sandstones and shales,
including red beds, with subordinate stromatolitic
carbonates.
Nares Strait Group.
Up to 1200 m thick, this group
represents the oldest strata of the central basin. It is
dominated by sandstones with one main interval of
tholeiitic volcanics including flows, sills and volcani
clastic deposits. The succession represents deposition
in alluvial plain, littoral and offshore environments.
Malachite, chalcocite and hematite occur as coatings
and blebs in various volcanic rocks anomalous in Cu,
Ag and Ba. Further, drainage geochemistry indicates
a gold potential in the volcanics.
dominated by sandstones with one main interval of
tholeiitic volcanics including flows, sills and volcani
clastic deposits. The succession represents deposition
in alluvial plain, littoral and offshore environments.
Malachite, chalcocite and hematite occur as coatings
and blebs in various volcanic rocks anomalous in Cu,
Ag and Ba. Further, drainage geochemistry indicates
a gold potential in the volcanics.
Baffin Bay Group.
This group, up to 1300 m thick,
consists of shallow water, multicoloured siliciclastic
rocks:sandstones and quartz-pebble conglomerates,
with im portant intervals of shales and siltstones, rep-
resenting mixed continental to marine shoreline envi-
ronments, with syn-depositional faulting. Malachite
staining on pale sandstones in red-bed sequences is
widespread with pyrite, chalcopyrite, bornite and
chalcocite occurring as flecks and disseminations.
with im portant intervals of shales and siltstones, rep-
resenting mixed continental to marine shoreline envi-
ronments, with syn-depositional faulting. Malachite
staining on pale sandstones in red-bed sequences is
widespread with pyrite, chalcopyrite, bornite and
chalcocite occurring as flecks and disseminations.
Dundas Group.
This 23 km thick package is composed
of sandstones, siltstones and shales with lesser
amounts of carbonate and evaporite. Deposition was
in an overall deltaic to offshore environment. Dark
shales can contain stratiform pyrite, and minor spha-
lerite occurs in a se-quence of interbedded shale and
limestone. Neopro-terozoic sills and dykes unusually
rich in titanium are the source of placer ilmenite on
the south coast of Steensby Land where heavy miner-
al sands on active and uplifted beaches have grades
of c. 43% TiO
amounts of carbonate and evaporite. Deposition was
in an overall deltaic to offshore environment. Dark
shales can contain stratiform pyrite, and minor spha-
lerite occurs in a se-quence of interbedded shale and
limestone. Neopro-terozoic sills and dykes unusually
rich in titanium are the source of placer ilmenite on
the south coast of Steensby Land where heavy miner-
al sands on active and uplifted beaches have grades
of c. 43% TiO
2
and c. 12% TiO
2
, respectively.
Sediment/sill and sediment/dyke contacts are charac-
terised by rusty weathering caused by pyrite, chal-
copy rite, galena and sphalerite occurring in thin
quartz-calcite veins, lenses and pods in both sedi-
ments and dolerites.
terised by rusty weathering caused by pyrite, chal-
copy rite, galena and sphalerite occurring in thin
quartz-calcite veins, lenses and pods in both sedi-
ments and dolerites.
Mineral potential of the Thule Basin
Bache
Peninsula
Peninsula
Cape Combermere
Qaanaaq
Pituffik
(Thule Air Base)
Kap
York
Devon
Island
hti
m
S
uo
S
dn
M
l
P r u d h
o e
L a n
d
g e
I ng l
efi
el
d
La
nd
80°W
80°W
70°W
70°W
100 km
Baffin Bay
Stee
nsby Lan
d
Stee
nsby
Lan
d
Inland Ice
Ellesmere
Island
FRANKLINIAN BASIN
THULE BASIN
SHIELD
Lower Palaeozoic Devonian
Mesoproterozoic?Neoproterozoic
Palaeoproterozoic
Archaean
1000 km
C A
N
A D A
Greenland
Na
Ba
ffi
n
I
s
l
a
n
d
Geological map of the Thule region. Na = Nanisivik.
Narssârssuk Group.
This group represents the
youngest strata. It is 1.52.5 km thick composed
of dominantly fine-grained carbonatered bed
siliciclastic rocks with evaporites representing
cyclic deposition in a low energy, hypersaline,
peritidal environment.
of dominantly fine-grained carbonatered bed
siliciclastic rocks with evaporites representing
cyclic deposition in a low energy, hypersaline,
peritidal environment.
Regional structures
The entire basin is dissected by the Thule half-
graben system dominated by WNWESE-trending
faults. Along master faults displacement of several
kilometres has taken place. The faults can show
hydrothermal alteration and be mineralised with
quartz, barite, pyrite and chalcopyrite and
drainage geochemistry indicates a potential for
gold. This mineralisation is probably associated with
the Franklinian Neoproterozoic magmatic episode,
well known from Arctic Canada.
graben system dominated by WNWESE-trending
faults. Along master faults displacement of several
kilometres has taken place. The faults can show
hydrothermal alteration and be mineralised with
quartz, barite, pyrite and chalcopyrite and
drainage geochemistry indicates a potential for
gold. This mineralisation is probably associated with
the Franklinian Neoproterozoic magmatic episode,
well known from Arctic Canada.
Mineral potential
The following deposit types are the most obvious
exploration targets:
exploration targets:
1.
Unconformity-associated U (-Ni-Co-Au).
The
unconformity at the base of the Thule Basin
provides a target for this type of mineralisation.
provides a target for this type of mineralisation.
2.
Red-bed type Cu
. Red-bed Cu mineralisation
occurs both in the volcanic rocks of the Nares
Strait Group and in fluviatilecontinental sand-
stones of the Baffin Bay Group. The volcanic
rocks have an additional potential for gold.
Strait Group and in fluviatilecontinental sand-
stones of the Baffin Bay Group. The volcanic
rocks have an additional potential for gold.
3.
Shale-hosted Pb-Zn (SEDEX type).
Pyrite-spha-
lerite-bearing sequences of alternating black
shale and stromatolitic limestone of the Dundas
Group could host stratiform Pb-Zn deposits.
Group could host stratiform Pb-Zn deposits.
4.
Carbonate-hosted Pb-Zn (MVT type).
The
Narssârssuk Group is lithologically comparable
and a time equivalent to part of the Bylot
Supergroup of the Borden Basin, Baffin Island,
that hosts the Nanisivik Pb-Zn deposit. The
Thule strata thus have a potential for similar
MVT deposits.
and a time equivalent to part of the Bylot
Supergroup of the Borden Basin, Baffin Island,
that hosts the Nanisivik Pb-Zn deposit. The
Thule strata thus have a potential for similar
MVT deposits.
5.
Contact/Skarn-hosted Cu, Pb, Zn.
The base me tal
mineralisation associated with sills and dykes of
the Dundas Group has a limited tonnage poten
tial. It should, however, be tested for gold.
the Dundas Group has a limited tonnage poten
tial. It should, however, be tested for gold.
6.
Vein-type Au.
Hydrothermal veins hosted by the
WNWESE-trending regional faults cutting both
the shield and the Thule Basin have a potential
for Au mineralisation
the shield and the Thule Basin have a potential
for Au mineralisation
Concluding remarks
Given the relatively unexplored character of the
region, the Thule Basin seems to offer excellent
exploration targets for a number of commodities,
especially Zn, Pb, Cu, Au and U.
region, the Thule Basin seems to offer excellent
exploration targets for a number of commodities,
especially Zn, Pb, Cu, Au and U.
Key references
Dawes, P.R. 1997:
The Proterozoic Thule Supergroup, Greenland
and Canada: history, lithostratigraphy and development.
Geology of Greenland Survey Bulletin
174
, 150 pp.
Dawes, P.R. 2006:
Explanatory notes to the Geological map of
Greenland, 1:500 000, Thule, Sheet 5. Geological Survey of
Denmark and Greenland Map Series 2, 97 pp. + map.
Thomassen, B., Dawes, P.R., Steenfelt, A. & Krebs, J.D. 2002:
Qaanaaq 2001: mineral exploration reconnaissance in North-
West Greenland. Geol. of Greenland Survey Bulletin
191
, 133143.
Geological Survey of Denmark
and Greenland (GEUS)
Řster 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
Authors
B. Thomassen & P.R. Dawes, GEUS
Editor
K. Secher, GEUS
Layout
Henrik Klinge Pedersen, GEUS
Photographs
GEUS unless otherwise stated
Printed
February 2008 © GEUS
Printers
Schultz Grafisk
ISSN
1602-8171
The landmark of the Thule region, table mountain Dundas Fjeld (Uummannaq) 225 m high. Dundas Group is capped
by a Neoproterozoic Franklinian basalt sill.
by a Neoproterozoic Franklinian basalt sill.
