Orogenic gold mineralization in southern West and

Report
Orogenic gold mineralisation in the
Archean North Atlantic craton,
southern West and South-West
Greenland
Jochen Kolb1, Denis M. Schlatter1, Annika
Dziggel2, Alexander F.M. Kisters3
¹Department of Petrology and Economic Geology, Geological
Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350
Copenhagen K, Denmark
2Institute of Mineralogy and Economic Geology, RWTH Aachen
University, Wüllnerstr. 2, 52064 Aachen, Germany
3Department of Earth Sciences, Stellenbosch University,
Matieland 7602, South Africa
Mineralizing system of orogenic
gold deposits
increasing intensitiy of alteration
Fluid/wallrock
reactions
Au deposition
Diffusion
CONDUIT
Dispersion
SOURCE ROCK
Ridley et al. 1996
hydrothermal alteration
Main devolatilization
440 – 520°C
Philipps and Powell 2010
Groves et al. 1993
Goldfarb et al. 2001
Gold production vs. gold ages
North Atlantic craton
Schematic
geologocal
map of
Greenland
Geological map of South-West Greenland
Paamiut gold province
Tartoq gold province
Characteristics of gold mineralization
Paamiut gold province
• 5 occurrences; 40 km
strike
• Auriferous quartz veins in
higher-order structures
• Au-only + As, W, Mo, Bi
• Ore mineralogy: Po-ApyCcp
• Hydrothermal alteration
mineralogy
– Proximal Hbl
– Distal Qtz-Hbl/Oam-BtTur-Ank ± Grt, Ms, Cal
– Sulfide-poor (< 5 vol.%)
Tartoq gold province
• ≥ 3 occurrences; 40 km
strike
• Auriferous quartz veins in
higher-order structures
• Au-only + As, Ag, W, Sb,
Bi
• Ore mineralogy: Apy-CcpPy
• Hydrothermal alteration
mineralogy
– Qtz-Ms-Chl-Ank
– Sulfide-poor (< 5 vol.%);
except BIF
The Paamiut gold province: structure
• Metamorphic dates
– 2850 – 2830
Ma: Paamiut
orogeny
– 2760 – 2740
Ma:
Tasiusarsuaq
orogeny
NW
mesozonal gold
Mellembydgen
Au
Akuliaq
Au Au
Au
metamorphosedgold
Akulleq glacier
Au
SE
The Tartoq gold province: structure
±Au
±Au
Au
Au
• Metamorphic dates
– 2850 – 2830 Ma: Paamiut
orogeny
– 2760 – 2740 Ma:
Tasiusarsuaq orogeny
Geological map
of southern
West
Greenland
Sermilik prospect
Bjørnesund occurrence
Ca. 2840 Ma
Characteristics of gold mineralization
Sermilik gold prospect
• ≥ 2 locations; 4 km strike
• Ca. 2740 Ma
• Auriferous quartz veins in
folds and shear zones
• Gold-only + Ag, As
• Ore mineralogy: Po-Ccp-PyIlm-Mag
• Hydrothermal alteration
mineralogy
– Qtz-Grt-Bt-Kfs (660°C,
7.5-8 kbar)
– Sulfide-poor (< 5 vol.%)
Tectonic model for the Sermilik
prospect: Tasiusarsuaq orogeny
N
Qarliit Nunat
Tasiusarsuaq terrane
thrust
2800 - 2740 Ma
2720 Ma
Sermilik
2740 Ma
Au Au
S
Grædefjord
Færingehavn &
Tre Brødre terranes
undiff.
Ilivertalik
2800 Ma
Geological
map of
southern
West
Greenland
Characteristics of gold mineralization
Godthåbsfjord gold
province
Tasiusarsuaq gold
province
• ≥ 5 prospects; 110 km
strike
• 2985 Ma, 2715 Ma, 2630 Ma
• Gold-quartz±carbonate
veins
• Ore mineralogy: Po-CcpApy-Py-Ilm-Mag
• Hydrothermal alteration
mineralogy
• ≥ 7 locations; terranescale
• Ca. 2675 Ma
• Quartz veins ± Au
• Ore mineralogy: Po-CcpPy-Ilm-Mag
• Hydrothermal alteration
mineralogy
– Inner Qtz-Hbl ± Bt
– Proximal Qtz-Grt-Bt-Hbl-Sil
(530-630°C, 4-6 kbar)
– Distal Bt ± Grt
– Sulfide-poor (< 5 vol.%)
– Inner Qtz-Hbl ± Bt, Ep, Rt
– Proximal Qtz-Grt-Bt-Hbl ±
Ms (650°C, 3.5-4 kbar)
– Distal Bt ± Grt
– Sulfide-poor (< 5 vol.%)
Structure of the
Godthåbsfjord and
Tasiusarsuaq gold provinces
Model for 2670-2580 Ma orogenic gold
fa
ul
t
eq
A
ta
n
pr
ov
in
ce
Akia terrane
Isua
Kapisilik terrane
Ivi
nn
gu
it f
au
lt
26
60
-2
60
0
Ma
Bjørneøen
Store Malene
Qilanngaarsuit
< 2715 Ma, > 2560 Ma
Færingehavn &
Tre Brødre
terrane
undiff.
0
58
2
05
26
Storø
2630 Ma
Ma
Q
2 5 ô rq u
60 t
Ma
G
od
th
åb
sf
jor
d
go
ld
Qussuk
Tasiu
sars
uaq
2670
-261
0
2670 Ma
gold
prov
ince
Ma
Tasiusarsuaq terrane
Conclusions
• Several stages of orogenic gold mineralization
•
•
•
•
•
ca. 2990 Ma Isukasia orogeny
2850 – 2830 Ma Paamiut orogeny
2800 – 2740 Ma Tasiusarsuaq orogeny
2720 – 2700 Ma Tre Brødre orogeny
2670 – 2580 Ma Kapisilik orogeny
• Hypozonal orogenic gold
– Tasiusarsuaq gold province: single-stage – no potential
– Godthåbsfjord gold province: multi-stage (?) – small deposits
• Mesozonal orogenic gold
– Paamiut gold province – not explored, good potential
– Tartoq gold province – not explored, good potential

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