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 SOURCE ROCK CONDUIT Fluid/wallrock reactions Au deposition increasing intensitiy of alteration Dispersion Diffusion hydrothermal alteration Ridley et al. 1996 Main devolatilization 440 – 520°C Philipps and Powell 2010 Groves et al. 1993

Gold production vs. gold ages Goldfarb et al. 2001 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-Apy-Ccp Hydrothermal alteration mineralogy Proximal Hbl Distal Qtz-Hbl/Oam-Bt-Tur-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-Ccp-Py 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

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-Py-Ilm-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

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-Ccp-Apy-Py-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.%) ≥ 7 locations; terrane-scale Ca. 2675 Ma Quartz veins ± Au Ore mineralogy: Po-Ccp-Py-Ilm-Mag Hydrothermal alteration mineralogy 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

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