New insights on the THO-Superior boundary: Tectonic and metallogenic implications John Percival, GSC Nicole Rayner, GSC Herman Zwanzig, MGS Linda Murphy, MGS Joe Whalen, GSC Martha Growdon, Indiana U. Tullibee Lake July 2006
Kisseynew Domain: Poor cousin to the Flin Flon, Thompson & Lynn Lake belts Sea of Burntwood migmatite Upper amphibolite to granulite facies metamorphism Poorly exposed Few geophysical anomalies Discouraging tectonic, crustal structure models
White et al. 2002
Motivation Declining Ni reserves (TGI 3 directive) Mel zone discovery Granite crustal probes suggest Archean contamination Quartz-rich rich (Ospwagan?) sediments Cr, Ni anomalies in till (e.g.( Osik Lk) Aeromagnetic anomalies on 2006 TGI 3 Wuskwatim Lake survey
Significant findings 1890-1880 Ma magmatic arc built on the Superior margin: possible back-arc arc setting of 1883 Ma Molson and Thompson-type mafic-ultramafic magmatism Superior crust with Ospwagan cover extends at least 90 km west of the Superior boundary zone, including exposed Thompson-type targets
1883 Ma Thompson-type mafic-ultramafic magmatism 1883 M 1883 Ma Molson dykes 1883 Ma Josland sills
EXTRACT OF 2006 WUSKWATIM LAKE SURVEY Silicate,- sulphide-facies BIF Wuskwatim Lake Basement orthogneiss culminations
Multicomponent orthogneiss
Basement-cover unconformity Quartzite Tonalite orthogneiss
Composite stratigraphic section
Basement Geochronology
SHRIMP results for granulite-facies tonalitic orthogneiss Probable crystallization age Probable metamorphic resetting/regrowth Probable inheritance
SHRIMP results for charnockite n=34 emplacement at granulite or mm overprint 2.66 Ga inheritance or crystallization 3.2 Ga late metamorphism 1.80 Ga 1.8 3.1 2.6 mixing T DM = 3.1 Ga
Cover sequence Geochronology Typical Burnt- wood wacke Pipe Fm in Pipe Pit Quartzite cut by dyke Quartzite at unconformity
Atik Lake Pluton Geochronology
SHRIMP results for Footprint Lake granodiorite crystallization age 1879-1882 Ma Th/U typically > 1 εnd = -9.3
SHRIMP results for Atik Lake granodiorite crystallization age ca. 1.88 Ga Th/U typically > 1 εnd = -10.3
Geochronology-summary Archean basement: 3.2-2.8 Ga crystallization, 2.65 Ga metamorphism Quartzites in cover sequence have Archean provenance, like Ospwagan Gp. Paleoproterozoic plutons are 1880 Ma, contaminated by Archean crust
Stratigraphic correlation 1890-70 1880
Structural Geometry F 3 F 4
Autochthonous basement interpretation
Basement-cored nappe interpretation
??
Bouguer Gravity Anomalies White et al. 2005
Potential mineralization types Thompson-type Ni in mafic-ultramafic intrusions in equivalents of Pipe Formation Iron formation-hosted gold (Lupin( Lupin, Musselwhite type) Diamonds in Archean lithosphere: kimberlites in eastern Kisseynew?
New Exploration targets Wuskwatim Lake- Burntwood River Sulphide-silicate facies iron formation (probable Pipe Fm equivalent) Kawaweyak Lake Sulphide-silicate facies iron formation Mafic-ultramafic intrusions Sulphide (po) occurrences Tullibee-Neuls Lake Probable basement Iron formation Mafic-ultramafic sills Osik Lake Cr, Ni anomaly in till
Conclusions; Questions 1880 Ma magmatism on Superior margin: -was the Flin Flon-Snow Lake belt proximal? -back-arc exploration models?
Conclusions; Questions 1880 Ma magmatism on Superior margin: -was the Flin Flon-Snow Lake belt proximal? -back-arc exploration models? NE Kisseynew domain is underlain by Superior basement and probable Ospwagan Gp cover: -is basement contiguous, or a rifted fragment? -what is its southwestern extent?
Conclusions; Questions 1880 Ma magmatism on Superior margin: -was the Flin Flon-Snow Lake belt proximal? -back-arc exploration models? NE Kisseynew domain is underlain by Superior basement and probable Ospwagan Gp cover: -is basement contiguous, or a rifted fragment? -what is its southwestern extent? Sulphide-bearing mafic-ultramafic sills within BIF-bearing units are possible Pipe Fm equivalents -are Thompson-type orebodies present?