New insights on the THO-Superior boundary: Tectonic and metallogenic implications

Transcription

1 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

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3 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

4 White et al. 2002

5 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

6 Significant findings 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

7 1883 Ma Thompson-type mafic-ultramafic magmatism 1883 M 1883 Ma Molson dykes 1883 Ma Josland sills

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12 EXTRACT OF 2006 WUSKWATIM LAKE SURVEY Silicate,- sulphide-facies BIF Wuskwatim Lake Basement orthogneiss culminations

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14 Multicomponent orthogneiss

15 Basement-cover unconformity Quartzite Tonalite orthogneiss

16 Composite stratigraphic section

17 Basement Geochronology

18 SHRIMP results for granulite-facies tonalitic orthogneiss Probable crystallization age Probable metamorphic resetting/regrowth Probable inheritance

19 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 mixing T DM = 3.1 Ga

20 Cover sequence Geochronology Typical Burnt- wood wacke Pipe Fm in Pipe Pit Quartzite cut by dyke Quartzite at unconformity

21 Atik Lake Pluton Geochronology

22 SHRIMP results for Footprint Lake granodiorite crystallization age Ma Th/U typically > 1 εnd = -9.3

23 SHRIMP results for Atik Lake granodiorite crystallization age ca Ga Th/U typically > 1 εnd = -10.3

24 Geochronology-summary Archean basement: 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

25 Stratigraphic correlation

26 Structural Geometry F 3 F 4

27 Autochthonous basement interpretation

28 Basement-cored nappe interpretation

29 ??

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31 Bouguer Gravity Anomalies White et al. 2005

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33 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?

34 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

35 Conclusions; Questions 1880 Ma magmatism on Superior margin: -was the Flin Flon-Snow Lake belt proximal? -back-arc exploration models?

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37 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?

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39 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?