Structural geology and gold metallogeny of the New Britannia mine area, Snow Lake, Manitoba

Structural geology and gold metallogeny of the New Britannia mine area, Snow Lake, Manitoba Chris Beaumont-Smith Manitoba Geological Survey Boundary zone New Britannia

Trans-Hudson Orogen 50 km 100 km 100 km Modified Zwanzig, H.V. 1999

Flin Flon-Snow Lake Deposits PRE-ACCRETION ASSEMBLAGES (>1.88 Ga) JUVENILE ARC ASSEMBLAGES OCEAN FLOOR ASSEMBLAGES EVOLVED ARC ASSEMBLAGE SYN/POST-ACCRETION ROCKS (<1.88 Ga) FELSIC-MAFIC PLUTONS (>1.84, <1.84 Ga) SUCCESSOR ARC & BASIN DEPOSITS Missi suite Burntwood suite Major fault (<1.84 Ga) Gold deposit

Snow Lake Deposits 55º 15' Ca. 1890 Ma Amisk Group volcanic rocks Snow Lake 10km Ca. 1875. 1855, 1830 Ma plutonic rocks Ca. 1845 Ma Burntwood Group turbidites Ca. 1845 Ma Missi Group fluvialalluvial sedimentary rocks Successor-arc pluton, basin deposits Late plutons Missi Group Burntwood Group Early plutons and gneiss Successor-arc plutons Layered mafic sills Early plutons, mixed gneiss Major fault Early juvenile assemblages Arc volcanic rocks Arc-rift basalt Ocean-floor basalt

Snow Lake Geology SQUALL SQUALL LAKE LAKE Margaret zones Moon Gertie K7 K7 K5 K5 Allochthonous volcanic rocks bound by younger sedimentary rocks Syn- to post-metamorphic thrusting South zone HERBLET HERBLET LAKE LAKE Birch zone McLeod McLeod Road Road Thrust Thrust No. 3 zone Birch Birch Fault Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence 0 500 0 500 SNOW SNOW LAKE LAKE New Britannia

Stratigraphy SQUALL LAKE K7 K5 Amygdaloidal dacite Margaret zones Moon Gertie South zone HERBLET LAKE Birch zone McLeod Road Thrust No. 3 zone Birch Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks SNOW LAKE Fault (thrust, other) Road Gold deposit Gold occurrence Amygdaloidal tuff breccia 0 500

Stratigraphy SQUALL LAKE K7 K5 Aphyric tuff breccia Margaret zones Moon Gertie South zone HERBLET LAKE Birch zone McLeod Road Thrust No. 3 zone Birch Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks SNOW LAKE Fault (thrust, other) Road Gold deposit Gold occurrence Bedded lapilli tuff 0 500

Stratigraphy SQUALL LAKE K7 K5 Mafic lapilli tuff Margaret zones Moon Gertie South zone HERBLET LAKE Birch zone McLeod Road Thrust No. 3 zone Birch Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks SNOW LAKE Fault (thrust, other) Road Gold deposit Gold occurrence Bedded lapilli tuff 0 500

Stratigraphy SQUALL SQUALL LAKE LAKE K7 K7 K5 K5 Pillowed basalt Margaret zones Moon Gertie South zone HERBLET HERBLET LAKE LAKE Birch zone No. 3 zone McLeod McLeod Road Road Thrust Thrust Snow Lake Fault Birch Birch Fault Fault New Britannia mine Mafic sediment Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW SNOW LAKE LAKE 0 500 0 500

Stratigraphy SQUALL SQUALL LAKE LAKE K7 K7 K5 K5 Bedded lapilli tuff Margaret zones Moon Gertie South zone HERBLET HERBLET LAKE LAKE Birch zone McLeod Road Thrust No. 3 zone Birch Birch Fault Fault McLeod Road Thrust Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW SNOW LAKE LAKE 0 500 0 500

Stratigraphy SQUALL LAKE K7 K5 Staurolite schist Margaret zones Moon Gertie South zone HERBLET LAKE Birch zone No. 3 zone Snow Lake Fault Snow Lake Fault McLeod Road Thrust McLeod Road Thrust Birch Fault Birch Fault New Britannia mine Cross-bedded arenite Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW LAKE 0 500

Gold in Manitoba 2008 Stratigraphy Granoblastic gabbro SQUALL SQUALLLAKE LAKE K7 K7 K5 K5 Margaret Margaretzones zones Moon MoonGertie Gertie South Southzone zone HERBLET HERBLET LAKE LAKE tlt auul FFa chh rirc BBi Birch Birchzone zone MM ccl Lee ood dr No. No.33zone zone Ro oaa dd TTh hrru SSnno uss owwllak tt akeefa Fauultl t New NewBritannia Britanniamine mine Missi MissiGroup Grouparenite arenite Burntwood BurntwoodGroup Groupturbidites turbidites Gabbro Gabbro Mafic Maficvolcaniclastic volcaniclasticrocks rocks SNOW SNOWLAKE LAKE Basalt Basalt Sneath SneathLake Lakepluton pluton Felsic Felsicvolcaniclastic volcaniclasticrocks rocks Fault Fault(thrust, (thrust,other) other) Road Road Gold Golddeposit deposit Gold Goldoccurrence occurrence 0 0 500 500 Ophitic gabbro

F 1 Folding SQUALL LAKE LAKE K7 K5 S-asymmetrical F 1 fold Margaret zones Moon Gertie South zone HERBLET LAKE LAKE Birch zone McLeod McLeod Road Road Thrust Thrust No. 3 zone Birch Birch Fault Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW LAKE LAKE Unfolded F 1 0 0 500 500

F 2 Folding SQUALL LAKE LAKE K7 K5 Margaret zones Moon Gertie South zone HERBLET LAKE LAKE Birch zone McLeod McLeod Road Road Thrust Thrust No. 3 zone Birch Birch Fault Fault S-asymmetrical S 2 Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW LAKE LAKE F 2 mineralization 0 0 500 500

D 2 Thrust Faulting SQUALL LAKE LAKE K7 K5 Margaret zones Moon Gertie South zone HERBLET LAKE LAKE Birch zone McLeod McLeod Road Road Thrust Thrust No. 3 zone Birch Birch Fault Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW LAKE LAKE 0 0 500 500

F 3 Folding SQUALL LAKE LAKE K7 K5 Margaret zones Moon Gertie South zone HERBLET LAKE LAKE Birch zone McLeod McLeod Road Road Thrust Thrust No. 3 zone Birch Birch Fault Fault Snow Lake Fault New Britannia mine Missi Group arenite Burntwood Group turbidites Gabbro Mafic volcaniclastic rocks Basalt Sneath Lake pluton Felsic volcaniclastic rocks Fault (thrust, other) Road Gold deposit Gold occurrence SNOW LAKE LAKE F 3 chevron folds 0 0 500 500

Gold Mineralization Structurally controlled gold mineralization Mineralization focussed at stratigraphic contacts Arsenopyrite association High degree of silicification Pre- to Syn-mineralization potassium metasomatism and carbonate alteration

New Britannia Mineralization Hogg, 1957 Alexis Minerals

New Britannia Mineralization Hogg, 1957

New Britannia Mineralization Biotite-muscovitecarbonate-rich matrix Boudinaged silicification Ladder veins Howe Sound Fault

Boundary Zone 37 37 44 44 34 34 54 54 51 51 40 40 51 51 42 42 68 68 58 58 40 40 46 46 46 46 33 3338 38 53 53 50 50 40 40 46 46 52 52 44 44 65 65 53 53 43 43 50 50 50 50 50 50 50 50 58 58 57 57 53 53 53 53 54 54 433536E 6083577N 45 45 46 49 46 49 49 49 48 48 51 51 51 51 54 54 51 51 56 56 Quartz Pyroxene porphyritic dyke Pyroxene porphyritic tuff breccia Mafic sediment Felsic lapilli tuff Felsic tuff breccia Amygdaloidal dacite Geological contact Quartz vein Overturned bedding S 2 foliation 2 Lineation, stretching, L 2 intersection, F 2 2 2 433486E 6083542N 0 10 Overturned stratigraphy

Boundary Zone 37 37 44 44 34 34 54 54 51 51 40 40 51 51 42 42 68 68 58 58 40 40 46 46 46 46 33 3338 38 53 53 50 50 40 40 46 46 52 52 44 44 65 65 53 53 43 43 50 50 50 50 50 50 50 50 58 58 57 57 53 53 53 53 54 54 433536E 6083577N 45 45 46 49 46 49 49 49 48 48 51 51 51 51 54 54 51 51 56 56 Quartz Pyroxene porphyritic dyke Pyroxene porphyritic tuff breccia Mafic sediment Felsic lapilli tuff Felsic tuff breccia Amygdaloidal dacite Geological contact Quartz vein Overturned bedding S 2 foliation 2 Lineation, stretching, L 2 intersection, F 2 2 2 433486E 6083542N 0 10 Overturned stratigraphy

No. 3 Zone Alexis Minerals

No. 3 Zone Reactive veins Alexis Minerals

Schematic Cross Section Alexis Minerals

No. 3 Zone Biotite alteration Strain gradient N Covered Carbonate alteration Quartz vein Altered mafic volcaniclastic 5

Summary PMAP 2008-1 Mineralization Deformation 1900 1850 1800 1750 Remobilization Shear-hosted Accretion Brittle Faulting? Metamorphism D 1 D 2 D 3 D 4 D 5 Peak Sedimentation Burntwood Group Missi Group Magmatism Volcanism Pre-Accretion Missi Group U-Pb Age Data Zircon U-Pb Age, 2 error Zircon Pb-Pb Age, 2 error Age (Ma) 1920 1910 1900 1890 1880 1870 1860 1850 1840 1830 1820 1810 1800 1790 1780 1770 1760 1750 1740 1730 1720 1710 1700

References Hogg, N. 1957: Nor-Acme mine; in Structural Geology of Canadian Ore Deposits, Canadian Institute of Mining and Metallurgy, Congress Volume, p. 262 275. Zwanzig, H.V. 1999: Structure and stratigraphy of the south flank of the Kisseynew Domain in the Trans-Hudson Orogen, Manitoba: implications for 1.845-1.77 Ga collision tectonics; in NATMAP Shield Margin Project, Volume 2, Canadian Journal of Earth Sciences, v. 36, no. 11, p. 1859-1880