Re-assessment of Bird River greenstone belt stratigraphy. Paul Gilbert Manitoba Geological Survey

Transcription

1 Re-assessment of Bird River greenstone belt stratigraphy Paul Gilbert Manitoba Geological Survey

2 Location of Bird River Belt Bird River Belt Winnipeg

3 Bird River Belt projects initiated in 2005 Paul Gilbert (Manitoba Geological Survey) ~ 1: scale mapping Manuel Duguet (Post doctoral student, Univ. of Waterloo) ~ Regional mapping (1: scale) with focus on structural geology Paul Kremer (MGS), Caroline Mealin ~ Economic geology theses (MSc Univ. of Waterloo) TANCO pegmatite, Bird River Sill

4 Outline of presentation 1. Regional setting and stratigraphy of BRB 2. Volcanic geochemistry 3. Economic implications 4. Summary

5 Bird River Belt regional setting MANITOBA ONTARIO BIRD RIVER SEPARATION LAKE

6 Bird River Belt stratigraphy 1. MORB-type volcanic rocks 2. Continental arc-type sequence 3. Younger sedimentary rocks

7 Bird River Belt stratigraphy Lamprey Falls Fm (MORB) Bird River Sill Flanders Lake Fm North panel arc Booster Lake Fm South panel arc Lamprey Falls Fm (MORB)

8 Bird River Belt stratigraphy Highway junction area

9 BRB north panel highway junction area Diverse arc assemblage Lamprey Falls Fm (MORB) Peterson Creek Fm Bird River Sill Booster Lake Fm

10 BRB north panel cross-section Line of cross-section Peterson Creek Fm upper Diverse Arc assemblage lower cglm

11 BRB north panel composite stratigraphic section South North Polymictic conglomerate Line of composite section South North

12 Lamprey Fall Formation basalt Pillowed basalt Lamprey Fall Formation at Winnipeg River Megaphyric basalt Polygonal jointing Altered pillowed basalt

13 Stratigraphic column - highway junction area Polymictic conglomerate Spherulitic rhyolite

14 Stratigraphic column - highway junction area In-situ breccia, flow lamination Heterolithic volcanic breccia Turbidite Volcaniclastic mass-flow

15 Bird River Belt south panel ~ Bernic Lake Formation Bernic Lake Formation Carbonate-facies iron formation Aphyric pillowed basalt Mass-flow volcaniclastic deposit

16 Bird River Belt geochemistry 1. MORB-type volcanic rocks 2. Continental arc-type sequence ~ (a) North panel calcalkaline (b) South panel tholeiitic

17 Lamprey Falls Fm (MORB) Bird River Belt stratigraphy North panel arc Booster Lake Fo. South panel arc Lamprey Falls Fm (MORB)

18 Mafic to intermediate volcanic rocks BRB North panel Bird River Belt north panel mafic to intermediate volcanic rocks

19 Bernic Lake Fm south part BRB north panel volcanic rocks Bernic Lake Fm north part Bird River Belt mafic to intermediate volcanic rocks Mafic to intermediate volcanic rocks, Bernic Lake Fm.

20 BRB north panel felsic volcanic rocks Bernic Lake Fm south part Bernic Lake Fm north part Bird River Belt felsic volcanic rocks Felsic volcanic rocks, Bernic Lake Fm.

21 Lamprey Falls Formation (MORB) Lamprey Falls Formation

22 Bird River Belt all volcanic rocks Colour key Jensen cation plot NORTH PANEL BERNIC LK FM NORTH BERNIC LK FM SOUTH * LAMPREY FALLS FM Th-Zr-Nb ternary (Wood, 1980)

23 Pearce,1980 Bird River Belt tectono-stratigraphic setting Floyd and Winchester, 1975 Colour key NORTH PANEL BERNIC LK FM NORTH BERNIC LK FM SOUTH * LAMPREY FALLS FM

24 Bird River Belt tectono-stratigraphic setting Gorton and Schandl, 2000 Colour key NORTH PANEL BERNIC LK FM NORTH BERNIC LK FM SOUTH * LAMPREY FALLS FM

25 Bird River Belt tectono-stratigraphic setting Gorton and Schandl, 2000 Colour key NORTH PANEL BERNIC LK FM NORTH BERNIC LK FM SOUTH * LAMPREY FALLS FM

26 Transect through Bird River Belt (SW Superior Province) Transect Line Man Ont Lake Winnipeg Ont North Caribou superterrane English River Winnipeg River South-north Transect Lake Superior Winnipeg River North Caribou superterrane

27 Economic considerations

28 Bird River Belt economic geology Maskwa- Dumbarton Mine Tanco Mine

29 Bird River Belt ~ current exploration for base metals and PGE

30 Summary Neoarchean Bird River Belt consists of arc-type rocks that were deposited on the margins of a flanking continental terrane. Arc-type components include tholeiitic, calc-alkaline and MORB-type basalts (arc-rift origin?). Tectonic setting is continental arc - BRB rests on continental lithosphere. Volcanic rocks primarily intermediate to felsic (not bimodal type sequence) due to influence of continental lithosphere underplating. Current active mineral exploration for base-metals and PGE is focused on Bird River Sill and related intrusions, as well as MORB-type Lamprey Falls Formation. New sources for rare element pegmatites akin to Tanco deposit are also being sought. Bird River Belt mapping project by MGS is in the final stage of field investigations and a report is under preparation.