Bird River Belt in southeastern Manitoba: a Neoarchean volcanic arc in the Western Superior Province. Paul Gilbert Manitoba Geological Survey

Transcription

1 Bird River Belt in southeastern Manitoba: a Neoarchean volcanic arc in the Western Superior Province 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. Regional tectonic evolution 4. Economic geology

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

6 Bird River Belt stratigraphy 1. MORB-type volcanic rocks [ >2745 Ma ] 2. Continental arc-type sequence [ ~2730 Ma] 3. Younger sedimentary rocks [~ 2704 Ma]

7 Bird River Belt stratigraphy Northern MORB type North panel arc Bird River Sill ERS Flanders Lake Fm Booster Lake Fm South panel arc Southern MORB type WRS

8 Bird River Belt North Panel Highway Junction area

9 BRB North Panel highway junction area Diverse arc assemblage Northern MORB Fm Peterson Creek Fm Bird River Sill Booster Lake Formation Booster Lake Fm

10 BRB North Panel cross-section Line of cross-section Peterson Creek Fm NORTH SOUTH upper Diverse Arc assemblage conglomerate lower

11 BRB North Panel composite stratigraphic section SOUTH South Booster Lake Formation NORTH North Peterson Creek Formation Diverse Arc assemblage Polymictic conglomerate Line of composite section Bird River Sill North NORTH South SOUTH

12 MORB-type basalt formations Northern MORB-type basalt Pillowed basalt Southern MORB-type basalt at Winnipeg River Megaphyric basalt Altered pillowed basalt Polygonal jointing

13 Arc-type rocks (highway junction area) SOUTH Booster Lake Formation Peterson Creek Formation Polymictic conglomerate Diverse Arc assemblage Bird River Sill NORTH Spherulitic rhyolite

14 Arc-type rocks (highway junction area) In-situ breccia, flow lamination Booster Lake Formation Peterson Creek Formation Heterolithic volcanic breccia Diverse Arc assemblage Bird River Sill Turbidite Volcaniclastic mass-flow

15 South Panel (Bernic Lake Formation) Bird River Belt South Panel (= Bernic Lake Formation)

16 Western Bird River Belt: Bernic Lake Formation

17 Bird River Belt south panel ~ Bernic Lake Formation N Upper BLF N Upper BLF Middle BLF Middle BLF S Lower BLF Lower BLF S

18 Bernic Lake Formation Upper BLF volcanic breccia N Upper BLF Middle BLF Middle BLF pillow basalt & alteration Lower BLF S Lower BLF altered felsic volcanic bx

19 BRB North Panel BRB South Panel SOUTH N Booster Lake Formation Booster Lake Formation Upper BLF Peterson Creek Formation Middle BLF Diverse Arc assemblage Lower BLF Bird River Sill Southern MORB type NORTH S

20 Bird River Belt ~ Geochemistry of volcanic rocks

21 Bird River Belt ~ main tectonostratigraphic components Northern MORB type Booster Lake Fm 3. Late orogenic sedimentary rocks [~ 2700 Ma] North panel CA arc 2. Continental arc-type sequence ~ (a) North panel calcalkaline [ 2731 ±1 Ma] (b) South panel tholeiitic [ 2725 ±1] South panel TH arc Southern MORB type 1. MORB-type volcanic rocks [ >2745 ±5 Ma]

22 Bird River Belt ~ All volcanic rocks North Panel South Panel North Panel South Panel Jensen (1976) Irvine and Baragar (1971)

23 Northern and Southern MORBtype Formations MORB-type Formations ~ - Oldest volcanics - Intruded by 2745 Ma Bird River Sill - Back-arc, rift-associated Northern and Southern MORBtype Formations

24 Bird River Belt North Panel mafic to intermediate volcanic rocks BRB North Panel Mafic to intermediate volcanic rocks

25 Bernic Lake Fm south part BRB north panel volcanic rocks Bernic Lake Fm north part North Panel Mafic to intermediate volcanic rocks South Panel Bernic Lake Formation in eastern BRB mafic to intermediate volcanic rocks

26 Bernic Lake Fm south part BRB north panel felsic volcanic rocks Bernic Lake Fm north part North Panel Felsic volcanic rocks South Panel Bernic Lake Formation in eastern BRB felsic volcanic rocks

27 Bird River Belt South Panel Bernic Lake Fm Main part (E) Bernic Lake Fm Main part (W)

28 Bird River Belt North vs South Panels North Panel North & South Panels North Panel South Panel (Bernic Lake Fm)

29 Bernic Lake Formation ~ Main vs Upper part Bernic Lake Formation ~ Main and Upper parts (East) Bernic Lake Formation ~ Main and Upper parts (West)

30 Pearce (1983) Bird River Belt ~ Tectonic affinity of volcanic rocks

31 Wood (1980) Bird River Belt ~ Tectonic affinity of volcanic rocks

32 Bird River Belt ~ Tectonic affinity of volcanic rocks Gorton and Schandl (2000) SUBDUCTION-RELATED EXTENSION-RELATED

33 Bird River Belt ~ Nd-Sm isotope data Nd-Sm isotope data εnd of mantle = +1.4 at 2.7Ga

34 Bird River Belt ~ Tectonic history

35 Western Superior Province MANITOBA Section line in next slide ONTARIO North Caribou ST BIRD RIVER Uchi SP English River SP Winnipeg River SP

36 Tectonic history of southwest Superior Province North Caribou Superterrane N S Winnipeg River Subprovince Ma? N S

37 Tectonic history of southwest Superior Province North Caribou Superterrane N S Winnipeg River Subprovince N S

38 Bird River Belt economic geology Maskwa- Dumbarton Mine (Cu, Ni) Tanco Mine (Li, Cs, Ta) present

39 Bernic Lake development (1929, 1957) Bernic Lake 1929 Jack Nutt Mines headframe Bernic Lake 1957 Montgarry Shaft headframe Bernic Lake 1929 crusher, mill buildings assay office

40 Bernic Lake (recent) Bernic Lake 1929 Jack Nutt Mines headframe

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

42 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. Tectonic setting is continental arc seismic data suggest the BRB rests on continental lithosphere. Volcanic rocks primarily intermediate to felsic (not bimodal type sequence) due to influence of continental lithosphere underplating. Progression from subduction to an extensional tectonic setting is documented in the BRB from North to South panels. Current active mineral exploration for base-metals and PGE is focused on Bird River Sill and related intrusions, as well as MORB-type basalt formations. New sources for rare-element pegmatites akin to Tanco deposit are also being sought.