Geology and metallogeny of the Rice Lake area, southeast Manitoba:

overview and synthesis

Geology and metallogeny of the Rice Lake area, southeast Manitoba:

overview and synthesis

Manitoba Mining & Minerals Convention 2008:Gold in Manitoba

Manitoba Mining & Minerals Convention 2008:Gold in Manitoba

Scott AndersonManitoba Geological Survey

Scott AndersonScott AndersonManitoba Geological SurveyManitoba Geological Survey

Rice Lake, looking northtoward the Rice Lake mine

Manito

baOntar

io

Wabigoon

Uchi

Winnipeg R.

Berens River

Oxford-Stull

LakeWinnipeg

Northern Superior

English R.

Quetico

WawaLake

pSu erior

Island L.

Munro

200 km

metavolcanic rocks of mainlyoceanic affinity

metavolcanic rocks of mainlycontinental affinity

and isotopic influence> 2.8 Ga continental terranes

Greenstone belts

3.9- 2.81 Ga Northern Superior superterrane 3.0 - 2.87 Ga North Caribou terrane3.4 - 2.8 Ga Winnipeg River terrane

metasedimentary and assoc.granitic rocks

granitoid rocks

Regional setting:Western Superior Province

Regional setting:Western Superior Province

North Caribou Terrane

North Caribou Terrane

RICE LAKE BELTRICE LAKE BELT

NATMAPNATMAP

• collage of continental andoceanic terranes(ca. 3.9-2.7 Ga)

• amalgamated via platetectonic processes

• terminal collisionca. 2.69-2.67 Ga

• collage of continental andoceanic terranes(ca. 3.9-2.7 Ga)

• amalgamated via platetectonic processes

• terminal collisionca. 2.69-2.67 Ga

Gold deposits:>50k oz. Au>1M oz. Au

Gold deposits:>50k oz. Au>1M oz. Au

• south margin of NCT• 3.0-2.7Ga subduction-accretion complex• north-verging subduction zone

• south margin of NCT• 3.0-2.7Ga subduction-accretion complex• north-verging subduction zone

* Percival et al., 2006: CJES, v. 43, p. 1085-1117.* Percival et al., 2006: CJES, v. 43, p. 1085-1117.

NCTNCTRegional setting:

Uchi SubprovinceRegional setting:

Uchi Subprovince

TerraneTerrane

NorthCaribou

Regional setting:Rice Lake greenstone belt

Regional setting:Rice Lake greenstone belt

NORTH CARIBOUNORTH CARIBOU

UCHIUCHI

ENGLISH RIVERENGLISH RIVER

• several Meso- and Neoarcheansupracrustal assemblages

• differing geology, age and chemistry• range in age from ca. 3.0 to 2.7 Ga

• several Meso- and Neoarcheansupracrustal assemblages

• differing geology, age and chemistry• range in age from ca. 3.0 to 2.7 Ga

Local geology: Rice Lake areaLocal geology: Rice Lake area

• Three supracrustal assemblages:Little Beaver (LBA)Bidou (BA; incl. RRPS)San Antonio (SAA)

• Crustal-scale Wanipigow SZLBA on north (NCT)BA and SAA on south (Uchi)

• Angular unconformity separatesBA in footwall from SAA inhangingwall

• Three supracrustal assemblages:Little Beaver (LBA)Bidou (BA; incl. RRPS)San Antonio (SAA)

• Crustal-scale Wanipigow SZLBA on north (NCT)BA and SAA on south (Uchi)

• Angular unconformity separatesBA in footwall from SAA inhangingwall

North CaribouTerrane

Rice Lake Au mineSan Gold #1 Au mineAu deposit, prospect

Rice Lake Au mineSan Gold #1 Au mineAu deposit, prospect

Bidou assemblage:arc to back-arc volcanism

(2.75-2.715 Ga)

Bidou assemblage:arc to back-arc volcanism

(2.75-2.715 Ga)

Schematiclithostratigraphy ofBidou assemblage

Schematiclithostratigraphy ofBidou assemblage

Four distinct lithostratigraphic units:• Independence Lake (IL)• Rainy Lake road (RLR)• Townsite (TS)• Round Lake (RL)

Four distinct lithostratigraphic units:• Independence Lake (IL)• Rainy Lake road (RLR)• Townsite (TS)• Round Lake (RL)

• north-younging strat.succession

• depositional orintrusive contact rel.(not tectonostratigraphy)

• dominated by coarseepiclastic deposits

• felsic volcanic rocks haveuniform chemical affinity

• mafic volcanic rocksexhibit systematicvariation up-section

• north-younging strat.succession

• depositional orintrusive contact rel.(not tectonostratigraphy)

• dominated by coarseepiclastic deposits

• felsic volcanic rocks haveuniform chemical affinity

• mafic volcanic rocksexhibit systematicvariation up-section

RL

RLR

TS

IL

Bidou assemblage:coarse epiclastic rocksBidou assemblage:

coarse epiclastic rocks

• dacite > andesite, rhyolite• coarsely porphyritic (pl ± qz, hb)• mono- to heterolithic, matrix-supported,

crudely stratified, with well rounded clasts• deposited mainly as sub-aqueous,

high-density debris flows• medial to distal volcaniclastic apron on a

subaerially-exposed volcanic complex• no clear examples of primary pyroclastic

deposits• volcanic source area dominated by

porphyry effusions and cryptodomes

• dacite > andesite, rhyolite• coarsely porphyritic (pl ± qz, hb)• mono- to heterolithic, matrix-supported,

crudely stratified, with well rounded clasts• deposited mainly as sub-aqueous,

high-density debris flows• medial to distal volcaniclastic apron on a

subaerially-exposed volcanic complex• no clear examples of primary pyroclastic

deposits• volcanic source area dominated by

porphyry effusions and cryptodomes

Andesite breccia (19)Andesite breccia (19)

Dacite breccia (16)Dacite breccia (16)

Heterolithic breccia (16)Heterolithic breccia (16)

• subset of samples exhibit chemical affinity toCenozoic adakites (suprasubduction-zonemagmas, possible contribution fromslab-melts)

• subset of samples exhibit chemical affinity toCenozoic adakites (suprasubduction-zonemagmas, possible contribution fromslab-melts)

Felsic volcanic and plutonic rocks:geochemistry

Felsic volcanic and plutonic rocks:geochemistry

RLR dacite breccia:εNd 0.3 (at 2.73 Ga), TCR 3.03 Ga

TS QFP rhyolite:εNd 1.1 (at 2.715 Ga), TCR 2.94 Ga

RLR dacite breccia:εNd 0.3 (at 2.73 Ga), TCR 3.03 Ga

TS QFP rhyolite:εNd 1.1 (at 2.715 Ga), TCR 2.94 Ga

• εNd and crustal-residence model ages (TCR)indicate derivation from melts that interactedwith older, isotopically-evolved crust

• εNd and crustal-residence model ages (TCR)indicate derivation from melts that interactedwith older, isotopically-evolved crust

• Strongly enriched and fractionated LREE• Weakly enriched or depleted HREE• Strong negative Nb; lack negative Eu• High Th/NbN; La/YbN; Zr/Y

• Strongly enriched and fractionated LREE• Weakly enriched or depleted HREE• Strong negative Nb; lack negative Eu• High Th/NbN; La/YbN; Zr/Y

N = 26N = 26Indicative of a continental magmatic arc (NCT margin)Indicative of a continental magmatic arc (NCT margin)

Calcalkalic volcanic-arcCalcalkalic volcanic-arc

(Pearce et al. 1984)

Independence Lake unit: arc volcanism

(ca. 2.75-2.724 Ga)

Independence Lake unit: arc volcanism

(ca. 2.75-2.724 Ga)

Massive and brecciatedandesite flow (6)

Massive and brecciatedandesite flow (6)

Stratified andesite breccia (5b)Stratified andesite breccia (5b)

Heterolithic conglomerate (4)Heterolithic conglomerate (4)

• detrital zircons in overlyingrocks <2.75 Ga

• intruded by RRPS (2.724 Ga)• complex contact relationship

to east and north with RLR unit(synvolcanic faulting)

• detrital zircons in overlyingrocks <2.75 Ga

• intruded by RRPS (2.724 Ga)• complex contact relationship

to east and north with RLR unit(synvolcanic faulting)

Pillowed Fe-tholeiite (10)Pillowed Fe-tholeiite (10)

Greywacke, conglomerateand chert (8)Greywacke, conglomerateand chert (8)

Rainy Lake road unit:arc-extension

(<2.727 Ga; ca. 2.724 Ga)

Rainy Lake road unit:arc-extension

(<2.727 Ga; ca. 2.724 Ga)

Back-arc basin tholeiiteBack-arc basin tholeiite

continental crustback-arc crustmantlewedge

back-arc ridge

riftedcontinental

arc

trench

slab

back-arcbasin

continental crustback-arc crustmantlewedge

back-arc ridge

riftedcontinental

arc

trench

slab

back-arcbasin

2727±2 Ma2727±2 Ma

Initiation of short-livedback-arc basinInitiation of short-livedback-arc basin

• restricted marine basin• 2.727 Ga detrital zircons• intruded by ca. 2.724 Ga RRP

• restricted marine basin• 2.727 Ga detrital zircons• intruded by ca. 2.724 Ga RRP

D1 deformationextensional faulting

(ca. 2.724 Ga)

D1 deformationextensional faulting

(ca. 2.724 Ga)

Clastic sulphide layerClastic sulphide layer

Stringer chlorite-garnetalteration

Stringer chlorite-garnetalteration

Solid sulphide (py) layer

Chl-gt alteration (DDH F-83-4)

Solid sulphide (py) layer

Chl-gt alteration (DDH F-83-4)

Phyllite clasts in clastic dikeEarliest observed fabric (S1)Phyllite clasts in clastic dikeEarliest observed fabric (S1)

5.45 % Zn, 1940 ppb Au5.45 % Zn, 1940 ppb Au

2cm2cm

Synvolcanic fault:• abrupt facies transition• changes in unit thickness• angular discordance• conduit for hypabyssal

gabbro laccolith andapophysis of RRP

• exhalative activity

Synvolcanic fault:• abrupt facies transition• changes in unit thickness• angular discordance• conduit for hypabyssal

gabbro laccolith andapophysis of RRP

• exhalative activity

* Eskay Creek-type setting* Eskay Creek-type setting

• clastic (transported)sulphide

• clastic (transported)sulphide

Ross River Plutonic suite:syn-extension magmatism

(ca. 2.724 Ga)

Ross River Plutonic suite:syn-extension magmatism

(ca. 2.724 Ga)

Bt granodiorite (11a)(96-03-RRP)Bt granodiorite (11a)(96-03-RRP)

Spherulitic pl-qz-hb porphyry dikeSpherulitic pl-qz-hb porphyry dike

• high-level (narrow aureoles;quench textures)

• apophysis of RRP controlledby extensional fault

• rapid exhumation (main sourceof detritus for overlying TS unit)

• high-level (narrow aureoles;quench textures)

• apophysis of RRP controlledby extensional fault

• rapid exhumation (main sourceof detritus for overlying TS unit)

2724±2 Ma2724±2 Ma

Townsite unit:resurgent arc volcanism(<2.724 Ga; >2.715 Ga)

Townsite unit:resurgent arc volcanism(<2.724 Ga; >2.715 Ga)

Arc basaltArc basalt

Pillowed basalt (15)Pillowed basalt (15)

Pebbly felsicsandstone (12)Pebbly felsicsandstone (12)

RRPS(or age-

equivalent)source

RRPS(or age-

equivalent)source

Clastic dike cuttingandesite flow breccia (6)Clastic dike cuttingandesite flow breccia (6)

• subaerial to shallow-subaqueousfan setting

• ca. 2.724 Ga detrital zircons• main source is RRPS, or age equivalent

• subaerial to shallow-subaqueousfan setting

• ca. 2.724 Ga detrital zircons• main source is RRPS, or age equivalent

Volcanicconglomerate (18)Volcanicconglomerate (18)

Round Lake unit:resurgent arc volcanism

(<2.724; 2.715 Ga)

Round Lake unit:resurgent arc volcanism

(<2.724; 2.715 Ga)

Basalt dike (17)Basalt dike (17)

SanukitoidSanukitoid

Rhyolitic QFP (21)Rhyolitic QFP (21)2715±2 Ma

Basalt lapilli tuff (18c)Basalt lapilli tuff (18c)

• subaerial to shallow-subaqueousfan setting

• 2.715 Ga hypabyssal rhyolite sill(youngest recorded volcanism in RLB)

• subaerial to shallow-subaqueousfan setting

• 2.715 Ga hypabyssal rhyolite sill(youngest recorded volcanism in RLB)

D2 deformation regional tilting

(<2.715 Ga)

D2 deformation regional tilting

(<2.715 Ga)

Arc accretion?Back-arc basin inversion?Arc accretion?Back-arc basin inversion?

• Bidou tilted to near-vertical and erodedprior to deposition of SAA

• pronounced angular unconformity

• Bidou tilted to near-vertical and erodedprior to deposition of SAA

• pronounced angular unconformitySAA

BA

Change infold vergence

San Antonio assemblage:fluvial sedimentation

(<2.705 Ga)

San Antonio assemblage:fluvial sedimentation

(<2.705 Ga)

Trough cross-bedded arenite (27)Trough cross-bedded arenite (27)

Tonaliteconglomerate (26)

Tonaliteconglomerate (26)

Greywacke and mudstone (29)Greywacke and mudstone (29)

NCTdetritus

NCTdetritus

BidoudetritusBidou

detritus

Dashed line; SHRIMP data, Percival et al. 2006Dashed line; SHRIMP data, Percival et al. 2006

• post-dates arc magmatism• youngest detrital zircon

2.705 Ga (Percival et al. 2006)

• post-dates arc magmatism• youngest detrital zircon

2.705 Ga (Percival et al. 2006)

Uplift and erosion related toterminal collision?

D3 deformation:thrust faulting

(ca. 2.69-2.68 Ga?)

D3 deformation:thrust faulting

(ca. 2.69-2.68 Ga?)

S0-S2S0-S2

F3F3

• SAA structurally overlain to west by BA• older-over-younger map pattern; thrust fault• layer-parallel S2 fabric; <2.705 Ga

• SAA structurally overlain to west by BA• older-over-younger map pattern; thrust fault• layer-parallel S2 fabric; <2.705 Ga

Basin inversion during earlystage of terminal collisionBasin inversion during earlystage of terminal collision

D4 deformationsinistral transpression

(ca. 2.69-2.68 Ga?)

D4 deformationsinistral transpression

(ca. 2.69-2.68 Ga?)

S0-S2S0-S2

S3S3

L3L3

CC

SS

C’C’

Crustal thickeningCrustal thickening

• first ‘regional’ deformation• greenschist-facies regional

metamorphism • NE-SW shortening strongly

partitioned in three distinctmacroscopic domains

• first ‘regional’ deformation• greenschist-facies regional

metamorphism • NE-SW shortening strongly

partitioned in three distinctmacroscopic domains

Sinistral-reversenon-coaxial shearSinistral-reversenon-coaxial shear

Bulk flattening and stretchingBulk flattening and stretchingUpright subhorizontal foldingUpright subhorizontal folding

Gold mineralization:general characteristicsGold mineralization:general characteristics

• quartz-carbonate veins• shear zone or fracture control • quartz, subordinate carbonate (ank>cal),

albite, chlorite, sericite• low-sulphide content (<5%)• pyrite; other sulphides negligible• free gold, assoc. with pyrite• high Au:Ag (>5:1)• low base metals and pathfinder

elements (e.g., As, Bi, B, Sb, W)• narrow, zoned wall-rock alteration

proximal: ankerite-albite-sericite-pyritedistal: chlorite-calcite

• evidence of wall-rock sulphidation• considerable depth extent (>2 km),

yet negligible variation

• quartz-carbonate veins• shear zone or fracture control • quartz, subordinate carbonate (ank>cal),

albite, chlorite, sericite• low-sulphide content (<5%)• pyrite; other sulphides negligible• free gold, assoc. with pyrite• high Au:Ag (>5:1)• low base metals and pathfinder

elements (e.g., As, Bi, B, Sb, W)• narrow, zoned wall-rock alteration

proximal: ankerite-albite-sericite-pyritedistal: chlorite-calcite

• evidence of wall-rock sulphidation• considerable depth extent (>2 km),

yet negligible variation

Dube et al., 2007Dube et al., 2007

Rice Lake district• first discovery of gold in Manitoba (1911)• several significant deposits• Rice Lake and SG-1 mines (San Gold Corp.)• Rice Lake deposit >2.3 million ounces Au

(production + reserves, resources)

Rice Lake district• first discovery of gold in Manitoba (1911)• several significant deposits• Rice Lake and SG-1 mines (San Gold Corp.)• Rice Lake deposit >2.3 million ounces Au

(production + reserves, resources)

‘Mesothermal’‘Shear-hosted’‘Mother-lode’‘Orogenic’

‘Mesothermal’‘Shear-hosted’‘Mother-lode’‘Orogenic’

AKA:AKA:

• brittle-ductile shear zones• shear and tensile fracture arrays• competent rock types, with

strength anisotropies• shear-hosted veins – massive,

laminated and brecciated• evidence of ‘fault-valve’ (Sibson et al.,

1988) behaviour• extension-vein stockworks –

intensify into hydraulic breccia• subhorizontal extension veins

• brittle-ductile shear zones• shear and tensile fracture arrays• competent rock types, with

strength anisotropies• shear-hosted veins – massive,

laminated and brecciated• evidence of ‘fault-valve’ (Sibson et al.,

1988) behaviour• extension-vein stockworks –

intensify into hydraulic breccia• subhorizontal extension veins

• synkinematic vein emplacement• brittle-ductile (mid-crustal) conditions• high fluid pressure

(transiently supralithostatic)

• synkinematic vein emplacement• brittle-ductile (mid-crustal) conditions• high fluid pressure

(transiently supralithostatic)

Gold mineralization:style

Gold mineralization:style

RLM; 3096ERLM; 3096E

SG-1; L6ESG-1; L6ERLM; 4670 (A-vein)RLM; 4670 (A-vein)

RLM; 3096ERLM; 3096ERLM; 2998WRLM; 2998W

RLM; 3096ERLM; 3096E

WingoldWingold

RLM; 3098ERLM; 3098E

Big FourBig Four

RLM; 3096WRLM; 3096W

• subhorizontal σ1• subvertical σ3• supralithostatic Pf

• subhorizontal σ1• subvertical σ3• supralithostatic Pf

• far-field NE-SW, subhorizontal shortening(see also Davies, 1953; Lau, 1988; Lau and

Brisbin, 1996; Brommecker, 1991)

• far-field NE-SW, subhorizontal shortening(see also Davies, 1953; Lau, 1988; Lau and

Brisbin, 1996; Brommecker, 1991)

Gold mineralization:kinematic framework

Gold mineralization:kinematic framework

Section view (looking east)Section view (looking east)

Plan viewPlan view

Pencils point northPencils point north

• near-field σ1 roughlyNNE-SSW

• near-field σ1 roughlyNNE-SSW

Gold mineralization:structural timing

Gold mineralization:structural timing

• post-dates at least initialincrements of regional D4

• post-dates at least initialincrements of regional D4

3096E; 1st sublevel3096E; 1st sublevel

• regional NE-SW compressive stress• high fluid pressures• shear and hydraulic fracturing of

competent rock-types• enhanced permeability• channeling of metamorphic fluids• decompression-induced precipitation

D5 deformation (main)dextral transpression

(ca. 2.68-2.65 Ga?)

D5 deformation (main)dextral transpression

(ca. 2.68-2.65 Ga?)

SG-1; L6ESG-1; L6E

Wanipigow shear zoneWanipigow shear zone

Wanipigow shear zoneWanipigow shear zone

• regional shift to NW-SE shortening• pervasive fracture cleavage (early)• strain partitioned into

discrete high-strain zones (main)• overprints Au mineralization

• regional shift to NW-SE shortening• pervasive fracture cleavage (early)• strain partitioned into

discrete high-strain zones (main)• overprints Au mineralization

Orogen-scale change in plateconfiguration?

Terminal collision insouthern Superior Province?

Orogen-scale change in plateconfiguration?

Terminal collision insouthern Superior Province?

Geoscientific Report GR2008-1Released 20/11/2008

To conclude…To conclude…

• ca. 300 million year history (ca. 70 m.y. in this talk!)• ca. 300 million year history (ca. 70 m.y. in this talk!)

• includes continental rift, continental arc ormarginal oceanic-arc, arc-rift settings

• includes continental rift, continental arc ormarginal oceanic-arc, arc-rift settings

• indications of potential forVHMS Cu-Pb-Zn(Au,Ag); arc-rifts

• indications of potential forVHMS Cu-Pb-Zn(Au,Ag); arc-rifts

• complex deformation history:ca. 2.69-2.65 Ga continent-continentcollision

• complex deformation history:ca. 2.69-2.65 Ga continent-continentcollision

• north-verging subduction / accretion complex• north-verging subduction / accretion complex

• orogenic gold deposits: NE-SWcompressional regime; locallysignificant structural overprint

• orogenic gold deposits: NE-SWcompressional regime; locallysignificant structural overprint

Rice Lake district:Rice Lake district:

More info…More info…