Wg

Wgb

Wgb

Wgb

Wmfv

Wmfv

Wmfv

Wms

Wmsv

Wmsv

Wifb

Wif

Wms

Wmsv

Wmz

Wmfv

Wmfv

Wg

Whm

Wmsb

Wmsb

Wmsb

Wmsb

Wvsm

Wvsm

Wvsm

Wlvs

Wmmv

Wmmv

Wgd

Wvsm

Wmsb

Wmsa

Wfvs Wmiv

Wfvs

Wg

Wif

Wmiv

Wmiv

Wif

Wiv

Wgmz

Wiv

Wmfv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wgn

Wmz

Wmz

Wg

Wmv

Wmv

Wfv

Wg

Wg

Wg

Wg

Wmv

Wmv

Wgb

Wmfv

Wmfv

Wms

Wifb

Wmsv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wui

Wgb

Wg

Wfvs

Wgmz

Wmiv

Wfvs

Wms

Wg

Wms

Wmz

Wmz

Wfv

Wfv

Wvs

Wfvs

Wif

Wifb

Wif

Wms

Wif

Wg

Wms

Wgmz

Wfv

Wfv

Wms

Wlvs

Wlvs

Wmmv

Wmmv

Wmfv

Wg Wifb

Wmfv

Wmsv

Wif

Wg

Wmiv

Wmsv

Wmsv Wmiv

Wifb

Wg

Wgb

Wms

Wms

Wg

Wmv

Wg

Wmfv

Wmv

Wmv

Wif

Wgmz

Wfv

Wg

Wg

Wfvs

Wfvs

Wif

Wgb

Wg

Wgb

Wgb

Wgb

Wmfv

Wmfv

Wmfv

Wms

Wmsv

Wmsv

Wifb

Wif

Wms

Wmsv

Wmz

Wmfv

Wmfv

Wg

Whm

Wmsb

Wmsb

Wmsb

Wmsb

Wvsm

Wvsm

Wvsm

Wlvs

Wmmv

Wmmv

Wgd

Wvsm

Wmsb

Wmsa

Wfvs Wmiv

Wfvs

Wg

Wif

Wmiv

Wmiv

Wif

Wiv

Wgmz

Wiv

Wmfv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wgn

Wmz

Wmz

Wg

Wmv

Wmv

Wfv

Wg

Wg

Wg

Wg

Wmv

Wmv

Wgb

Wmfv

Wmfv

Wms

Wifb

Wmsv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wui

Wgb

Wg

Wfvs

Wgmz

Wmiv

Wfvs

Wms

Wg

Wms

Wmz

Wmz

Wfv

Wfv

Wvs

Wfvs

Wif

Wifb

Wif

Wms

Wif

Wg

Wms

Wgmz

Wfv

Wfv

Wms

Wlvs

Wlvs

Wmmv

Wmmv

Wmfv

Wg Wifb

Wmfv

Wmsv

Wif

Wg

Wmiv

Wmsv

Wmsv Wmiv

Wifb

Wg

Wgb

Wms

Wg

Wmv

Wg

Wmfv

Wmv

Wmv

Wif

Wgmz

Wfv

Wg

Wg

Wfvs

Wfvs

Wif

Wgb

Wifb

Wmv

Wui

Wmv

Wui

VERMILION GRANITIC

COMPLEX

 SABASKONG

 BATHOLITHIC

 SUITE

 BAUDETTE

 INTRUSIVE

 ROCKS

 WARROAD

INTRUSIVE

 ROCKS

 LONG POINT

 INTRUSIVE

 ROCKS

VERMILION GRANITIC

COMPLEX

 SABASKONG

 BATHOLITHIC

 SUITE

 BAUDETTE

 INTRUSIVE

 ROCKS

 WARROAD

INTRUSIVE

 ROCKS

 LONG POINT

 INTRUSIVE

 ROCKS

RAINY LAKE–SEINE RIVER FAULT

RAINY LAKE–SEINE RIVER FAULT

VERMILION FAULT

VERMILION FAULT

QUETICO FAULT

QUETICO FAULT

BAUDETTE FAULT

BAUDETTE FAULT

BORDER FAULT

BORDER FAULT

FOUR TOWN FAULT

FOUR TOWN FAULT

BLACK RIVER FAULT

BLACK RIVER FAULT

STAR-3 FT-20

FT-8

FT-9

FT-18

FT-17

FT-14

T20-1

T25A-2

T25B-2

ROS-1

ROS-2

HAN-1 HAN-2

YWT-1

YWZ-1 YWZ-2

YWQ-1

YWM-1

YWL-1

YWI-1

W1-1

W3-1

W9-1

D-1 W13-1

WB-1

BD-2 SP-1A SP-2

YWA-3,4

CUS-22

CUS-23

CUS-24

CUS-25

CUS-20

CUS-19

CUS-16

CUS-17

CUS-18 40920 40919

40918

40917

40926 CUS-27A

B35-1

MED-1

B24-1,2,3

B24-4

B21-3 B21-2 MSD-1

MDD-1

BD-P-2

B-B-2

CUS-15

BD-1

BD-3 BD-2

CUS-11

BD-II-1

BD-II-2

CUS-10

CUS-9

RR16-1

B-3-3

CUS-7A

A-1-1

A-8-1

A-9-1

A-4-2

FT-19

HC-1

FT-4

A-9-2

T25A-1

 FT-22

 FT-23

FT-10

FT-15,16

CUS-7

J-1

YGZ-1

W1-84

M-1

A-10-1

BD-N-1

FT-6

R-3

STAR-1

STAR-2

B-2

MR1-84

MR2-84

G-1

B-1

BLT-2

BLT-1

B31-1

B31-2

B31-3

B31-5

B31-4

MQD-1

MQD-2

LW346-2

LW346-1

UBD-1

UBD-2

CUS-2A

CUS-5A

UBD-4

CUS-26A

UBD-3

SQW-1

B54-1

B5-1

B-57-1

B7-1

B-3-1

B-3-2 B7-3

B7-2

M-PL-1B2

M-PL-3B2

1760

FT-21 FT-7

FT-12,13

CUS-21B

MMD-1

B58-1

STAR-3 FT-20

FT-8

FT-9

FT-18

FT-17

FT-14

T20-1

T25A-2

T25B-2

ROS-1

ROS-2

HAN-1 HAN-2

YWT-1

YWZ-1 YWZ-2

YWQ-1

YWM-1

YWL-1

YWI-1

W1-1

W3-1

W9-1

D-1 W13-1

WB-1

BD-2 SP-1A SP-2

YWA-3,4

CUS-22

CUS-23

CUS-24

CUS-25

CUS-20

CUS-19

CUS-16

CUS-17

CUS-18 40920 40919

40918

40917

40926 CUS-27A

B35-1

MED-1

B24-1,2,3

B24-4

B21-3 B21-2 MSD-1

MDD-1

BD-P-2

B-B-2

CUS-15

BD-1

BD-3 BD-2

CUS-11

BD-II-1

BD-II-2

CUS-10

CUS-9

RR16-1

B-3-3

CUS-7A

A-1-1

A-8-1

A-9-1

A-4-2

FT-19

HC-1

FT-4

A-9-2

T25A-1

 FT-22

 FT-23

FT-10

FT-15,16

CUS-7

J-1

YGZ-1

W1-84

M-1

A-10-1

BD-N-1

FT-6

R-3

STAR-1

STAR-2

B-2

MR1-84

MR2-84

G-1

B-1

BLT-2

BLT-1

B31-1

B31-2

B31-3

B31-5

B31-4

MQD-1

MQD-2

LW346-2

LW346-1

UBD-1

UBD-2

CUS-2A

CUS-5A

UBD-4

CUS-26A

UBD-3

SQW-1

B54-1

B5-1

B-57-1

B7-1

B-3-1

B-3-2 B7-3

B7-2

M-PL-1B2

M-PL-3B2

1760

FT-21 FT-7

FT-12,13

CUS-21B

MMD-1

B58-1

W8-1

A-6-1

W8-1

A-6-1

BD-1

B21-1

A-4-1

A-6-2

YWA-

 1,2

BD-1

B21-1

A-4-1

A-6-2

YWA-

 1,2

B-Q-1

B-Q-1

FT-2

FT-1

FT-2

FT-1

CUS-5

CUS-5

FT-3

FT-3

KIB-43B

KIB-67

KIB-64

KIB-65

KIB-66

KIB-69

OB-501

OB-502

OB-503

OB-505

OB-506

OB-507

OB-508

OB-509

OB-510

OB-511

OB-512

OB-513

OB-514

OB-515

OB-516

OB-518

OB-519

OB-520

OB-521

OB-517

KIB-43B

KIB-67

KIB-64

KIB-65

KIB-66

KIB-69

OB-501

OB-502

OB-503

OB-505

OB-506

OB-507

OB-508

OB-509

OB-510

OB-511

OB-512

OB-513

OB-514

OB-515

OB-516

OB-518

OB-519

OB-520

OB-521

OB-517

 80

 80

 80

 85

 77

 80

 80

 80

 85

 77

 65

 75

 75

 80

 65 85

 75

 80

 70

 80

 85

 65

 80

 60

 85

 28

 68

 84

 65

 85 60

 85

 85

 76

 80

 50

 60

 87

 68 85 55 50

 68

 85

 71

 46

 80

 80

 80

 85

 80

 72

 75

 66

 70

 80 85

 85

 75

 60

 85

 65

 65

 75

 75

 80

 65 85

 75

 80

 70

 80

 85

 65

 80

 60

 85

 28

 68

 84

 65

 85 60

 85

 85

 76

 80

 50

 60

 87

 68 85 55 50

 68

 85

 71

 46

 80

 80

 80

 85

 80

 72

 75

 66

 70

 80 85

 85

 75

 60

 85

 65

 75

 25

 50

 65

 75

 25

 50

 65

















 



































 



















 

















 



































 



















 

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

MISCELLANEOUS INVESTIGATIONS SERIES

MAP I–2358–B (Sheet 1 of 2)

Pamphlet accompanies map

MAP A. MINERAL RESOURCE POTENTIAL FOR VOLCANOGENIC MASSIVE SULFIDE DEPOSITS

MAP B. MINERAL RESOURCE POTENTIAL FOR GABBRO AND ULTRAMAFIC INTRUSION-HOSTED NICKEL-COPPER-PLATINUM GROUP ELEMENT DEPOSITS

Base from U.S. Geological Survey, 1954 (U.S. area revised 1955)

100,000-foot grid based on Minnesota coordinate system, north zone

10,000-meter Universal Mercator grid zone 15

Transverse Mercator projection

Geology simplified from Day and others (1994)

Edited by Lorna M. Carter

Digital cartography by Alessandro J. Donatich

Manuscript approved for publication July 28, 1998

REGIONAL BEDROCK MINERAL RESOURCE ASSESSMENT OF THE ROSEAU 1° x 2° QUADRANGLE, NORTHERN MINNESOTA

By

Terry L. Klein, Warren C. Day, Robert J. Horton, and Gregory N. Green

1999

Mineral resource assessment tracts

Tract I—Granitoid, gabbro, and ultramafic plutonic 

rocks

Tract II—Graywacke-argillite-type metasedimentary 

rocks of the Quetico subprovince

Tract III—Graywacke-argillite-type metasedimentary 

rocks of the Wabigoon and Wawa subprovinces

Tract IV—Metasedimentary rocks derived from 

volcanic sources

Tract V—Mafic to intermediate metavolcanic rocks 

of the Wabigoon subprovince

Tract VI—Roof pendants of mafic to intermediate 

volcanic rocks in granitoid rocks of the Wabigoon 

subprovince

Tract VII—Felsic and bimodal metavolcanic rocks 

containing massive sulfide layers with low levels of 

base metals

EXPLANATION OF MINERAL RESOURCE POTENTIAL FOR MAP B

Mineral resource assessment tracts

Tract I—Granitoid plutonic rocks of the Wabigoon subprovince

Tract II—Granitoid and metasedimentary rocks of the Wabigoon, Wawa, and Quetico subprovinces

Tract III—Felsic metavolcanic and metavolcanic-sedimentary units of the Wabigoon subprovince

Tract IV—Mafic metavolcanic units of the Wabigoon and Wawa subprovinces

Tract V—Large metamorphosed gabbro or gabbro-peridotite bodies of the Wabigoon subprovince

Tract VI—Magnetic iron-formation associated with mafic metavolcanic and metasedimentary rocks of 

the Wabigoon subprovince

Tract VIII—Highly deformed bimodal metavolcanic 

rocks in the central part of the Wabigoon 

subprovince containing base-metal-bearing massive 

sulfide layers

Tract IX—Bimodal metavolcanic rocks in the central 

part of the Wabigoon subprovince containing 

base-metal-bearing massive sulfide layers

Tract X—Fine-grained metamorphosed layered tuffs, 

chert, and subordinate amounts of felsic 

volcaniclastic rocks containing a pyritic massive 

sulfide lens with generally low base-metal content

Tract XI—Mafic metavolcanic rocks with minor 

amounts of felsic metavolcanic rocks of the Wawa 

subprovince

Tract XII—Magnetic iron-formation

EXPLANATION OF MINERAL RESOURCE POTENTIAL FOR MAP A









I N/D

II N/D

III N/D

IV L/B IV L/C

V M/B V M/C

VI L/B

VII M/B VII M/C

VIII H/C

IX H/B IX H/C

X H/C

XI L/B

XII L/B

I N/C

II N/B II N/C

III L/C

IV M/B

V M/B V M/C

VI N/C

5 5 0 10 15 20 25 30 KILOMETERS

SCALE 1:250 000

5 0 5 15 20 MILES 10

CONTOUR INTERVAL 50 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Wgmz

Wmz

Wgn

Wg

Wgb

Wui

Wms

Wmsa

Wif

Wifb

Wmsv

Wfvs

Wfv

Wmfv

Wiv

Wmiv

Wmv

Wvs

LATE ARCHEAN UNITS OF THE WABIGOON SUBPROVINCE

Post-tectonic intrusive rocks (younger than about 2,700 Ma)

Granodiorite, quartz monzonite, and granite

Hornblende monzonite

Granodiorite gneiss

Pre- and syn-tectonic intrusive rocks (about 2,700–2,736 Ma)

Granitoid rocks

Mafic intrusive rock

Ultramafic to mafic intrusive rocks

Supracrustal rocks

Metasedimentary rocks, undivided

Metasedimentary rocks, amphibolite facies

Iron-formation

Chert-rich iron-formation

Metasedimentary and metavolcanic rocks

Felsic metavolcanic and volcaniclastic metasedimentary rocks

Felsic metavolcanic rocks

Mafic and felsic metavolcanic rocks

Intermediate metavolcanic rocks

Mafic to intermediate metavolcanic rocks, undivided

Mafic metavolcanic rocks

Metavolcanic and metasedimentary rocks, undivided

LATE ARCHEAN UNITS OF THE QUETICO SUBPROVINCE

Intrusive and migmatitic rocks

Hornblende monzonite

Schist-rich migmatite

Supracrustal rocks

Metasedimentary rocks, undivided

LATE ARCHEAN UNITS OF THE WAWA SUBPROVINCE

Intrusive rocks

Granodiorite, quartz diorite, and tonalite

Supracrustal rocks

Layered volcanic-sedimentary rocks

Metavolcanic rocks, undivided

Approximate contact—Dashed where inferred

Fault—Dashed where inferred. Arrows show relative horizontal 

movement

Fault rock—Schist, mylonite, phyllonite, and cataclasite. May 

include rocks of both Early Proterozoic and Archean age

Strike and dip of bedding

Inclined

Vertical

Overturned

Strike and dip of schistosity

Inclined

Vertical

Location of outcrop

Location of numbered drill hole—See Klein and Day (1989) for 

geologic data and Klein and others (1987) and Klein (1988) 

for geochemical data for drill holes

DESCRIPTION OF MAP UNITS FOR MAPS A–C

Whm

Wvsm

Wmsb

Wgd

Wlvs

Wmmv





A-9-1

 80

 80

 25

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

This map is also available as a PDF at http://greenwood.cr.usgs.gov

I N/D

I N/D

I N/D

I N/D

II N/D

II N/D

II N/D

III N/D

III N/D

IV L/B

IV L/B

IV L/C

V M/B

V M/B

V M/C

V M/C

VI L/B

VI L/B

VII M/B

VII M/B

VII M/B

VII M/C

VIII H/C

IX H/C

X H/C

XI L/B

XII L/B

XII L/B

XII L/B

VI N/C

VI N/C

VI N/C

I N/C

I N/C

I N/C

I N/C

II N/B

II N/B

II N/B

II N/C

II N/C

II N/C

II N/C

III L/C

III L/C

IV M/B

IV M/B

IV M/B

IV M/B

IV M/B

IV M/B

IV M/B

V M/B

V M/C

V M/C

V M/C

IX H/B

II N/B

Table 2. Diagnostic and permissive criteria for volcanogenic massive sulfide deposits

Diagnostic criteria:

1. Presence of volcanic rocks.

Geophysical indicators: irregular aeromagnetic patterns and relative gravity highs.

2. Proximity to felsic volcanic centers characterized by coarse felsic volcaniclastic breccias and fragmental rocks, 

subvolcanic intrusive rocks.

3. Evidence for hydrothermal fluids associated with massive sulfide deposits.

a. Exhalite, volcanogenic chert-sulfide horizons, Algoma-type iron-formation, manganese-rich layers.

b. Hydrothermal alteration such as Mg-, Fe-, and K-enrichment and Na-depletion.

c. Base-metal and pathfinder-element enrichment (Zn, Cu, ± Se, In, Sb, Sn, or B) as indicated by bedrock and Bhorizon soil samples.

d. Presence of barren, pyrite-rich massive sulfide horizons.

4. Presence of base-metal massive sulfide deposits as indicated by bedded sulfide mineral deposits or stockwork feeder 

zones, or bedrock electrical conductors.

Permissive criteria:

1. Presence of graphitic sediments.

Table 3. Resource potential for volcanogenic massive sulfide deposits in the Roseau 1°x2° quadrangle

Tract No. Diagnostic criteria Sum of Resource Confidence

(map A) 1 2 3 4 tract scores potential level

I 0 0 0 0 0 None D

II 0 0 0 0 0 None D

III 0 0 0 0 0 None D

IV 1 0 1a,b 0 2 Low B, C

V 101a,b,c 1 3 Moderate B, C

VI 1 0 1c 0 2 Low B

VII 1 1 1a 0 3 Moderate B, C

VIII 1 1 1a,b,c,d 1 4 High C

IX 1 1 1a,b,c,d 1 4 High B, C

X 111a,b,d 1 4 High C

XI 1 0 0 0 1 Low B

XII 0 1 1a,b,c,d 0 2 Low B

aChert.

b

Mg or Fe enrichment.

c

Base-metal anomalies.

d

Massive sulfide horizons present.

Table 4. Diagnostic criteria for nickel-copper-platinum group element deposits in gabbro and ultramafic rocks

in the Roseau 1°x2° quadrangle

1. Presence of layered gabbro, dunite, peridotite, pyroxenite, anorthosite, and norite intrusions or komatiitic volcanic 

rocks or subvolcanic sills.

2. Anomalously high concentrations of nickel, copper, ± cobalt, platinum group elements; presence of nickel and (or) 

copper sulfide or arsenide minerals.

Table 5. Resource potential for gabbro- and ultramafic-intrusion-associated nickel-copper-platinum group element 

deposits and komatiite nickel-copper deposits in the Roseau 1°x2° quadrangle

Tract No. Diagnostic criteria Sum of Resource Confidence 

(map B) 1 2 tract scores potential level

I -1 0 -1 None C

II -1 0 -1 None B, C

III 0 0 0 Low C

IV 1 1 2 Moderate B

V 1 0 1 Moderate B, C

VI -1 0 -1 None C
Wg

Wgb

Wgb

Wgb

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Wmfv

Wmfv

Wms

Wmsv

Wmsv

Wifb

Wif

Wms

Wmsv

Wmz

Wmfv

Wmfv

Wg

Whm

Wmsb

Wmsb

Wmsb

Wmsb

Wvsm

Wvsm

Wvsm

Wlvs

Wmmv

Wmmv

Wgd

Wvsm

Wmsb

Wmsa

Wfvs Wmiv

Wfvs

Wg Wif

Wmiv

Wmiv

Wif

Wiv

Wgmz

Wiv

Wmfv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wgn

Wmz

Wmz

Wg

Wmv

Wmv

Wfv

Wg

Wg

Wg

Wg

Wmv

Wmv

Wgb

Wmfv

Wmfv

Wms

Wifb

Wmsv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wmiv

Wg

Wg

Wui

Wgb

Wg

Wfvs

Wgmz

Wmiv

Wfvs

Wms

Wg

Wms

Wmz

Wmz

Wfv

Wfv

Wvs

Wfvs

Wif

Wifb

Wif

Wms

Wif

Wg

Wms

Wgmz

Wfv

Wfv

Wms

Wlvs

Wlvs

Wmmv

Wmmv

Wmfv

Wg

Wifb

Wmfv

Wmsv

Wif

Wg

Wmiv

Wmsv

Wmsv Wmiv

Wifb

Wg

Wgb

Wms

Wms

Wg

Wmv

Wg

Wmfv

Wmv

Wmv

Wif

Wgmz

Wfv

Wg

Wg

Wfvs

Wfvs

Wif

Wgb

Wmv

Wui

VERMILION GRANITIC

COMPLEX

 SABASKONG

 BATHOLITHIC

 SUITE

 BAUDETTE

 INTRUSIVE

 ROCKS

 WARROAD

INTRUSIVE

 ROCKS

 LONG POINT

 INTRUSIVE

 ROCKS

RAINY LAKE–SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

BAUDETTE FAULT

BORDER FAULT

FOUR TOWN FAULT

BLACK RIVER FAULT

STAR-3 FT-20

FT-8

FT-9

FT-18

FT-17

FT-14

T20-1

T25A-2

T25B-2

ROS-1

ROS-2

HAN-1 HAN-2

YWT-1

YWZ-1 YWZ-2

YWQ-1

YWM-1

YWL-1

YWI-1

W1-1

W3-1

W9-1

D-1 W13-1

WB-1

BD-2 SP-1A SP-2

YWA3,4

CUS-22

CUS-23

CUS-24

CUS-25

CUS-20

CUS-19

CUS-16

CUS-17

CUS-18 40920 40919

40918

40917

40926 CUS-27A

B35-1

MED-1

B24-1,2,3

B24-4

B21-3 B21-2 MSD-1

MDD-1

BD-P-2

B-B-2

CUS-15

BD-1

BD-3 BD-2

CUS-11

BD-II-1

BD-II-2

CUS-10

CUS-9

RR16-1

B-3-3

CUS-7A

A-1-1

A-8-1

A-9-1

A-4-2

FT-19

HC-1

FT-4

A-9-2

T25A-1

 FT-22

 FT-23

FT-10

FT-15,16

CUS-7

J-1

YGZ-1

W1-84

M-1

A-10-1

BD-N-1

FT-6

R-3

STAR-1

STAR-2

B-2

MR1-84

MR2-84

G-1

B-1

BLT-2

BLT-1

B31-1

B31-2

B31-3

B31-5

B31-4

MQD-1

MQD-2

LW346-2

LW346-1

UBD-1

UBD-2

CUS-2A

CUS-5A

UBD-4

CUS-26A

UBD-3

SQW-1

B54-1

B5-1

B-57-1

B7-1

B-3-1

B-3-2 B7-3

B7-2

M-PL-1B2

M-PL-3B2

1760

FT-21 FT-7

FT-12,13

CUS-21B

MMD-1

B58-1

W8-1

A-6-1

BD-1

B21-1

A-4-1

A-6-2

YWA-

 1,2

B-Q-1 FT-2

FT-1

CUS-5

FT-3

KIB-43B

KIB-67

KIB-64

KIB-65

KIB-66

KIB-69

OB-501

OB-502

OB-503

OB-505

OB-506

OB-507

OB-508

OB-509

OB-510

OB-511

OB-512

OB-513

OB-514

OB-515

OB-516

OB-518

OB-519

OB-520

OB-521

OB-517

 80

 80

 80

 85

 77

 65

 75

 75

 80

 65 85

 75

 80

 70

 80

 85

 65

 80

 60

 85

 28

 68

 84

 65

 85 60

 85

 85

 76

 80

 50

 60

 87

 68 85 55 50

 68

 85

 71

 46

 80

 80

 80

 85

 80

 72

 75

 66

 70

 80 85

 85

 75

 60

 85

 65

 75

 25

 50

 65



















 



































 

















 

Pamphlet accompanies map

MAP C. MINERAL RESOURCE POTENTIAL FOR ARCHEAN LODE GOLD DEPOSITS Base from U.S. Geological Survey, 1954 (U.S. area revised 1955)

100,000-foot grid based on Minnesota coordinate system, north zone

10,000-meter Universal Mercator grid zone 15

Transverse Mercator projection

Geology simplified from Day and others (1994)

Edited by Lorna M. Carter

Digital cartography by Alessandro J. Donatich

Manuscript approved for publication July 28, 1998

REGIONAL BEDROCK MINERAL RESOURCE ASSESSMENT OF THE ROSEAU 1° x 2° QUADRANGLE, NORTHERN MINNESOTA

By

Terry L. Klein, Warren C. Day, Robert J. Horton, and Gregory N. Green

1999

EXPLANATION OF MINERAL RESOURCE POTENTIAL FOR MAP C

Mineral resource assessment tracts

Tract I—Metasedimentary rocks of the Quetico subprovince located more than 2 km from 

known or inferred shear zones

Tract II—Plutonic and supracrustal rocks of the Wawa subprovince located more than 2 km 

from known or inferred shear zones

Tract III—Metasedimentary rocks of the Quetico subprovince located within 2 km of known or 

inferred shear zones

Tract IV—Granitoid and supracrustal rocks of the Wabigoon subprovince located more than 2 

km from known or inferred shear zones

Tract V—Rocks within 2 km of known or inferred shear zones of the Wabigoon subprovince 

that do not have positive diagnostic criteria other than proximity to shear zones

Tract VI—Large granitoid plutons and some mafic and felsic volcanic rocks characterized by 

tellurium anomalies in overlying soils

Tract VII—Rocks of the Quetico and Wabigoon subprovinces located within 2 km of the Four 

Town and Border faults and overlain by soils containing geochemical anomalies possibly 

related to gold deposits

Tract VIII—Metavolcanic rocks and granitoid rocks of the Wabigoon subprovince that contain 

low-level gold and base-metal anomalies in small shear zones near Birchdale, Minn. (VIII 

M/C), and southwest of Warroad, Minn. (VIII M/B)

Tract IX—Bimodal (mafic-felsic) metavolcanic rocks between the Border fault and the 

Vermilion fault that show evidence of hydrothermal alteration possibly related to gold 

deposits

Tract X—Highly deformed metavolcanic rocks of the Wabigoon subprovince that contain lowlevel gold anomalies and quartz-calcite veins

I L/B

II L/B

III L/B

IV L/B

V L/B

VI L/B

VII M/B

VIII M/B VIII M/C

IX M/B

X H/B X H/C

5 5 0 10 15 20 25 30 KILOMETERS

SCALE 1:250 000

5 0 5 15 20 MILES 10

CONTOUR INTERVAL 50 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

This map is also available as a PDF at http://greenwood.cr.usgs.gov

I L/B

I L/B

I L/B

I L/B

II L/B

III L/B

III L/B

III L/B

IV L/B IV L/B

IV L/B

IV L/B

IV L/B

IV L/B

V L/B

VI L/B

VI L/B

VII M/B

VII M/B

VIII M/B

VIII M/C

IX M/B

X H/B

X H/B

X H/B

X H/C

X H/C

X H/C

Table 6. Diagnostic and permissive criteria for Archean low-sulfide gold-quartz vein deposits in the 

Roseau 1°x2° quadrangle

Diagnostic criteria:

1. Presence of anomalous gold and silver concentrations in drill core or B-horizon soil samples.

2. Proximity to shear zones (<2 km), or presence of structural “breaks,” dilatant zones, or highly sheared rock.

3. Evidence of appropriate hydrothermal alteration.

a. Vein and (or) ribbon quartz.

b. Carbonate alteration minerals.

c. Potassic alteration (sericite).

d. Anomalous boron (exclusive of high abundances typical of sedimentary rocks and massive sulfide deposits).

e. Anomalous concentrations of As, Se, W, Hg, Sb, Te, Mo, Bi, Zn, and (or) Cu in soil or rock samples.

f. Disseminated or vein-filling arsenopyrite or pyrite.

Permissive criteria:

1. Presence of chemically favorable host rock, such as iron-formation and iron-rich tholeiitic basalt.

2. Presence of fuchsite or scheelite.

Table 7. Resource potential for Archean low-sulfide gold-quartz vein deposits in the Roseau 1°x2° quadrangle

[Superscript letters indicate which type of hydrothermal alteration is present in a given tract. Criterion 3f, presence of 

disseminated or vein-filling arsenopyrite or pyrite, was not recognized in the present study]

Tract No. Diagnostic criteria Sum of Resource Confidence 

(map C) 1 2 3 tract scores potential level

I 0 0 0 0 Low B

II 0 0 0 0 Low B

III 0 1 0 1 Low B

IV 0 0 1d,e 1 Low B

V 0 1 0 1 Low B

VI 0 0 1e 1 Low B

VII 0 1 1a,b,e 2 Moderate B

VIII 0 1 1a,b,c,d 2 Moderate B, C

IX 0* 1 1d,e 2 Moderate B

X 111a,b,c,d,e 3 High B, C

*Gold present in this tract is related to massive sulfide deposits.

a

Vein and (or) ribbon quartz.

b

Carbonate alteration minerals.

c

Potassic alteration (sericite).

d

Anomalous boron (exclusive of high abundances typical of sedimentary rocks and massive sulfide deposits).

e

Anomalous concentrations of As, Se, W, Hg, Sb, Te, Mo, Bi, Zn, and (or) Cu in soil or rock samples.
U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

REGIONAL BEDROCK MINERAL RESOURCE ASSESSMENT OF THE

ROSEAU 1° x 2° QUADRANGLE, NORTHERN MINNESOTA

By

Terry L. Klein, Warren C. Day, Robert J. Horton, and Gregory N. Green

1999

Pamphlet to accompany

MISCELLANEOUS INVESTIGATIONS SERIES

MAP I–2358–B
i

CONTENTS

Introduction ..................................................................................................................................... 1

Regional geologic setting ................................................................................................................... 1

Geology of the Wabigoon subprovince 2 ..........................................................................................

Geology of the Quetico subprovince 2 .............................................................................................

Geology of the Wawa subprovince 2 ...............................................................................................

Assessment of mineral resource potential ..................................................................................... 2 .........

Volcanogenic massive sulfide deposits 4 ............................................................................................

Nickel-copper-platinum group element deposits in gabbro and ultramafic rocks, and titanium-vanadium

in gabbro ................................................................................................................................ 7

Algoma-type iron-formation ......................................................................................................... 8

Archean low-sulfide gold-quartz vein deposits 9 .................................................................................

Miscellaneous deposits ............................................................................................................... 12

Summary and conclusion ................................................................................................................. 12

References cited ............................................................................................................................. 12

FIGURES

[Figures at end of text]

1. Generalized geologic map showing regional bedrock geology 16 ..........................................................

2. Chart showing relation between levels of resource potential and certainty 17 ..........................................

3. Generalized geologic map showing distribution of drill holes containing intervals of coarse felsic

volcaniclastic breccia and rhyolite flows in bedrock ...................................................................... 18

4. Generalized geologic map showing distribution of drill holes containing iron-formation and

iron-formation layers inferred from aeromagnetic interpretation 19 ...................................................

5. Generalized geologic map showing distribution of drill holes containing hydrothermal chert intervals 20 ......

6. Generalized geologic map showing distribution of average assay intervals in drill holes having

copper concentrations greater than 500 ppm 21 ............................................................................

7. Generalized geologic map showing distribution of average assay intervals in drill holes having

zinc concentrations greater than 500 ppm 22 .................................................................................

8. Generalized geologic map showing distribution of drill holes containing massive sulfide intercepts ........... 23

9. Generalized geologic map showing distribution of bedrock sample localities having greater than

500 ppm chromium ............................................................................................................... 24

10. Generalized geologic map showing distribution of bedrock sample localities having greater than

500 ppm nickel ..................................................................................................................... 25
ii

11. Generalized geologic map showing distributions of (1) bedrock sample localities in which drill-hole

assays were greater than 0.1 ppm Au and (2) glacial till sample localities in which the nonmagnetic

fraction of heavy mineral concentrates (HMC) contained greater than 400 ppb Au 26 ..........................

12. Generalized geologic map showing distribution of highly deformed rocks observed in drill core 27 ...........

13. Generalized geologic map showing distribution of bedrock from drill core in which carbonate

veins (mostly calcite) were encountered 28 ....................................................................................

14. Generalized geologic map showing distribution of drill holes containing quartz veins in bedrock ............ 29

TABLES

[Tables 2–7 repeated on map sheet]

1. Permissive mineral deposit types in the Roseau 1°x2° quadrangle 3 ........................................................

2. Diagnostic and permissive criteria for volcanogenic massive sulfide deposits 5 ..........................................

3. Resource potential for volcanogenic massive sulfide deposits in the Roseau 1°x2° quadrangle .................. 5

4. Diagnostic criteria for nickel-copper-platinum group element deposits in gabbro and ultramafic rocks in the

Roseau 1°x2° quadrangle .......................................................................................................... 9

5. Resource potential for gabbro- and ultramafic-intrusion-associated nickel-copper-platinum group element

deposits and komatiite nickel-copper deposits in the Roseau 1°x2° quadrangle 9 ..................................

6. Diagnostic and permissive criteria for Archean low-sulfide gold-quartz vein deposits in the Roseau

1°x2° quadrangle ................................................................................................................... 10

7. Resource potential for Archean low-sulfide gold-quartz vein deposits in the Roseau 1°x2° quadrangle 10 ....

Note: Data expressed in feet in this report (text, p. 6–7, fig. 8, in particular) are from previous work and are

retained in the original measurement unit for precision. For conversion to metric, multiply feet by 0.3048.
1

INTRODUCTION

The U.S. Geological Survey has undertaken a

series of mineral resource studies in the Roseau 1°x2°

quadrangle of northern Minnesota, which consist of

regional geologic mapping, mineral deposit studies,

and geophysical and geochemical surveys and analysis. Results of these studies have been used to determine the mineral resource potential for several

types of metallic deposits in this region. This pamphlet briefly summarizes the regional geology of the

study area, the approach and criteria that were used

to assess the metallic mineral resource potential, and

the results of that assessment.

The approach used in this assessment consists

of the first two steps of the three-step method of

mineral resource assessment summarized by Shawe

(1981). The first step was to identify the genetic

types of deposits that are found, or are likely to exist,

within the geologic terranes present in the study

area. Permissive genetic deposit types were defined

by extrapolation from geologically similar, adjacent

terranes in Canada and by inference from terranes

elsewhere in the world having a similar geologic

history and age.

The second step in the assessment process

was to compare, using a consistent framework of

features referred to as recognition criteria, the geologic, geochemical, and geophysical features of the

permissive genetic deposit types with similar features

from tracts identified in the assessment area. The

presence or absence of these recognition criteria in a

given area provides the basis for both the delineation

of an assessment tract and the assessment of its mineral resource potential. The genetic models used in

this study were largely based on those presented in

Eckstrand (1984a), which include mineral deposits

from all major types in the Archean Superior

province. All published deposit models were supplemented or updated with the results of recent

studies or deposit models (Klein and Day, 1994).

Metallic mineral deposits contained in the immediately adjacent areas of Ontario are typical of

those found elsewhere in the Canadian Shield. Numerous mineral prospects and several small, formerly

productive mines in the adjacent parts of Ontario are

summarized by Klein and others (1995, 1997), based

on earlier studies by Poulsen (1984), Beard and Garrat (1976), and Fletcher and Irvine (1954). Similarities in host-rock type, alteration style, ore minerals,

structural setting, and stratigraphic relationship of the

mineral deposits in the study area with those features

in the adjacent area were used to establish principal

recognition criteria. Mineral deposit types that are

permissive in the study area, based on our extrapolations, are summarized in table 1. Other pertinent

resource-related geologic data for this area of northern Minnesota are summarized in Day and others

(1990, 1994), Frey and Venzke (1991), Jirsa and

Boerboom (1990), Klein (1991, 1994a), Klein and

Day (1989), Klein and others (1995), Listerud (1976),

Boerboom and others (1989), Martin and others

(1988, 1989, 1991), and Ojakangas and others

(1977). Geochemical data for this area are

summarized in Englebert and Hauk (1991), Frey and

Venzke (1991), Klein (1994b), Klein and others

(1987, 1988, 1994), and Martin and others (1988,

1989, 1991). The results of a metallic mineral resource assessment in the laterally equivalent rock

units of the adjacent International Falls, Minn., 1°x2°

quadrangle are presented in Klein and others (1997).

This report uses the definition of the term

“mineral resource” that was previously adopted by

U.S. Bureau of Mines and U.S. Geological Survey

(1980). Because of the small number of nearby

mines and well-explored prospects in the study area,

and the sparse production and reserve data, only the

potential for undiscovered conventional metallic

mineral resources has been assessed. Although the

number of permissive mineral deposit types is large

(table 1), only those deposit types that are hypothetical resources, for example, those that are known in

nearby, similar geologic terranes, have been considered. The mineral resource potential for industrial

commodities or unconventional “low-grade” resources was not evaluated.

The assessment as presented here is based on

the level of knowledge as of August 1997. Because

all assessments are time and data dependent, new

data and geologic concepts of ore genesis and the

stratigraphic and structural framework of the area, as

well as economic factors, could significantly alter future mineral resource assessments of the same area.

REGIONAL GEOLOGIC SETTING

The Roseau quadrangle lies within the western

extent of the exposed part of the Archean Superior

province of the Canadian Shield. The study area

encompasses three subprovinces of the Superior

province: Wabigoon in the north, Quetico in the

south, and Wawa along the southern boundary of

the quadrangle (fig. 1). Quaternary glacial deposits

cover most of the study area and obscure the

Precambrian bedrock geology. However, the regional geologic framework can be pieced together

using geologic data from outcrops and drill cores integrated with geophysical information (aeromagnetic

and gravity data) and soil geochemical data.

In general, the subprovincial boundaries are

delineated by major through-going dextral transpressive fault zones (fig. 1). In the eastern part of the

study area, the northeast-striking Rainy Lake–Seine

River fault forms the boundary between the Wabigoon and Quetico subprovinces (Ojakangas, 1972;

Ojakangas and others, 1977, 1979). The fault is a

0.5–1 km wide zone of intense ductile shear deformation with extensive development of phyllonite,

chlorite±biotite schist, and mylonite. Ductile deformation in the fault zone has caused intense flattening

and stretching of primary structures. The strong

schistosity (or mylonitic fabric) commonly contains

quartz and carbonate stringers, lenses, and boudins

indicating the presence of metamorphic fluids in the

fault zone during deformation. The Rainy Lake–

Seine River fault is offset by the Vermilion fault (fig.

1) and continues southwestward as the Four Town

fault. The southern terminus of the Wabigoon-
2

Quetico subprovincial boundary is interpreted from

the aeromagnetic data to be transitional between the

mafic and felsic volcanic rocks of the Wabigoon

subprovince and the garnet-biotite schists of the

Quetico subprovince and is interpreted to be the

Four Town fault.

Rocks of the Wabigoon subprovince in the

area have undergone three major episodes of deformation. The earliest recognized event (D1 ) occurred after volcanism and sedimentation (post 2,755

Ma), and took place during or slightly after intrusion

of tonalitic, granodioritic, and gabbroic plutons. This

episode was associated with deformation that produced recumbent and isoclinal folds (Poulsen and

others, 1980; Day and Sims, 1984) and development

of an early S1 foliation. The second major episode

(D2) was associated with the regional Late Archean

ductile transpressive deformation. A penetrative

cleavage (S2 ) forms a S-C mylonitic fabric with the

earlier S1 foliation. Motion along the major faults (or

deformation zones) took place at this time. All kinematic indicators reveal that the transpression was

dextral. The third episode of deformation (D3) was

an Early Proterozoic event in which brittle motion

along the fault zones produced pseudotachylite

(Peterman and Day, 1989).

GEOLOGY OF THE WABIGOON SUBPROVINCE

The Wabigoon subprovince (fig. 1) is a greenstone-granite terrane made up of supracrustal sequences (volcanic and associated pyroclastic, epiclastic, and chemical sedimentary rocks) that were invaded by ultramafic, gabbroic, and granitic rocks. In

general, the supracrustal sequences have undergone

low- to moderate-grade regional metamorphism.

These supracrustal rocks were deformed prior to intrusion of large volumes of syn- to post-tectonic

granitoids (pre-D1; Day and others, 1990).

Blackburn and others (1991) noted that the

central part of the Wabigoon subprovince (east of

the study area) has platform metasedimentary rocks

overlying 3.0-Ga granitoid basement. In the western

part of the subprovince, which extends into the study

area, the pre-intrusive volcanic and sedimentary sequences range from 2,775 to 2,718 Ma. Subsequent syn- to post-D2 metasedimentary sequences

are between 2,695 and 2,686 Ma. One of these

latter “Timiskaming-type” epiclastic metasedimentary

sequences, the Seine Group, is exposed to the east

of the study area in the Rainy Lake area (Day, 1990).

However, no such sequences were noted in this

study area.

The Late Archean rocks, as well as the major

subprovincial bounding faults, are crosscut by the

Early Proterozoic 2.1-Ga Kenora-Kabetogama dikes

(not shown in fig. 1). The swarm has a minimum

strike extent of 310 km and breadth of 270 km (Case

and others, 1990). Individual dikes range from 1 m

to 100 m wide and can be traced along strike for

more than 50 km. The dikes range in composition

from gabbro to diorite; they commonly have a fineto medium-grained texture and characteristically lack

tectonic fabric.

GEOLOGY OF THE QUETICO SUBPROVINCE

Rocks of the Quetico subprovince (fig. 1) are

poorly exposed in the study area, and, as a consequence, detailed information is limited to a few

sparse drill holes. Where exposed immediately east

of the study area (Southwick and Ojakangas, 1979;

Day and others, 1990; Klein and others, 1997), the

Quetico subprovince consists of medium- to highgrade (amphibolite facies), regionally metamorphosed

metasedimentary rocks (garnet-biotite schist), gneiss,

and granite. The metasedimentary rocks are composed mostly of metagraywacke and metatuff with

interlayered amphibolite. The Quetico subprovince is

cored by the Vermilion Granitic Complex (Late

Archean), a granite-migmatite complex consisting of

metasedimentary rocks intruded by tonalite, monzodiorite, and batholithic bodies of the Late Archean

Lac La Croix Granite (Southwick and Sims, 1980;

Day and Weiblen, 1986).

GEOLOGY OF THE WAWA SUBPROVINCE

The Wawa subprovince (fig. 1) is a granitegreenstone terrane composed of interlayered

metavolcanic and metasedimentary rocks that were

intruded by granitoid bodies. The contact between

rocks of the Quetico and Wawa subprovinces is gradational from the metasedimentary rocks to the north

into the layered volcanic and metasedimentary rocks

to the south (Jirsa and Boerboom, 1990). The grade

of metamorphism decreases from medium grade

(amphibolite facies) in the Quetico to low grade

(greenschist facies) southward into the Wawa subprovince. The Wawa supracrustal rocks grade into

metasedimentary rocks (biotite schist), which have an

aeromagnetic signature similar to that of the

metasedimentary rocks of the Quetico subprovince

to the north (Day and others, 1994).

Recent mapping by Jirsa (1990) and Jirsa and

Boerboom (1990) outlined the structural evolution of

the area east of Lower Red Lake. Their studies reveal that the supracrustal rocks underwent several

periods of deformation. The earliest event (D1 ) was

associated with large-scale folding (F1). The second

deformation (D2) produced cleavage, flattening, and

local refolding of F1 folds, and boudinage and folding

of D1 axial planar veins. A later deformation event

(D3) produced localized folding and was associated

with movement and deformation along major faults

in the area.

ASSESSMENT OF MINERAL RESOURCE

POTENTIAL

Once appropriate deposit models were selected, tracts that might contain deposits similar to

those described by the deposit models were defined

on the basis of diagnostic criteria. Recognition
3

Table 1. Permissive mineral deposit types in the Roseau 1°x2° quadrangle

I. Syngenetic-diagenetic mineral deposits

A. Volcanogenic base- and precious-metal massive sulfide deposits

B. Algoma-type iron-formation

II. Epigenetic mineral deposits

A. Archean lode gold deposits

III. Magmatic mineral deposits

A. Intrusion-hosted deposits

1. Chromite in ultramafic intrusive rocks

2. Gabbro-associated deposits

a. Copper, nickel, and platinum-group elements

b. Gabbro-hosted titanium and vanadium

3. Felsic intrusive rocks

a. Copper and molybdenum porphyry deposits

4. Alkalic intrusive rocks

a. Kimberlite-hosted diamonds

b. Ultramafic copper, uranium

c. Nephelinitic carbonatite rare-earth elements, uranium, niobium, and tantalum

B. Volcanic-hosted deposits

1. Komatiite-hosted nickel, copper, and platinum-group elements

criteria are geologic, geophysical, or geochemical

features that suggest a particular mineral deposit type

may be present in a given area.

Recognition criteria for deposit models are divided into two types:

1. Diagnostic criteria present in most, or all,

of the deposits considered essential for the formation

of that deposit type. The presence of these features

is a favorable indication that a particular type of deposit may be present in a given area. Conversely,

the absence of diagnostic criteria indicates little likelihood for the occurrence of a particular deposit type.

2. Permissive features that are present in

some deposits and that, although not essential for

deposit formation, may indicate the presence of a

particular mineral deposit type.

The delineation of potential metal-bearing

domains or assessment tracts was based largely upon

two types of diagnostic criteria:

1. The presence of favorable host rocks in the

case of syngenetic and magmatic deposits types.

2. The presence of favorable structures in the

case of epigenetic gold deposits.

The presence of other diagnostic criteria, such

as electrical conductors or magnetic anomalies, geochemical anomalies, coarse-grained felsic volcanic

rocks, or chert layers, enhances the potential for

massive sulfide deposits in a given area. Extensive

chlorite-carbonate alteration, arsenic, antimony,

molybdenum, and base-metal anomalies, and multiple

episodes of vein formation are considered diagnostic

criteria to increase the potential for epigenetic lode

gold deposits.

Few permissive criteria were defined because

the amount of bedrock information was not sufficiently consistent or detailed. Therefore, the permissive criteria were not used as a primary component of the resource assessment and are only presented as supplemental information on the character

of each tract.

Through the application of the above assessment method, the study area was judged to have

possible undiscovered resources in five deposit types.

These include (1) volcanogenic massive sulfide deposits (table 1, IA), (2) ultramafic- and gabbro-hosted

copper, nickel, and platinum-group elements (PGE)

(table 1, IIIA, 2a), (3) gabbro-hosted titaniumvanadium deposits (table 1, III, 2b), (4) Archean lode

gold deposits (table 1, II, A) and (5) Algoma-type

iron-formation (table 1, I, B). The mineral resource

potential for other deposit types listed in table 1 was

not assessed because analogs are not known to exist

in the adjacent parts of the Superior province or sufficient knowledge of geologic, geochemical, or geophysical details is lacking to evaluate them in the

study area.

Assessment tracts for the five possible deposit

types in the Roseau quadrangle were in large part

established from a geologic map (1:250,000) of the

area by Day and others (1994). Geochemical information on bedrock samples contained in Klein

(1994b), Klein and others (1987, 1988, 1994), and

Frey and Venzke (1991) and the results of a soil geochemistry survey by Riddle and others (1992) were

also used to evaluate the assessment tracts.

After each assessment tract was geographically defined, an objective score based on the sum of

point values for each diagnostic criterion was assigned. In each assessment tract, where a criterion

described in the diagnostic criteria was met, a value

of 1 was assigned. A tract with the known absence

of a criterion was assigned a minus 1 for that criterion. A score of 0 was assigned if the information

was not sufficient to establish the presence or absence of a given criterion. The summed score allows

an assessment tract to be ranked on the basis of its

relative favorability with other tracts for the same

deposit type in the study area. Subjective interpretation of these scores was used to establish the probability rank of each assessment tract for each deposit
4

type. The value of these scores of relative favorability is not directly comparable between deposit types.

For example, a score of 3 out of a possible 3 for one

type of deposit may give it a high resource potential,

whereas a score of 3 of a possible 5 for another type

of deposit may indicate only a moderate resource

potential.

The assignment of resource potential in this

study area was accompanied by a qualitative expression of the certainty, which indicates the level of confidence placed on the estimate of resource potential.

This value is related directly to such characteristics as

the degree of exposure of bedrock or the amount of

exploration that has taken place in a given area. We

have adopted the convention suggested by Goudarzi

(1984) having four levels of certainty ranging from

A, which represents the lowest level of confidence,

to D, the highest. Level A indicates mineral assessment tracts whose information is insufficient for assessment of a particular commodity. Level B indicates tracts having general geologic, geochemical,

and geophysical characteristics that are known well

enough to suggest a level of mineral potential, but

where several key elements of knowledge needed

for mineral assessment are lacking. Level C indicates

tracts in which the available information gives a good

indication of the mineral resource potential but

where a key element of knowledge is missing or of

less than ideal quality. Level D indicates tracts whose

level and quality of available information clearly define the mineral resource potential. When these

confidence levels are referred to in the following

sections, level B will be designated as indicating a

low degree of certainty, level C as indicating a

moderate degree of certainty, and level D as indicating a high degree of certainty. The relation between

the level of certainty and the resource potential is illustrated in figure 2.

The assessment tracts and the outline of the

Roseau 1°x2° quadrangle are plotted in maps A, B,

and C. The tract boundaries and numbers are different for each type of deposit.

VOLCANOGENIC MASSIVE SULFIDE DEPOSITS

Diagnostic criteria were developed for volcanogenic copper-zinc±silver±gold massive sulfide

deposits using a volcanic-hosted massive sulfide

model adapted from models by Lydon and others

(1984), Lydon (1984a, 1984b), Franklin and others

(1981), and Franklin (1990). The resource potential

for each of the 12 massive sulfide assessment tracts

in the study area (map A) was defined on the basis of

the diagnostic criteria summarized in table 2. The

resource potential for each tract was derived from

the subjective interpretation of the assessment tract

scores presented in table 3.

Included in Tract I (map A) are all granitoid,

gabbro, and ultramafic intrusive rocks in the study

area. Volcanogenic massive sulfide deposits are not

found in intrusive rocks, and, therefore, the rocks in

Tract I are considered to have no potential for massive sulfide deposits.

Tracts II and III (map A) include graywackeargillite-type metasedimentary rocks of the Quetico

subprovince and in the Wabigoon and Wawa subprovinces, respectively. The sedimentary environments in which these rocks were formed do not contain volcanogenic massive sulfide deposits elsewhere

in the world. Accordingly, Tracts II and III are considered to have no potential for volcanogenic massive sulfide deposits.

Tract IV (map A) consists predominantly of

metasedimentary rocks derived from volcanic

sources. These, for the most part, were deposited in

a distal environment with respect to volcanic centers.

These rocks have a low potential for volcanogenic

massive sulfide deposits. However, they have a low

potential for massive sulfide in contrast to “no potential” for the graywacke-argillite units defined in Tracts

II and III because the metasedimentary rocks of Tract

IV were probably deposited in an environment more

proximal to the volcanic centers. Distal massive sulfide accumulations may form in this environment or

proximal massive sulfide deposits may be transported

by large-scale gravity-sliding into this environment,

but the occurrence of massive sulfide deposits in

rocks of this type is extremely rare in the Superior

province. Variation in the degree of confidence between B and C is directly related to the number of

drill holes within a tract and the thickness of the

glacial cover in the area.

The mafic- to intermediate-composition

metavolcanic rocks in Tract V (map A) include those

from the Wabigoon subprovince. Samples from this

tract contain scattered chert and iron-formation and

anomalous base-metal values (Klein, 1994a). Soils

that overlie metavolcanic rocks in this tract also have

anomalous base-metal values (Carlson and Clark,

1995). Mineral resource potential for volcanogenic

massive sulfide deposits is moderate in this tract because of the presence of several diagnostic criteria

that are indicators of submarine hydrothermal activity

of the type that may form massive sulfide deposits

(see table 3). Many of the bedrock geochemical

anomalies in this tract are from graphitic rocks that

were drilled on the basis of their anomalous electromagnetic properties. These interlayered graphitic

rocks have characteristically high background values

in base metals and do not necessarily indicate metal

enrichments due to hydrothermal activity. The lack

of significant amounts of coarse felsic volcanic rocks

(those formed proximal to a volcanic vent) (fig. 3)

may indicate that vigorous copper- and zinc-bearing

hydrothermal systems necessary to generate economic volcanogenic massive sulfide deposits did not

develop because these metavolcanic rocks did not

form near the most favorable part of the volcanic

complex. However, that coarse felsic volcanic rocks

are lacking (fig. 3) may result from the lack of comprehensive information on the character of the

bedrock and may not preclude the presence of massive sulfide deposits or the possibility that gravity

transport may have superimposed massive sulfide

bodies upon finer grained, distal volcanic rocks.

Classification is dependent upon the recognition of
5

Table 2. Diagnostic and permissive criteria for volcanogenic massive sulfide deposits

Diagnostic criteria:

1. Presence of volcanic rocks.

Geophysical indicators: irregular aeromagnetic patterns and relative gravity highs.

2. Proximity to felsic volcanic centers characterized by coarse felsic volcaniclastic breccias and fragmental rocks,

subvolcanic intrusive rocks.

3. Evidence for hydrothermal fluids associated with massive sulfide deposits.

a. Exhalite, volcanogenic chert-sulfide horizons, Algoma-type iron-formation, manganese-rich layers.

b. Hydrothermal alteration such as Mg-, Fe-, and K-enrichment and Na-depletion.

c. Base-metal and pathfinder-element enrichment (Zn, Cu, ± Se, In, Sb, Sn, or B) as indicated by bedrock

and B-horizon soil samples.

d. Presence of barren, pyrite-rich massive sulfide horizons.

4. Presence of base-metal massive sulfide deposits as indicated by bedded sulfide mineral deposits or stockwork

feeder zones, or bedrock electrical conductors.

Permissive criteria:

1. Presence of graphitic sediments.

Table 3. Resource potential for volcanogenic massive sulfide deposits in the Roseau 1°x2° quadrangle

Tract No. Diagnostic criteria Sum of Resource Confidence

(map A) 1 2 3 4 tract scores potential level

I 0 0 0 0 0 None D

II 0 0 0 0 0 None D

III 0 0 0 0 0 None D

IV 1 0 1a,b 0 2 Low B, C

V 101a,b,c 1 3 Moderate B, C

VI 1 0 1c 0 2 Low B

VII 1 1 1a 0 3 Moderate B, C

VIII 1 1 1a,b,c,d 1 4 High C

IX 1 1 1a,b,c,d 1 4 High B, C

X 111a,b,d 1 4 High C

XI 1 0 0 0 1 Low B

XII 0 1 1a,b,c,d 0 2 Low B

aChert.

bMg or Fe enrichment.

cBase-metal anomalies.

dMassive sulfide horizons present.
6

felsic volcanic rocks either as a readily identifiable

magnetic unit in aeromagnetic surveys or from drillhole information. Composition of the volcanic rocks

in this region, poorly known because of the scarcity

of drill holes and outcrop, is based largely on geophysical discrimination of felsic from mafic volcanic

rocks, which locally is uncertain because of the effects of hydrothermal alteration and regional or contact metamorphism. Parts of this mineral assessment

tract are given either a low or a moderate degree of

confidence, because the level of knowledge of the

character of the volcanic rocks is directly related to

density of drill holes and the thickness of glacial

cover.

Tract VI contains mafic- to intermediatecomposition volcanic rocks of the Wabigoon subprovince that are roof pendants in a large granite

pluton exposed in outcrops south of Baudette, Minn.

This tract also includes an area south of Roseau,

Minn., where volcanic rocks of unknown character

constitute a roof pendant in a large unexposed granitoid pluton (map A). This tract has low potential because it lacks the significant diagnostic criteria: felsic

volcanic rocks and massive sulfide prospects. A

broad multielement geochemical anomaly in soils that

may be related to base-metal massive sulfide accumulations is generally coincident with this tract (Carlson

and Clark, 1995). The significance of this anomaly

has not been determined.

Tract VII (map A) is underlain by felsic

metavolcanic rocks (Wfvs, Wfv) in the BirchdaleIndus, Minn., area and by bimodal metavolcanic rocks

(Wmfv) in the west-central part of the study area

(Day and others, 1994). The lithologic units in this

tract locally include distinctive coarse felsic volcanic

breccia (fig. 3) and locally abundant iron-formation

and hydrothermal chert (figs. 4, 5). However,

drilling has not encountered significant base-metal

enrichment, even where exploration has been relatively intense, for example, drill holes north of Oaks

Corner, Minn. (figs. 6, 7; see Klein, 1994a). In the

Indus, Minn., area, which is immediately east of the

study area, exploration drilling and outcrop sampling

of several electrical conductors in these metavolcanic

rocks have encountered only pyrite- and pyrrhotiterich massive sulfide lenses having low base- and

precious-metal concentrations (Listerud, 1976). Soil

geochemistry from this study in the same area also

indicates only low-level anomalies of unknown origin

(Carlson and Clark, 1995). Even though the rock

units in Tract VII contain appropriate host rocks and

indications of hydrothermal activity, the overall character of the volcanic rocks, the lack of base-metal

concentrations encountered in bedrock drilling, and

the low-level soil geochemical anomalies indicate that

the potential of this tract may be rated only as moderate for base-metal-bearing massive sulfide deposits.

The area along the western boundary of the study

area has not been extensively explored and is covered by thick glacial deposits; its classification is made

with less confidence than in the area north of Oaks

Corner, Minn. (map A).

Bimodal metavolcanic rocks (Wmfv) in the

central part of the Wabigoon subprovince in the

study area (Day and others, 1994) are included in

Tract VIII. This belt of rocks included in the tract

(map A) contains five drill holes in which coarse felsic

metavolcanic rocks, chert, thin base-metal-bearing

massive sulfides, and extensive chloritized rocks have

been encountered (figs. 3, and 5–8). The rocks are

highly deformed in this area because they lie between two subparallel fault segments (Day and

others, 1994). The relatively continuous conductor

drilled in holes LW-342-1, LW-342-2, BD-1, BD-2,

and BD-3 is the most significant prospect in this belt.

Interlayered chert and massive sulfide layers with intercepts of 25 ft and 70 ft were encountered in

segments of drill holes BD-2 and LW-342-1, respectively (see Klein, 1994b). Sulfide-rich layers from

both of these holes are zinc rich (Klein, 1994a).

Results from BD-2 show concentrations ranging

from 2,000 to 5,000 parts per million (ppm) in many

4- to 6-ft assay intervals. Assays from LW-346-1

show values of as much as 2,000 ppm zinc in one 4-

ft interval. This tract is considered to have high potential for massive sulfide deposits.

An extensive amount of drilling in Tract IX has

encountered rocks in 13 drill holes that contain

coarse felsic volcanic rocks, iron-formation, chert,

and barren and base-metal-rich massive sulfide layers

(figs. 3–8), as well as sericite- and chlorite-rich rocks

(Klein and Day, 1989). The most significant basemetal deposit was encountered in drill hole BD-N-1

(map A). The results of assays of 5-ft intervals over a

330-ft interval of drill core range from 2,000 to

7,000 ppm zinc and from 200 to 1,100 ppm copper

(Klein, 1994a). The mineralized interval is interlayered with porphyritic rhyolite, graphite-rich rocks,

and chert and is associated with adjacent intense

chlorite, sericite, and silica alteration (see Klein,

1994b). In drill hole B-24-2, a 100-ft interval of interbedded massive sulfide layers (from 2 to 25 ft

thick) and rhyolite breccias and tuffs was encountered. Base metals are only enriched in one 0.5-ft

interval that assayed 5 percent zinc, 2,900 ppm lead,

and less than 25 ppm copper (Klein, 1994a). Because of the abundant diagnostic criteria, Tract IX

(map A) has high potential for massive sulfide deposits. The volcanic rocks that are included in the

easternmost block of Tract IX may correlate with

those in the western part and by analogy have high

potential for massive sulfide deposits. A broad soil

geochemical anomaly interpreted to reflect buried

massive sulfide deposits extends over the area

(Carlson and Clark, 1995). However, the eastern

part of Tract IX has a low degree of confidence in its

classification because of the lack of subsurface data.

In Tract X (map A), seven drill holes intersected chert (brecciated in part) and a pyritic massive

sulfide lens interbedded with fine-grained layered

tuffs (figs. 5, 8), and subordinate amounts of felsic

volcaniclastic rocks. Base-metal concentrations were

low in most of the pyritic layers, which range from

intercepts of 1 ft to more than 100 ft. Only drill hole

FT-21 contains significant zinc concentrations (an 80-

ft interval ranging from 175 to 1,080 ppm zinc).

Gold concentrations range from 0.1 to 2.75 ppm in

scattered assay intervals (2–5 ft) of pyritic massive
7

sulfides and brecciated chert in drill holes FT-7, FT10, FT-12, and FT-14. Chert intercepts range from

15 ft to 60 ft in thickness (Klein, 1988). Even

though base-metal concentrations are low in Tract X

(map A), it is considered to have a high potential for

base-metal massive sulfide deposits on the basis of

strong indications of the presence of massive sulfide

bodies.

Tract XI (map A) consists of subsurface

metavolcanic rocks in the southeastern part of the

study area, in the Wawa subprovince. Significant

exploration of these rocks has not taken place. The

protoliths for these variably metamorphosed, generally medium grade rocks (Jirsa and Boerboom,

1990) are principally mafic volcanic rocks with a minor component of felsic volcanic rocks. The degree

of deformation is moderate to high in this tract, and

several northwest-striking fault segments are present.

Because most of the volcanic rocks probably are

mafic, a low potential for volcanogenic massive sulfide deposits is assigned to this tract. Exploration

immediately south of the study area has concentrated

on a bimodal mafic to felsic volcanic sequence that is

not present in the study area (Jirsa and Boerboom,

1990).

Magnetic iron-formation, included in Tract XII

(map A), is considered to have low potential for

base-metal massive sulfide deposits. These ironoxide-rich rocks, although sometimes spatially associated with massive sulfide deposits in this area and

elsewhere, do not themselves normally contain economic base-metal accumulations. The presence of

iron-rich rocks is one of the diagnostic criteria (see 3a

in table 2) for massive sulfide deposits, which indicates the possible presence of submarine hydrothermal vents of the type that may control the emplacement of massive sulfide deposits.

NICKEL-COPPER-PLATINUM GROUP ELEMENT

DEPOSITS IN GABBRO AND ULTRAMAFIC

ROCKS, AND TITANIUM-VANADIUM IN GABBRO

Favorable host rocks for nickel-copper-PGE

deposits in layered mafic-ultramafic rocks and titanium-vanadium in anorthosites, based on the deposit

models of Eckstrand (1984b, c) and Gross and Rose

(1984), respectively, have been identified in the

Roseau 1°x2° quadrangle. Small deposits of titanium

associated with the upper part of the nearby Grassy

Portage gabbro and the Bad Vermilion anorthosite

(both informal units) in the Mine Center area of

Ontario (Poulsen, 1984) and nickel-copper deposits in

the lower part of the Grassy Portage intrusion, the

Dobie intrusion in the Emo area of Ontario (Fletcher

and Irvine, 1954), and the recent discovery of Ni-CuPGE deposits in magmatic sulfide minerals within a

layered mafic-ultramafic body, northeast of Baudette,

Minn. (Nuinsco Resources Limited, 1995), are typical

of those found elsewhere in Canadian greenstone

terranes. Nickel sulfide deposits are associated,

worldwide, with olivine-spinifex-bearing komatiites in

both stratiform and stratabound accumulations

(Lesher, 1989). Although no nickel deposits are

known to be associated with komatiitic metavolcanic

rocks in the Roseau quadrangle, komatiites are present within greenstone belts in the Wawa subprovince (Williams and others, 1991). The

Shebandowan mine in the Wawa subprovince, east

of the study area, is the largest Archean nickelcopper deposit in the Superior province. Minor

komatiites are known within the western Wabigoon

subprovince (Blackburn and others, 1991).

The nickel-copper-PGE potential of the study

area has been assessed on the basis of the presence

of favorable host rocks (mafic-ultramafic intrusions or

komatiites). The identification of komatiites and ultramafic rocks in greenstone belts is usually difficult

because of widespread serpentinization of ultramafic

rocks during regional metamorphism. Primary textures in these rocks are generally obscured or destroyed during alteration, making it difficult to interpret even the simplest relationships—for example,

whether the rocks were intrusive or extrusive.

However, ultramafic and mafic rocks are typically

enriched in nickel and chromium relative to more

magmatically evolved rocks. As a consequence, favorable host rocks in the study area were defined as

those rocks with chromium and nickel concentrations

greater than 500 ppm (figs. 9, 10). These thresholds

will discriminate rocks that are in the compositional

range of some high-magnesium basalt and melagabbro and will include all the more magnesian rocks,

such as komatiites and basaltic komatiites and their

intrusive equivalents, for example, pyroxenite, peridotite, and dunite. The intrusive or extrusive nature

of the rocks in most cases could not be determined

from textures observed in drill core. However, because both komatiitic nickel-copper deposits and

intrusion-hosted gabbroic and ultramafic nickelcopper deposits are associated with high-chromium

and high-nickel rocks, this distinction is not necessary

for the resource assessment.

The nickel-copper-PGE assessment is dependent on the ability to determine the presence of suitable host rocks, as in other deposit types considered

in this assessment. Because most of the area is covered with glacial deposits, the ability to recognize favorable host rocks is mostly restricted to interpretations based on these rocks having a distinctive, consistent, and resolvable magnetic signature. Small intrusive or extrusive ultramafic bodies cannot always

be reliably distinguished, based solely on aeromagnetic surveys, because they have undergone varying

degrees of serpentinization, chloritic alteration, and

metamorphism that may have reduced their magnetic intensity.

The potential for gabbro-anorthosite-hosted

titanium-vanadium deposits cannot be accurately assessed in the study area because the compositional

variation of most of the buried gabbro bodies is not

well known. The sparse subsurface exploration data

have not confirmed whether the magmatically

evolved rocks (anorthosite) associated with these deposits are present in most of the gabbro bodies.

However, any of the gabbro bodies in the study area

(Day and others, 1994) that have a high-intensity

magnetic signature (Bracken and others, 1989) are

considered as a potentially favorable host for
8

titanium-vanadium deposits. These same rocks may

host nickel-copper sulfide accumulations in their

more mafic lower parts such as that found in the

Grassy Portage intrusion (Poulsen, 1984). The diagnostic criteria for nickel-copper-PGE assessment are

given in table 4, and the scores for the six assessment

tracts are given in table 5.

Granitoid rocks in the Wabigoon subprovince

(Day and others, 1994) are included in Tract I (map

B). They are not considered to have potential for

nickel-copper-PGE deposits because they are unfavorable host rocks (table 5).

Tract II consists of granitoid and metasedimentary rocks in the Wabigoon, Wawa, and Quetico

subprovinces. These rocks are considered to have

no potential for nickel-copper-PGE deposits because

they are unfavorable hosts. These rocks are also apparently not intruded by Archean mafic or ultramafic

rocks that could be favorable hosts. The extreme

contrast in magnetic properties between gabbroic or

ultramafic intrusions and the granitoids and

metasedimentary rocks in the Wabigoon, Wawa, and

Quetico subprovinces should allow detection of even

small gabbro bodies that would otherwise be undetectable in the magnetically highly textured metavolcanic units such as those in the Wabigoon and Wawa

subprovinces. Variation in the degree of confidence

between B and C is directly related to the number of

drill holes in a tract and the thickness of the glacial

cover in the area.

Felsic volcanic and volcanic metasedimentary

units (Day and others, 1994) in the Wabigoon subprovince are texturally diverse and may contain some

mafic or ultramafic volcanic rocks. Distinguishing

these from the more felsic host rocks, using the

aeromagnetic survey data, may be difficult. These

felsic rocks are included in Tract III (map B) and are

thought to have low potential (table 5) for nickelcopper-PGE deposits because of their dominantly

felsic composition, even though small bodies of rocks

with favorable compositions may be unrecognized

within these largely felsic units.

Highly altered basaltic komatiite and chloriteand serpentine-altered ultramafic (in part, probably

komatiitic) rocks are inferred to be present locally,

based on their distinctive geochemistry, in Tract IV

(map B). Concentrations of nickel and chromium

greater than 500 ppm in outcrop and drill-core

samples of non-quartz-bearing, ferromagnesian mineral-rich rocks are considered to indicate the presence of ultramafic rocks (data from Klein and others,

1987, 1988; Klein, 1994a; Frey and Venzke, 1991).

The distribution of these relatively chromium- and

nickel-rich rocks is shown in figures 9 and 10. Spatially, these ultramafic rocks are commonly associated

with the dominantly mafic volcanic units in the Wabigoon and Wawa suprovinces (Day and others,

1994), and, on that basis, we include these mafic

volcanic units in Tract IV (map B). This tract has a

moderate potential for nickel-copper-PGE deposits in

ultramafic volcanic or intrusive rocks.

Most of the large gabbro bodies in the study

area have distinctive magnetic characteristics. These

intrusions, defined in Tract V (map B), have a

moderate potential for gabbro-hosted nickel-copperPGE deposits. Included in this tract is the layered

gabbro-peridotite body south of Warroad, Minn.,

which was encountered in several drill holes (see

Klein and Day, 1989; Klein and others, 1987). Contacts of this body are defined on the basis of magnetic and gravity data (Bracken and others, 1989;

Horton and Chandler, 1988). No nickel sulfide minerals were encountered in limited exploration of this

body. Several small gabbro sills containing nickel sulfide minerals were intersected in drill holes R-2-1 and

R-2-2 (fig. 10, and map B). These sills do not have a

magnetic expression that is detectable by regional

aeromagnetic surveys because they contain few

magnetic minerals or because they are masked by

the adjacent magnetically “noisy” mafic volcanic and

bimodal volcanic units (see Klein, 1994b, for graphic

lithologic log of R-2-2; Klein, 1994a, for Ni assays).

The potential for nickel-copper-PGE deposits in small

gabbro bodies of this type is considered to be the

same as that of the mafic volcanic and bimodal volcanic units in the Wabigoon and Wawa subprovinces

(Tract IV, map B).

Recent exploration in southwestern Ontario

has outlined a potential Ni-Cu-PGE deposit in a

gabbro-pyroxenite body in the volcanic rocks of the

Wabigoon subprovince, about 50 km northeast of

Baudette, Minn. (prospect area in the northeastern

part of the area of fig. 11) (Blackburn and Hinz,

1996). A 3-m sulfide-rich intercept with 3.3 percent

Ni, 2.3 percent Cu, 3.5 g/t Pt, and 7.9 g/t Pd is

contained within a body of mafic-ultramafic host

rocks that is at least 135 m thick and that has a strike

length of 1,200 m (Nuinsco Resources Limited, unpublished company report, June 1996). Proximity of

the mineralized rocks to similar rocks southeast of

Baudette, Minn., somewhat increases the potential

for deposits of this type in the study area even

though rocks in the two areas are mapped as different units.

Iron-formation associated with mafic metavolcanic and metasedimentary rocks in the Wabigoon

subprovince is included in Tract VI (map B) and is

considered to have no potential for nickel-copperPGE sulfide deposits. Magnetic iron-formation is not

generally considered a favorable host for the

accumulation of these elements elsewhere, and

deposits are not known to be present in them.

ALGOMA-TYPE IRON-FORMATION

In the Wabigoon subprovince in the northeast

corner of the study area, a thin unit of magnetic ironformation, explored by drilling at its west end, can be

traced for a distance of more than 30 km by aeromagnetic data (Bracken and others, 1989). Many

other thin iron-formations are easily distinguished because of their extremely magnetic character. Several

have been intersected in drill holes.

The metasedimentary rocks of the Quetico

subprovince (Day and others, 1994) lack known ironformation and, in the study area, lack the characteristic magnetic anomalies caused by iron-formation,

even though the character of the host rock is
9

Table 4. Diagnostic criteria for nickel-copper-platinum group element deposits in gabbro and ultramafic

rocks in the Roseau 1°x2° quadrangle

1. Presence of layered gabbro, dunite, peridotite, pyroxenite, anorthosite, and norite intrusions or komatiitic

volcanic rocks or subvolcanic sills.

2. Anomalously high concentrations of nickel, copper, ± cobalt, PGE; presence of nickel and (or) copper sulfide

or arsenide minerals.

Table 5. Resource potential for gabbro- and ultramafic-intrusion-associated nickel-copper-platinum group

element deposits and komatiite nickel-copper deposits in the Roseau 1°x2° quadrangle

Tract No. Diagnostic criteria Sum of Resource Confidence

(map B) 1 2 tract scores potential level

I -1 0 -1 None C

II -1 0 -1 None B, C

III 0 0 0 Low C

IV 1 1 2 Moderate B

V 1 0 1 Moderate B, C

VI -1 0 -1 None C

permissive. These rocks do not have potential for

Algoma-type iron-formation, because iron-formation

has not been reported in rocks of this type elsewhere

in the subprovince and bedrock in the subprovince

lacks the characteristic magnetic anomalies associated

with iron-formation found in other parts of the study

area. The plutonic rocks of the Wabigoon and

Quetico subprovinces do not have potential for ironformation, except in roof pendants or rafts of country rock, because of their igneous origin.

Iron-formation layers in the study area are less

than 10 m thick, based on the results of drilling and

by inference from the aeromagnetic data. No substantive amount of structural thickening, which is

commonly necessary to produce an economic deposit from thin layers of banded iron-formation, is

apparent in the aeromagnetic map (Bracken and

others, 1989). The location of the known and inferred Algoma-type iron-formation is summarized in

figure 4, based on the geologic map of Day and

others (1994). Because the known and inferred

thickness of iron-formation layers is thought to be

less than that needed for exploitation, the mineral resource potential for iron-formation has not been

assessed.

ARCHEAN LOW-SULFIDE GOLD-QUARTZ

VEIN DEPOSITS

Diagnostic criteria for Archean low-sulfide

gold-quartz vein deposits (table 6) are based on the

deposit model of Klein and Day (1994). This model

is derived from several models (Thorpe and Franklin,

1984a, b) and reviews on the formation of Archean

Au-quartz vein deposits (Hodgson and MacGeehan,

1980; Hodgson, 1989; Roberts, 1987). Twelve

tracts were defined, and the resource potential for

them is summarized in table 7 and map C.

Tract I consists of metasedimentary rocks of

the Quetico subprovince (map C) that (1) are located

more than 2 km from known or inferred shear

zones, (2) are not sheared, and (3) do not contain

anomalous gold concentrations (figs. 11, 12). This

tract is considered to have low potential for Archean

low-sulfide Au-quartz vein deposits (table 7). The assessment has a moderate degree of confidence because shear zones in these rocks are somewhat difficult to detect if density and magnetic contrasts between units are low. Most of the rock units in the

metasedimentary part of the Quetico subprovince

have low-intensity magnetic signatures (Bracken and

others, 1989), which does not allow the delineation

of offsets or abrupt linear terminations of rock units

that are normally used, along with magnetic surveys,

to identify possible shear zones. Basal till samples in

several drill holes near Littlefork, Minn., immediately

east of the study area in the adjacent International

Falls 1°x2° quadrangle (Klein and others, 1997), contain relatively coarse grained gold from an undetermined source, which suggests that the source of the

gold is nearby in the metasedimentary rocks of the

Quetico subprovince (Martin and others, 1988).

Tract II (map C) includes plutonic and

supracrustal rocks of the Wawa subprovince that are

more than 2 km from known or inferred shear zones

or isolated intervals of highly deformed rocks in drill

holes (fig. 12). These rocks are assigned a low potential for Archean low-sulfide Au-quartz vein deposits (table 7). However, the geologic, geophysical, and geochemical characteristics by which the

presence of the diagnostic criteria was determined

are poorly known in this tract, and, therefore, the

assessment has a low degree of confidence.

Tract III, located along a segment of the

Vermilion fault, is in rocks of the Quetico subprovince (map C). Because of the lack of past
10

Table 6. Diagnostic and permissive criteria for Archean low-sulfide gold-quartz vein deposits in the

Roseau 1°x2° quadrangle

Diagnostic criteria:

1. Presence of anomalous gold and silver concentrations in drill core or B-horizon soil samples.

2. Proximity to shear zones (<2 km), or presence of structural “breaks,” dilatant zones, or highly sheared rock.

3. Evidence of appropriate hydrothermal alteration.

a. Vein and (or) ribbon quartz.

b. Carbonate alteration minerals.

c. Potassic alteration (sericite).

d. Anomalous boron (exclusive of high abundances typical of sedimentary rocks and massive sulfide

deposits).

e. Anomalous concentrations of As, Se, W, Hg, Sb, Te, Mo, Bi, Zn, and (or) Cu in soil or rock samples.

f. Disseminated or vein-filling arsenopyrite or pyrite.

Permissive criteria:

1. Presence of chemically favorable host rock, such as iron-formation and iron-rich tholeiitic basalt.

2. Presence of fuchsite or scheelite.

Table 7. Resource potential for Archean low-sulfide gold-quartz vein deposits in the

Roseau 1°x2° quadrangle

[Superscript letters indicate which type of hydrothermal alteration is present in a given tract. Criterion 3f,

presence of disseminated or vein-filling arsenopyrite or pyrite, was not recognized in the present study]

Tract No. Diagnostic criteria Sum of Resource Confidence

(map C) 1 2 3 tract scores potential level

I 0 0 0 0 Low B

II 0 0 0 0 Low B

III 0 1 0 1 Low B

IV 0 0 1d,e 1 Low B

V 0 1 0 1 Low B

VI 0 0 1e 1 Low B

VII 0 1 1a,b,e 2 Moderate B

VIII 0 1 1a,b,c,d 2 Moderate B, C

IX 0* 1 1d,e 2 Moderate B

X 111a,b,c,d,e 3 High B, C

*Gold present in this tract is related to massive sulfide deposits.

aVein and (or) ribbon quartz.

bCarbonate alteration minerals.

cPotassic alteration (sericite).

dAnomalous boron (exclusive of high abundances typical of sedimentary rocks and massive sulfide deposits).

eAnomalous concentrations of As, Se, W, Hg, Sb, Te, Mo, Bi, Zn, and (or) Cu in soil or rock samples.

production of this type, even in well-exposed,

adjacent areas in Canada, Tract III has a low potential

for Archean low-sulfide Au-quartz vein deposits (table

7). However, in Tract III, the presence of a fracture

system of the same age as that which may be goldbearing elsewhere suggests that rocks in this tract are

more favorable for gold deposits than rocks in other

parts of the Quetico subprovince. No anomalous

gold concentrations are known in bedrock or soils in

this tract. The degree of confidence placed in the

assessment of Tract III is low because few bedrock

samples are available to evaluate for the diagnostic

criteria and only one soil geochemistry traverse

crosses the structure (see Carlson and Clark, 1995).

Granitoid and supracrustal rocks in the Wabigoon subprovince that are located more than 2 km

from known or inferred shear zones are included in

Tract IV (map C). These rocks contain isolated drill

holes, some of which intersect carbonate and quartz

veins (figs. 13, 14). None of the carbonate and

quartz veins encountered contain enrichments in gold

(fig. 11) or associated elements, nor does the
11

geochemical analysis of overlying soils indicate

anomalies thought to indicate lode gold potential (see

Carlson and Clark, 1995). The western parts of this

tract (map C) have had little exploration drilling. Due

to problems with access, the same area was poorly

sampled during the soil geochemistry survey (Carlson

and Clark, 1995). Rocks in this tract are assigned a

low potential for Archean low-sulfide Au-quartz vein

deposits. Because of sparse knowledge of the

bedrock in most of this tract, the assessment for this

tract has a low degree of confidence.

Rocks adjacent to several major known or inferred shear zones in the Wabigoon subprovince are

included in Tract V (map C). The bedrock geochemistry and the extent and character of hydrothermal alteration along these segments are

poorly known, and most of these tracts are largely

unsampled by soil geochemistry (Carlson and Clark,

1995; this report, figs. 11–14). This tract has a low

potential for Archean low-sulfide Au-quartz vein deposits and a low degree of confidence in its

classification.

Tract VI (map C) is underlain by large granitoid bodies and a subordinate amount of mafic and

felsic volcanic rocks. Bedrock in this tract is seen in

only a few outcrops and in two shallow bedrock

cores. The boundary of the tract is defined by

widespread tellurium anomalies in soil samples

(Carlson and Clark, 1995). Because tellurium enrichment is commonly associated with Archean lowsulfide Au-quartz vein deposits, these anomalies may

reflect hydrothermal activity related to the formation

of gold deposits. The tract lacks any definitive indications of shear zones in the aeromagnetic data

(Bracken and others, 1989) or in the two bedrock

drill holes. However, the lack of contrast in the

magnetic properties of these granitoids makes the

presence of shear zones difficult to detect. Even

though the tellurium soil anomalies may indicate the

presence of potential gold-bearing hydrothermal systems, the lack of diagnostic criteria 1 and 2 (table 6:

gold enrichment and sheared rocks) requires the tract

to be ranked as having low potential for Archean

low-sulfide Au-quartz vein deposits. Due to lack of

information on the character of its bedrock, the assessment of this tract has a low degree of

confidence.

Tract VII (map C) is underlain by deformed

rocks near the Four Town and Border faults, northeast-striking structures in the west and central parts

of the study area (Day and others, 1994). The tract

is considered to have moderate potential for the

presence of Archean low-sulfide Au-quartz vein deposits (table 7) on the basis of the presence of these

inferred fault zones and anomalous metal concentrations in soil samples (Carlson and Clark, 1995). This

classification has a low degree of confidence because

of a lack of bedrock data for this tract.

Metavolcanic rocks and granitoid rocks in the

Wabigoon subprovince near Birchdale, Minn. (east of

the study area), contain low-level gold and basemetal anomalies in several exploration drill holes (figs.

6, 7, 11). A small mineralized shear zone was reported in drill hole MR 86-1, immediately east of the

study area near Birchdale (Klein and Day, 1989), although it was not detected in the airborne magnetic

survey. Because anomalous gold and zinc concentrations are present in this minor shear zone (see

Klein, 1994a, for assays), Tract VIII, in the Birchdale

area, has a moderate potential, with moderate confidence, for Archean low-sulfide Au-quartz vein deposits. The classification of moderate potential for

the Warroad, Minn., area is based on the presence of

quartz and carbonate veins and small shear zones intersected in scattered drill holes. However, because

these shear zones are not apparently regional in nature and the sampled drill core intervals lack gold

mineralization, this part of Tract VIII has a higher

degree of confidence than the area near Birchdale,

Minn. (table 7 and map C).

A small wedge-shaped area, underlain mostly

by bimodal metavolcanic rocks located between the

Border fault and the Vermilion fault in the central

part of the study area (Day and others, 1994), is included in Tract IX (map C). The bedrock contains

evidence of shearing (fig. 12) and petrographic evidence of hydrothermal alteration (figs. 13, 14).

However, the scattered gold anomalies shown in

figure 11 may be related to massive sulfide deposits

and are not necessarily considered to be indicative of

epigenetic gold deposits. Tract IX has been assigned

a moderate potential for Archean low-sulfide Auquartz vein deposits (table 7) with a moderate degree

of confidence.

Tract X, composed of highly deformed rocks

along parts of the Rainy Lake–Seine River, Baudette,

Quetico, and Black River faults (Day and others,

1994), is assigned a high potential for Archean lowsulfide Au-quartz vein deposits because of the coincidence of gold anomalies in bedrock and till samples

(fig. 11), structurally favorable shear zones (fig. 12),

calcite and quartz veins (figs. 13, 14), and metal

anomalies in the thin overburden. Anomalous soil

geochemistry (Carlson and Clark, 1995) and several

gold anomalies in the nonmagnetic fraction of heavy

mineral concentrates from till samples (Martin and

others, 1991) may indicate the presence of epigenetic Archean lode gold deposits. These geochemical gold anomalies have been used to partially define

the boundaries of this tract. Recent bedrock drilling

on gold anomalies found in basal till by the Ontario

Geological Survey (Bajc, 1991) have indicated the

presence of a gold deposit in southwestern Ontario,

northwest of Baudette, Minn. (fig. 11), in felsic volcanic rocks north of the Quetico fault (Blackburn and

Hinz, 1996). Initial announcements by Nuinsco Resources Limited indicated substantial amounts of gold

contained in this deposit with a preliminary estimate

of 55 million tons at 0.075 g/t Au (Nuinsco Resources Limited, 1995). Gold grades range from 0.7

to 3.4 g/t over intercepts of 30–50 m (Anonymous,

1997). Along the Quetico fault and subsidiary structures east of the study area, where they are exposed

near Mine Centre, Ontario, gold deposits typically

contain less than 350 kg gold (Poulsen, 1984). The

small size of these known deposits may be due to the

dominance of lateral movement over vertical movement (Sibson, 1989) and the resulting lack of
12

development of subsidiary structures. In Minnesota,

some exploration has taken place along parts of

these structures included in Tract X (map C).

MISCELLANEOUS DEPOSITS

The Canadian part of the Quetico subprovince, although well exposed, has not produced

any metallic resources. However, the metasedimentary belts have received relatively little exploration.

Pegmatite-hosted deposits contain rare earth elements, Nb-Ta, Li, U, and Th, at some places in the

belt; however, they were not evaluated during this

study. Recently, some exploration for Ni, Cu, and

PGE in syntectonic mafic and ultramafic bodies in the

Quetico subprovince has taken place in Canada. The

results of this exploration were not available for this

assessment.

SUMMARY AND CONCLUSION

The supracrustal rocks of the Wabigoon and

the Wawa subprovinces in the Roseau quadrangle,

northern Minnesota, contain several areas of moderate to high potential for volcanogenic Cu-Zn-rich

massive sulfide deposits, Archean low-sulfide Auquartz vein deposits, and Ni-Cu deposits in ultramafic

rocks.

High potential for volcanogenic massive sulfide

deposits is found in several tracts in the central part

of the study area (map A). Tract VIII, located southeast of Baudette, Minn. (map A), contains many drill

holes that intersect variably deformed bimodal volcanic rocks. These rocks contain many of the diagnostic criteria that are favorable for volcanogenic

massive sulfide deposits (table 3). Drill holes in Tract

IX (map A), which is located approximately 40 km

southwest of Baudette, Minn., contain several significant intercepts of base-metal-bearing massive sulfide

in bimodal volcanic rocks. Near the common corner

of Beltrami, Lake of the Woods, and Roseau Counties, evidence of thick massive sulfide intercepts,

siliceous exhalites, and explosive felsic volcanic activity is found in several drill holes. These favorable

rocks define Tract X (map A).

Some gabbroic rocks and possible isolated occurrences of komatiitic volcanic rocks in the greenstone parts of the Wabigoon and Wawa subprovinces have a moderate potential for magmatic or

komatiitic Ni-Cu deposits. Some of these deposits

typically contain enrichments in the platinum-group

elements. Tract V, in the central part of the area of

map B, has a moderate potential for Ni-Cu deposits

in a large, poorly explored gabbroic body. The

greenstones that make up much of Tract IV may

contain komatiitic nickel deposits. Several drill holes

in the study area encountered highly deformed or

altered rocks of uncertain origin having ultramafic

compositions.

Areas of high potential for Archean low-sulfide

Au-quartz vein deposits are located in Tract X (map

C) along several segments of the Rainy Lake–Seine

River fault and the Vermilion fault. In addition,

several tracts with moderate and high potential for

these deposits, such as Tracts VII, VIII, and IX (map

C), underlie large areas of the central part of the

Roseau 1°x2° quadrangle.

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485–539.
Lower Red Lake

Upper

Red Lake

Wawa subprovince

Quetico

subprovince

48°

94° 49°

96° Lake of the Woods

Roseau

Baudette

Quetico

subprovince

Warroad

Wabigoon

subprovince

Study area

MINNESOTA

49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv

Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmv

Wmsv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

EXPLANATION

Figure 1. Generalized regional bedrock geologic map.

16

0

0

10

10

20 MILES 

20 KILOMETERS
HIGH

POTENTIAL

MODERATE

POTENTIAL

LOW

POTENTIAL

LOW

POTENTIAL

LOW

POTENTIAL

NO

POTENTIAL

UNKNOWN

POTENTIAL

MODERATE

POTENTIAL

MODERATE

POTENTIAL

HIGH

POTENTIAL

HIGH

POTENTIAL

INCREASING LEVEL OF CERTAINTY

INCREASING LEVEL OF RESOURCE POTENTIAL

U/A H/B

M/B

L/B

H/C

M/C

L/C

H/D

M/D

L/D

N/D

AB C D

17

Figure 2. Relation between levels of resource potential and certainty (from Goudarzi, 1984).
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing coarse-grained

felsic volcanic rocks and flows—

Numbered when referred to in text

EXPLANATION

18

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 3. Generalized geologic map showing distribution of drill holes containing intervals of 

coarse felsic volcaniclastic breccia and rhyolite flows in bedrock.

LW-342-1,2

BD-1, LW-346-1

BD-N-1

B-24-2

FT-21
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing iron-formation

EXPLANATION

19

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 4. Generalized geologic map showing distribution of drill holes containing iron-formation and 

iron-formation layers inferred from aeromagnetic interpretation.
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing hydrothermal

chert interval—Numbered when 

referred to in text

EXPLANATION

20

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 5. Generalized geologic map showing distribution of drill holes containing 

hydrothermal chert intervals.

LW-342-1,2

BD-1, LW-346-1

BD-N-1

B-24-2

BD-2

BD-3

FT-21
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole with average intercept of 

greater than 500 ppm Cu—Numbered

when referred to in text

EXPLANATION

21

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 6. Generalized geologic map showing distribution of average assay intervals in drill holes having copper 

concentrations greater than 500 ppm. Average assay = (drill-hole length x assay) / drill intercept length.

BD-N-1

B-24-2

Oaks

Corner
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole with average assay interval

greater than 500 ppm Zn—Numbered

when referred to in text

EXPLANATION

22

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 7. Generalized geologic map showing distribution of average assay intervals in drill holes having zinc 

concentrations greater than 500 ppm. Average assay = (drill-hole length x assay) / drill intercept length.

LW-342-1,2

BD-1, 

LW-346-1

BD-N-1

B-24-2 FT-21

Oaks

Corner

BD-2

BD-3
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole having a total intercept of

more than 2.5 ft of massive sulfide—

Numbered when referred to in text

EXPLANATION

23

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 8. Generalized geologic map showing distribution of drill holes containing massive sulfide intercepts.

LW-342-1,2

BD-1, LW-346-1

BD-N-1

B-24-2

FT-21

BD-2

BD-3
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Bedrock samples having greater than

500 ppm Cr

EXPLANATION

24

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 9. Generalized geologic map showing distribution of bedrock sample localities

having greater than 500 ppm chromium.
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Bedrock sample localities having greater

than 500 ppm Ni—Numbered when 

referred to in text

EXPLANATION

25

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 10. Generalized geologic map showing distribution of bedrock sample localities 

having greater than 500 ppm nickel.

R-2-1

R-2-2
FT-7,10,12

FT-14

Prospect

area

49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv

Wms Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing assay intercepts

greater than 0.1 ppm Au—Numbered

when referred to in text

Till sample

Till sample containing greater than

400 ppb Au in HMC

EXPLANATION

26

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 11. Generalized geologic map showing distributions of (1) bedrock sample localities in which drill-hole 

assays were greater than 0.1 ppm Au and (2) glacial till sample localities in which the nonmagnetic fraction of 

heavy-mineral concentrates (HMC) contained greater than 400 ppb Au.
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing highly deformed

rocks

EXPLANATION

27

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 12. Generalized geologic map showing distribution of highly deformed rocks observed in drill core.
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing substantial amounts

of carbonate alteration minerals

EXPLANATION

28

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 13. Generalized geologic map showing distribution of bedrock from drill core in which 

carbonate veins (mostly calcite) were encountered.
49°

96° 94°

48°

Wg

Wmv

Wg

Wmv

Wg Wmz

Wg

Wg

Wg

Wmv

Wmfv

Wgb

Wgb

Wmfv

Wg

Wmv

Wmv

Wmv

Wui

Wms

Wmsv Wmv

Wmsv Wmfv

Wg

Wmz

Wg

Wms

Wmv

Wg

Wg Wmz

Wgb

Wfvs

Wg

Wfvs

Wfvs

Wmsb

Wvsm Wvsm Wg

Wgb

Wms

Wmsv Whm

Wfv

Wmfv

Wg

Wmv Wmv

Wfvs

Wg

Wmz

Wg

Wfv Wms

Wmv Wg

Wmfv

Wgn

Wms

Wvsm

Wgb

Wmfv

Wmsb

Wmsb

Wmv

Wmsv

Wms

Wmfv

Wmfv

Wui

Wfv

Wmsv

Wmv

Wmv

Wmsv Wmv

Wmfv

Wgb

Wvsm

 BORDER

FAULT

RAINY LAKE–

SEINE RIVER FAULT

VERMILION FAULT

QUETICO FAULT

FOUR TOWN

FAULT

Lower

Red Lake

Upper Red Lake

Lake 

of the

Warroad Woods

Roseau

Baudette

CANADA

UNITED STATES

ONTARIO

MINN

Wg

Wgn

Wmz

Wgb

Wui

Wmsv

Wms

Wfv

Wfvs

Wmfv

Wmv

Late Archean units

Wabigoon subprovince

Granite

Granitic gneiss

Monzonite

Gabbro

Ultramafic to mafic intrusive rocks

Volcaniclastic and volcanic rocks

Iron-formation

Biotite schist (metagraywacke)

Felsic volcanic rocks

Felsic volcaniclastic rocks

Mafic and felsic volcanic rocks

Intermediate to mafic volcanic rocks

Wmsv

Wmv

Whm

Wvsm

Wmsb

Late Archean units

Wawa subprovince

Volcaniclastic and volcanic rocks

Intermediate to mafic volcanic rocks

Quetico subprovince

Hornblende monzonite

Schist-rich migmatite

Garnet-biotite schist (metagraywacke)

Contact

Fault—Opposed arrows show relative 

movement where known

Drill hole

Drill hole containing quartz veins

in bedrock

EXPLANATION

29

0

0

10

10

20 MILES 

20 KILOMETERS

Figure 14. Generalized geologic map showing distribution of drill holes containing 

quartz veins in bedrock.