3-D, Siripunvaraporn

Algorithm: Siripunvaraporn, Egbert, Lenbury & Uyeshima,2005, PEPI, 150, 3-14.Data: impedances (off-diagonal elements only, real andimaginary parts), 16 frequencies.Error floors: 5%.Static shift incorporated: no.Mesh: 56x56x33, aligned with survey lines.

2 1 0 1 22

1.5

1

0.5

0

2 1 0 1 22

1.5

1

0.5

0

2 1 0 1 22

1.5

1

0.5

0

2 1 0 1 22

1.5

1

0.5

0

A comparison of two- and three-dimensional modelling of audiomagnetotelluricdata collected at the world’s richest uranium mine, Saskatchewan, Canada

1Geological Survey of Canada, 615 Booth St., Ottawa, ON, Canada; 2Department of Earth Sciences, Memorial University of Newfoundland,St. John’s, NL, Canada; 3GSY-USA, Inc., San Francisco, CA, USA; 4Department of Physics, Mahidol University, Bangkok, Thailand; 5Departmentof Physics and Institute for Geophysical Research, University of Alberta, AB, Canada.

J.A. Craven1, C.G. Farquharson2, R.L. Mackie3, W. Siripunvaraporn4, V. Tuncer5, and M.J. Unsworth5.

Conductivity(S/m)

0

2

1

0

2

1

0

2

1

0

2

1

3-D, Farquharson

Algorithm: Farquharson, Oldenburg, Haber & Shekhtman,2002, SEG Expanded Abstracts, 21, 649.Data: impedances (off-diagonal and diagonal elements,real and imaginary parts), 11 frequencies (1280-3.8Hz).Errors: variances estimated from processing (i.e., vari-ances in edi file).Static shift incorporated: no.Mesh: 60x70x40, aligned NS-EW.

1 2 3 4

Distance (Km)

-1500

-1250

-1000

-750

-500

-250

0

250

500

750

Ele

vatio

n(m

a.s.

l.)

0 1 2 3 4 5

Distance (Km)

-1375

-687

0

687

Ele

vatio

n(m

a.s.

l.)

0 1 2 3 4

Distance (Km)

-1500

-1250

-1000

-750

-500

-250

0

250

500

750

Ele

vatio

n(m

a.s.

l.)

0 1 2 3 3

Distance (Km)

-1500

-1250

-1000

-750

-500

-250

0

250

500

750

Ele

vatio

n(m

a.s.

l.)

3-D, Mackie

Algorithm: Mackie, Rodi & Watts, 2001, SEG ExpandedAbstracts, 20, 1501.Data: lnZxy & lnZyx, Zxx & Zyy, tipper, 9 frequencies(1000-10Hz).Error floors: 5% for lnZxy & lnZyx, 20% for Zxx & Zyy,0.02 for tipper.Static shift incorporated: yes.Mesh: 56x44x79, aligned with survey lines.

Resistivity(Ωm)

2-D, Tuncer

Algorithm: Rodi & Mackie, 2001, Geophysics, 66, 174-187.Data: TE & TM apparent resistivities and phases, andtipper.Error floors: 20%, 5%, 0.025, respectively.Static shift incorporated: yes.

Location of the McArthur River mine inSaskatchewan, Canada.

?

?

VRVR

P2P2

Rein

deer

Lake

Lake

Wol

last

on

CreeLake

AthabascaLake

Hearne Craton

Hearne Craton

Rae CratonRae Craton

Peter

Lake

Dom

ain

Peter

Lake

Dom

ain

MooreLakescomplex

Virg

inR.

Dom

ain

Virg

inR.

Dom

ain

Virg

inR.

Domain

Virg

inR.

Domain

Mudjat

ikDom

ain

CarswellStructureCarswellStructure

TaltsonMagmatic

Zone

Rottenstone Domain

Rottenstone DomainBath.

Watham

an

Bath.

Watham

anEaster

n

Wollas

ton

Wollas

ton

West &

Trans

Mudjat

ikDom

ain

Dodge

Domain

Tantato

Domain

Train Lake

DomainBeaverlodgeDomain

Rae

Zemlak Domain

Nolan Domain Ena

Lloyd= Taltson

DomainZone

Domain

Lloyd = Taltson

57o

58oN

59oN

60oN102oW104oW106oW108oW110oW112oW

xx

x

xx

x

xx

xx

Key Lake

Cigar Lake

MidwestCluff Lake

Key Lake

Cigar LakeRabbit LakeEagle Point

McClean LakeMidwestCluff Lake

McArthur RiverMcArthur River

MooreLakesMooreLakes

Millennium

LaRocque LakeLaRocque Lake

MauriceBay

MauriceBay

Maybelle R.Maybelle R. Shea Ck.Shea Ck.

Dawn Lake

Current/Past Mine / Mill Planned Mine x Deposit / OccurrenceMajor Sequences, Athabasca Group

Basementdomains

& zonesStrike-slip basementDip-slip reactivatedGeneralized fault zones

UraniumCity

Sask

atch

ewan

Alb

erta

SaskatchewanNorthwest Territories

FortChipewyan

StonyRapids

Ath

abas

caUranium Multidisciplinary Study

EXTECH IV

Ath

abas

caUranium Multidisciplinary StudyA

thab

asca

Uranium Multidisciplinary Study

100 km

AthabascaBasin

AthabascaBasin

Geological map of the Athabasca Basin.

~ 500 m

sandstone

basement

graphitic fault

clay alteration

uranium pod

silicified cap

Schematic geological section of the McArthur Riveruranium deposit. The graphitic fault zone extends forseveral kilometres into and out of the plane of thediagram; the uranium pod and silicified cap onlyextend tens of metres into and out of the diagram.The extent of the clay mineralization is unknown.

ContextInnovative 3-D modelling algorithms are becoming increasingly popular and useful forMT exploration. This study facilitates the comparison of multiple modelling algorithmsby assembling the results of independent modell ing studies on a grid ofaudiomagnetotelluric data collected in northern Saskatchewan, Canada. The surveyarea was directly over the world‘s richest uranium deposit (190 000 tons of U grading23%) located at the unconformity between tilted Paleoproterozoic basement granitoidsand supracrustals of the Wollaston-Mudjatik transition domain and the relatively flat-lying, unmetamorphosed but pervasively altered, Paleo- to Mesoproterozoicsiliciclastic strata within the Athabasca Basin. The primary goal of the survey was toinvestigate the utility of MT to delineate the basement graphitic units commonly asso-ciated with high grade U deposits and to determine the feasibility of MT to detect thealteration in the overlying sandstones associated with the mineralizing events.

Summary

6.4e+06

6.405e+06

Nor

thin

g(m

)

495000 500000

Easting (m)

line 224

line 254

line 276

line 304

line 304

line 276

line 254

line 224

depth = 500m

depth = 750m

depth = 1km