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Geology of the Shea Creek uranium deposits - part of an expanding uranium district in the Western Athabasca Basin

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Conference Paper

Geology of the Shea Creek uranium deposits - part of an expanding uranium district in the Western Athabasca Basin

Abstract

Geology of the Shea Creek uranium deposits - part of an expanding uranium district in the Western Athabasca Basin David Rhys1, Sierd Eriks1 and Luke van der Meer1 The Shea Creek project (UEX Corporation, 49%; AREVA Resources Canada Inc., 51%), is host to the Kianna, Anne, Colette and 58B deposits. At a cut-off grade of 0.30% U3O8, UEX recently reported indicated resources from the project of 1,872,600 tonnes grading 1.54% U3O8 containing 63.57 million pounds of U3O8, and additional inferred resources of 1,068,900 tonnes grading 1.04% U3O8 containing 24.53 million pounds of U3O8. Local geology comprises 400 to 800 metres of Athabasca Group sandstone which unconformably overlie Lloyd Domain amphibolite-grade granitic and pelitic gneisses. The latter includes the Saskatoon Lake Conductor (“SLC”), a 40 to 80 metre thick north-northwest trending and west-southwest dipping graphitic pelitic gneiss unit that is spatially associated with mineralization. The gneiss sequence is affected by penetrative syn-metamorphic deformation that occurred in at least two foliation forming phases during the 1950-1900 Ma Taltson orogeny. These peak metamorphic fabrics are overprinted by northeast-trending, right-lateral/oblique, retrograde mylonitic shear zones (D3; probable Hudsonian age) including the regional Beatty River Shear zone, and northeast-trending second and third order narrow mylonitic shear zones which offset the SLC. Post-Athabasca faulting remobilizes these mylonites, and is also associated with up to 50 metres of reverse displacement of the unconformity along the R3 fault at the base of the SLC. Textural and geometrical relationships suggest that uranium mineralization was coeval with the late faulting, and that the architecture of the older D3 shear zones may have had a fundamental control on the position of mineralization. Uranium mineralization at Shea Creek occurs in three stacked styles that encompass the full range of types of unconformity uranium deposits. Most extensive is flat lying, massive pitchblende-hematite and chlorite matrix breccia hosted mineralization which straddles the unconformity along, and immediately east of, the trace of the SLC. Breccia mineralization occurs both as pitchblende-coffinite fragments and as matrix replacement, suggesting it may have occurred in pulses that temporally spanned brecciation. Continuous unconformity mineralization occurs along the SLC for much of the 2.5 km known strike extent of the Shea Creek deposits, and is thickest and highest grade where basement mineralization lies beneath it. Basement mineralization forms a significant portion of the Shea Creek uranium inventory, and is most extensive at Kianna. It comprises a) concordant reverse fault hosted mineralization which often extends from the unconformity downward into granitic gneiss in the immediate footwall of the SLC, and b) discordant fault, vein and replacement pitchblende mineralization which occurs in steep, east-west to west-northwest trending, zones that may extend for several hundred metres below the unconformity, and which occurs along or beside remobilized mylonitic shear zones. Basement mineralization thickens where concordant and discordant faults intersect, forming west-plunging oreshoots. Lensoidal zones of perched mineralization are locally present up to several tens of meters above the unconformity often where reduced, pyritic chlorite alteration extends into the Athabasca sandstone above areas of basement and thicker unconformity mineralization. Mineralization at Shea Creek is open along strike, where only reconnaissance drill testing has been completed, and in untested areas between deposits. Individual deposits are also largely open, especially in basement areas, and new, open basement zones that may form en echelon steps to the north of Kianna, and basement zones at 58B and at Colette South are as yet only partially defined. A large, uraniferous chlorite alteration plume extends several hundred metres above the Colette deposit in the northern parts of the project. This plume is centered above an untested east-west trending fault zone that may have been a major fluid source and structural control to the known deposits, and to open mineralization to the north on UEX and AREVA’s adjacent Douglas River property. With an already significant resource base, the exploration potential of this large and intense mineralizing system is probably only just being realized. 1 UEX Corporation, 808 Nelson Street, Suite 1007, Box 12151, Vancouver, BC, V6Z 2H2.
Shea Creek deposits
Gl fhSh C k i
G
eo
l
ogy o
f
t
h
e
Sh
ea
C
ree
k
uran
i
um
deposits: an expanding uranium district in
the Western Athabasca Basin
the
Western
Athabasca
Basin
David Rhys, Sierd Eriksand Luke van der Meer
UEX Corporation
Saskatchewan Geological Survey Open House, Nov. 29, 2010
Shea Creek deposits
Forward-Looking Statements
This presentation contains forward-looking statementsthat are based on UEXs current
expectations, estimates, forecasts and projections. These forward-looking statements
include statements re
g
ardin
g
UEXs resource estimates, outlook fo
r
ou
r
future operations,
plans and timing for the commencement or advancement of exploration activities on our
properties, and other expectations, intention and plans that are not historical fact. The
words estimates,projects,expects,intends,believes,plans, or their negatives or
other
comparable
words
phrases
are
intended
to
identify
forward
-
looking
statements
.
other
comparable
words
phrases
are
intended
to
identify
forward
looking
statements
.
Such forward-looking statements are based on certain factors and assumptions and are
subject to risks, uncertainties and other factors that could cause actual results to differ
materially from future results expressed or implied by such forward-looking statements.
Important factors that could cause actual results to differ materially from UEXs expectations
ild
titi
lti
t
it tti
f
d ill
lt
d
l
dditi l
dilli
i
nc
l
u
d
euncer
t
a
i
n
ti
es re
l
a
ti
n
g
t
o
i
n
t
erpre
t
a
ti
on o
f
d
r
ill
resu
lt
san
d
g
eo
l
o
g
y, a
dditi
ona
l
d
r
illi
n
g
results, continuity and grade of deposits, public acceptance of uranium as an energy source,
fluctuations in uranium prices and currency exchange rates, changes in environmental and
other laws affecting uranium exploration and mining, and other risks and uncertainties
disclosed in UEXs Annual Information Form and othe
r
filin
g
s with the securities commission
g
on SEDAR. Many of these factors are beyond the control of UEX. Consequently, all forward-
looking statements made in this presentation are qualified by this cautionary statement and
there can be no assurance that actual results or developments anticipated by UEX will be
realized. For the reasons set forth above, investors should not place undue reliance on such
forward
looking
statements
Except
as
required
by
applicable
law
UEX
disclaims
any
forward
-
looking
statements
.
Except
as
required
by
applicable
law
,
UEX
disclaims
any
intention or obligation to update or revise forward-looking information, whether as a result
of new information, future events or otherwise.
Shea Creek deposits
Location and setting
Shea Creek
Located in the western Athabasca Basin just south of the former Cluff
Lake mine site
Most advanced of ten western Athabasca projects that are jointly owned
by UEX Corp. (49%) and AREVA Resources Canada
Shea Creek deposits
Location and infrastructure
Cluff
Lake
Project is 13 km south of
AREVA’s past producing Cluff
Lake
deposits
Lake mine complex, which
produced 64 million pounds of
U3O8between 1980 and 2002
Douglas River
Project
James
Creek
Project
Exploration operated by
AREVA and run out of the Cluff
Lake Camp
Shea
Erica
Project
Contiguous with the UEX-
AREVA (49%-51% owned)
Dou
g
las River and Erica
Creek
Project
g
projects
Road accessible with all
weather highway 955 running
weather
highway
955
running
through center of property;
airstrip at Cluff Lake
Nikita
Project
Shea Creek deposits
History
Project first systematically explored during the early 1990’s by Amok
and COGEMA (predecessors to AREVA) with airborne and ground EM
surveys identifying the NNW trending Saskatoon Lake Conductor
surveys
,
identifying
the
NNW
trending
Saskatoon
Lake
Conductor
(SLC)
In 1992, second drill hole to test the SLC intersected low grade
i i li ti SE f th A d it F ll d illi t
uran
i
um m
i
nera
li
za
ti
on
SE
o
f
th
e
A
nne
d
epos
it
.
F
o
ll
ow up
d
r
illi
ng
t
o
the northwest intersected the Anne deposit and subsequently Colette.
Between 1994 and 2000, COGEMA drilled 156 holes mainly at Anne
and Colette. No drilling between 2001 and 2003 due to low U price.
In 2004, UEX signed an option agreement to earn 49% from AREVA
b
y
fundin
g
$30 million in ex
p
loration. Between 2004 and 2010, more
yg p
than 200 drill holes were completed which defined additional
mineralization, and led to the discovery and ongoing definition of the
Kianna and 58B deposits.
UEX fully earned its 49% interest in the project in December, 2007
Shea Creek deposits
Resources based on drilling to Dec. 31, 2009
May, 2010 N.I. 43-101 complaint resources for the Kianna, Anne and
Colette deposits estimated by K. Palmer, P. Geo. of Golder Associates:
At a cut-off grade of 0.30% U3O8:
Indicated = 1,872,600 tonnes at 1.54% U3O8(63.57 million pounds U3O8
Inferred = 1
,
068
,
900 tonnes at 1.04% U
3
O
8
(
24.53 million
p
ounds U
3
O
8
)
,,
3
8
(p
3
8
)
- At this cutoff, this is the largest pre-development resource in the Athabasca
Basin
At a higher cut
-
off grade of 1.50% U3
O
8:
Indicated = 509,500 tonnes at 3.78% U3O8(42.57 million pounds U3O8
Inferred = 188,700 tonnes at 2.83% U3O8(11.77 million pounds U3O8)
The resources exclude results of the 2010 drilling that include expansion of
the Kianna deposit and identification of the 58B deposit. Mineralization is
still open in many areas
resources are growing and exploration potential is
still
open
in
many
areas
resources
are
growing
and
exploration
potential
is
exceptional
Shea Creek deposits
Geological setting
Property underlain by 400
to 800 m of Athabasca
sandstone cover
Underlying basement is
Archean to Proterozoic
Lloyd Domain granitic and
Careen Lake pelitic gneiss
Deposits lie immediately
south of the Carswell
58B
meteorite impact structure;
no local effects
Beatty River shear zone
dominant structure in area;
pre-Athabasca mylonite
with second and third order
tt t th
s
t
ruc
t
ures
t
o nor
th
;
probable Hudsonian age
Shea Creek deposits
North property geology
Deposits associated with the
NNW trending, moderate
WSW dipping Saskatoon
L k C d t (“SLC”) th t
L
a
k
e
C
on
d
uc
t
or
(“SLC”)
th
a
t
is surrounded by felsic
granitic gneiss
Th SLC i 30 t 60 thi k
Th
e
SLC
i
s
30
t
o
60
m
thi
c
k
and comprises pelitic
gneisses which are graphite-
rich and faulted (R3) in lower
rich
and
faulted
(R3)
in
lower
portions, as well as
interlayered garnetiferous
granitic gneiss
granitic
gneiss
Granitic gneiss in SLC dated
at 1930-1910 Ma (Brouand
et al 2002)
et
al
.,
2002)
SLC offset by NE trending
pre-Athabasca mylonites
Shea Creek deposits
Saskatoon Lake
conductor cross section,
view north
Granitic gneiss SHE-095-3, 788 to 791.5 m
Gra
p
hitic
,
py
ritic
Garnetite : SHE-038A, 742.2 m - 752.1 m
p,py
pelitic gneiss
Hole SHE-061A,
766.3 to 764.7 m
Shea Creek deposits
Pre-Athabasca Deformation
history F2 folds SHE-121-2, 800 to 803.3 m
Syn-metamorphic deformation during the
1950-1900 Ma Taltson orogeny comprises
th t di i S1
iit
sou
th
wes
t
di
pp
i
ng
S1
gne
i
ssos
ity
,
overprinted down-dip verging minor F2 folds
and S2. May lie on the overturned lower limb
of a regional D2 anticline
Ml it
i
fli
i
of
a
regional
D2
anticline
Retrograde steeply dipping, northeast
trending mylonitic shear zones (D3) up to
l t id itd ithiht
M
y
l
on
it
e
i
n
f
e
l
s
i
c gne
i
ss
SHE-122-1, 898.5
severa
l
me
t
ers w
id
e assoc
i
a
t
e
d
w
ith
r
i
g
ht
lateral displacements of the SLC.
These are pre-Athabasca shear zones
subsidiary to the Beatty River Shear zone
Spatially associated with sheeted EW
trendin
g
q
uartz veinlets +/- dravite
,
and
gq
,
locally remobilized by late faults, clay
alteration associated with uranium Mylonite cuts S2: SHE-114-5, 960.6 m
Shea Creek deposits
Graphitic, concordant faults
Concordant, west-southwest dipping shear zones with pressure solution
fabrics, carbonaceous cataclastic breccia and late clay gouge developed
along lower, most graphitic portions of the SLC forming the R3 fault.
Reverse shear sense indicators; probable both pre-Athabasca and post-
Athabasca displacements. Early displacement may have been coeval
with m
y
lonites.
y
Fluid flow and sericite-clay alteration coeval with shear zone activity
R3 shear zone, SHE-114-2, 738.5 to 740.3 m Oblique fabrics imply reverse kinematics
SHE-123-6, 771.4 m
Shea Creek deposits
Reverse displacement along
R3 structure + remobilized
R3
structure
+
remobilized
mylonites offsets unconformity
approximately 30 to 50 m
Interaction of re erse fa lts
Interaction
of
re
v
erse
fa
u
lts
and earlier NE trending
mylonites where they
intersect: sites for uranium
intersect:
sites
for
uranium
Unconformity elevation map
Shea Creek deposits
Uranium mineralization
Mi li ti tli d t
Mi
nera
li
za
ti
on ou
tli
ne
d
t
o
date along a 3 km strike
length of the Saskatoon Lake
conductor
conductor
Four deposits currently
known: Anne, Kianna, 58B
and Colette
and
Colette
Mineralization comprises
unconformity, basement and
perched mineralization styles
perched
mineralization
styles
Unconformity mineralization
traced continuously over >1
km from SE Anne to
Kianna
km
from
SE
Anne
to
Kianna
Many areas open, gaps in
testing between Kianna, 58B
and Colette
and
Colette
Open to NW (Douglas
Project) and SE
Shea Creek deposits
Shea Creek deposits display
the full range of stacked
mineralization styles seen in
the Athabasca Basin:
Unconformity
mineralization (UC) is
developed along and east of
th S k t L k
th
e
S
as
k
a
t
oon
L
a
k
e
Conductor
Basement mineralization
(UB)
dldili
(UB)
d
eve
l
ope
d
ma
i
n
l
y
i
n
footwall of conductor
Alteration plume developed
above: may contain multiple
above:
may
contain
multiple
alteration fronts and perched
mineralization (UP)
Low concentrations of Ni
As
Low
concentrations
of
Ni
-
As
-
Co : “basement signature”,
local high Au (up to 56 g/t Au)
Shea Creek schematic cross section
looking NNW showing typical features
Shea Creek deposits
Unconformity mineralization
Most extensive style, pancake-like zone
straddle the unconformity, replacing basal
sandstone and upper basement
SHE-115-3, 744-746 m: Kianna deposit
In highest grade areas occurs as nodules and
massive pitchblende +/- coffinite aggregates
in red-orange hematite-clay matrix
Fragments and also matrix replacement in
chlorite-dravite-clay matrix sandstone breccia
S
y
n-faultin
g
timin
g
su
gg
ested b
y
textures
SHE-95-3, 721 m: Anne deposit
y
gggg y
SHE-114-3, 749.2 to 749.4 m:
SHE-102-01, samples from 718-721 m
pressure solution fabrics along R3
fault overprint mineralized chlorite-
dravite breccia
Shea Creek deposits
SHE-115-3 intercept
Bleached sandstone,
Illit d i t d
Illit
e
d
om
i
na
t
e
d
Shea Creek deposits
Basement mineralization
Developed mainly in granitic gneiss in the
footwall of the SLC in areas of intense clay-
chlorite alteration, may exploit earlier faults
Intercepts so far up to 200 m below the
unconformity
Mineralization in east-west to ENE trending,
SHE-096-03, 761 -764 m steep to moderate north dipping veins, and in
WSW dipping concordant zones along faults,
lithologies: intercepts form W plunging oreshoots
Pitchblende + hematite +/- coffinite veins and
disseminations
SHE-115-11, 862.2-865.3 m N
Equal Area
(
Schmidt
)
()
SHE-123-02, 786.7 m,
Kianna South SHE-115-06, 877.5 m, Kianna Axial N = 96
Shea Creek deposits
Perched mineralization
Flat-lying lenses of mineralization in
Athabasca sandstone “perched” up to
60 b th f it l t
60
m a
b
ove
th
e uncon
f
orm
it
y;
l
eas
t
voluminous style of mineralization but
may be very high grade
Often stacked above areas of basement
mineralization and thickest unconformity
mineralization
SHE-114-5, 680 .1 to 687.7 m = 27.7% U
3
O
8
Occur in clay-chlorite alteration often
above chlorite breccias, alternate with
hematite and pyrite redox fronts in
3
8
sandstone
Often occur along up dip projection of
basement-hosted faults into the
sandstone column
Pyrite replacing hematite in redox
front spatially associated with
perched mineralization
Shea Creek deposits
Anne and Kianna
deposits:
lhi
p
l
an map s
h
ow
i
ng
deposit setting
and unconformit
y
y
grade-thickness
contours
Shea Creek deposits
Anne section 6750N
looking NNW
Unconformity
Unconformity
mineralization with
basement zone “roots” of
concordant mineralization
Fragments of sandstone
locally occur in basement
breccia mineralization up to
breccia
mineralization
up
to
50 m below unconformity:
faults open and permeable
into basement
Perched mineralization at
up dip projection of R3 fault
Shea Creek deposits
Anne section 6875N
looking NNW
Thick, high grade zones
of discordant basement
mineralization extend
mineralization
extend
downward from the
unconformity
mineralization and
j
oin
j
concordant basement
mineralization below in
granite gneiss
Shea Creek deposits
Kianna section
lki t
l
oo
ki
ng wes
t
Stacked
mineralization –
perched,
unconformity and
basement
EW trending, steeply
dipping basement
mineralization
exploits corridor of
pre-mineral mylonites
to depths of >200 m
bl f it
b
e
l
ow uncon
f
orm
it
y
Additional
mineralization
recently indentified in
new zones to the
north
Shea Creek deposits
Kianna wireframe model: view northeast
Shea Creek deposits
Colette south section
8670N, view NNW Ar
ea
s
h
o
w
s
stac
kin
g
o
f
ea s o s stac g o
unconformity, perched and open
basement mineralization
Shea Creek deposits
Exploration potential: North Colette-Douglas River
Vertical
exagerration
sandstone
exagerration
x2.5
Athabasca
58B
DGS
10 i t t
Basement
1 to >10 ppm U >20% chlorite (modal XRD in
cla
y
-sized fraction
)
Kianna
58B
Colette
DGS
-
10
i
n
t
ercep
t
0.53% eU3O8/3.7 m
y
)
Long section looking NE along Shea Creek trend:
Chlorite + anomalous U plume extends to >500 m
above Colette and Douglas projects (Robbins, 1997)
Plan map: little drilling north
of Colette Deposit on
Douglas project
Shea Creek deposits
Property scale targets
58B
Outside immediate area of
deposits, SLC is untested or only
very sparsely tested, with only 23
58B
very
sparsely
tested,
with
only
23
widely spaced holes along >20 km
of strike length
Anomalous radioactivity and
Anomalous
radioactivity
and
prospective alteration in several
drill holes
Parallel conductors to west and
Parallel
conductors
to
west
and
east
Near deposit upside: e.g.
G 100
G
eotechnical holes
100
m west
and 150 m east of Kianna
intersected unconformity
mineralization (0 63% eU
O
/0 7
mineralization
(0
.
63%
eU
3
O
8
/0
.
7
m) and 3 m of dravite-rich breccia,
respectively
Shea Creek deposits
Conclusions: a growing district
Warning: forward looking statements!
Cluff Lake and Shea Creek form a significant and growing western
Athabasca uranium district
Most production historically at Cluff from basement style mineralization
suggests further potential at Shea
Mineralization o
p
en in man
y
areas, both in basement and at
py
unconformity, including new zones in the basement north of Kianna, and
open basement mineralization down dip in south Colette from 2007
intercepts such as 3.23% U3O8over 8.0 metres in drill hole SHE-111-06.
5+ km of Shea Creek trend along the SLC on Douglas River property
nearly completely untested, 400 m of strike length between Kianna and
58B tested b
y
onl
y
one drill hole, and >10 km south southeast of Anne
yy
tested by only a few drill holes (including the Shea “discovery hole” SHE-
02 = 0.73% U3O8/0.7 m) : significant exploration upside
Parallel conductors with alteration, resistivity lows (e.g. Klark Lake)
Parallel
conductors
with
alteration,
resistivity
lows
(e.g.
Klark
Lake)
$7.9 million budget for 2011 exploration at Shea and $9.7 million total for
West Athabasca – should be an exciting year
Shea Creek deposits
Acknowledgements
Thanks to the AREVA team for its ongoing
discoveries, discussions and contributions.
In particular John Robbins Sheldon
In
particular
John
Robbins
,
Sheldon
Modeland, Erwin Koning and Jeff Carroll
Leo Horn Ke in Palmer and Dan Bald in
Leo
Horn
,
Ke
v
in
Palmer
and
Dan
Bald
w
in
also have contributed significantly
We also thank the management and
directors of both companies for their
continued support of the project
continued
support
of
the
project
... The extensive alteration surrounding the high-grade mineralisation can also broaden the footprint of the deposit in conductivity. The geologic model from drilling shows the alteration zone can have a vertical extent of 50-100 m at the Anne Deposit and more than 250 m at the Kianna Deposit (Rhys et al. 2010). Drilling also indicates that the mineralisation and alteration of Anne under the unconformity dips to the west (−X), resulting in thicker mineralisation on the west than on the east, which explains the wedging conductor in our conductivity model. ...
Article
Measurement of the electric field (E-field) data due to an inductive loop source in a controlled source electromagnetic (CSEM) survey is not common, because E-field data, usually involving grounded electrodes, are expensive to acquire and difficult to interpret. With the recently developed capability of versatile 3D inversion, we revisit the idea of measuring E-field in a large ground loop survey for mineral exploration. 3D modeling and inversion approach helps us quantitatively understand the detectability and recoverability of the proposed survey configuration. Our detectability study using forward modeling shows that the relative anomaly (percentage difference) in E-field does not decay with a lower induction number, but the conventional magnetic field data (dB/dt) does. Our recoverability study examines how much and what kind of information can be extracted from Efield data for the reconstruction of a 3D model. Synthetic inversions show that: (1) E-field data are good at locating the lateral discontinuity, whereas dB/dt has better depth resolution. (2) E-field is less sensitive to the background conductivity, and thus is prone to misinterpretation because of bad initial model in inversion. We recommend warm-start the E-field inversion with an initial model from a separate dB/dt inversion. (3) E-field data may be severely contaminated by near-surface heterogeneity, but an inversion can recover the deep target concealed by the geologic noise. (4) Even one line of single-component E-field data can greatly improve the horizontal resolution in a dB/dt inversion. Finally, we investigate a field data set of both E-field and dB/dt measurements at a uranium deposit. The field example confirms that the E-field and magnetic field data contain independent information that is both crucial in the accurate recovery of subsurface conductivity. Our synthetic and field examples demonstrate the benefit of acquiring E-field data along with magnetic field data in an inductive source survey. This article is protected by copyright. All rights reserved
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