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Quo Vadis Exploration?
© Condor Consulting 2011
The evolution of the use of
geophysics in the search for
blind VHMS deposits in the
Abitibi greenstone belt,
Ontario-Québec Canada
Ken Witherly
Condor Consulting, Inc.
Michel Allard
Xstrata Zinc Canada
The Target
© Condor Consulting 2011
Abitibi Subprovince of
the Superior Province (Archean)
CHIBOUGAMAU
SELBAIE
MATAGAMI
JOUTEL
NORMETAL
GREVET
KIDD CREEK
LARONDE
KAMISKOTIA
NORANDA
LOUVICOURT
50 km
© Condor Consulting 2011
MINING CAMP
Mt
KIDD CREEK
161.4
NORANDA
132.2
CHIBOUGAMAU
52.3
SELBAIE
47.3
MATAGAMI
47.7
VAL D’OR
48.9
LA RONDE
59.3
GREVET
10.7
NORMETAL
10.2
KAMISKOTIA
7.9
JOUTEL
9.6
%Cu
2.41
1.86
1.80
1.00
0.84
1.65
0.44
0.46
2.17
1.23
1.60
%Zn g/tAu
6.17 0.05
2.36 4.16
1.68
1.92 0.61
8.80 0.46
1.58 0.51
2.31 4.10
8.41 0.10
5.40 0.85
1.47 0.05
2.95 0.33
62 VHMS Deposits (>0,2Mt)
Discovery vs time
Stone age
Experimental
15
Joutel
Golden age
Analog, qualitative
copper
New age
Digital, quantitative
Geophysical contribution in 43 cases
Norita
Bell Allard S
Poirier
New Hosco
10
Lac Garon
Orchan
Selbaie B
Louvicourt
Matag. Lake
Lac Scott
B- Hébert
Louvem
Selbaie A1-A2
Aldernac 7-8
Kidd Creek
Magusi
Norita Est
Explo-Zinc
P- Dodge 1
Estrades
Caber
Perseverance
New Comex
Ribago
Caber nord
Equinoxe
Norbec
Lemoine
G- Langlois
Bell Allard
Bracemac/
New Insco
Ansil
Orchan ouest
McLeod
Laronde Penna
West-Ansil
Jay Copper
5
Aldermac
East-sullivan
Normetal
Gallen
Waite Amulet
Gallen s-t
Newbec
0
Coniagas
Mobrun
Barvallee
Vendome
Abcourt
Laronde
Manitou
Kam Kotia
Quemont
Vauze
Millenbach
Horne
Horne z5
Joliet
Potter
Delbridge
30-40
40-50
1920-30
© Condor Consulting 2011
50-60
60-70
Corbet
70-80
Isle-Dieu
80-90
90-2000
2000-
Depth to the top
62 VHMS Deposits (>0,2Mt)
30
From surface
Kidd Creek
Selbaie
Matagami Lake
Perseverance
Orchan
Bell Allard sud
Phelps Dodge 1
Lac Garon
Norita
New Hosco
Mobrun
Gallen
Magusi
Baie fabie
Poirier
Estrades
Explo-Zinc
Joutel Copper
Vendome
Barvallée ( vendome)
New Comex
Lac Scott
Lemoine
Jay Copper
Louvem
25
20
15
10
5
0
GonzagueLanglois Laronde
East-Sullivan
Abcourt
Horne
Newbec
Waite Amulet
Normétal
Manitou
Coniagas
Kam Kotia
Potter
0
Aldermac
Vauze
Joliet
1
© Condor Consulting 2011
50m
From drill holes
50 blind deposits
West-Ansil
Equinoxe
Caber
Bracemac
Quémont
Delbridge
McLeod
Louvicourt
Caber nord
Bouchard-Hbert
Norbec
Isle Dieu
Gallen (underg.)
200m
Norita Est
Bell Allard
Ribago
Millenbach
La Ronde (Penna)
Corbet
500m
Orchan west
Ansil
Horne (zone 5)
1000m
1500m
Depth of drilling vs time
Abitibi Subprovince
Shallow drilling <100 m
© Condor Consulting 2011
Deeper drilling >100 m
Fewer new VHMS discoveries?
Hypotheses explaining the relative decrease in new
discoveries.
All the big deposits have been found. The
undiscovered ones are typically too small, too deep
and therefore uneconomic.
Since the Abitibi has been intensively explored in
the past, the chance of finding is decreasing; this
results in less exploration effort which in turn
leads to fewer discoveries and so on.
Intrinsic limits of detection technologies and
geological knowledge
© Condor Consulting 2011
1999 : Difficult time for
Noranda and the industry
 October 1999: Closing of Mine Gaspé, Murdochville. 300 lay
off
 November 2001: Noranda annonces temporary closure of its
smelting infrastructures
 April 2002: Definitive closure of the smelter.
300 more
lay off.
$2010
$5.00
$0.00
“ask not what your country can do for you - ask what
you can do for your country.”
Quebec government asked the industry:
“what your country can do for you?”
to prevent more infrastructure closings.
The industry (Noranda) suggested tax credits on exploration
work!
Solution : an incentive plan
40% refundable tax credit for non-producing companies
20% for producers + 40% non-refundable tax credit
applicable on capital tax for all exploration work .
2001 Exploration Objectives:
•
Generate high quality VMS exploration targets in order to
discover 5-50 Mt deposit with NSR > 80$/t
•
Find new ore to replace 3 years reserves of Louvicourt
•
Provide Noranda Horne smelter with polymetallic
concentrate having gold credits
•
Prevent more closure following the one of Gaspe Smelter in
Murdochville in August 2002.
$/ton vs VHMS tonnage
Economic model
$700
Smaller higher grade deposits
(brownfield target)
US$/ton
$600
IDEAL ABITIBI TARGET
$500
Larger lower grade deposits
(greenfield target)
$400
$300
$200
$100
0,1Mt
© Condor Consulting 2011
1Mt
10Mt
100Mt
MegaTEM Rational :
New Search space
Relatively few deposits found at a depth below 50 m
Limited drilling below 100 m
In-house tests had demonstrated that the
MEGATEM system could detect typical VHMS at
least to a depth of 250 m.
Typical VHMS deposit has a high in-situ value
(Figure 5). A stand alone 20 Mt deposit shows an insitu value of 350$US/t (at current prices) is
deemed as an attractive target
Exploration risk could be shared with the
government and junior companies.
© Condor Consulting 2011
MegaTEM Rational :
New Search space
Relatively few deposits found at a depth below 50 m
Limited drilling below 100 m
In-house tests had demonstrated that the
MEGATEM system could detect typical VHMS at
least to a depth of 250 m.
Typical VHMS deposit has a high in-situ value
(Figure 5). A stand alone 20 Mt deposit shows an insitu value of 350$US/t (at current prices) is
deemed as an attractive target
Exploration risk could be shared with the
government and junior companies.
© Condor Consulting 2011
The Dream
AEM Performance
Best Case
1975 = 10% (Input)
1990 = 46% (GEOTEM)
2001 = 100% (MEGATEM)
200m
1975
1975
1990
1990
2001
2001
50 m
100 m
150 m
200 m
Repeat the sequence of discoveries generated by the first airborne surveys
during the late ‘50s:
Brunswick 12, Mattagami Lake, Kidd Creek…
The Dream
Nb 35
deposits
30
25
20
15
10
5
0
Prospecting and
shallow geophysics
40
Kidd Creek
Horne
MEGATEM
200m
Perseverance
TARGETS
Lack of deposit due to the limitation of the
Normétal
previous technology. Potential range 50-200 m
Selbaie
1975
1975technology
for VMS discoveries using the present
Grevet
50 La
m Ronde
Matagami Lake
100Mobrun
m
0
© Condor Consulting 2011
1990
1990
Equinoxe
150 mCaber
200
Quémont
mDelbridge
Norbec
Louvicourt
2001
Isle Dieu
Bouchard-Hébert
Corbet
La Ronde (z20)
Bell Allard
Millenbach
2001
Norita Est
Ribago
Orchan west
MEGATEM
TARGETS
Ansil
Horne zone 5
Stratigraphic drilling
50
200
500
Deposits to Top (metres)
1000
1200
MegaTEM Surveys
Coverage from 2001-2006: (180 207 lkm)
Including 140 000 by Xstrata and partners
© Condor Consulting 2011
Typical VMS Terrain
TMI
50 km
EM Ch 3
Typical VMS Terrain
Zoom in…
TMI
10 km
EM Ch 3
Area and Target Selection
1) “Subjective” priorities based on the following
criteria:
Favorable geology (Scale 2-3)
Coincident MAG-EM anomalies
Isolated anomalies (avoid formational)
On Xstrata properties or open ground
Untested by previous drilling
2) “Objective” priorities based on a large geologicalgeochemical database was used in parallel to
query AEM results using intelligent GIS
algorithms.
© Condor Consulting 2011
Area and Target Selection
© Condor Consulting 2011
End Results
On the Québec side
40,000 EM picks
349 AEM anomalies were followed up
203 were drilled tested for a total 267 DDHs.
While discoveries can occur well after the
initial generative work, at this stage no new
deposits have been attributed to the
MEGATEM initiative.
WHY ?
© Condor Consulting 2011
WHY ?
• Geological concepts/models
• Geophysical technology
• Managing “luck”
© Condor Consulting 2011
Scales 1 and 2
© Condor Consulting 2011
Scale 1 : Deposit Scale
Typical VHMS
Massive sulphides
Exhalite
Sp
Sp
Hydrothermal
alteration zone
and pipe
chlorite, sericite, quartz
Adapted from J Lydon
© Condor Consulting 2011
Stockwork
Cp+Py+Po stringers
Magnetite zones
Scale 2 : Property scale ex:
Noranda camp
Local Felsic dome
VHMS
Synvolcanic faults
© Condor Consulting 2011
mafics
After Gibson,
1999
Scale 3: Area selection cartoon
© Condor Consulting 2011
Scale 3: Magnetic and density
modeling
© Condor Consulting 2011
Smaller probability of finding
a large barren deposit
EROSION
100m
100 x 1Mt
500m
26 x 10Mt
Assuming
a uniform vertical distribution (down to 500m) and
a statistically true size distribution
5 x 100Mt
l
L
th
400
1250
50
100 000 000.00
200
500
25
10 000 000.00
© Condor Consulting 2008
100
175
15
1 050 000.00
© Condor Consulting 2011
nb
eroded
5 (4%)
26 (20%)
100 (76%)
0
4
25
remaining outcropping 0-100m
5
25
75
2
5
8
0
3
9
outcropping
blind
0-100m
40%
19%
11%
60%
81%
89%
0%
7%
12%
False Positives
1.
Few good targets in the right geological setting.
♦
2.
Barren sulfides (mainly Py-Po stringers)
Numerous targets that appear like VHMS targets but are
not in the right geological setting
♦
Barren sulfides and graphite
One easy solution : no selection of “ formational” conductors
Consequence : Lost opportunity or reduced search space
VHMS have been found in the so-called “formational” settings
THUS : Need for better predictive models
“Only good fishermen are successful,
first by selecting the good lakes and then the good spots”
© Condor Consulting 2011
The evolution :
Reid Mahaffy example
Gravity data at this scale can
help to constrain and refine
EM conductors
in gravity lows
© Condor Consulting 2011
Quo Vadis
Toronto, 2 June 2011
Xstrata Zinc has entered into a binding agreement with
Sabina Gold and Silver Corporation to purchase the
Hackett River and Wishbone exploration properties in
the Western Kitikmeot region of Nunavut, North
Canada. Under the terms of the agreement, Xstrata
will pay a cash consideration of C$50 million and will
grant a silver royalty to acquire the properties.
Additionally, Xstrata will commit a further C$50 million
in exploration and to complete a bankable feasibility
study within four years of the transaction’s closing.
© Condor Consulting 2011
Now and into the future
Near mine exploration will remain quite effective.
Incremental advances in technology can be expected and in the
right geological circumstances, ex: Lalor Deposit
The efficacy of geophysical techniques to search at depth (2-3
km) will remain challenging.
More integrated modeling of multiple data sets is expected to
help define areas of interest.
Specific targeting (i.e. where to drill) will likely require some new
definitions of geoscience infrastructure such as systematic
seismic-MT transects and deep drilling for geological control and to
feed-back into modeling.
Economically the shortest returns could be realized if the means
could be developed to target effectively in the areas classified now
as “formational conductors”
© Condor Consulting 2011
PDAC 2011
© Condor Consulting 2011
ASEG 2009
© Condor Consulting 2011
SEcG-I
© Condor Consulting 2011
SEcG-II
© Condor Consulting 2011
Way Ahead…
© Condor Consulting 2011
Way Ahead…
© Condor Consulting 2011