Novel and sometimes unappreciated applications of Geophysics to

Novel and sometimes
unappreciated applications of
Geophysics to assist in exploration,
mine planning and management
within the economics of the project
Simon Bate, AEGIS Instruments (Pty) Ltd
Lobatse, Botswana
CDM Mining Summit, Cape Town, 2013
Geologists, geophysicists, and engineers
working with a single, shared, consistent
model of the earth
geologist
geophysicist
engineer
•rock type
•alteration
•ore vs. waste
•grade
•conductivity
•magnetism
•density
•seismic velocity
•UCS, stress
•rock quality
•faults / shears
•soft / brittle
•geometry
•geometry
•geometry
The Voorspoed Site
Length: 389.6m
Vert.: 44m
The Voorspoed Site
Benchmark Study: Results (Azimuth 2)
Zone of Magnetic Interference
31950 S
PLAN VIEW
32000 S
Optical_Out
Optical_In
EMS3_In
32050 S
EMS4
EMS3_Out
Small deviations
due to mag effects
Gyro_Out
Gyro_In
EMS2_In
EMS2_Out
50m
EMS1_Out
32100 S
9700 E
9650 E
9600 E
9550 E
9500 E
9450 E
EMS1_In
At cost varying from 0.5% to
3% of the cost of drilling;
Which survey would you
prefer?
Who is accountable?
TOWARDS AN
AUTOMATED PROCEDURE FOR FINDING
CONFINED CONDUCTORS
IN A
CONDUCTIVE HALFSPACE
Objective
To develop an efficient interpretation method
for a large number of ground TEM soundings
in searching for confined conductors in a
conductive environment
Choice of Survey Geometry
Resulting anomaly map
CASE HISTORY
• COAL – Site in southern Africa
– Suitability for underground longwall mining
High Resolution Reflection Seismics
Comparison of quality of source signal
75g dynamite
VIBSIST-1000
0 ms
100 ms
200 ms
300 ms
400 ms
500 ms
Line A: Stacked Data
0 ms
100 ms
200 ms
300 ms
400 ms
500 ms
Line A: Migrated Data
255 m
306 m
357 m
408 m
459 m
Line A: Detail of Migrated Data
CONCLUSIONS
• Successfully mapped top of coal at depths of
300m and more
• Mapped individual coal layers within the coal
sequence
• Mapped vertical movement about normal faults to
accuracies of better than 10m – estimated 7m
resolution or better
CASE HISTORY
•DIAMONDS – Finsch Mine, South Africa
- mapping kimberlite contacts, internal
structure and determining kimberlite volumes
in an underground mining environment
High Resolution Reflection Seismics
Images from Kimberlite Delineation by Seismic Side-Scans from Boreholes
by Cosma, Wolmarans & Enescu. EAGE Spain 2005
Borehole survey locations at precursor
on the left and main pipe on the right.
Single-hole migrated profile obtained
from borehole 65-232 and interpreted
reflector elements overlaid onto the
Block 5 main pipe model (yellow).
Cross-hole migrated profile obtained from
boreholes 65-219 and 65-220 and
interpreted reflector elements overlaid
onto the Block 5 precursor (blue)
and main pipe model (yellow).
CONCLUSIONS
• Maps geological contacts at distances of 150m and
more from the boreholes
• Maps major internal structural events
• Increased level of confidence in geological model
• Indicated potential for use in determining kimberlite
volumes with more accuracy
• Indicated potential for reducing risk in resource
estimation
• Able to complete the survey in a working mine
environment
CASE HISTORY
• DIAMONDS – Debswana Diamond Mining Co.
– Jwaneng Resource Extension Project
Titan24 MT Distributed Array
Wireline Logging
High Resolution Surface Seismic
OBJECTIVES
• Map individual kimberlite bodies to depths of 1000m or
more below surface
• Map the locations of the kimberlites to accuracies of 25m
or less for geological and volume modelling
• Map the individual facies within the kimberlite if possible
• Map the host lithologies and structural events
• Define the physical parameters for host rocks and
kimberlites with wireline logging to assist Titan24
interpretation, kimberlite facies delineation and derivation
of geotechnical parameters
• Geotechnical & engineering studies for the suitability of a
possible site for the development of an underground shaft
Jwaneng Mine
resistive
GOCAD Model + Constrained Titan
2D MT Resistivity Inversion
conductive
Survey Layout
Result Analysis: 2D from 1D start
NE
Line 1
Fault B
Centre Pipe Fault D
?
Correlation
?
Dolerite dyke
SW
Modelled
QVK
Section of the South pipe
where the multivariate
classification appears to
show a zone of QVK
misclassified during
visual logging
Additional
QVK
High Resolution Seismic Survey
• equipment used same as for coal site studies in
South Africa
• used radio link technology to record signals
from geophones either side of the
inaccessible area around the mine site
• recorded on 2 or 3 lines while source used
along one line only for 2.5D coverage
• recorded data from all shot sites on hydrophone
in deep hole beneath proposed site. This
allowed the data to be processed to produce
a “poor man’s” 3D dataset
Migrated 3D in line profiles, courtesy of Cameco Inc
The Millenium Uranium Project, Saskatchewan
3D surface & 3D VSP in line profiles, courtesy of Cameco Inc
The Millenium Uranium Project, Saskatchewan
CONCLUSIONS
• Lithologies and structure mapped to 1000m
• Constrained inversions map kimberlite form
• Constrained inversions map breccia zones and general
outline of individual facies
• Wireline data assists in kimberlite facies discrimination,
breccia discrimination and geotechnical evaluation
• Wireline data provides much greater detail for logging core
and subtle variations in lithology
• The high resolution seismic surveys confirmed the
Geotechnical Department conclusions, released at the same
time, that the proposed shaft site was not a viable option
CASE HISTORY
• BASE METALS – Tati Nickel Mining Co.
– Selkirk Mine: Nickel, PGE, Copper
Titan24 DCIP Distributed Array
Borehole Electromagnetics
Regional Geology of the Phoenix
and Selkirk Mines Areas
HISTORICAL GEOLOGICAL MODEL
Selkirk Massive Sulphide
in Metagabbros
Barren cummulate gabbro
Granites
OBJECTIVES
• Confirm or refute new geological model of host
mineralised metagabbros extending to the
southern margin of the Selkirk Mining Lease
• Determine the electrical and polarisable signature
of the remains of the Selkirk Massive Sulphide
Deposit and surrounding disseminated
mineralisation
• Delineate additional blind targets, with similar
geophysical signatures, close to Selkirk
Selkirk Mine – Titan24 Down Plunge
DSLK002
DSLK003
Selkirk Orebody
CONFIRMATION OF NEW
GEOLOGICAL MODEL
Selkirk Mine – Down Plunge
DSLK002 – at southern margin of previous drilling
- Quartz veined basal contact mineralisation
3.47m of 11.34 g/t Au
DSLK003 – down plunge from previous drilling
- a 57m package of disseminated and semi-massive sulphides
averaging 0.35% Ni and 0.47% Cu
- including 1.42m of massive sulphide
grading 2.79% Ni and 2.21% Cu
Selkirk Mine – DSLK003
Central Tx Loop 300x300m
CONCLUSIONS
• New stratigraphic model confirmed
• Titan24 DCIP investigated to depths of 500-600m
• Down plunge extent of Selkirk mineralised horizon
extended from 700m to 1500m
• Discrete low resistivity, high chargeability targets
confirmed to reflect significant Ni, Cu & PGE
mineralisation of similar grades and widths
• Intention of development of Selkirk Mine as an open pit
operation supported by knowledge of down plunge
potential for future possible underground operation
DMT CoreScan®3
high-tech core logging tool
DMT CoreScan3 is a portable core imaging device
developed for drill core image acquisition, storage
and evaluation of full and slabbed core.
Furthermore, whole core boxes can be scanned in
one image.
Full core is rotated 360°around its cylindrical axis
while the line-scan camera, positioned parallel to
the axis of rotation, scans its surface. Full core is
scanned at a rate of ~20 sec/m and the image can be
stored as BMP, PNG, TIF or JPG files.
DMT CoreScan3 - optical drill-core acquisition and storage unit (standalone)
“360°Full Core Mode“
Scanning during rotation of the core
360°
5 pixel / mm
"unrolled" image of the core mantle
“Plane Mode“
Scanning of slabbed core and core boxes
Resolution: 5 – 40 pixel/mm
Surface image of the slabbed core
CoreStructure
TM
Analysis
Structural Analysis
 Software system for quantitative structural
evaluation, analysis and presentation
 Geological structures are evaluated by pickup
routines (bedding, foliation, joints, faults, veins,
self-determined)
 Acquired structures can be N-oriented in connection
with geophysical logs or oriented drill cores
 Geomechanical parameters: RQD, FD, FS
 The orientation of the borehole together with the
structures are presented graphically and in the case
of deviated boreholes, the dip direction and dip of
the structures are corrected directly on request
CoreStructure AnalysisTM
Quantitative Statistics