Post on 19-Jan-2021
Seismic Methods for Hard Rock Mineral ExplorationNed Stolz
Group Leader -
Continental Geology and GeophysicsMinerals and Natural Hazards Division
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 2
Why should we use seismic for hard rock mining exploration?
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 3
Seismic Basics
Force
Distance from Source
vztFF o cos
Sonic velocity
RC
= (2
2
–
1
1
)/(2
2
+ 1
1
)
= p
/s
Wave equation
Reflection coefficient
Poisson’s ratio
No loss of resolution with depth!
Plenty of contrast in hard rock!
Measure of rock strength!
Seismic can image the geological signatures of mineralising processes
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 4
Reduced RocksOxidised Zone
Gold
Oxidised fluid
A Deposition Model -
Gold Orebody
Fluids need pathways porosity fractures brittle rocks
Fluids need drivers heat intrusions and volcanism
ReducedZone
ReducedZone
Felsic Magma
Reduced fluid from mantle?
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 5
Rock Properties -
Gold Deposit
4500
5000
5500
6000
6500
7000
2.5 3 3.5
Density (gm/cc)
P-w
ave
Velo
city
(m/s
)
Basalt
Sulphidic Sed
Felsics
basalt
felsic
ultramafic
ultramafic
basalt
Sulphidic sed
p s Gold
•
Felsic -
basalt contrast
•
Gold deposited in fracture zones caused by contrasts in rock strength
Downhole Geophysical Log
Gamma
Kambalda Physical Properties0m
1040m(After Turner, et al, 2007)
(After Stolz, 2004)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 6
A Deposition Model –
Nickel Orebody
Ore channel
•
Distinctive stratigraphy and geometry
(After Williams, Whitford, Kepic, and Urosevic, 2012)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 7
Density (g/cm3)
Velocity m
/s
Rock Properties -
Nickel Deposit
Meta S
NiBslt
UM = UltramaficBslt = BasaltMeta S = MetasedimentNi = Nickel ore
UM
Seismic forward model for Ni orebody
•
Nickel ore can be directly detected and mapped
Kambalda Physical Properties
(After Williams, Whitford, Kepic, and Urosevic, 2012)
UM
Meta S
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 8
Kambalda Nickel and Gold Field
Location PlanSuper Pit
Kambalda
50km
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 9
Argo Au
● Victory Au
Kambalda Ni
Kambalda Nickel and Gold Field
5km
3D seismic survey3D seismic survey
2D seismic lines2D seismic lines
Seismic data acquired by Mining Companies
Lake LefroyLake Lefroy
KambaldaKambalda
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 10
Kambalda Geology
Geology PlanFelsic Sediment
Meta sediment
Dolerite
Basalt
Dolerite
Ultramafic
Basalt
Felsic Intrusion
Stratigraphic Column
Kambalda
Victory Au
5km
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 11
North
Bismuth
< 0.1 ppm
> 0.2 ppm
Gravity lows interpreted as felsic intrusions
Bi anomalism denotes oxidised zones
Thrust Fault
Playa Fault
Victory Au mine
Residual Gravity, Major faults, and Bismuth Geochemistry
Plan View
Victory Gold Mine
Fault
Bismuth shows oxidised zones
Seismic line (After Stolz and Lally, 2006)
Interpreted Felsic
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 12
3.5 km
10 km
Surface
Victory Seismic Line Section View
(After Stolz, 2004)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 13
Victory Gold Mine
Bismuth
< 0.1 ppm
> 0.2 ppm
Thrust Fault
Playa Fault
Victory Seismic Line
Seismic line, Major Faults, and Bismuth Geochemistry
Perspective View
Z
N
E
Felsic Intrusion(After Stolz and Lally, 2006)
Au Au
Surface
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 14
Long - Victor Nickel Mine
Plan View
Location
Perspective viewNi orebodies
3D Seismic Survey
N
(After Williams, Whitford, Kepic, and Urosevic, 2012)
1km
Lake Lefroy
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 15
Depth (Km)Inlines 10 m apart
Long South
McLeay
1.0
0.5
1.5
Long - Victor Nickel MineProfiles from 3D Seismic Survey
Forward model
(After Williams, Whitford, Kepic, and Urosevic, 2012)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 16
Footwall Basalt
Fault
McLeay Nickel Orebody
Long - Victor Nickel MineSeismic “line” from 3D Seismic Survey
Ultramafic
(After Williams, Whitford, Kepic, and Urosevic, 2012)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 17
Long - Victor Nickel MineTime Slices from 3D Seismic Survey
Channel
380ms 390ms 400ms
Channel
(After Williams, Whitford, Kepic, and Urosevic, 2012)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 18
Long - Victor Nickel MineBasalt contact and faults interpreted from 3D seismic data volume
Basalt contact Major fault
Minor faults
(After Williams, Whitford, Kepic, and Urosevic, 2012)
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 19
Hard Rock Conclusions• High resolution - low ambiguity method with no loss of
resolution with depth
• Detects contrasts in sonic velocity, density and rock strength
• Images the geological signatures of mineralising processes– Fluid drivers– Fluid pathways– Deposition sites– Stratigraphy and geometry– High contrast ores
• 2D and 3D seismic provides high resolution data for detailed interpretation of lithology, structure and mineral alteration
Stolz, E., Urosevic, M., and Connors, K., 2004, Reflection seismic surveys at St Ives gold mine, WA, ASEG 17th Geophysical Conference and Exhibition, Sydney, Extended Abstract.
Stolz E. and Lally, J., 2006, The St Ives gold camp – a case study of 3D regional scale modelling, Kalgoorlie 2006 AIG, Conference Presentation
Turner, G., Craske, T., Kepic, A., Stolz, E., and Urosevic, M., 2007, Seismic reflection surveys to assist nickel and gold exploration in the WA goldfields, ASEG 19th Geophysical Conference and Exhibition, Perth, Extended Abstract.
Urosevic, M., Kepic, A., Stolz, E., and Juhlin, C., 2007,Seismic exploration of ore deposits in Western Australia, in "Proceedings of Exploration 07: Fifth Decennial International Conference on Mineral Exploration" edited by B. Milkereit, 2007, p. 525-534
Williams, P., Whitford, M., Kepic, A., and Urosevic, M., 2012, Recent experiences concerning the use of high definition seismic reflection applied to Komatiitic Nickel Deposits, Western Australia, 74th EAGE Conference & Exhibition, Copenhagen, Denmark, Extended Abstract.
The following organisations are gratefully acknowledged:
Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 20
References and Acknowledgements