seismic methods for hard rock mineral exploration · seismic methods for hard rock mineral...

20
Seismic Methods for Hard Rock Mineral Exploration Ned Stolz Group Leader - Continental Geology and Geophysics Minerals and Natural Hazards Division

Upload: phungduong

Post on 21-Aug-2018

227 views

Category:

Documents


1 download

TRANSCRIPT

Page 1: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

Seismic Methods for Hard Rock Mineral ExplorationNed Stolz

Group Leader -

Continental Geology and GeophysicsMinerals and Natural Hazards Division

Page 2: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 2

Why should we use seismic for hard rock mining exploration?

Page 3: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 4: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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?

Page 5: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 6: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 7: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 8: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

Seismic methods for hard rock mineral exploration; 34th IGC Brisbane 8

Kambalda Nickel and Gold Field

Location PlanSuper Pit

Kambalda

50km

Page 9: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 10: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 11: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 12: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 13: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 14: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 15: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 16: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 17: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 18: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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)

Page 19: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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

Page 20: Seismic Methods for Hard Rock Mineral Exploration · Seismic Methods for Hard Rock Mineral Exploration ... Seismic can image the geological signatures of ... Seismic methods for hard

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