geophysical expressions of ore systems · methodology technique airborne surface borehole marine...

© Condor Consulting 2014

Geophysical Expressions of Ore Systems Our Current Understanding

Saskatchewan Geological Open House

December 2, 2014

Ken Witherly

Condor Consulting, Inc.


The business challenge

MinEx Consulting

Depth of cover for base metals discoveries

(>0.1% Cu-equiv.) made in Western world



Depth to top of ore body for (>0.1 Moz) gold

discoveries made in Western world

MinEx Consulting



Average depth of cover for discoveries-all metals

Western world: 2003-2012

MinEx Consulting


The business opportunity

Jon Hronsky (2009)

Modeling for a Voisey’s Bay style orebody in remote WA (30 Mt @ 2.5% Ni, 2% Cu; 20 m thick, 60° dip)


The business opportunity

Courtesy of D Wood (after Chitombo)

Planned or possible Super Block Caves


Defining the Foot Print/Foot Path

Modified from Australian Academy of Sciences (2010)


In the range of 0 - 250 m

Ford et al. (2007)

Matrix of geophysical techniques


In the range of 250 m - 1.5 km

METHODOLOGY TECHNIQUE AIRBORNE SURFACE BOREHOLE MARINE

POTENTIAL FIELDS Magnetics X X X X

Gravity X (limited

bandwidth)

X X X

ELECTROMAGNETICS

(EM)

active source X (limited

bandwidth)

X X limited

passive X (limited

bandwidth)

X ? limited

ELECTRICAL resistivity ø X X limited

chargeability X (limited

bandwidth)

X X limited

SEISMIC seismic ø X X X

Ø = not applicable X = nominal

Matrix of geophysical techniques-II

Condor Consulting


Some hope…

1.8 km

Conductive

shale ZTEM 2D inversion

ZTEM 3D inversion

ZTEM airborne EM mapping conductive horizon at 1.8 km


Going to depth…

“We can see deep but things are blurry”

Joel Jansen-Teck


Logging while drilling

Hillis (2012)

Plans of the DET-CRC; coil tube drilling and log-while drilling


Cheng et al. (2009)

Logging while drilling…the hope

With more petrophysical information…


Cheng et al. (2009)

Logging while drilling…the hope

…better subsurface models can be produced with a

higher likelihood of successful testing


Examples-porphyry Cu-Au-Bingham Deposit-Utah

Steinberger et al. (2013)

Geology


Examples-porphyry Cu-Au-Bingham Deposit-Utah

Steinberger et al. (2013)

TMI-RTP Geological model derived from TMI-RTP


Examples-porphyry Cu-Au-Pebble Alaska

Anderson et al. (2013)

TMI-RTP

TMI-RTP


Examples-porphyry Cu-Au-Pebble Alaska

Anderson et al. (2013) TMI-RTP


McMonnies and Gerrie (2007)

Examples-porphyry Cu-Au-Resolution Arizona

Geology MT section; unconstrained inversion

MT section; constrained inversion


Townsend et al. (2010)

Examples-Carlin gold-Carlin Nevada

Mapping structures & stratigraphy


Unconformity uranium model

JNR Uranium


Variations in physical properties; density; either high or low.

Jefferson et al. 2006

Low density halo High density halo


Features not seen before and as yet unexplained

Condor Consulting

~10 km



Condor Consulting

~10 km

But no conductor!


Data Integration


Data integration will be critical; but real integration is much more than simply having all your data on the same ‘bus’ (platform)…


The HR issues are significant!

Condor Consulting


Where we are…

• The concept of mineral systems in now 20 years old-ideas take time to

gain acceptance.

• The geophysical signatures of mineral systems are now starting to

be recognized.

• Some deposit styles will have larger signatures than others.

• Subsurface information will be critical to effective vectoring.

• Data integration will be judged on the metric that the whole is

greater than the sum of the parts…


Acknowledgments

• Cam McCuaig, Graham Closs and Richard Schodde have provided much

insight into the issues related to undercover exploration.


There is hope!

Undercover 2020-Sept 2010

Geologists working with geophysical data to map undercover porphyry Cu-Au systems.

geophysical expressions of ore systems · methodology technique airborne surface borehole marine...

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