Dear All;
With the passing of the millennium soon upon us, chance would have it I read
the a piece by Andy Green of the CSIRO regarding the role of geophysical
technology and exploration discovery. Andy does a nice job of summarizing
the "where we are at" issues from an academic's perspective.
For those of us who have spent a lot of time in the discover business,
nobody can ever cover all the issues, if for no reason other than what we do
is still very much evolving and we all make our judgments thru by and large
our own finite experiences. I do find the differences are often ones of
emphasis as opposed to being on drastically different pages (i.e. we all see
more or less the same board and chess pieces but how these are 'played'
makes for a world of difference!)
A few points I saw were:
-Andy cites a hit rate of 1:1000 (number of drill holes needed to find an
economic deposit). This figure seems like it has been around for time
immemorial. A lot of things have changed since that figure was first offered
up (I think Norm Paterson and or Duncan Derry came out with this sort of
number in the early 1960s), why is this ratio so tenacious?
-Andy touches on the issue of cheaper drilling as being a decisive means to
improve the cost of discovery. While not his main thesis, we never the less
seem to see this age old issue still hanging around (seemingly) unresolved.
Why has it not been addressed? I think because the exploration industry has
not felt this issue to be of primary importance. While not a comprehensive
sampling, from my experience I know of companies who had reputations for
drilling many more holes than others (for the same $ spent) as well as those
who did the opposite. Both had a lousy discovery record. I think the
exploration community has sensed this over time and feels things work best
when a balance is maintained. But how is this balance defined?
-Discovery thru "bump finding"; I think this is one of the most poorly
understood aspects of exploration success and geophysics. My examination of
the discovery record in Canada over 50 years using airborne EM (one of the
classic bump finding approaches), shows that the earlier and most often
successful users, (i.e. the people we'd want to emulate), had a very good
grasp of the deposit models they were after. From a distance, this might
have seen like 'bump finding' but it was not; it was the robust linkage of
geophysics with geology. Those who came after tended to treat in much more
as a bump finding exercise and hence time and time again, these late comers
spent more and found less than the those who were in early and understood
what they were after. Where you want to be on the curve is at the point that
a specific deposit style has just been characterized (i.e. the "spectral"
content it's bump has been mapped) and you can then screen for look-a-likes
very very quickly. Mother Nature of course, still controls the ground rules
and there is sometimes simply only a few (or one) of a deposit to be found
via any means.
-Geophysical parameters: Andy does not touch on things like seismoelectic or
electrochemical (i.e. KSPK) phenomena. While these may not be 'pure'
geophysical techniques, they have been given only limited study and have
almost no commercial application. I expect we'll see there will be some
settings where such hybrid techniques can play an important role, once their
potential is better understood. This also applies to developing closer ties
between geophysics and geochemistry, this is where I see the most fertile
ground for reducing the numbers of sterile drill tests.
Thanks for this piece to Andy and the CSIRO (appeared in the July 2000
Exploration & Mining Research News). If you want to subscribe or view the
full newsletter, visit:
http://www.syd.dem.csiro.au/unrestricted/dempublication/ermn12.pdf
Best regards
Ken Witherly
P.S. For some reason, the CSIRO's PDF scan of their own document was a bit
harsh to Andy's two figures. Mine are not great but more legible than those
at this site. Otherwise, I would have simply passed on a pointer to the
site.
Green Explore Success.doc
