2016
IN ASSOCIATION WITH
EXPLORATION
Duncan Crone
James Duncan Crone, 1929-2011, was a
pioneering Canadian mining geophysicist,
explorationist and entrepreneur.
Crone, known and recognised in the
mining and exploration community
around the globe, was a very innovative,
practical-minded geophysicist who made
numerous important contributions to the
advancement of mining geophysics and
to mineral exploration discoveries during his long career.
He was born in Toronto. Following graduation, with
a degree in Mathematics and Physics, he joined the
remarkable group of innovative geophysicists
working for Newmont in Jerome, Arizona under the
legendary Dr Arthur Brant. That group included Harry
Seigel and Len Collett. Here, the practical
application of Induced Polarisation to mineral
exploration was born. Later, with co-operation from
Newmont, Crone would use what he learned in
Jerome to build practical IP and EM instrumentation
which were simple to operate and extremely reliable.
In the early 1950s he returned to Canada and joined
Radar Exploration where he was involved with
magnetic, gravity, and vertical loop EM surveys
following up early airborne EM surveys for massive
sulphide deposits. One of his achievements during
this time was to successfully apply gravity surveys to
distinguish graphite from massive sulphides in the
Bathurst mining camp.
In recognition of his abilities and the growing
importance of geophysics, Duncan was asked to set
up a geophysics department at Noranda Mines,
serving as Noranda’s first Chief Geophysicist from
1956 until 1962. His focus at that time was to
develop practical, portable EM systems that could be
used to find near-surface massive sulphides. The
JEM and the Shootback EM method were invented
and developed, constituting great improvements
over other instrumentation available at that time. The
Shootback method was an ingenious way to remove
the effects of topography on tilt-angle EM surveys.
A borehole EM system was also developed during
this time at Noranda, but borehole geophysics was a
difficult concept to sell to sceptical geologists and
mining engineers, as Crone would later discover.
In 1962, he founded Crone Geophysics Ltd where
the Shootback EM method was further improved and
put into production. His innovation and inventiveness
led him to produce numerous practical and portable
instruments such as the CEM (Horizontal Shootback
EM with larger coils than the JEM), the VEM (Vertical
Loop EM transmitter hoisted on a mast, with tilt-angle
CEM receiver), and the RADEM (VLF receiver).
These were sold to a worldwide market. Crone,
always close to the action in mineral exploration,
was involved with numerous discoveries while
consulting for Amoco and Mattagami Lake Mines
among others, many of which were based on his
picks of priority targets from airborne surveys, and
followed-up with his EM instruments.
In the 1970s, as Induced Polarisation became more
widely used around the world, Crone also saw the
need for a practical, lightweight, easy to operate IP
system. This led to the development of a batterypowered IP transmitter and compact receiver which
facilitated shallow IP surveys in difficult and remote
locations as well as borehole IP surveys.
Realising that there was a growing need to look
deeper into the earth, and drawing on early instrumentation and research by Newmont, he began to
develop borehole and surface time-domain EM
equipment, which he named Pulse EM. The original
Crone surface Pulse EM system, developed in 1973,
was a small, portable, multi-turn loop and an
analogue receiver which was used initially in the
Sultanate of Oman where, serendipitously, the first
field test outlined three massive sulphide orebodies.
This was the first commercially available surface
time-domain EM system in the world, and it was an