Page 86 - Geochemical Remote Sensing of The Sub-Surface

Geoelectrochemistry and stream dispersion 63

Mineral I 9, V q~, V Mineral ~,v II~,v Mineral
Chalcopyrite [ +0.17 Penflandite -0.32 Pyrrh.o.tite +0.6 ]1 -0.5 Pyrrhotite
Pentlandite [ s Chalcopyrite -0.5 Pyrrhotite +0.9 1-1.5 Pyrrhotite
Pyrrhotite .....
Penflandite -0.14
Pyrrhotite -0.15
I,A
I, A

15 15 B
A

1[ 10

!
!

at //
\ \ _,,4,, / / J./ _
~, .,4",' ,/ / _
V"
I" I
,' _
.-
+1 0 -1 ~V v +1 0 -1 q~, V r
Fig. 2-41. The CPC polarisation curves of sulphide ore bodies, Kola peninsula, Russia: (A)
copper-nickel ores; (B) pyrrhotite mineralisation.

example, to introduce 160 A using the 12-channel Russian SPK instrument, it is
necessary to have the current circuit resistance less than 0.56 f2. In order to meet this
requirement a special cable with a resistance of 0.7f2/km is used. The SPK instrument
can then investigate ore bodies from metres to kilometres in size and at depths up to
1000 m.
The best CPC results are obtained on ore bodies with favourable texture (massive,
veined, banded, laminated, etc.), when the ore body as a whole is an electronic
conductor. For such ore bodies CPC is able to:

9 determine the mineral composition of ore bodies;
9 estimate the total surface area and size of ore bodies;
9 indicate the mineral concentration and reserves of ore bodies;
9 assist correlation of different ore intersections;
9 assist investigation of ore body location.

Determination of mineral composition of the ore body requires finding the
electrochemical reaction potentials that take place on the ore body surface due to the
current that is introduced. Values of the electrochemical reaction potentials correspond
to the cross points of lines tangential to the flexure of the polarisation curve and the
potential axis (Figs. 2-41 and 2-42). The average mineral composition of an ore body is