Page 83 - Geochemical Remote Sensing of The Sub-Surface
P. 83
60 O.F. Putikov and B. Wen
J lim, mA/cm2 I
10" i ! II
A j
0.1 "~ IIi !
1-10 -4 1"10 -3 1"10 1 1-10 -l 1
aj mA
, ,
0,17 ) crn s
Fig. 2-38. Dependence of limiting current density on rate of current density excitation. Surface of
spherical electrodes, cmZ: o- 1.5; A- 3.0; v- 10; x- 40; [-~- 120; I- experimental data for spherical
electrodes; II- theoretical dependence for a plane electrode (reproduced with permission from
Korostin, 1976).
1
Iog~o J,~rn - 3 IOg~o a + Iog~o b (2.40)
where,
]
-
This means that for the bi-logarithmic co-ordinates of a planar ore body there is a
linear dependence of the limiting current density on the current density rate. The
corresponding slope coefficient is 1/3. Results of laboratory physico-chemical simulation
(Korostin, 1976) confirmed this dependence for the interval of current density rate 'B'
(Fig. 2-38).
Contact polarisation (CPC)
The essence of the CPC method consists of recording and interpreting polarisation
curves obtained when the polarisable electrode is an electron-conducting ore body (Fig.
2-39). One pole of the current source, electrode A, is connected to the ore body by
means of a special device (e.g., in a borehole intersection through the ore body). The
