Page 65 - Geochemical Remote Sensing of The Sub-Surface

42 O.F. Putikov and B. Wen

Fig. 2-20. Scheme of a field installation of CHIM: 1- current source; 2- ore body; 3- halo of
dispersion; 4- host rocks; AI-As- element collectors; B- auxiliary earth electrode (reproduced with
permission from Ryss et al., 1987a).

m = Sql:

where, S = square of the membrane, q = the flow density of metal.

Taking into account that q = uC,E, we have,

m = SuC~Ex.

This means that SuC,E is a constant for a homogeneous rock and that the
accumulated metal mass is a linear function of time. The relationship is represented as a
geoelectrochemical hodograph (Fig. 2-21, branch I) in which the angle of inclination of
the curve to the time axis, x, depends on the concentration, C,.
Another case represents an inhomogeneous medium with different metal
concentrations at different depths, for example, a dispersion halo with concentration C,
and an ore body with concentration C2. The dependence of metal accumulation, m, as a
function of time, x, is shown in Fig. 2-21. It is possible, in principle, after determination
of the time xt and the angles (~1 and o~ 2 to estimate depths and concentrations of metals in
the different layers of the inhomogeneous medium. But because of the low movability of
ions in rocks, only branch I of the geoelectrochemical hodograph is used for ground (or
halo) mode CHIM. Branch II of the geoelectrochemical hodograph is used in borehole
(or basic) mode CHIM.