Page 90 - Geochemical Remote Sensing of The Sub-Surface

Geoelectrochemistry and stream dispersion 67

of the ore body surface is an average S0av of n values that were found from equation
(2.46),

l
Soav - 2. Soj (2.48)
n i=1

After substitution of S0i by S0av in equation (2.46) it is possible to define the
concentration of the separate minerals Ci. The error can be reduced by using the average
borehole concentration Ci,v instead of concentration Ci.
Using CPC, for each ore cross-section we obtain n independent values of S0i ( i = 1,
2,...,n) according to equation (2.46). Then the number of boreholes required to calculate
with the given accuracy the total ore body surface S0av (or concentration Ciav ) is less than

relative to the number of boreholes required without using the CPC method. This
demonstrates the economic effectiveness of the CPC method for evaluation and
preliminary exploration of ore deposits.
If an ore body of thickness H has a lens shape of 1~ x 12 and H<<ll, H<<12, we have
approximately,

Ill 2 ~ So~ v /2

After substitution of the average values of concentration C~av and total ore body
surface S0av in equation (2.46) we obtain,

So~ vC i~v - kloo I ,im ~ " 100

where S0avCiav is the reserve of the i-th mineral in m 2 %. Then the reserves Mi of the i-th
mineral in mass units are (Ryss, 1973, 1983),

Soav klool tim i H avdav " 100
M j- 2 CiavH ~vd~v - 2 (2.49)

where Hav and dav are the average thickness of the ore body and ore density respectively
determined by means of drilling.
An example of CPC polarisation curves obtained at a sulphide copper-nickel ore
body on the Kola peninsula are shown in Fig. 2-44 and the interpretation of these curves
is given in Table 2-111 (Ryss, 1973). The geological data used are the concentrations of
minerals and metals in relative mass units (Cpnt~0.03; Ccp~0.015; Ccp+pyr~0.07; Cy'~0. l;
Cni~0.01; Ccu~0.005) and the size parameters of the ore body (Hav~2m, dav=3500 kg/m3,
S0~15• m2). These are used in equations (2.46) and (2.49) with kt00 = 500 m2/A for