Page 71 - Geochemical Remote Sensing of The Sub-Surface

48 O.F. Putikov and B. Wen

Pb, ~tg I,
l~176 A

0 2 4 6 8 10kin
II"~.., II',.,II'~.II _'7~.II~U"~II"~.II"~II~ II ~II'%..II",-.II
-1 ~.,--x~--x., - -xJ- -~- -,~ --x., - -x.,- -x~-

--x.,--x.,--~
-2 "~-'~'-'~-'~- - - -~- "~-'~-"~'-"~- ~'-
"~"- "~--'~-~'~-
---x..,** "~,**-x.,t, "~%~.'~r -x.,** -x...o--'~ro-~....~'x.. --
-3 --- ,-~00 ,.,,..,0, -,,.,0. --.-,-o oo ,-~,0- ,;.k-_..~"-~
................ li
li "x-,Ill 2t'x~--i 3 ['x.,**l 41--::=i 5 ~
Fig. 2-26. Results obtained by the CHIM method over an oil deposit in Byelorussia and schematic
geological section: 1- Permian-Cretaceous-Quaternary clays, sands, coals; 2- marly siliceous clay
formations; 3- Carboniferous sand-clay formations; 4- middle-late Devonian sandstones,
aleurolites, marls; 5- oil deposit (reproduced with permission from Ryss et al., 1990).

data (Fig. 2-27). The advantage of an MDE survey compared to a CHIM survey is its
low cost. Consequently MDE is applied in reconnaissance surveys at scales 1:25000-
1:10000 and more detailed follow-up is performed with a CHIM survey.
The results of MDE investigations along a profile over the Mirona copper-nickel
sulphide ore body in the Pechenga ore field (Kola peninsula) are shown in Fig. 2-28. The
ore body, grading 0.4-1% Ni, is related to an ultrabasic intrusion in tuffaceous
sedimentary rocks. These rocks are covered by a moraine 10-15 m thick. The MDE
element-collectors over the ore body have values up to 12.5 mg/1 Ni, 10 mg/l Cu and
15.8 mg/1 Fe, compared to background concentrations of 1-2.5 mg/1 Ni, 0.5-1.5 mg/l Cu
and 2.5-3 mg/1 Fe. This survey was carried out in order to determine the nature of
gravimetric anomalies and induced polarisation and other electrical prospecting
anomalies. A number of geophysical anomalies were considered non-prospective as a
result of low concentrations of nickel and copper in the MDE survey. Subsequent
drilling has verified this conclusion. However, the MDE survey at Karic-Gavr, on the
edge of the Pechenga structure, produced high-contrast nickel and copper anomalies in
the region of an IP anomaly (Fig. 2-29) and a subsequent borehole revealed copper-
nickel sulphide mineralisation, grading 2.4% Cu and 0.12% Ni, at a depth of 120 m (Fig.
2-30).
The stockwork-type porphyry-copper ore bodies at Kyzyl-Tu in central Kazakhstan
are covered by allochthonous sediments 20-30 m thick. The conventional geochemical