Page 68 - Geochemical Remote Sensing of The Sub-Surface

Geoelectrochemistry and stream dispersion 45

Fig. 2-23. Results obtained by the CHIM method over tin stockwork ore in Primorsky Kray,
Russia: results of lithogeochemicai survey (A) at surface, (B) in rocks in trenches, and (C) results
of CHIM survey; 1- Quaternary sediments; 2- aleurolites and sandstones; 3- tin stockwork ore; 4-
small veins of tin mineralisation; 5- small veins of polymetallic mineralisation (reproduced with
permission from Alekseev et al., 1981).

In Byelorussia the early Proterozoic crystalline basement, represented by biotite-
granite-gneisses, migmatites, micaceous slates and quartzites with acid intrusions and
(gabbro-)diabase dikes, is concealed beneath Quaternary fluvio-glacial sediments 30-150
m thick. Beryllium mineralisation, the product of regional and local metasomatism,
occurs in the concealed basement. The Be data of a CHIM survey expressed very well
the ore body known from boreholes 1 and 2 and revealed a further anomaly. Drilling of
boreholes 3 and 4 on this anomaly confirmed the existence of a previously-unknown ore
body (Fig. 2-24).
The value of CHIM in prospecting for gold deposits is shown by the "Prijutinsky"
section near the Enisey river in Eastem Siberia. This section comprises phyllite slates
beneath proluvium sediments. The known placer gold mineralisation is in phyllites
covered by gravels and clays 5-7 m thick (Fig. 2-25). Mining has indicated the
distribution of gold (Fig. 2-25A). The curve of gold mass extracted by CHIM (Fig. 2-
25B) corresponds satisfactorily to the gold concentration distribution obtained from
mining. The deposit was further explored by drilling only of the CHIM anomalous
zones, with a 3-4-fold reduction in expenditure.