par CRISTIAN MIHAIL
Entreprise de prospections géologiques et géophysiques, Bucarest
The paper shows the results – confirmed by drifts and drillings – of
the experimentation for electrical prospecting methods (field measurements
and mathematical and geological interpretation), for the discovery of new hydrothermal
polymetallic mineralized zones. The differential applying of these methods
to the mineralization types pointed out – by the self potential (SP)
and induced polarization (IP) methods – the stocks in the Racsa area,
the Gutai Mountains (Figs. 1, 2 and 3) and – by the resistivity method – the
quartz-bearing veins disseminated polymetallic mineralization in the Batarci
(Fig. 4) and Baile Turtului (Fig. 9) areas, the Oas Mountains.
On the basis of the cation-exchange properties of the clay minerals (membrane
polarization), we suggest the application of the IP method indirectly in the
investigation, by deep drilling with a view to detecting deep metallic levels
in the magmatic areas where the fractured zones are filled with hydrothermal
transformed minerals (Figs. 5 and 6). We insist on the non-abandonment of the
SP method, especially because the SP minimums are not susceptible to be influenced
by the cation-exchange capacity of the clay minerals, unlike the IP method.
In order to help the direct interpretation of the maximum resistivity anomalies,
we elaborated two mathematical models, starting from Georgescu method (Figs.
7 and 8). For the detection, the discrimination and the determination of the
strike of the geophysical (and geochemical) anomalies against a "noisy
background", we elaborated two FORTRAN IV programmes for profile intercorrelation
and for statistical summation of the measurements. The tests in the computer
showed (Fig. 10) the validity of these programmes and the superiority of the
map obtained by statistical analysis of the measured data.
In order to detect new polymetallic mineralized zones, we recommend the extension
of the geoelectrical methods – with the afferent procedures for mathematical
and geological interpretations – over the whole magmatic regions, where
the erosion, bringing the polymetallic mineralized levels towards the surface,
makes very effective the application of these methods, limited so far to a
realatively small sphere of investigation.