ИСТИНА

Sand-gravel mixtures are widely used as multipurpose minerals. Different modifications of resistivity methods are traditionally applied for locating and mapping sand-gravel mix (SGM) deposits. This method allows us to determine sand-gravel bodies against the background of more conductive enclosed rocks. The challenge faced by geophysicists today is not only to determine the boundaries of SGM deposits, but also, to locate the zones with high gravel contents within SGM deposits. Studies conducted in Kaluga region, Russia, have showed that additional measurement of induced polarization makes it possible not only to detect boundaries of deposits, but it also allows us to identify areas with high content of gravel fraction. The measurements were made at both known SGM deposits that are now being developed and at new prospecting areas where drilling has been done after geophysical surveys. The study results show that all SGM deposits are characterized by high values of induced polarization. Authors suggest that the anomalies of the induced polarization are probably associated with electronically-conducting minerals, such as magnetite and pyrite, contained in grains of gravel. The geophysical results were confirmed by drilling data and laboratory measurements of induced polarization on samples. The grain size measurements were also made and thereafter compared with results of laboratory measurements. The high content of gravel material in the samples correlates well with high polarization values.