ZTEM survey in the Outokumpu region.

A helicopter-borne geophysical survey over the Outokumpu mining camp area of Finland acquired 1 250 km of data at line spacings of 2 km, 1 km and 0.5 km with geophysical sensors that included a Z-axis tipper electromagnetic (ZTEM) system and a caesium magnetometer. Results included in- and cross-line ZTEM tipper components at frequencies of 25, 37, 75, 150, 300 and 600 Hz, total magnetic intensity data and various derivatives of ZTEM tipper data. Although the two-dimensional, three-dimensional and high-resolution 3D inversion results are generally in good agreement, showing similar locations of conductive zones but with considerable depth variation, the 3D inversion model with the finest mesh yields the best results. In general, black schists and sulphides have low resistivity and thus can be interpreted as conductors in this type of data; the report finds it unlikely that ZTEM would respond directly to Outokumpu deposits, but that it images the black shale and serpentinite units and possibly the surrounding hydrothermal mineralised halo.
A helicopter-borne geophysical survey over the Outokumpu mining camp area of Finland acquired 1 250 km of data at line spacings of 2 km, 1 km and 0.5 km with geophysical sensors that included a Z-axis tipper electromagnetic (ZTEM) system and a caesium magnetometer. Results included in- and cross-line ZTEM tipper components at frequencies of 25, 37, 75, 150, 300 and 600 Hz, total magnetic intensity data and various derivatives of ZTEM tipper data. Although the two-dimensional, three-dimensional and high-resolution 3D inversion results are generally in good agreement, showing similar locations of conductive zones but with considerable depth variation, the 3D inversion model with the finest mesh yields the best results. In general, black schists and sulphides have low resistivity and thus can be interpreted as conductors in this type of data; the report finds it unlikely that ZTEM would respond directly to Outokumpu deposits, but that it images the black shale and serpentinite units and possibly the surrounding hydrothermal mineralised halo.