The predicted geology of the Outokumpu Deep hole is shown in Figs. 3 and 4 (Fig. 3, major rock units of the OKU hole cross-section, Fig. 4, predicted geology of the hole). The prediction is based on available geological data, previous shallow diamond drilling results, and geophysics, particularly reflection seismics, which was carried out in 2002 in the Outokumpu area.

According to the prediction, the deep drill hole will intersect mostly mica schist in the depth intervals of 0-1000 and 1200-1500 m. The mica schist includes often thin black schist layers with graphite and Fe-sulphides. Reflection seismics indicates reflectors in the uppermost 1 km which seem to follow to the structural grain of the known Outokumpu formation rocks about 3 km NW from the hole site. We expect to meet layers of black schist and/or rocks of the Outokumpu association (quartzite, skarn, serpentinite, talc schist, sulphides) at 1000-1200 m.

The main target of the drilling is the (presumably) mafic rock body at 1500-2000 m. This rock type has strong seismic reflectivity and high P-velocity, and at the moment it is interpreted as amphibolite, gabbro, basalt or metadiabase. Similar reflectors have been recorded in a wide area on the metasediment-covered margin of the Archaean craton, but the geological character of the reflectors is not yet known. For instance, they may represent Paleoproterozoic 2.1-2.2 Ga sills intruded to the craton margin during the continental break-up, and deformed later in the orogeny.