Abstract

The geochemistry of different till size fractions and studies of heavy minerals have been used in mineral exploration in the ribbed moraine terrain in southern Finnish Lapland. The Peräpohja Schist Belt and layered intrusions along its southern margin have known potential for economic Au, Co, Cu, Fe, Zn, U and PGE mineralization. In till, high element concentrations related to mineralization in the local bedrock preferentially occur in the near-surface (less than 2 to 3 m depth) of ribbed moraine ridges. The ridges formed subglacially by gouging of local bedrock, which favoured the deposition of rock material derived from the local bedrock surface into till on the surficial part of ridges. The short distance of glacial transport (<500 m) is indicated by clast angularity, the abundance of locally derived boulders in the upper till and at the surface, and by the preservation of euhedral pyrite and chalcopyrite crystals and native Au grains in the heavy mineral concentrates. Detailed studies show that ribbed moraine ridge tops can be used for mineral exploration because they are more likely to be composed of local bedrock than are the sediments comprising the ridge core.

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