Mineralogy and geochemistry of the Kivilompolo Mo mineralization, in the Peräpohja belt, northern Finland

Abstract. The Kivilompolo molybdenum occurrence is a small porphyritic mineralization hosted by granitic gneiss of the Kierovaara suite at the north-western margin of the Paleoproterozoic Peräpohja belt. The discovery of high-grade Au and Au-Co deposits in the Peräpohja belt provided the impetus for studying this mineralization. Using a combination of field work, petrography, whole-rock geochemistry and electron probe microanalysis, a deposit classification is proposed for the mineralization. The mineralization consists of abundant, coarse grained molybdenite flakes contained within quartz veins, in addition to pyrite, pyrrhotite and chalcopyrite. The veins are hosted within deformed granitic gneisses of the Kierovaara suite. The mineralization displays hybrid characteristics of two end-member molybdenum porphyry systems, arc-related molybdenum porphyry deposits and Climax-style or alkali-feldspar rhyolite-granite porphyry molybdenum deposits. It is not possible to conclusively classify the mineralization as either end member. It is proposed that the Kivilompolo mineralization represents a point on a spectrum of deposits between these two end members. The potential for finding other mineralizations of this style in the region was also evaluated. As porphyry systems typically form multiple deposits in the same region, there is potential for further discoveries. However, due to the small size of this mineralization and the extensive deformation and alteration that has affected the region, the likelihood of finding these deposits is small, and the economic potential of any discoveries is limited