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Browsing by Author "Ioannou, Christos"

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  • Ioannou, Christos (2020)
    The Siivikko-Kellojärvi area forms the southern part of the Kuhmo greenstone belt. The rocks in the area are mainly tholeiitic and komatiitic lavas. In some occasions primary textures can still be observed in the rocks, including spinifex and pillow lavas in mafic and ultramafic volcanic rocks, evident of marine environment. The purpose of this M.Sc. thesis is to investigate the possible hydrothermal alteration processes involved in the formation of the Siivikkovaara Ni-Cu-Zn-Pb mineralized sulfide body. The goal of the M.Sc. thesis is to examine the Siivikkovaara Ni-Cu-Zn-Pb mineralized body using mineralogy, whole-rock geochemistry, mineral chemistry and sulfur isotope geochemistry (δ34S values). Komatiites in the present study have a Cr content of 0.28-0.62 wt.% and show a positive correlation between MgO and Cr, following a cotectic olivine-chromite cumulate trend. Analyses of the studied samples show an average Pd + Pt value of 300 ppb. Given the results, the mineralization represents an enriched body in Pd + Pt, relative to the majority of deposits in Finland. Samples presented in the current study are mildly depleted in (La/Sm)N and generally LREE, relative to chondrite values. The analysed minerals show an average δ34S value of 0.45‰. The source of sulfur is magmatic and cannot be related with any other geological setting. Enrichment in some elements may be attributed to later post-magmatic modification of the mineralization and remobilization of the elements. Komatiitic rocks of the studied samples were derived from Cr-saturated magmas. Cr depletion in tremolite rock may be related with alteration processes or post-magmatic modification. REE data suggest a rather primitive and uncontaminated magma for the studied samples. The studied komatiites are principally of Aluminum-Undepleted komatiite-type. Owing to the poor exposure and extensive post-magmatic modification, any solid conclusions on the origin of the mineralized body are rather difficult. Therefore, more work can be done in the studied samples to further examine the assumption of a possible black-smoker setting.