Petrological and mineral potential investigation of the Suvasvesi granitoid intrusion and associated pegmatites

The Paleoproterozoic (1870 ± 4 Ma) Suvasvesi intrusion belongs to the Heinävesi granitoid suite that intrudes the Paleoproterozoic Ylä-Kaleva metasedimentary rocks (migmatitic paragneisses) of the Karelian domain (Viinijärvi suite). The Suvasvesi intrusion is ca. 10 x 30 km in size and majority of its areal extent is located under and south of lake Suvasvesi in Northern Savonia. The Heinävesi suite has previously been associated with the Svecofennian post-kinematic (1.88–1.87 Ga) granitic–quartz monzonitic magmatism mostly present within the Central Finland granitoid complex (CFGC). The Heinävesi suite, however, intrudes clearly older (>1.92 Ga) country rocks east of the CFGC area and, based on Nd isotope composition (εNd@1880 -6.6 to -1.9), taps a significantly more enriched crustal source than the post-kinematic intrusives within the CFGC (εNd@1880 -1.1 to +0.5). The mineralogy, petrology, and lithology of the Heinävesi suite are in general rather poorly studied and the regional geological framework would clearly benefit from a better understanding of its petrogenesis. This is true especially as there is increasing interest in for example the graphite potential of the Heinävesi area (e.g., Pitkäjärvi, Aitolampi, and Haapamäki prospects; beowulfmining.com) and the Geological Survey of Finland is also directing its mapping projects into the area in search of other critical resources such as cobalt. In order to probe its mineralization potential and to clarify the regional geological framework, a reconnaissance-scale mapping project including petrographic, geochemical, and mineral chemical analysis to describe the Suvasvesi granite intrusion and to study its relation to the regionally widespread pegmatitic dykes intruding the Viinijärvi suite, is to be conducted. The project is to be realized as a MSc thesis project in which the student is responsible for mapping the Suvasvesi intrusion and the surrounding mica gneisses, sampling, sample preparation, and petrographic and geochemical analyses under the supervision of the PI and experts of local geology from the Geological Survey of Finland. Further thermodynamic partial melting modeling based on the acquired data set in order to constrain the source components, geochemical evolution, and possible enrichment processes related to the Suvasvesi intrusion magmas will be also conducted.