Metal anomalies in till in the Sarvlaxviken area, Lovisa, southern Finland

Geochemical investigations of till is a widely used method in metal exploration as the till commonly inherits the geochemical signature (including the metal contents) of the parent bedrock. In this investigation, over 2000 till samples were collected in the Sarvlaxviken area, southern Finland, where several polymetallic (Cu, Zn, Pb, As, Sn, W and In) veins recently have been discovered in Proterozoic crust along the border between Late Svecofennian granites and the Wiborg Batholith. The bedrock is commonly covered by compact and poorly sorted basal till, formed during the Late Weichselian glaciation event. Several glacial-transported boulders, with high contents of Cu, Zn, As, Sn, Mo and Bi and derived from the local bedrock, have also been discovered on top of the till and provide evidence for concealed mineralisation in the local bedrock under the till cover. The frequent distribution of till in the Sarvlaxviken area provides excellent conditions for the search of such hidden mineralisation by means of systematic till sampling, even if large farm field areas, composed of clay-rich sediments, and seawater-covered areas (Sarvlaxviken bay), had to be avoided in the sampling program. The till samples were collected during university courses and training programs led by the authors and were analysed in a costefficient and certified laboratory. Obtained geochemical data were statistically processed by using K-means clustering algorithms which can be used to treat large sets of geochemical data. The results provided anomalies that mainly occur in till with a thickness ofPeer reviewe

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

Geological investigations of a part of the crystalline basement in the Baltic Sea have been performed on a drill core collected from the depth of 1092-1093 m beneath the Phanerozoic sedimentary cover offshore the Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with the SIMS U-Pb zircon method. Inherited zircon cores from this migmatized granodioritic orthogneiss have an age of 1854 +/- 15 Ma. Its chemical composition and age are correlated with the oldest generation of granitoids of the Transscandinavian Igneous Belt (TIB), which occur along the southwestern margin of the Svecofennian Domain in the Fennoscandian Shield and beneath the Phanerozoic sedimentary cover on southern Gotland and in northwestern Lithuania. It is suggested that the southwestern border of the Svecofennian Domain is located at a short distance to the SW of the investigated drill site. The majority of the zircon population shows that migmatization occurred at 1812 +/- 5 Ma, with possible evidence of disturbance during the Sveconorwegian orogeny

4th Finnish National Colloquium of Geosciences Turku, 14–15 March 2018: Abstract Book

The Transscandinavian Igneous Belt (TIB) is a major magmatic complex along the western margin of the Svecofennian Domain in the Fennoscandian Shield in which several granitoid generations (TIB 0, TIB 1, TIB 2 and TIB 3) have been recognized (Larson & Berglund 1992). Recent studies have also identified the presence of the 1.77–1.81 Ga TIB 1 generation at several drill sites below the Phanerozoic sedimentary cover in the Baltic Sea region: Kvarne on southernmost Gotland (Sundblad et al. 2003), Böda Hamn and Valsnäs on northern and central Öland, respectively (Salin et al. 2018), as well as E-7, offshore on the Latvian/ Lithuanian border (Salin et al. 2016). In this study, we report U–Pb zircon ages from the Precambrian basement in the Baltic Sea region at two more sites: percussion drilling material from Frigsarve (southern Gotland) and drill core D1-1 from the Lithuanian offshore region. Zircons from Frigsarve yielded a LA-ICP-MS age of 1845 ± 4 Ma, which is comparable with the age of the TIB 0 generation in southeastern Sweden. According to crystal morphology and SIMS ages, the zircons from the D1-1 drill core belong to two generations. The larger zircon grains have an age of 1792 ± 8 Ma, which is similar to the TIB 1 generation. The smaller zircon grains are 1744 ± 7 Ma old and are interpreted to record a later 1.73–.68 Ga high-grade metamorphic event, which is widespread in Western Lithuania (Skridlaite et al. 2014). In conclusion, all data from previous and current studies show that the Transscandinavian Igneous Belt extends over vast areas in the Baltic Sea region, from Öand and southern Gotland to the offshore regions of Latvia and Lithuania.</p