Geochronology, geochemistry and structural setting of the Uunimäki gold mineralisation, SW Finland
: Tuomas Leskelä, Jaakko Kara, Iiro Pitkälä, Pietari Skyttä, Markku Väisänen, Markku Tiainen, Hanna Leväniemi, Janne Hokka, Yann Lahaye
: Ilmo Kukkonen, Suvi Heinonen, Hanna Silvennoinen, Fredrik Karell, Elena Kozlovskaya, Arto Luttinen, Kaisa Nikkilä, Vesa Nykänen, Markku Poutanen, Pietari Skyttä, Eija Tanskanen, Timo Tiira and Kati Oinonen
: LITHOSPHERE
: 2018
: LITHOSPHERE 2018: TENTH SYMPOSIUM ON STRUCTURE, COMPOSITION AND EVOLUTION OF THE LITHOSPHERE: PROGRAMME AND EXTENDED ABSTRACTS
: REPORT
: 67
: 65
: 68
: 978-952-10-9594-8
: 978-952-10-9595-5
: http://www.seismo.helsinki.fi/ilp/lito2018/Lito2018_Abstract_Volume_color.pdf
: https://research.utu.fi/converis/portal/detail/Publication/37200266
The Uunimäki gabbro was studied by zircon U-Pb geochronology which yielded an age of ~1.89 Ga, making it one of the oldest plutonic rocks in the Häme Belt. Geochemical analysis of the gabbro reveals that it lacks several characteristics for typical subduction zone rocks: (i) it does not have a negative Ta-Nb anomaly compared to average NMORB-composition, (ii) it shows a rather unfractionated REE pattern, (iii) it lacks clear enrichment of fluid-mobile elements (e.g. Ba, Rb, Th, Pb). Structurally, the Uunimäki gabbro is located at the intersection of several regional features: (i) steep NE-plunging folds, (ii) a ENE-WSW-trending deformation zone immediately to the north and (iii) a large N-S-trending deformation zone to the west. The gabbro itself has been deformed under both brittle and ductile conditions by primarily NW-SE-trending faults and shears.
