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Geochronology, geochemistry and structural setting of the Uunimäki gold mineralisation, SW Finland




List of Authors: Tuomas Leskelä, Jaakko Kara, Iiro Pitkälä, Pietari Skyttä, Markku Väisänen, Markku Tiainen, Hanna Leväniemi, Janne Hokka, Yann Lahaye
Publication year: 2018
Book title *: LITHOSPHERE 2018: TENTH SYMPOSIUM ON STRUCTURE, COMPOSITION AND EVOLUTION OF THE LITHOSPHERE: PROGRAMME AND EXTENDED ABSTRACTS
Title of series: REPORT
Number in series: 67
ISBN: 978-952-10-9594-8
eISBN: 978-952-10-9595-5

Abstract

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.


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Last updated on 2019-21-08 at 22:20