Svecofennian intra-orogenic gabbroic magmatism: a case study from Turku, southwestern Finland

JENNI NEVALAINEN, MARKKU VÄISÄNEN, YANN LAHAYE, ESA HEILIMO, Sören Fröjdö

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    Abstract

    Using single-grain zircon U-Pb dating by LA-MC-ICPMS and whole-rock geochemistry, we have studied the Palaeoproterozoic gabbroic rocks from Moisio in southwest Finland. Three ages were obtained. The interpreted intrusion age is ~1.86 Ga, which places it in the 1.87±1.84 Ga intra-orogenic period of southern Svecofennia. The other ages, ~1.89 Ga and ~1.83 Ga, are inferred to be inherited and metamorphic ages, respectively. The K, LREE, LILE, Fe-, P-, Ti- and F-concentrations reveal two compositionally distinct groups: (i) an enriched monzogabbro group and (ii) a less enriched gabbro group. The composition of the monzogabbro group resembles the other intra-orogenic intrusions from southern Svecofennia, whereas the unrelated gabbro group is more comparable to the synorogenic rocks in the region. The magma source the monzogabbro experienced a subduction related carbonate metasomatism, induced by sediment subduction and subduction erosion. Evidently, the Moisio monzogabbro represent enriched, mantle derived magmatism in southern Svecofennia as a part of the intra-orogenic igneous activity. The intra-orogenic magmatism is considered to have conveyed considerable amounts of heat from the mantle into the crust contributing to subsequent lateorogenic high-grade metamorphism.a
    Original languageUndefined/Unknown
    Pages (from-to)93–112
    JournalGeological Society of Finland
    Volume86
    Issue number2
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

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