Specifics of Neoarchean Plume–Lithospheric Processes in the Kola–Norwegian Province of the Fennoscandian Shield: I. Composition and Age of the Komatiite–Tholeiite Association

Аннотация

The paper reports newly obtained geological and isotopic-geochemical data on the volcano-sedimentary complex of the Uraguba Neoarchean greenstone structure in the Kola–Norwegian province of the Fennoscandian Shield. New U–Th–Pb geochronologic data (SIMS) on the metadacite (2790 ± 9 Ma) from a rock unit of interbedding metadacite, komatiite tuff, and lava breccia and on veins of plagioclase–microcline granite (2697 ± 10 and 2696 ± 9 Ma) that cuts the komatiite constrain the time span when supracrustal complex of the Uraguba structure was produced and underwent tectono-metamorphic transformations to approximately 100 Ma. The metavolcanic rocks of the komatiite–tholeiite association of the Uraguba structure belong to two distinct isotopic-geochemical types, which are spatially separated from one another and were produced by melting different mantle sources. Geological and isotopic-geochemical data indicate that the Uraguba structure is analogous to such unique tectonic structures on cratons as the Neoarchean Belingwe and Bulawayo belts in the Zimbabwe Shield, Kalgoorlie Belt in the Eastern Goldfilds province at the Yilgarn Craton, Kuhmo–Tipasjarvi Belt in the Karelian epi-Archean craton, and the Warawoona Paleoarchean Belt in the Pilbara Craton.