Mesoarchean kola-karelia continent

• Main Authors: Mints, Michael V., Dokukina, Ksenia A., Konilov, Alexander N., Kaulina, Tatiana V., Belousova, Elena A., Dokukin, Peter A., Natapov, Lev M., Van, Konstantin V.
• Other Authors: Condie, Kent, Harvey, F. Edwin
• Format: Book Part
• Language: English
• Published: Geological Society of America 2015
• Subjects: Fennoscandian
• Online Access: https://researchers.mq.edu.au/en/publications/b7206e5d-7081-4b6a-aacd-82a82df94f72; https://doi.org/10.1130/2015.2510(02; http://www.scopus.com/inward/record.url?scp=84943149545&partnerID=8YFLogxK

The Mesoarchean Kola-Karelia continent in the eastern Fennoscandian Shield includes three tectonic provinces, Kola, Karelia and Belomoria, that were formed by the Paleoarchean and Mesoarchean microcontinents. Traces of Mesoarchean tonalite-trondhjemite-granodiorite (TTG)-type early crust were documented in all of the most ancient units of the Kola-Karelia continent. Ancient crust was revealed and dated in the Ranua and Iisalmi microcontinents, 3.5-3.4 Ga; Vodlozero and Khetolambina microcontinents, 3.25-3.15 Ga; Kuhmo-Segozero microcontinent, 3.0 Ga; Murmansk and Inari-Kola microcontinents, 2.93 Ga; and Kianta microcontinent, 2.83-2.81 Ga. In the older (>3.0 Ga) tectonic units and microcontinents, the ancient crust was possibly formed in brief bursts of endogenic activity. In younger microcontinents (3.0-2.93 Ga), these processes could continue until 2.8 and even 2.72 Ga. The tectonic settings in which early TTG crust has been produced are largely uncertain. The primary melt glassy inclusions with a glass phase in cores of prismatic zircon crystals from TTG gneisses provide evidence for the volcanic origin of gneiss protolith. Suggested genetic modeling of TTG-type complexes assumes that felsic K-Na melts with positive Eu anomaly are a product of dry high-temperature partial melting of the previously formed mafic-to-felsic crustal rocks and/or thick older TTG crust. Positive Eu anomaly in the eutectic is directly related to the predominance of plagioclase and K-feldspar in the melt. TTG-type crust melted to produce granitegranodiorite (GG) rocks. Earliest microcontinents are separated by Mesoarchean greenstone belts (mainly 3.05-2.85 Ga, in some cases up to 2.75 Ga), which are fragments of paleo-islandarc systems accreted to their margins: the Kolmozero-Voronya, Central Belomorian, Vedlozero-Segozero, Sumozero-Kenozero, and Tipasjärvi-Kuhmo-Suomussalmi belts; and the mature island arcs (microcontinents): Khetolambina and Kovdozero. These structural units are characterized by significant extent, close to ...