MAGMATIC SYSTEMS OF THE EARLY PALEOPROTEROZOIC BALTIC LARGE IGNEOUS PROVINCE OF SILICEOUS HIGH-MAGNESIUM (BONINITE-LIKE) SERIES
E.V. Sharkov, K.A. Evseeva, I.S. Krasivskaya, amd A.V. Chistyakov
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry,
Russian Academy of Sciences, 35 Staromonetny per., Moscow, 119017, Russia
Keywords: Siliceous high-Mg series, Early Paleoproterozoic, Baltic Shield, large igneous province, magmatic system
Pages: 952-965
Abstract
The Early Paleoproterozoic (2.5-2.3 Ga) Baltic large igneous province (BLIP) of siliceous high-magnesium series (SHMS) is localized in the eastern Baltic Shield. Within the Kola and Karelian cratons, the BLIP is made up of volcanics (from low-Ti picrites and basalts through andesites to dacites and rhyolites) in rift structures, gabbronorite dike swarms, and large layered mafic-ultramafic intrusions. Small synkinematic mafic-ultramafic intrusions are abundant in the Belomorian mobile belt. All this suggests the existence of mantle superplume beneath the region at that time. The major difference of the BLIP from Phanerozoic large igneous provinces is the composition of magmatic melts: In the BLIP, they were close in geochemistry to subduction-related magmas but were generated in within-plate environment. This suggests that the SHMS magmas were generated as a result of the melting of highly depleted mantle source and the subsequent large-scale assimilation of the lower-crust matter by primary mantle-derived high-temperature magmas during their ascent to the surface. Magmatic systems of the BLIP include four activity levels: (1) head of local plumes, where primary mantle-derived melts were generated; (2) lower crust, where mantle-derived magmas were contaminated by crustal matter and transformed into SHMS magmas; (3) upper crust, where transitional magma chambers (preserved as large layered intrusions) were localized; and (4) volcanic plateaus at the surface and subvolcanic sills beneath them.
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