Origin of the Middle Paleoproterozoic Tiksheozero Ultramafic-Alkaline-Carbonatite Complex, NE Fennoscandian Shield: Evidence from Geochemical and Isotope Sr-Nd-Hf-Pb-Os Data

This article reports new geochemical, Sr-Nd-Hf-Pb and Re-Os data on the rocks of Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic-alkaline-carbonatite complex confined to northeastern margin Karelian Craton. We focus poorly studied silicate rocks. Based petrographic geochemical research, are subdivided into two groups: an ultramafic-mafic series depleted in REE, other incompatible elements alkaline enriched these elements. Isotope studies showed that all have juvenile isotope signatures were likely derived from a primitive OIB-type mantle source with possible contributions subcontinental lithospheric (SCLM). Insignificant crustal contamination is recorded by Pb Os isotopic compositions. The element enrichment depletion mildly allowance for insignificant confirm their derivation different primary melts. However, narrow range Sr, Nd, Hf, compositions compact clusters 207Pb/204Pb-206Pb/204Pb, Nd-87Sr/86Sr Hf-Nd diagrams indicate origination common source. A model subsequent two-stage melting being most consistent this complex.