Open AccessA tectonic remnant of the mesoarchean oceanic lithosphere in the Belomorian Province, Fennoscandian Shield
Author(s) -
А. И. Слабунов,
A. A. Shchipansky,
В. А. Степанов,
I. I. Babarina
Publication year - 2019
Publication title -
geotektonika
Language(s) - English
Resource type - Journals
ISSN - 0016-853X
DOI - 10.31857/s0016-853x2019246-71
Subject(s) - geology , mafic , peridotite , geochemistry , lithosphere , subduction , oceanic crust , crust , continental crust , mantle (geology) , partial melting , petrology , craton , earth science , tectonics , paleontology
The results of the detailed geological mapping, coupled with the isotope-geochemical study of a metamorphosed mafic-ultramafic complex known as the Central Belomorian Belt located in the Belomorian province of the Fennoscandian Shield, are reported.
The protholith of the complex is ~ 2.9—3.1 Ga old. It has been subjected to two 2.87 and 1.87 Ga structural-metamorphic reworking. This complex is one of the oldest in the Belomorian Province.
We present several lines of evidence showing that these lithologies constitute a tectonic remnant of the Mesoarchean oceanic lithosphere, rather than any other mafic-ulramafic complex from the other geodynamic settings. The Central-Belomorian high grade mafic-ultramafics reveal a clear geochemical coherency, which implies their genetic relationships. Their mafic protholiths stem from the partial melting of a mantle peridotite protholith. The petrologic modelling has shown that primary melts were formed in the garnet lherzolite field at a pressure of 3.5–3.8 GPa at ambient mantle potential temperatures of 1520–1550 °С which led to an emergence of ~ 25–30 thick oceanic crust. The available geochemical data suggest that the complex was formed at the initial stage of subduction. It marks the start of early continental crust-forming processes in the Belomorian Province.