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Geological Society, London, Memoirs; 2004; v. 30; p. 75-85;
DOI: 10.1144/GSL.MEM.2004.030.01.08
© 2004 Geological Society of London

Timanide Hinterland

Late Neoproterozoic granitoid magmatism in the basement to the Pechora Basin, NW Russia: geochemical constraints indicate westward subduction beneath NE Baltica

V. Pease1, E. Dovzhikova2, L. Beliakova2 & D. G. Gee3

1 Department of Geology and Geochemistry, Stockholm University, SE-106 91 Sweden, and Laboratory for Isotope Geology, Swedish Natural History Museum, Stockholm, Sweden vicky.pease{at}geo.su.se
2 Timan-Pechora Scientific Research Centre, Pushkina 2, 169400 Ukhta, Russia vicky.pease{at}geo.su.se
3 Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden vicky.pease{at}geo.su.se

A unique collection of deep (up to 4.5 km) drillcores from across the Pechora Basin of NW Russia indicate that the Precambrian basement beneath Palaeozoic sediments mainly comprise Neoproterozoic metasedimentary and magmatic complexes. These Neoproterozoic rocks are variously deformed and metamorphosed. They are intruded by granitoids of latest Neoproterozoic age (557 ± 6 Ma, 95% confidence). The granitoids are variably deformed, metamorphose their country rock, and represent syn- to post-tectonic magmatism. Major element, trace element, and Sm-Nd and Rb-Sr isotopic data indicate that these intrusions represent continental arc magmatism. Their geochemistry indicates assimilation of older crust by a magma derived from a depleted mantle source. We infer that the granitoids were generated by westward subduction of oceanic crust beneath Baltica (present day coordinates) at c. 560 Ma.