Age, evolution and regional setting of the Palaeoproterozoic Umba igneous suite in the Kolvitsa–Umba zone, Kola Peninsula: constraints from new geological, geochemical and U–Pb zircon data

Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

“…WNag, west Nagssugtoqidian belt; ENag, east Nagssugtoqidian belt; 1, Boothia Somerset granulite terrane and Taltson Thelon orogen; 2, Kolvitsa Umba zone. Kozlova et al (1991) and Alexejev (1997) reported Grt Opx Sil association and high Al Opx from the Umba block of the Kolvitsa Umba zone in Kola Peninsula (in Glebovitsky et al, 2001). The Opx Sil association is considerd to be formed by the replacement of Mg Grt − Al Opx during cooling at constant pressure.…”

“…Another Grt Spl Qtz association in other lithoplogy gives UHT condition of >900°C. In addition, Glebovitsky et al (2001) described decompression textures of Crd Opx and Opx Spr Crd rims around Grt, and Crd moat around Opx Sil intergrowths. Critical textural relationships, mineral compositions and additional coexisting phases are unclear from available literature, although it seems reasonable to suppose that the UHT metamorphism of Umba block experienced IBC path at early stage, and followed by ITD at 850 900°C.…”

“…Critical textural relationships, mineral compositions and additional coexisting phases are unclear from available literature, although it seems reasonable to suppose that the UHT metamorphism of Umba block experienced IBC path at early stage, and followed by ITD at 850 900°C. Conventional U Pb zircon dating of the porphyritic charnokite which is exposed adjacent to the UHT rocks, yield discordant age of 1.91 1.97 Ga, and was interpreted as an age of their emplacement (Glebovitsky et al 2001). The charnokite endebite suite is considered to have formed due to subduction in an island arc setting (Glebovitsky et al 2001).…”

“…Conventional U Pb zircon dating of the porphyritic charnokite which is exposed adjacent to the UHT rocks, yield discordant age of 1.91 1.97 Ga, and was interpreted as an age of their emplacement (Glebovitsky et al 2001). The charnokite endebite suite is considered to have formed due to subduction in an island arc setting (Glebovitsky et al 2001). Another 1.91 Ga high grade metamorphic event is estimated from the Kolvista belt (Frisch et al 1995).…”

Charnockitization of feldspar-free orthopyroxene-clinopyroxene-phlogopite metaultramafite in the lapland granulite belt, southern Kola Peninsula: Compositional trends of rocks and minerals, P-T parameters, and fluid regime

“…The age of the single episode of granulite metamor phism of all rocks in the Lapland Belt and the age of the synmetamorphic anatectic charnockite and ender bite is Svecofennian, 1912-1925Ma (Bibikova et al, 1993Bogdanova et al, 1996;Bushmin et al, 2009;Glebovitsky et al, 2001). The protolith of the granu lites is much older: the dacite, which is thought to have been the protolith of the acid Opx Bt ± Grt Kfs Pl Qz gneisses in the Por'ya Bay nappe, was dated at the Meso to Neoarchean (2799 ± 4 Ma), and the age of the basite protolith of the Opx Cpx ± Grt ± Hbl ± Bt Pl mafic granulites was estimated as Paleoproterozoic (2315 ± 23 Ma) (Korikovsky et al, 2014).…”