First Th-U-Pb single zircon dating of metasomatites from the Belomorian mobile belt

Rare-earth and rare elements in zircons of different ages from corundum-bearing rocks of Khitoostrov (Northern Karelia)

“…CL images demonstrate a dark gray outer rim, often with a sectorial structure. The 207 Pb/ 206 Pb age of the dark gray outer rim (1887 ± 16 Ma) closely corresponds with the ages of zircon rims from corundum bearing rocks of Khitoostrov Island [7]. The Th/U ratio with in the rims of both types is low (<0.06, table), which is typical for meta morphic zircons [8].…”

“…Zircons from corundum bearing rocks. The results of zircon dating in corundum bearing rocks provide evi dence for the possible presence of cores with an age of >2.8 Ga [6,7] corresponding to the age interval of the formation of the Chupa Series protolith. However, most of the inherited grains were formed at the early stages of granulitic metamorphism.…”

Oxygen isotopic composition as an indicator of ruby and sapphire origin: A review of Russian occurrences

“…As shown by numerous previous studies, this mineral resulted from high-grade metamorphism at 1.9-1.8 Ga (Serebryakov et al, 2007;Vysotskii et al, 2011;Vysotskiy et al, 2014;Bindeman and Serebryakov, 2011). The protolith consists of Archean and Paleoproterozoic volcano-sedimentary rocks that were totally altered to the low-temperature aluminous metasomatite under the influence of glacial water at 2.2-2.4 Ga, during the Siderian-Rhyacian (Paleoproterozoic) glaciation Bindeman et al, 2014).…”

“…Some authors believe that all the corundum occurrences in the region are structurally related to the nappes, being situated near the contact of felsic and mafic rocks (Terekhov and Levitskii, 1991;Levitskii, 2005;Terekhov, 2007). Others, however, suggest an association of the corundum-bearing rocks with zones of strike-slip displacement, where they form lens-and bed shape bodies resulted from high-pressure alkaline metasomatism (Serebryakov and Aristov, 2004;Serebryakov et al, 2007). In any case, the corundum-bearing metamorphic units consist of high-pressure amphibolite and less commonly granulite, with a protolith with ages of between 3 and 2.5 Ga.…”

“…The ruby and sapphire mineralization appeared between 1.9 and 1.8 Ga, during the collision-related metamorphism. An intermediate event of mafic magmatism is reflected by zircon ages between 2.4 and 2.2 Ga, a time that corresponds to the Siderian-Rhyacian glaciation (Bibikova et al, 2004;Serebryakov et al, 2007;Vysotskii et al, 2011;Bindeman et al, 2014).…”