Mineralogical, geochemical and isotopic (C, O, Sr) features of the unique high-grade REE-Nb ores from the Tomtor deposit (Arctic Siberia, Russia)Sergey Zhmodik, Elena Lazareva, Nikolay Dobretsov, Viktor Ponomarchuk and Alexander TolstovE3S Web Conf., 98 (2019) 12027DOI: https://doi.org/10.1051/e3sconf/20199812027