Layered Nb-REE ores in the Tomtor Complex (Arctic Siberia): Formation conditions Elena Lazareva, Sergey Zhmodik, Nikolay Dobretsov, Alexander Tolstov, Nikolay Karmanov, Andrey Dar’in and Ivan Kirichenko E3S Web Conf., 98 (2019) 05011 Published online: 07 June 2019 DOI: 10.1051/e3sconf/20199805011