E3S Web Conf.
Volume 98, 201916th International Symposium on Water-Rock Interaction (WRI-16) and 13th International Symposium on Applied Isotope Geochemistry (1st IAGC International Conference)
|Number of page(s)||5|
|Section||Modeling of Hydrogeochemical and Ore Formation Processes|
|Published online||07 June 2019|
Layered Nb-REE ores in the Tomtor Complex (Arctic Siberia): Formation conditions
VS Sobolev Institute of Geology and Mineralogy SB RAS, pr. Akademika Koptyuga 3, 630090, Novosibirsk
2 A.A. Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, pr. Akademika Koptyuga 3, 630090, Novosibirsk
3 Research Geological Enterprise (NIGP), Alrosa PJSC, Chernyshevskoye Highway 16, 678170, Mirny, Sakha (Yakutia)
* Corresponding author: firstname.lastname@example.org
We study a unique deposit of Nb-REE ores that occur as three orebodies overlying weathered rocks of the Tomtor ultramafic alkaline-carbonatite complex in the northern Sakha Republic (Yakutia). The formation conditions of the rich Tomtor ores remain poorly constrained. Our hypothesis is that these ores, composed of detrital and authigenic minerals, were deposited in a hydrothermal lake. The Eh-pH parameters of water are reconstructed from REE distribution in ores and in monazite, with reference to results of thermodynamic calculations. The stability fields of hydrous Ce, La, and Nd phosphates in the Pourbaix diagrams are proximal in a region within a small range of pH (4-6) and Eh (-0.25 -+0.25 V). Monazite apparently formed by dehydration of the precursor phase of hydrous REE phosphate. This inference is supported by coexistence of Fe3+ and Fe2+ minerals.
© The Authors, published by EDP Sciences, 2019
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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