ISSN 1819-7140, Russian Journal of Pacific Geology, 2017, Vol. 11, No. 4, pp. 297–307. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.A. Cherepanov, N.V. Berdnikov, A.V. Shtareva, V.O. Krutikova, 2017, published in Tikhookeanskaya Geologiya, 2017, Vol. 36, No. 4, pp. 65–76.
Formation Conditions and Rare-Earth Mineralization of Riphean
Carbonaceous Shales of the Upper Nyatygran Subformation,
Russian Far East
A. A. Cherepanov, N. V. Berdnikov*, A. V. Shtareva, and V. O. Krutikova
Kosygin Institute of Tectonics and Geophysics, Far East Branch, Russian Academy of Sciences,
ul. Kim Yu Chena 65, Khabarovsk, 680000 Russia
Received April 27, 2016
Abstract⎯Graphitic and graphite varieties are distinguished in the carbonaceous shales of the Riphean
Upper Nyatygran Subformation in the Melgin fragment of the Turan block, eastern Bureya Massif. The pro-
tolith of the graphitic shales had a terrigenous source related to island-arc volcanism. Pelagic sedimentation
played a great role in the formation of the protolith of the graphite shale. These rocks were juxtaposed during
the formation of an accretionary wedge on an active continental margin. The carbonaceous shales are char-
acterized by high (>600 ppm) REE + Y contents, especially in the zones of brecciation and hydrothermal
reworking. Detrial monazite enriched in LREE and MREE is the main carrier of REE mineralization in the
graphitic shales. The main REE carrier in the graphite shales is REE phosphate (xenotime) formed during
lithogenesis of sediments. Preliminary experimental treatment of the graphite shales of the Upper Nyatygran
Subformation by ammonium hydrofluoride shows their potential for economic extraction of REE and Y.
Keywords: carbonaceous shales, rare-earth elements, Upper Nyatygran Subformation, Bureya Massif, Rus-
sian Far East
Rare-earth elements (REE) are one of the scarcest
strategic materials, which are of great importance for
economic growth of developed countries. Almost 95%
of all REE entering the global market are extracted
and processed in China, whereas their production in
Russia accounts for less than 2%. Therefore, the
development of the raw material base for REE
extraction in Russia, including the Russian Far East, is
an urgent problem.
At present, REE are mainly mined from iron and
apatite ores related to carbonatites and associated
supergene zones (Bayan-Obo, China; Kovdor, Tom-
tor, Sakha-Yakutia, Russia). Small amounts of REE
are extracted from heavy sand, as well as from granite
and alkaline pegmatites. Some promising sources
include the Cu–U–Au ores of the Olympic Dam
deposit (Australia), oceanic sediments, and coals.
Economically important REE minerals are monazite,
xenotime, churchite, bastnaesite, parisite, yttrosyn-
chisite, fergusonite, euxenite, gagarinite, and yttroflu-
orite. The total REE content reaches 490–2000 ppm
in nepheline syenites  and 10–570 ppm in oolitic
iron ores , while carbonatite-related iron ores con-
tain up to 5–12% R
. Correspondingly, exploration
for REE deposits is aimed at discovering and studying
these rock types.
Our preliminary studies in cooperation with the
geologists of the Melgin team of FGUP Dal’geofizika
(Arapov, 2016) revealed high (>600 ppm) REE + Y
contents in the carbonaceous shales of the Upper
Nyatygran Subformation of the Melgin fragment of
the Turan Block in the eastern Bureya Massif; these
contents exceed those found in the ores of the eco-
nomic apatite deposits of the Kola Peninsula. As
shown in [7, 8], the treatment of graphite shales by
ammonium hydrofluoride provides an increase of two
orders of magnitude in the REE concentrations in
them, resulting in an economically significant output.
Preliminary experiments carried out using a similar
technique found that the graphite shales of the Upper
Nyatygran Subformation are promising for the eco-
nomic extraction of rare-earth elements and yttrium.
A comprehensive study of these shales may lead to the
recognition of a new type of mineralization, which is
able to form large-scale REE deposits in the carbona-
ceous metasedimentary rocks that are widespread in
the Russian Far East.
In this work, the mineralogical and petrological
study of the rocks of the Upper Nyatygran Subforma-
tion was undertaken to determine the geological con-