Some mineralogo-geochemical aspects of outlooks of complex
use of ores from deposits of U-Na formations of Ukraine.
Melnichenko B. *, Bondarenko S. **, Siomka V.
**, Grinchenko O. ***, Ivanov B. ****
* Institute of geochemistry of the environment,
Kiev, Ukraine; ** Institute of
geochemistry, mineralogy and ore formation of M.P.Semenenko,š Kiev, Ukraine; *** Kiev national
Taras Shevchenko university,š Kiev, Ukraine; **** GE
«Kirovgeology», SPE -46, Kiev, Ukraine.
Many uranium-ore formations of the world are often accompanied by rather
considerable concentrations of different useful element which can be
additionally extracted in the course of ore processing. Practically each
uranium-ore formation is characterized by the presence of particular complex of
colour, rare and noble metals which determine typical geochemical features of
this formation and in turn indicate peculiarities of its geological evolution. Proterozoic
deposits of uranium ore of Ukraine, that is genetically related to
sodium-uranium (albitite) formation of hydrothermal-metasomatic deposits, are
not an exception. Most uranium ore deposits and manifestations of this type
contain high concentrations of scandium, rare-earth elements, vanadium and
silver. Unlike geochemical and mineralogical features of scandium and
rare-earth elements that have been thoroughly studied on the Zheltorechenka
uranium deposit (Tarchanov 1991, Belevtsev, 1995) the behaviour of V and Ag are
not widely discussed in geological literature.
Deposits of U-Na
formation are widely distributed in the central part of the Ukrainian Shield,
mainly within Ingul'sk geoblock. Here four uranium-ore regions are outlined known
as Central (Vatutinka deposit), Novoukrainka (Novokonstantinovka deposit),
Kirovograd (Severinkovka, Michurinka deposits) and Krivorozhsk-Kremenchug
(Zheltorechena, Pervomaisk deposits) regions. All the uranium deposits are of
the same age and were formed in the course of paleo-proterozoic (1,8 - 1.7
billion years) activization of more ancient granito-gneissic substrate. But
till now there are no any widely accepted idea about the nature and conditions
of their formation. Some spatial and age relations established between the
process of ore mineralization and certain rock complexes or structural blocks
have rather contradictory nature. That fact testifies to it, that the processes
of ore-forming alkaline-sodic metasomatism developed practically on all
varieties of rocks from granitoids, migmatites, gneises to ferruginous
quartzites and carbonate rocks. Besides this the composition and geochemical
features of the uranium ores are practically similar for all the deposits of
the central part of the Ukrainian Shield. Sodic metasomatites are represented
by chlorite-epidote, riebeckite, riebeckite-aegirine, aegirine,
andradite-diopside, hydromica-phlogopite, carbonate-hematite albitites. Uranium
mineralization is represented by brannerite, uraninite and some minerals formed
as a result of metasomatic alteration of primary minerals. It is combination of
the primary hypogenic and different hypergene mineralizations that caused complex
mineralogic and geochemical zonation typical of many uranium deposits. But at the same time V and Ag were found
present at different content in ores of practically all the urainium deposits.
Vanadium. There are no any vanadium deposits found in
Ukraine.
The reliable evaluation of possible accompanying
extraction of vanadium from ores of albitite type have not been
performed yet. But the probable needs for this element on the nearest period
(till 2010) are estimated to be about 1000-1700 tons per year. Multiple
geochemical data on uranium deposits of the Inlul's geoblock indicate constant
presence of the vanadium directly in ores ores or in near-ore altered rocks
(Melnichnko, 1994). Some ore sites of uranium deposits of Zheltorechenka group
show high vanadium contents that reach up to 1 %, with ordinary values varying from
0,05 to 0,3 %. Similar values were found on similar uranium deposits of the
Kirovograd and Novoukrainka groups.
Preliminary geochemical and mineralogical investigations carried out by
us on the Vatutinka deposit have shown, that vanadium is constantly present
both in rich and poor ores with average contents of 0,02 to 0,07 %. It is also
found, that vanadium show high concentration only in some typomorphic minerals found
in uranium ores. (see Table. 1).
Mineral |
Content of V2O3 šin mineral (%) |
Mineral in ores (%) |
Number of analysis |
Aegirine |
0,10-0,49 (0,19) |
5-20 |
12 |
Riebeckite |
0.03 -0,32 |
1-10 |
8 |
Sphene |
0,34-0,82 (0,54) |
0,3 -3 |
12 |
Magnetite + hematite |
0,15-0,90 (0,40) |
0,2- 3 |
10 |
Brannerite |
0,1-2,85 (1,03) |
0,00-1 |
24 |
Davidite |
0,25- 4,10 (1,60) |
0,00-0,1 |
9 |
Lead titanates |
0,40-2,75 (1,20) |
0,00-0,1 |
7 |
Vanadium
forms its own minerals, such as óe-Wakefildite (CeVO4) with 18 % of V2O3,
for which identification additional detailed investigations are
need to be carried out. Simple calculations allow to draw some conclusions. If in the course of
separation of uranium ores the fraction of vanadium
bearing minerals averages 5-20 % it means, that total contents of V2O3
under the optimistical scenario can reach 0,15-0,25 %. It is not excluded, that
contents of vanadium are considerably high on the other uranium deposits and
therefore the importance of this problem is much higher.
Silver. This element was out of much attention for long period of time, though
the facts of some silver specialisation of sodic metasomatites were established
on several deposits of the Krivorozhsk-Kremenchug belt where some intervals
with high silver content of more than 1 % have been found (Belevtsev J.N.,
1995). Recently the ore
body with high silver concentrations were oulined within foot wall of the major
uranium-ore zone of the Vatutinka deposit. Spectral analysis data have shown
high silver contents of 300 g\t on five-meter interval of silicified albitites
in the northern part and 70 g\t on 4,8 m interval of silicified granites in the
central part of the Vatutinka deposit. Silver was found as native phase and enter
the compositon of matildite AgBiS2. Among associated minerals the
galena, pyrite, marcasite, chalcopyrite, sphalerite as well as minerals of
uranium, titanium and barium were found as predominate phases.
High
concentrations of vanadium and silver in ores of U-Na formation are
supplemented byš geochemical spectrum of
already known useful elements (TRE, Sc, Zr) which concentration is genetically
associated with processes of formation of alkaline metasomatites. This fact
testifies to unique feature of this formation and some peculiarities in behaviour
of the specific elements (including vanadium and silver) in
hydrothermal-metasomatic processes. Possible evaluation of possible extraction
of silver and vanadium during the processing of uranium ores might be
interpreted as urgent problem which resolved by specialists - technologist.
References:
Belevtsev Ya.N., Koval V.B, et. al. Genetic types and patterns of
distribution of uranium deposits of Ukraine. -š
Kiev, Naukova dumka. 1995
Tarhanov A.V., Kudlaev A.R., Petrin A.V., Kozyr'kov V.D. Zheltorechenska
vanadium-scandium deposit // Geology of ore deposits - 1991 - 33, ¹ 6 - P.
50-56.