Redistribution of radioactive mine wastes by slushﬂows and other processes in small mountain river basin in Russian Subarctics

Гаранкина, Е.В.; Беляев, В.Р.; иванов, м.; романенко, ф.; Гуринов, А.Л.; Туляков, Е.Д.; Кузьменкова, Н.В.

Авторы: Гаранкина Е.В., Беляев В.Р., иванов максим, романенко федор, Гуринов А.Л., Туляков Е.Д., Кузьменкова Н.В.
Сборник: European Geosciences Union General Assembly 2017
Серия: Geophysical Research Abstracts
Том: 19
Тезисы
Год издания: 2017
Издательство: Copernicus GmbH on behalf of the European Geosciences Union
Местоположение издательства: Germany
Аннотация: The Khibiny Mountains located in central part of the Kola Peninsula (Northern European Russia) are characterized by harsh climatic conditions and frequent occurrence of hazardous or even catastrophic processes. Most widespreadofthosearesnowavalanchestakingplaceeveryyearandslushﬂowswithaveragerecurrenceintervalof about 10 years. The latter represent speciﬁc type of hyperconcentrated gravitational ﬂow of oversaturated mixture of snow and water (20 to 70%) with relatively low sediment concentration (up to 10-15%). Most often slushﬂows form during spring snowmelt in small mountainous basins (in most cases up to 3-6 km2) with thick snowpacks or snow dams caused by avalanches in stream channels. Typically observed volumes vary in a range of 20000-40000 m3, while rare catastrophic events can reach 200000-500000 m3. Kinetic energy of frontal wave that can be up to several meters high and concentrates most of the largest debris is most likely lower than that of typical debris ﬂowofsimilarsize,mainlybecauseofmuchlowerslushﬂowdensity(900-1200kgm−3).Nevertheless,rareoccasional measurements of front wave velocity gave dramatic values of 20-25 m s−1 maximum. Such characteristics combined with unpredictable rapid formation make slushﬂows deﬁnitely hazardous processes that can cause serious damage to industrial and residential infrastructure as well as injuries or causalities to people. For example, the Khibiny Mountains have at least 200 locations where formation of slushﬂows was detected at least ones over the last 50 years. Widespread constructions and communications associated with intensive exploration of mineral resources as well as growing interest to the area as touristic attraction for skiing and other wintertime activities make the Khibiny Mountains an area of serious geomorphic hazards associated with slushﬂows. In this particular study, we considered the Hackman basin where heavy debris ﬂows occur at least ones per several decades. One of the unique features of that basin is that there was radioactive ore mine active in late 1930s on one of the steep valley sides. The mine was active only for several years as the production of radioactive minerals appeared to be much lower than expected. However, mine wastes are still remaining there as scree slopes on right valley side in its middle reach under several mine entrances. Colluvial material on these screes is highly enriched by several natural radionuclides including members of the 232Th decay chain. We have made an attempt to use this feature for ﬁngerprinting sediment redistribution along the valley by slushﬂows and ﬂuvial processes. Results of gammaspectrometric analysis of ﬁner sediment fractions from different geomorphic settings within the Hackman basin have shown that there is a systematic non-uniform spatial distribution of 232Th decay chain natural radionuclides closely related to its geological background and geomorphological structure. It proves that natural lithogenic radionuclide content in clastic sediments can be used for ﬁngerprinting of slushﬂows debris sources and sinks and, possibly for distinguishing between in situ slushﬂow deposits and those partly reworked by later ﬂuvial activities. The study was funded by RFBR Project №17-05-00630 A.
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