Current state, prospects and problems of the gold mining industry of the Trans-Baikal Territory

The article considers the current state, problems and prospects of gold mining in the Trans-Baikal Territory. There has been an increase in the volume of gold production from ore and placer deposits over the past 5 years. Placer deposits make up a significant part of the total production volume. The reduction of reserves in placers and the decrease in the quality of minerals in them open up new prospects for the extraction of precious metals, namely in ore gold mining. The extraction of placer gold, even with the best existing technologies, remains a sector of high environmental risk, in many settlements there is a gradual decline in the population and the “extinction” of settlements, as well as illegal gold mining is gaining momentum. Neither regional nor federal environmental supervision bodies have the opportunity to resist the destruction and degradation of nature from the extraction of placer gold. In general, this leads to an increase in the negative impact of placer gold mining on natural complexes and socio-economic sustainable development of regions and municipalities on the territory of which this type of activity is carried out, an increase in accumulated environmental damage.

Quantitative characteristics of zooplankton in the rivers of the Upper Amur Basin, exposed to the effects of placer gold mining

Research conducted in June and September 2020 showed that the species composition of rotifers and lower crustaceans in 17 water courses of the Upper Amur Basin, exposed to the effects of placer gold mining, included 43 species. Most of the water courses were researched for the first time. Based on the environmental and geographic assessment, the prevalent species were widespread and eurytopic. Most parts of the rivers were characterised by low quantitative characteristics (0.01–3.77 × 103 ind. m-3 and 0.06–54.64 mg m-3), which was explained by the hygrological conditions and long-term effects of mining in the river beds. A better productivity (up to 39 × 103 ind. m-3 and 228 mg m-3) was registered in the areas of former excavations in the river beds, with slower water exchange and better conditions for the development of zooplankton.

The impact of the placer gold mining in Eastern Transbaikalia (Russia) on the environment components of river valleys in the Amur River basin

Based on the results of the analysis of satellite images and field observations, data on the length of the gold-bearing placers disturbed by the development along a number of main tributaries of the Shilka and Argun rivers are presented, the formed technogenic relief forms are indicated. Depending on the method of development, two types of technogenic landscapes have been identified - the excavation-dump with hydromonitor mining and belt trench-dump when washing with drags. The main directions of research on the assessment of placer gold mining in the natural complexes of river valleys are proposed.

Information and computational GIS for monitoring the natural and technical systems of placer gold deposits

It is known that nowadays one of the main problems of mining is the depletion of reserves. The researchers consider mining waste as a source of replenishment of the resource base. Disputes on the prospects for technogenic raw material processing are becoming especially relevant. The object of research chosen by the authors in this article is the technogenic neoplasms resulting from dredging and hydraulic processing of placer gold. The paper presents the results of assessing the prospects and application of the information technologies, in particular, the analysis of data from remote sensing of the Earth in the design and organization of work to involve technogenic placers in operation. It is shown that these technologies are able to increase the efficiency of work and reduce labor costs at the stage of preliminary study of potential development targets. Technogenic complexes of depleted fields are a significant reserve of the mineral resource base of gold and other precious metals. This paper presents the results of the creation of a method for expert assessment of spatial and volumetric indicators of technogenic complexes of alluvial fields and other landscape objects using remote sensing of the territory and analysis of geological information. The Kerbinsky gold-bearing region of the Khabarovsk Region was chosen as the object of research.

The Internal Structure of Placer Gold of the North-East of the Siberian Platform as a Reliable Search Sign of Primary Sources

Typomorphic features of placer gold are carriers of the most important information necessary for the reconstruction of the history of the formation of placer and ore occurrences of gold and can be used as mineralogical criteria in the search for primary sources of placers. The study of these features is relevant for placer areas with unidentified gold sources, which include the territory of the north-east of the Siberian Platform. The internal structure of native gold is one of the most informative typomorphic features is. We studied the internal gold structures of modern placers and conglomerates of the Early Permian age in the north-east of the Siberian Platform. The purpose of the work: to identify the features of the internal structure of placer gold, depending on the chemical composition and the degree of its transformations, as well as the possibility of their use as a prospecting indicator. Structural etching of native gold was performed using the reagent: HCl + HNO3 + FeCl3 × 6H2O + CrO3 + thiurea + water. As a result of the research, it was found that the well-rounded high-grade gold of modern placers has undergone repeated redeposition through intermediate sources. The discovery of slightly rounded gold with an internal structure without signs of exogenous transformation indicates that it entered the modern alluvium from a nearby primary source. This was a prerequisite for setting up ore gold exploration, resulting in identification of apocarbonate hydrothermal-metasomatic formations with disseminated gold-sulfide mineralization were identified. Thus, the features of the internal structures of placer gold in combination with other typomorphic features are additional indications of determining the sources of formation of gold-bearing placers.

Typomorphism of Placer Gold and Prerequisites for the Discovery of Gold Ore Occurrences in the Southern Part of the Lena-Anabar Trough (North-East of The Siberian Platform)

The article examines the results of exploratory work carried out in the southern part of the Lena-Anabar trough in the north-eastern part of the Siberian platform. Alluvial deposits of the Polovinnaya river, which belongs to the Uele-Udzhinsky placer cluster, were sampled for predictive assessment of commercial prospects for placer occurrences of gold. The mineralogical-geochemical features of the placer gold were studied in order to identify potential primary sources. It is proved that the Mesozoic and Cenozoic deposits are the main sources of gold. Its typomorphic features are small size (-0.5 mm), toroidal and flake shape, shagreen surface with casts of pressing of the minerals, and high fineness (950-999 %). The internal structures of gold particles are represented by thick high-grade shells, translation lines and high-grade intergranular veinlets. Along with this, the discovery of the autochtonous gold of ore habit in the studied gold area suggested the presence of an additional primary source. Very small size (-0.2 mm) and angular-lumpy shapes of the individuals, almost unrounded surface and low fineness are typical features of slightly altered gold. The discovery of small (3-4mm) fragments of hydrothermal-metasomatic rocks in the alluvium of the Polovinnaya river confirms the above assumption. The epigenetic mineral composition of these fragments is represented by pyrite, potassium feldspar, fluorapatite, and quartz. Micro-X-ray spectral analysis determined the smallest (first microns) mineral phases of native gold, argentite, galena, sphalerite and greenockite in them. It is worth noting that the described fragments are quite fragile, and they are destroyed with a slight impact with a steel needle. The fragility of these fragments indicates the close proximity of the rewashed ore occurrences. In addition, increased gold content in small classes of heavy concentrate material of small-volume samples was determined according to atomic absorption analysis. All this together is a prerequisite for the discovery of ore occurrences with finely-dispersed and fine gold. It is assumed that the ore occurrences can be localized in the Anabar-Eekit fault zone, which extends parallel to the Pronchishchev ridge, through the Anabar-Olenek trough, to the Sololiy uplift of the Olenek arch. In the area of the Olenek arch, this zone is associated with superimposed gold-bearing low-temperature hydrothermal mineralization, expressed by K-feldspathization and sulfidization of the Permian deposits.

Aldan-Vilyui ore-placer gold-bearing province, Russia

Analysis of materials of the State Geological Map 1 : 1 000 000 (3rd generation) for the southern Sakha–Yakutiya territory in the course of compilation of the Minerogenic forecast map of the Russian Federation and its continental shelf, 1 : 2 500 000, and of the Map of the distribution regularities and forecast for porphyry goldcopper, large-tonnage black-shale gold, and epithermal gold deposits of the Russian Federation, 1 : 2 500 000, has allowed the authors to substantiate distinguishing the new Aldan-Vilyui ore-placer gold-bearing province with a total area of 450 000 km2 in the basins of the Lena, Aldan, and Vilyui rivers. The authors estimate the metallogenic potential of the province at 5000 t of gold. In the near future, this province may become a new extensive resource base of gold and related elements for the Russian Federation.

Evaluation of the contributions of gold derived from hypogene, supergene and surficial processes in the formation of placer gold deposits

Placer gold particles have traditionally been considered as either detrital products of weathering or authigenic minerals growing within placers. Recent advances in understanding of gold chemistry/bio-geochemistry demonstrate that gold growth in specific environments is plausible, but opinions differ on the importance of ‘new’ gold in the overall placer inventory. Here we draw upon visual inspection over 40,000 polished gold particle sections from locations worldwide to evaluate the implications of gold alloy composition and particle heterogeneity in determining the contributions of detrital and authigenic gold to fluvial placers. We conclude i. the detrital model of placer gold formation is widespread and demonstrable, ii. supergene gold may be a locally important constituent of fluvial placers, iii. gold-rich rims on placer gold particles comprise two distinct components: a surface micron-scale addition of pure Au and a tens- of- micron- scale inner rim formed by Ag depletion, iv. the importance to placer inventories of gold particle formation and modification by biogenic processes is considerably overstated.

The native gold extracted in the Amur Region for 150 years

Data on gold production history and typomorphic features of native gold from the Amur province are provided. It is shown that about 1,116 t of primarily placer gold was extracted for 150 years, with primary gold accounting for 23,8 %. Placer gold sample distribution is unimodal with a maximum ranging within 850–925 ‰. Mercury prevails in microimpurities, its content in some clusters reaches the first percentage points. In terms of composition impurities, placer gold corresponds to gold from fields and occurences of gold-quartz and gold-sulfide-quartz formations. Low-fineness gold, (799–700 ‰) less common in placers, resulted from destruction of gold-silver unit sources while that of average fineness (800–900 ‰) was a result of the same process related to gold-polymetallic and gold-sulfide units. Gold-copper-molybdenum porphyry deposits do not form placers. The prospects of primary and placer gold production in the Amur region are defined.

JUSTIFICATION OF UNDERGROUND TECHNOLOGY OF PLACER GOLD MINING IN THE FAR NORTH

A significant part of placer mineral deposits in the Arctic zone of Russia urges the need for its strategic development in the near and medium term. Applicably to underground mining of placer gold deposits, the problems of safe and efficient extraction of minerals by mines in the conditions of the Far North are considered. A substantiated choice of uncovering and mining technology for gold-bearing sand strata is proposed in the context of rational planning of mining operations associated with minimizing material and labor costs for uncovering and extracting a part of the deposit, as well as completeness of reserves depletion during the operational period. Safe parameters of structural elements of room mining systems have been determined by geomechanical assessments. Methods for additional support of the roof of mined-out rooms are proposed. The indicators of losses and dilution of gold-bearing sands in accordance with the sources of their formation were determined by the graphoanalytical method.