Modeling Changes in the Composition of River Water with Discharged Wastewater: A Case Study in NW Russia

The technogenic impact of the development of the Lomonosov diamond deposit is associated with the discharge of quarry and drainage water into the river, which has a special conservation status. Earlier studies on the composition of bottom sediments showed that there are signs of increased accumulation of heavy metals and radionuclides at wastewater discharge sites. The purpose of this work was to predict changes in the composition of surface water and bottom sediment in the river during the further development of mining operations with brackish and salty water captured by drainage systems, the presence of which was established in the zone of their future influence. For this, a simulation of changes in the composition of the water in the river was carried out using the GEOCHEQ software package by minimizing the free energy of the system using a convex simplex algorithm. It was found that the maximum salinity of surface water can reach 1.51 g/L. In this case, the MPC of Cl−, Na+, SO42−, Mg2+, Sr, V, and U can be exceeded for fishery watercourses. The genetic basis of the accumulation of these components in solutions for mixing was considered. According to the calculations, when about 5000 m3/h of drainage water is discharge d into the river, the mass of precipitated chemical elements will be 56–191 t/h, including up to 2.1 t/h of iron; therefore, accumulation in the discharge zone must be controlled.

Radon Over Kimberlite Pipes: Estimation of the Emanation Properties of Rocks (Lomonosov Diamond Deposit, NW Russia)

In this paper, using the example of the Lomonosov diamond deposit, experimental studies of rocks were carried out to assess the main radiation and physical factors affecting the formation of the radon field over the kimberlite pipes of the Arkhangelsk diamondiferous province. For various types of rocks, represented by vent kimberlites, tuffaceous-sedimentary rocks of the crater and enclosing and overlying sediments, the following were studied: porosity, density, activity of radium-226, activity of radon in a free state, level of radon production, and emanation coefficient. The research results showed that the greatest amount of radon in a free state is produced by rocks of the near-pipe space, represented by the enclosing Vendian V2 deposits and characterized by high values of the emanation coefficient, radium activity, radon production level and porosity. This fact is associated with the structural and geological features of the near-pipe space, which was exposed to the impact of kimberlite magma on the host rocks. The lowest values of these parameters are characteristic of the kimberlites of the vent facies, which limits the formation of free radon in the body of the pipe. The results of the experimental studies create prospects for the development of emanation methods for searching for kimberlite pipes in the conditions of the Arkhangelsk diamondiferous province.

Epigenetic aragonite in a sheared lherzolite xenolith from the Udachnaya kimberlite pipe

<p>Here we report the first finding of the high-pressure polymorph of calcium carbonate (aragonite) in the interstitial space of a sheared lherzolite xenolith from kimberlites of the Udachanaya diamond deposit (Siberian craton, Russia). Xenoliths with a sheared texture are the deepest mantle rocks sampled by kimberlite magma from 180-230 km depth. According to experimental data, aragonite is the high-pressure polymorph of calcium carbonate, which is stable at upper mantle pressure and temperature. Thereby aragonite is used as a reliable geobarometer in studies of magmatic and ultrahigh-pressure metamorphic rocks.<br>Aragonite was determined by Raman spectroscopy study. The Raman bands at 208 cm<sup>-1</sup>, 702-706 cm<sup>-1</sup> and 1462 cm<sup>-1</sup> are the identification features of aragonite. Chemical analyses of aragonite were obtained by scanning electron microscope with an energy dispersive system. Some analyses were verified by electron microprobe as well. The concentration of SrO in aragonite ranges from 0.5 to 8.8 wt.%. Aragonite has a Na<sub>2</sub>O concentration of 0.1-1.1 wt.%.<br>Aragonite (up to 100 µm) is the most common subordinate mineral from the interstitial space of this xenolith. It occupies on average 70 vol.% of the interstitial space. Aragonite grains consist of three chemically distinct zones. The first zone (core) is characterized by a low content of SrO (<1.5 wt.%) and low Mg# (~15). The second zone has roughly the same SrO but noticeably higher Mg# (~50). The third zone (rim) contains much higher concentration of SrO (up to 8.81 wt.%) and high Mg# (~50).<br>Sheared peridotite are located in the lithospheric mantle significantly below the aragonite-calcite equilibrium line. In particular, the investigated peridotite equilibrated at 1350°С and 69 kbar (~215 km). The presence of zoned aragonite from this peridotite means that this rock has been infiltrated by metasomatic agent. Numerical calculations reveals that such zoning can be preserved for 1 year at 1300°С (~equilibrium temperature of sheared peridotites) and for 10 years at 1000°С (~temperature of kimberlite magma at subsurface conditions). The short preservation time of zoning in aragonite (1-10 years) proves that aragonite could be formed immediately prior to kimberlite magmatism or after the capturing of the xenolith by kimberlite magma. Using adiabats of kimberlite magma and P-T parameters of aragonite stability in the upper mantle, aragonite in the studied sample was formed at the depth range of 80-215 km.<br>As the preservation time of zoning in aragonite is noticeably short (taking into account high temperatures), the best candidate for the role of an agent, which infiltrated the xenolith, is a primitive kimberlite melt of the Udachnaya pipe. The high percentage (70%) of aragonite in the interstitial space of the studied sheared lherzolite xenolith proves that such primitive kimberlite melt had carbonatitic composition. Our results show that not only different silicate-rich melts, but also carbonate or cabonated silicate melts might play a key role in mantle modifications. Carbonate melts are very suitable diamond-forming media and may support the idea of a genetic link between some diamonds and kimberlite magmatism.<br>This study was supported by the Russian Science Foundation (grant No 18-77-10062).</p>

Geology and mineral composition of Zarya kimberlite pipe, western Yakutia

The geological and tectonic settings of new primary low-grade diamond deposit, the Zarya pipe (Alakit-Markhinsky kimberlite field, Yakutian diamond province, Western Yakutia, Russia), are discussed. Data on the geological structure of the diatreme, mineral composition and kimberlite diamond content is presented. The factors determining the vertical and lateral heterogeneity of the mineral-indicative characteristics of kimberlites, diamond assemblage minerals, and diamonds are considered. It is concluded that diamond quality and grades increase with depth.

Women at the dawn of diamond discovery in Siberia or how two women discovered the Siberian diamond province

Exploration for diamonds in the Soviet Union started in the 1940s; however, it was not until the beginning of 1950s that the government acknowledged a strong need for locally mined diamonds. In this paper, based on publications from Russian literature, we recount a story of two female geologists, Larisa Popugaeva and Natalia Sarsadskhih.Natalia was the head of the mineralogical laboratory who implemented a new methodology to search for mineral indicators of primary diamond deposits. Larisa was a young geologist who joined Natalia's team in 1953.The work of these women led to the discovery, in 1954, of the first diamond deposit in the country – the kimberlite pipe ‘Zarnitsa’. In 1954, Natalia was unable to go into the field and, therefore, the discovery was made by Larisa. Credit for this discovery, however, was claimed by the higher officials from the Amakinskaya expedition, one of the largest diamond exploration organizations in the country. Multiple efforts to restore justice did not succeed, with Larisa only being awarded the title of the ‘Discoverer’ in 1970 and Natalia not until 1990. This paper provides a description of Larisa's and Natalia's lives up until the discovery of Zarnitsa, and a few significant events after.