Modern Minerals Formation Genesis in Kavalerovsky Tin–Ore District Technogenic System (Primorsky Krai)

: Parameters and conditions of crystallization for the majority of hypergenic and technogenic minerals have not yet been studied, as their determination is often di ﬃ cult due to their imperfect crystalline structure (X-ray amorphous) and formation in polymineral compounds. The article discusses the formation conditions of 20 hypergenic and technogenic minerals from technogenic waters in the mining industrial system of the Kavalerovsky district tin–sulﬁde deposits (Primorsky krai) in Russia. For various ratios of hypogenic minerals–host rocks in ore and in tailings in a wide temperature range (from − 25 to 45 ◦ C), the Eh-pH parameters and the minerals paragenesis were established. All hypergenic and technogenic minerals formed during modeling were found and diagnosed in the Kavalerovsky tin–ore district mining industrial technogenic system. (mine; sludge and drainage)


Introduction
The article shows the origin of hypergenic and technogenic minerals in nature on the example of the mining industrial system of the Kavalerovsky district tin-sulfide deposits (Primorsky krai) in Russia. Genesis is one of the complex issues of mineralogy, which is poorly covered in the scientific literature for hypergenic and technogenic minerals, due to their imperfect crystalline structure (X-ray amorphous) and formation in polymineral compounds. Sulfide oxidation in open-pit mines and tailings generates highly concentrated solutions from which hypergenic and technogenic minerals crystallize. It is important to know the Eh-pH parameters of the system in which they crystallize, temperature, pressure, association, ratio of primary (hypogenic) minerals, the oxidation of which leads to the formation of secondary (hypergenic and technogenic) minerals, and ratios of hypogenic minerals-host rocks in the tailings.
The Kavalerovsky district is located at the East of Primorsky krai, 450 km from the regional center, Vladivostok, Russia, and occupies an area of 421,520 hectares ( Figure 1). The whole district territory is represented by mountainous terrain, with the Sikhote Alin Ridge passing through [1]. The Kavalerovsky district facilities, including six mines and four concentrating mills of the Khrustalny mining and processing plant, are mainly located in the Zerkalnaya river basin. The mining started in 1941 with the Central (Dubrovskoe) deposit; the remaining mines and concentrating mills started operation in the 1960s and 1970s. In 1992, 15 deposits had been developed by underground mining.
The main mined element was Sn, and in the 1990s, In and Ag were extracted by-products. Sulfide minerals with an industrial content of Cu, Pb, and Zn were always stored in tailings dumps as mining wastes. In 2001, the tin-ore industry of the Kavalerovsky district ceased to exist, but the ore reserves were not depleted. The whole valley of the Fabrichny settlement, where the second largest concentrating mill complex and three big tailing dumps are located, has a large technogenic ecological impact. In the first tailings dump, wastes were stored from 1948 to 1968. Its area is 4 ha and the total weight of tailings is 8 million tons, with an average Sn content of 0.183%. The second and largest tailings dump in the district was in operation from 1968 to 1988. Its area is 7 ha, with a total wastes mass of 21.6 million tons and average Sn content of 0.14%. The third dump of factory wastes (4 ha, 5.2 million tons, Sn content of 0.122%) was accumulated from 1989 to 1997. The first and second tailings dumps have now been drained, and the third one is a sludge lake less than 1/10 of total object area.
At the second plant in Rudny, the ores of the Dubrovskoe deposit were processed from 1943 to 1990. During these years, a 1.7 ha tailings dump with 2.055 million tons of mining waste was created.
The third concentration mill was located in Vysokogorsk. From 1954 to 1976, the wastes were placed in the tailings dump on the territory of the settlement (1.1 ha, 0.9 million tons).
All tailings dumps mining wastes are represented by a grey color and finely dispersed mass consisting of pyrite, pyrrhotite, galena, sphalerite, arsenopyrite, chalcopyrite, quartz, fluorite, tourmaline, chlorite, and other minerals. Sometimes iron hydroxides, which are formed by the oxidation of sulfides, are colored in different shades of brown. Enrichment wastes are classified as fourth hazard class [3].
The increase in the surface contact of finely ground sulfides with weathering agents in layers of mines and tailings leads to the activation of hypergenic processes, which then transitions to the technogenic stage. The following minerals crystallize: chalcantite, gypsum, halotrichite, melanterite, pittitcite, and many others [2]. Some minerals are seasonal as they are formed during the dry season and disappear during the rainy season.
The purpose of this work was to establish parameters and conditions of crystallization for technogenic minerals that crystallize from technogenic waters using the physico-chemical modeling software complex Selektor. To achieve this goal, we wanted to: (1) determine the Eh-pH parameters of secondary minerals crystallization in a wide temperature range of −25 to 45 • C in cases of different sulfide minerals to host rock ratios, (2) find the temperature interval of minerals formation in the range of −25 to 45 • C, (3) identify the association or paragenesis of these minerals, (4) consider the dependence of mineral composition formation on the sulfide concentration in the system, and (5) to determine the influence of each sulfide on the Eh-pH system parameters and association of minerals that are formed from highly concentrated technogenic waters.

Materials and Methods
The formation of hypergenic and technogenic minerals from highly concentrated technogenic waters solutions in the Kavalerovsky tin-ore district was studied using physicochemical modeling. Mineral crystallization occurs in a wide range of Eh-pH system parameters and temperatures.
Physico-chemical modeling was conducted in the Selektor software complex (version 2010, K.V. Chudnenko and I.K. Karpov, Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russian Federation) [4]. The program is based on the convex programming mathematical approach, which allows an equilibrium to be established in heterogeneous systems by minimizing thermodynamic potentials (Gibbs energy). In Selektor, the phase and component composition of the thermodynamic multisystem at different temperatures and pressures can be calculated, considering the activity coefficients. Isothermal changes in thermodynamic functions are calculated using an equation of changes in the volume of condensed phases depending on temperature, pressure, and semi-empirical states of gases using the given parameters.
At the initial stage of model formation, the following components were required for systems: independent components, including chemical composition, and dependent components, which potentially exist in models. The dependent components can be present in the following phases and with the following thermodynamic properties: gases (atmospheric and from sulfide oxidation reactions), liquids (ions, molecules, and pieces formed in solutions), and solid (hypogenic, hypergenic, and technogenic minerals of the Kavalerovsky mining industrial system). Both thermodynamic properties are included in the program [4][5][6][7][8][9], and the values found in relevant sources [10,11] were used in the modeling.
The chemical composition in the models is as follows: atmosphere (Ar = 3.209 mol, C = 0.1036 mol, N = 53.9478 mol, O = 144.8472 mol) [12] for a total of 10 kg, 1 kg water (H 2 O), and 0.1 kg minerals or tailings. The following thermobarometric conditions were specified for modeling: temperature from −25 to 45 • C with a step of 5 • C and constant 1 bar pressure.
All the above characteristics were added into the Selektor software, which calculated the equilibrium composition of the gas, liquid, and solid phases of the system. The results of modeling were analyzed and verified.
The mineral composition of primary ores and host rocks obtained from the literature sources was used for modeling [13,14], as were drilling data [15]. Mine water formation was modeled as a result of sulfide oxidation (chalcocite, covellite, bornite, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, galena, and sphalerite): each separately, all together, and with successive exclusion of one mineral from the entire list. The formation of slurry and drainage water for closed (long idle) tailings dumps was modeled as a result of oxidation of the host rock and sulfides in different ratios. In addition, systems, with the exception of each sulfide, were simulated.
The results of sulfide oxidation modeling in the mine workings within the positive temperature range have been partially published for many districts [16]. The results of modeling 21 sulfide oxidation variants in the considered temperature range are presented below. The formation of highly concentrated mine waters led to crystallization of the following minerals: fibroferrite, chalcantite, posnjakite, wroewolfeite, antlerite, anglesite, bayldonite, and olivenite. In cryogenesis conditions, additional goslarite and duftite precipitate ( Table 1).  The formation of mine water occurs when all micropore solutions, the variants of which are described above, are merged. The study of hydrochemical samples of mine waters has shown that in the studied area, the pH value is in the range from 4.5 to 8.1 [17].
To create models of sulfide oxidation in contact with host rocks minerals, the composition listed in Tables 2 and 3   The processes of tailings oxidation and technogenic minerals formation at Khrustalnoe and Dubrovskoe deposits tailings dumps (Tables 2 and 3) were modeled in the temperature range from 0 to 45 • C. The mineral composition presented in this work is similar to previous works on minerals association but differs in the details (for example, alunogen is observed only in the models of the Khrustalnoe tailings dump). Therefore, we combined all the available results.
At negative temperatures, the following minerals are found (Table 1) Therefore, oxidation of the total tailings sulfide composition in deposits in the entire temperature range led the system's Eh-pH parameters to change from 0.42 to 1.15 V and 1.8 to 13.3. High alkaline pH values are typical for systems with the content of host rocks from 60% to 95% in negative temperature range, but such simulated systems also contain sulfates (fibroferrite, chalcantite, etc.) with insignificant masses (from 0.0001 to 0.5 g). Total dissolved solids (TDS) in the positive temperature range after minerals crystallization varies from 11.7 to 72.7 g/L. The TDS increases significantly under cryogenesis conditions with ice crystallization and liquid phase reduction.
In the absence of chalcopyrite ( Figure 6), all copper-containing minerals disappear from the models. In the range of positive temperatures in the models, the following are formed . Montmorillonite is absent in the models with a 20% sulfide content, and goethite, woodwardite, magnesite and allophane are absent in the models with a 80% sulfide content, but in the latter variant, alunogen, wroewolfeite, and chalcantite crystallize only in the range from −25 to −20 • C, as does anglesite.
In the range of low temperatures ( Figure 13) in the simulated systems, the following are found High pH values were found in models with high content of host rocks under cryogenic conditions; such systems contain sulfates (woodwardite, gypsum, etc.) with insignificant masses (from 0.00001 to 0.8 g) In the system, the following disappear with different sulfide contents: montmorillonite at 20%, goethite; and woodwardite, magnesite, duftite, bayldonite, and allophane at 80%; and the following appear: fibroferrite and olivenite at 10%, calcite only at 40%, as well as chalcantite, alunogen, and anglesite at 80%. Crystallization of a number of minerals is noted in a certain temperature range: starkeyite, olivenite, bayldonite, and montmorillonite at −25 to −5 • C; chalcantite at −25 to −10 • C; anglesite only at 0 • C.

Tailings Oxidation With Cementation Zone Sulfides
We also examined the processes of sulfide oxidation in contact with the host rock (at the ratios  9.5-11.2). As it was seen previously, the masses of sulfates in high alkaline pH cases are insignificant. Montmorillonite is absent in systems with a sulfide content of 20% or more, and goethite, woodwardite, magnesite, duftite, and allophane at 80%. The following minerals appear at various sulfide contents: gypsum at 10%, fibroferrite at 20%, and alunogen, antlerite, posnyakite, rovolfit, olivionite, and baildonite at 80%.
In the range of positive temperatures, in the absence of pyrite in the composition of sulfides, alunogen does not precipitate, and crystallization of anglesite is possible only in the presence of the enrichment of sulfide containing Pb (galena), duftite, and baildonite: Cu, Pb, and As. The presence of tenorite in paragenesis is observed only in the Khrustalnoe deposit. Antlerite, posnjakite, and wroewolfeite are present in the association when the tailings of the enrichment include minerals of the cementation zone or no arsenopyrite is present. Olivenite is deposited in the absence of galena or pyrrhotite in the system, as well as in the presence of minerals from the secondary sulfide enrichment zone.
In the range of negative temperatures, the association additionally includes starkeyite (−25 to −5 • C). The models do not contain sulfide; if all sulfides are present in the enrichment wastes, there is no As (arsenopyrite), and olivenite, baildonite, and duftite do not precipitate without Cu and As (chalco-and arsenopyrite), nor do baildonite and duftite without Pb (galena). Anglesite crystallizes only in models without arsenopyrite and sphalerite, as well as wroewolfeite and chalcantite in the presence of all sulfides or in the absence of arsenopyrite.
The factors determining hypergenic and technogenic minerals paragenesis formation during the sulfide ores oxidation in the mining industrial technogenic system are the presence of sulfide in the simulated system, the relationship between sulfides and the host rock, and temperature.
Comparison with previously reported findings [2] showed that all hypergenic minerals formed during modeling were found and diagnosed in the mining and industrial technogenic system in the Kavalerovsky district.
The formation of mine water occurs when all micropore solutions, the variants of which are described above, are merged. The study of hydrochemical samples of mine waters has shown that in the studied area, the pH values are in the range from 4.5 to 8.1 [17].

Conclusions
Modeling of the oxidation of ores and the tailings sulfide component in the temperature range from −25 to 45 • C showed that the solutions formed have Eh-pH parameters of 0.42-1.24 V and 0.1-14.7. High alkaline pH values were found in micropore solutions in the temperature range from −5 to −25 • C during mine waters formation (chalcocite and bornite oxidation), and formation of slurry and drainage waters (with high content of host rock minerals, from 60% to 95%). In such cases, the sulfates are precipitated, but their masses are insignificant and amounts to 0.01-2% of total precipitated minerals masses.
The following minerals are crystallized in models: Fe, Cu, Pb, Zn, Al, Ca, and Mg from different classes, including oxides, hydroxides, sulfates, carbonates, arsenates, and silicates. Both monomineral and polymineral formations (up to 12 minerals) can precipitate from saturated solutions, as it was seen in natural conditions [2]. The association of crystallized secondary minerals depends on the ores and tailings composition, which includes the presence of a cementing zone in the mineral system or the absence of one of the sulfides. The ratio of sulfide to host rock in the model is an important factor.
The process of mineral formation, the mass of precipitated minerals, and the content of elements in human-made waters depends on temperature. Most of the precipitated minerals are observed throughout the selected temperature range, and some crystallize only within a certain range in either the negative or positive temperature range. In cryogenic conditions, the process of mineral formation is no less active than in the range of positive temperatures. The mass of precipitated minerals varies from one hundred thousandths to hundreds of grams. The concentration of sulfide ores and their host rock elements in solution in the range of positive temperatures is in the tens of grams per liter, and in cryogenic conditions, the solutions are more concentrated and reach hundreds of grams per liter as part of the water precipitates in solid form (ice). All elements both before and after the fallout of hypergenic and human-made minerals from solutions are released into surface and ground water.
The annual mass of pollutants washed away in the warm period (April-October) by rainwater and melt water into water bodies from only one tailings dump of the Dubrovskoe deposit was calculated as (kg): As, 288; Cu, 66; Pb, 332; Zn, 194, and S, 1341 kg [14]. The total annual output of sulfide ore elements is more than 2.2 tons. Their content in modeled human-made waters exceeds background concentrations by 11,333 to 174,000 times, surpassing the maximum allowable concentration in fisheries by 1.7-34,659 times, and for cultural and domestic water by 1.02-17,387 times. Uncontrolled flow of such waters into the river network of the district will seriously negatively affect their quality. As drinking water in the Kavalerovsky district is withdrawn from the Vysokogorky brook, the quality control should be constant.
The obtained results showed that it is necessary to carry out a complex recultivation of tailings dumps, which are technogenic deposits, in the near future, taking into account the characteristics of solutions, revealed by physical and chemical modeling. At first, useful components should be extracted from tailings, otherwise they can be lost [27]. Consequently, all data can be used to develop specific methods for tailings management in both the area under consideration and other mining areas where sulphide-containing tailings are present.