Mineral waters and sediments of the ferruginous spring Ulan-Bulak Urulyunguevsky (South-Eastern Transbaikalia, Russia)

The data on the chemical composition and content of balneological components (Fe, H2SiO3, CO2, S2-) for three water samples from the Ulan-Bulak acidic ferruginous spring are presented. For the first time, carbonic water was released in the composition of the spring waters, the origin of which is explained by the ingress of hydrocarbonate water into an acidic medium, followed by dissociation according to the HCO3 - + H+ → H2CO3 → H2O + CO2 scheme. An acidic environment is formed as a result of oxidation of sulfide mineralization, presumably gold-bearing. From secondary minerals at the spring, modern sulfate minerals (gypsum, jarosite), hydromica (illite) were found, ocher sediments are widely developed. Given the uncertain nature of the formation of the spring waters, it is considered worthy of special studies, including an inspection of the presence of sulfide mineralization.

Laboratory-Based Bacterial Weathering of the Merensky Reef and Its Impact on Platinum Group Mineral Migration

Weathering of the Merensky reef was enhanced under laboratory conditions by Fe- and S-oxidizing bacteria: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. These bacteria preferentially colonized pyrrhotite and pyrite, versus pentlandite and chalcopyrite (all of which were common within the rock substrate), promoting weathering. Weathering of base metal sulfides resulted in the precipitation of Fe oxides, Fe phosphate, and elemental sulfur as secondary minerals. Fe pyroxene weathered readily under acidic conditions and resulted in mineral dissolution, while other silicates (orthopyroxene and plagio-clase) precipitated Fe phosphate spherules or coatings on their surface. The deterioration of the platinum group metal (PGM) matrix (base metal sulfides and silicates) and the occurrence of a platinum grain associated with platinum nanoparticles observed in the biotic thin sections demonstrate that biogeochemical acid weathering is an important step in the active release of intact PGM grains. A platinum grain embedded in secondary Fe oxides/phosphate that had settled by gravity within the weathering solution demonstrates that secondary minerals that formed during weathering of PGM-hosting minerals also represent targets in PGM exploration by trapping and potentially slowing PGM migration. Dispersion halos surrounding or occurring downstream from PGM occurrences will likely produce two physical target classes—i.e., grains and colloids—under surficial weathering conditions.

The Role of Microorganisms in the Formation, Dissolution, and Transformation of Secondary Minerals in Mine Rock and Drainage: A Review

Mine waste rock and drainage pose lasting environmental, social, and economic threats to the mining industry, regulatory agencies, and society as a whole. Mine drainage can be alkaline, neutral, moderately, or extremely acidic and contains significant levels of sulfate, dissolved iron, and, frequently, a variety of heavy metals and metalloids, such as cadmium, lead, arsenic, and selenium. In acid neutralization by carbonate and silicate minerals, a range of secondary minerals can form and possibly scavenge these potentially harmful elements. Apart from the extensively studied microbial-facilitated sulfide oxidation, the diverse microbial communities present in mine rock and drainage may also participate in the formation, dissolution, and transformation of secondary minerals, influencing the mobilization of these metals and metalloids. This article reviews major microbial-mediated geochemical processes occurring in mine rock piles that affect drainage chemistry, with a focus on the role of microorganisms in the formation, dissolution, and transformation of secondary minerals. Understanding this is crucial for developing biologically-based measures to deal with contaminant release at the source, i.e., source control.

Specific features of postmagmatic and hypergene kimberlite rock alteration research

Methods of studying postmagmatic and hypergene kimberlite rock alteration, as well as identifying secondary minerals and their associations are characterized. It is shown that secondary mineral formation processes took place in a wide temperature range and they are caused by their downward change of medium reaction from alkaline to acidic followed by neutralization, which resulted in dissolution, additional growth and emergence of new secondary mineral generations.

Petrogenesis of Neoproterozoic Ultramafic Rocks, Wadi Ibib–Wadi Shani, South Eastern Desert, Egypt: Constraints from Whole Rock and Mineral Chemistry

This contribution deals with new geology, petrography, and bulk-rock/mineral chemistry of the poorly studied ultramafics of Wadi Ibib–Wadi Shani (WI–WS) district, South Eastern Desert, Egypt. These ultramafics are dismembered ophiolitic rocks that can be subdivided into serpentinites and serpentinized peridotites. Primary minerals such as olivine and pyroxene are absent in serpentinites, but relics of them occur in serpentinized peridotites. Pseudomorph after olivine is indicated by common hourglass textures with less mesh, whilst schistose bastites reflect a pyroxene pseudomorph. Chromite can be subdivided into Cr-spinel and Al-spinel. Cr-spinel ranges from chromite to magnesochromite in composition, whereas Al-spinel belongs to the spinel field. Cr-spinel includes YCr (Cr/(Cr+Al+Fe+3), YAl (Al/(Al+Cr+Fe+3), and YFe+3 (Fe+3/(Fe+3+Al+Cr), similar to forearc peridotite, whilst Al-spinel is more similar to abyssal peridotite, and may be formed during inanition of subduction processes in proto forearc environments. The main secondary minerals are tremolite, talc, and chlorite—which is subdivided into pycnochlorite and diabantite—and their temperature ranges from 174 to 224 °C. The examined rocks had undergone high partial melting degrees (>25%), as indicated by the Cr# of their unaltered cores (Cr-spinel, >0.6), whole rocks (Al2O3, SiO2, CaO, and MgO), trace and REEs, depleted Na2O, Al2O3, and Cr2O3 of clinopyroxene, and high forsterite content ((Fo = 100 Mg/Mg + Fe), av. 95.23 mol%), consistent with forearc settings.

Chemical reactions and conditions of mineral formation at tailings storage facilities of the Russian Far East

Cassiterite-sulfide and polymetallic deposits of the Far Eastern Region (FER) were mined by both openpit and underground methods. This resulted in the emerging numerous mine workings and tailings storage facilities (TSFs) (abandoned without reclamation in latest decades) and the formation of mining technogenic mineralogical systems. Sulfide component of minerals in the mining technogenic system is subjected to hypergenic and technogenic processes (oxidation and hydrolysis reactions). As a result, highly concentrated technogenic solutions are formed, from which minerals of various classes precipitate. In this connection the purpose of this study was formulated as follows: to show the possibility of crystallization of technogenic minerals from micropore technogenic solutions. In achieving this goal the following tasks were solved: to demonstrate the possible reactions of oxidation and hydrolysis of technogenic minerals at the tailings storage facilities; to identify Eh-pH parameters of their precipitation from highly concentrated solutions; to determine their possible associations. The studies involved field observations and computations with the use of “Selector” software package. The study findings allow demonstrating possible chemical reactions and physico-chemical conditions of mineral formation for the following elements: Fe, Cu, Pb, Zn, Sb, Mg, Al, and Ca, including the following classes of minerals: oxides and hydroxides, sulfates, carbonates, arsenates and silicates. The paper presented for the first time the crystallization reactions of secondary minerals (37 ones) and their physico-chemical conditions. It was found that secondary minerals: jarosite, pitticite, siderite, tenorite, poznyakite, antlerite and ktenasite crystallize in the interval of positive temperatures, while scorodite, chalcantite, broshantite, cerussite, starkeyite, epsomite and rostite originate in cryogenic conditions (below 0 oC). All other minerals, the possibility of precipitation of which was shown in the paper, crystallized in the whole considered temperature interval, from −25 oС to +45 oС. Field studies and modeling data on formation of technogenic waters (solutions) and crystallization of secondary minerals on the surface of and inside tailings at the tailings storage facilities of the Far East showed high intensity of technogenic processes. Since the tailings storage facilities were not reclaimed, the process of environmental pollution, including the hydrosphere, would last for many decades.