Not Mining Sterilization of Explored Mineral Resources. The Example of Native Sulfur Deposits in Poland Case History

The sterilization of mineral resources makes considerable amounts inaccessible for future use and may be a barrier to the free supply of commodities. During the exploitation of mineral deposits, some parts of their resources become sterilized as inaccessible because of natural hazards or unfavorable economic conditions. Not mining land use and the social opposition against mining is the purpose of sterilization of considerable demonstrated mineral resources of deposits not yet engaged in exploitation. The native sulfur deposits in Poland are a good example of such “not mining” sterilization, which makes a considerable part of known resources inaccessible. On the northern border of the Carpathian Foredeep within the Miocene gypsum formation, the systematic exploration had demonstrated about 1 billion tons of sulfur resources located in the deposits of varied dimensions. The sulfur opencast mining and underground melting (the modified Frasch method) flourished from 1958 up to 1993. The increasing sulfur supply, recoverable from hydrocarbons, caused the closing down of sulfur mines, leaving a place with considerable untouched resources. About 67% of sulfur resources left by closed mines and of other explored but not exploited deposits are sterilized by the advancement of settlements, industrial plants, road construction, and by social opposition against mining.

Biogenic native Sulfur linked to the Neogene deposits from the Riffian Corridors (Northern Morocco): preliminary study and characterization

<p>Elemental sulfur in sedimentary rocks is commonly associated with evaporites and authigenic carbonates. The genesis of this evaporite hosted native sulfur has been traditionally considered as a result of bacterial sulfate reduction under specific geological and paleogeographic conditions. Some biogenic sulfur occurrences are found in the Mediterranean area associated with the Neogene formations (e.g. Hellin, Lorca, Teruel, Sicily). They are described as interbedded layers in large evaporitic sequences or as sulfur nodules enclosed in secondary gypsum or carbonate deposits. Quite similar geological settings are present in Northern Morocco where several sediment-hosted sulfur showings were noted. However, these potential sulfur occurrences in the Pre-Rif and post-nappe Neogene basins have not been studied and still basically unknown. This work aims to explore these occurrences and assess their potentials using preliminary field, mineralogical and geochemical data. Several potential areas were identified at the Tortono-Messinian formations of Oued Amlil, Arbaa Taourirt, Taghzout Tassa, and Boudinar basins. They show favorable settings composed mainly of gypsiferous marls, carbonate, and organic matter-rich black sediments. In terms of sulfur contents, preliminary XRD data confirmed the presence of elemental sulfur and geochemical analyses show total sulfur content reaching 18.5 wt.%. However, further fieldwork combined with advanced mineralogical and isotopic geochemistry is still necessary for this area to try understanding their paragenesis in comparison with other similar Mediterranean occurrences.</p>

METHODOLOGICAL PRINCIPLES OF GEOPHYSICAL STUDIES OF KARST DANGEROUS TERRITORIES

The article is devoted to the analysis of the methodological principles of applying geophysical research methods in the study of karst-hazardous territories. The tasks that are posed in specialized studies of karst and geophysical methods for their solution are given. Four stages of specialized studies of karst-hazardous territories are identified: reconnaissance-methodological, prospecting, reconnaissance and monitoring. The set of geophysical methods for the development of these stages are determined. It is noted that a rational set of geophysical methods in the study of karst processes is determined for each individual natural environment (individual site). The possibility of performing field research by a separate geophysical method in this area, the presence of differentiation in rocks according to their physical properties which are used by a specific geophysical method and economic efficiency of the application of this geophysical method were taken into account. As an example, some results of geophysical studies carried out in the framework of the Lyubensky field of native sulfur are given.

Hydrogeology and geochemistry of the sulfur karst springs at Santa Cesarea Terme (Apulia, southern Italy)

This work describes the geochemical and hydrogeological characteristics of Santa Cesarea Terme, an active sulfuric acid speleogenetic system located along the Adriatic coastline (Apulia, southern Italy). It represents a very peculiar site, where rising thermal and acidic waters mix with seawater creating undersaturated solutions with respect to CaCO3, able to dissolve and corrode limestone and create caves. The Santa Cesarea Terme system is composed of four caves: Fetida, Sulfurea, Gattulla, and Solfatara. Hypogene morphologies and abundant deposits of native sulfur (especially in Gattulla Cave) and sulfate minerals are present in these caves. Fetida and Gattulla caves were investigated primarily because they are easily accessible throughout the whole year through artificial entrances, the other caves being reachable only from the sea. Geochemical analysis of water, monitoring of cave atmosphere, and measurement of the stable isotopes of S, O, and H helped to identify the main processes occurring in this complex cave system. In particular, changes in Ba2+ and Sr2+ concentration allowed for the identification of two main domains of influence, characterized by marine and rising acidic waters.

The copper(II)-binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography

The growth of diffraction-quality crystals and experimental phasing remain two of the main bottlenecks in protein crystallography. Here, the high-affinity copper(II)-binding tripeptide GHK was fused to the N-terminus of a GFP variant and an MBP-FG peptide fusion. The GHK tag promoted crystallization, with various residues (His, Asp, His/Pro) from symmetry molecules completing the copper(II) square-pyramidal coordination sphere. Rapid structure determination by copper SAD phasing could be achieved, even at a very low Bijvoet ratio or after significant radiation damage. When collecting highly redundant data at a wavelength close to the copper absorption edge, residual S-atom positions could also be located in log-likelihood-gradient maps and used to improve the phases. The GHK copper SAD method provides a convenient way of both crystallizing and phasing macromolecular structures, and will complement the current trend towards native sulfur SAD and MR-SAD phasing.

Alteration and Mineralization Products of the Zannone Giant Pockmark (Zannone Hydrothermal Field, Central Tyrrhenian Sea)

The Zannone Giant Pockmark (ZGP) is a shallow-water (<−150 m) giant depression located on the shelf off Zannone Island (Pontine Archipelago, central Tyrrhenian Sea, Italy), hosting active hydrothermal vents. The ZGP seabed displays different fluid-venting morphologies (pockmarks, lithified pavements, mounds, and cone-shaped structures) and widespread bacterial communities. In this study, we analyzed ROV (Remote Operated Vehicle) images to gain information on seabed geology and the textural, mineralogical, and geochemical composition of authigenic crusts and gravel-sized clasts sampled close to active emissions. ROV images show authigenic dome-shaped crusts composed of native sulfur associated with barite, gypsum, amorphous silica, and secondary hydrothermal minerals (illite–montmorillonite). The gravel-sized clasts are mostly rhyolites strongly affected by hydrothermal alteration (Alteration Index > 88; depletion of some mobile elements and enrichment of some base metals), causing feldspar-destruction, silicification, formation of hydrothermal phyllosilicates, and precipitation of disseminated pyrite. More intense alteration implying the complete obliteration of the primary mineralogy or fabric is represented by quartz-pyrite samples. ZGP seabed morphology and petro-geochemical features of deposits point to the possible occurrence of a sulfide system linked to the degassing of magma similar to that feeding the Pleistocene products of Ponza Island.

Experimental Study of Pyrite Oxidation at 100 °C: Implications for Deep Geological Radwaste Repository in Claystone

The oxidation of pyrite is one of the near field processes of the chemical evolution of clay rock planned to host a deep geological radioactive waste repository during operation. Indeed, this process can lead to transitory acidic conditions in the medium (i.e., production of sulphuric acid, carbonic acid) which may influence the corrosion kinetics of the carbon steel components of some disposal cells. In order to improve the geochemical modelling of the long-term disposal, the oxidation of pyrite in contact with clays and carbonates at 100 °C must be evaluated. In this study, special attention was paid to the pyrite oxidation rate thanks to an original experimental set-up, involving several pyrite/mineral mixtures and a reactor coupled to a micro gas chromatograph (PO2 and PCO2 monitoring). Although thermodynamic modelling expects that hematite is the most stable phase in a pure pyrite heated system (low pH), experiments show the formation of native sulfur as an intermediate product of the reaction. In the presence of calcite, the pH is neutralized and drives the lower reactivity of pyrite in the absence of native sulfur. The addition of clay phases or other detrital silicates from the claystone had no impact on pyrite oxidation rate. The discrepancies between experiments and thermodynamic modelling are explained by kinetic effects. Two laws were deduced at 100 °C. The first concerns a pure pyrite system, with the following law: r P y = 10 − 4.8 · P O 2 0.5 · t − 0.5 . The second concerns a pyrite/carbonates system: r P y + C a = 10 − 5.1 · P O 2 0.5 · t − 0.5 where PO2 corresponds to the partial pressure of O2 (in bar) and t is time in seconds. Different mechanisms are proposed to explain the evolution with time of the O2 consumption during pyrite oxidation: (i) decrease of the specific or reactive surface area after oxidation of fine grains of pyrite, (ii) decrease of O2 pressure, (iii) growing up of secondary minerals (Fe-oxides or anhydrite in the presence of calcium in the system) on the surface of pyrite limiting the access of O2 to the fresh surface of pyrite, and (iv) change in the pH of the solution.

Volatile Chalcophile Elements in Native Sulfur from a Submarine Hydrothermal System at Kueishantao, Offshore NE Taiwan

We analyzed sulfur isotopes, trace elements and chalcophile elements (Se, Te, As, Sb, and Hg) in the native sulfur matrix from the Kueishantao hydrothermal system and conducted a systematic micro-analytical investigation. The sulfur matrix lacked all measured metals (e.g., Fe, Cu) and rare earth elements (REEs) while being significantly enriched in Te, As, Se (750–1500 ppm), Sb (around 100 ppm) and some Hg. The δ34S data (0.2–2.4‰) suggest a magmatic source leached from igneous rocks and a small contribution of seawater sulfates to the sulfur in hydrothermal deposits. Correlations between Te, As, Sb, and S (r2 = 0.30–0.61) indicate that these elements behave coherently in magmatic-hydrothermal processes. The enrichment factors and content ratios of these elements demonstrate their abundance in the sulfur matrix and minor fractionation after being partitioned into the metallic melt and forming a separate vapor phase to transport. Our study focuses on the native sulfur matrix in a shallow-water volcanic hydrothermal system, to which relatively little attention has previously been paid. This will expand our understanding of hydrothermal precipitates. The study of volatile chalcophile elements in the matrix will provide significant information about their sources, distributions and other geochemical behaviors in magmatic-hydrothermal processes and help to understand the Kueishantao hydrothermal circulation better.