Serpentinite Research Articles

Experimental and theoretical investigations into the surface chemical properties and separation of serpentine from quartz using xanthomonas campestris as a selective flocculant

Separation of fine serpentine (SPT) from quartz (QZ) both of d80 close to 20 µm using an eco-friendly microbial exo-polysaccharide, xanthomonas campestris (XCT), as a selective flocculant for SPT was conducted experimentally and substantiated theoretically. The adsorption of XCT onto SPT was observed to decrease with increase in pH, whereas that of QZ was nearly nil beyond pH 2.1. Zeta potential of SPT in presence of XCT decreased with increase in pH further attesting to the adsorption and anionicity of XCT. The FTIR studies confirmed the interaction of XCT with SPT in presence of sodium hexametaphosphate. The nature of intermolecular interactions present in complexes formed on SPT surface was revealed by quantum theory of atoms in molecules to be non-covalent. The electron density difference plot conducted on formed complexes indicated that electrons drifted from XCT to the surface of SPT. Selective flocculation SPT-QZ (1:1) mixture conducted at pH 6 and pH 7.5 in presence of 4 mg/L and 2 mg/L of sodium hexametaphosphate coupled with 100 mg/L of XCT yielded separation efficiency and selectivity ratio of 96.5 % and 71.2, respectively, after three desliming stages. Therefore, XCT is a potential selective flocculant for serpentine.

Micropropagation and cryopreservation of the rare endemic Colchicum figlalii germplasm

BACKGROUND: The natural population of Colchicum figlalii (Varol) Parolly & Eren grows in a narrow area of serpentine rock clearings at an altitude of 1900-2100 m in Southwestern Anatolia (Sandras Mountain, Mugla, Turkey). The species is regarded as endangered according to the IUCN Red List Categories. OBJECTIVE: To develop an optimum procedure for in vitro propagation and cryopreservation of germplasm of this rare endemic. MATERIALS AND METHODS: A total of 281 bulbs were used as in vitro culture starting material and after surface sterilization, clean material was obtained from 157 of them. Woody Plant Medium (WPM), Olive Medium (OM), and Murashige and Skoog medium (MS) were used for in vitro culture establishment. RESULTS: The maximum regeneration rate (˜67.3%) was obtained after four weeks of incubation on OM. The calli were successfully induced by using OM supplemented with 10.7 μM NAA from leaves of in vitro grown C. figlalii bulbs. A PVS2-vitrification procedure was used for cryopreservation of C. figlalii callus tissue. After cryo-storage, the best result for regeneration (66.7%) was obtained from calli treated with PVS2 for 75 min before plunging into liquid nitrogen. All rooted seedlings derived from cryopreserved calli were successfully acclimatized to greenhouse conditions. CONCLUSION: This study is an effective reference for future long-term conservation of similar species that are difficult to cryopreserve.

Natural hydrogen extracted from ophiolitic rocks: A first dataset

Serpentinization is an important geochemical process producing natural hydrogen (H2), and mafic and ultramafic serpentinized rocks, typically occurring in ophiolites and peridotite massifs, are major targets for H2 exploration. Understanding the volumes of H2 stored in these rocks is a key step towards establishing the potential of sepentinized systems to host H2 sources and reservoirs. Nonetheless, published data on the concentration of H2 directly extracted from serpentinized rocks are extremely scarce. This work provides a first dataset of H2 extracted by planetary ball mill from 58 rock samples from different ophiolites in Greece, peridotites of the Tekirova ophiolite in Turkey, and chromitites and surrounding talc schist from an Archean-Paleoproterozoic greenstone belt in Brazil. The highest H2 concentrations, from 0.1 mL/kg (considered as a threshold above which artificial H2 by milling is negligible) to 16.2 mL/kg, were found in serpentinized harzburgites or dunites, and in chromitites hosted within serpentinized peridotites. The H2 content of other mafic rocks that are not in contact or influenced by a serpentinized system, mostly basalts, is below 0.1 mL/kg. Serpentinized peridotites represent the logical source rocks of H2 (i.e., hydrogen in peridotites is generally autochtonous) and chromitites, lacking significant olivine and serpentinized minerals, may host H2 derived by the surrounding serpentinized rocks (hydrogen in chromitites is mostly allochtonous). The H2 dataset of this work can be used as a reference for further studies on the capacity of ophiolitic rocks to produce and host natural hydrogen.

Weathering of Wood and Rocks and the Role of Coating in Protection

This article explores the effect of weathering on the degradation of wood and rocks and discusses its prevention strategies and safety aspects. Weathering, including natural, enhanced, accelerated, silicates, polymer degradation and erosion is discussed in this article. Rocks weather naturally very slowly and gradually. Minerals weathering and silica-rich layer formation during single-stage and two-stage carbonation like serpentinization of rocks are discussed. A substantial amount of work has been performed for polymeric coatings globally to extend the life of coating surfaces. The ideal coating system would combine the advantages of performance offered by solvent-based coatings with the advantages offered by water-based coatings in the areas of environmental protection, health and safety. Weathering prevention will stop the wastage of materials.

The development of an in vitro propagation and conservation system for the endangered serpentine fern Asplenium cuneifolium Viv.

Asplenium cuneifolium Viv. is an endangered fern species restricted to European serpentine rocks, which face a risk of being easily damaged by both natural and anthropogenic agents. Establishing a comprehensive system of effective micropropagation and long-term storage of this species is therefore desirable. Freshly collected spores of A. cuneifolium were subjected to direct storage at 5 °C and in liquid nitrogen (LN). The viability of spores stored at 5 °C decreased by 10% after 1 year, whereas storage in LN did not change the initial spore viability even after 3 years. For the initiation of the gametophyte culture, disinfected spores were sown onto half-strength Murashige and Skoog medium (½MS) supplemented with 0.06 M sucrose. Following 6 months, abundant proliferation of secondary gametophytes was achieved. For the cryopreservation of gametophytes, encapsulation-vitrification and encapsulation-dehydration, were compared. Of these two methods, encapsulation-vitrification ensured survival of gametophytes of 64.5–93%, while encapsulation-dehydration guaranteed their 100% viability. The acceleration of syngamy on secondary gametophytes was achieved using a medium with macro- and micronutrients reduced to the 1/8 of the MS free of NH4NO3 and vitamins. The syngamic sporophytes could be multiplied by somatic embryogenesis (SE) induced on etiolated stipe explants in an ½MS medium devoid of any plant growth regulators. Adding 0.3 M of sucrose to the medium almost quadrupled the efficiency of the SE. The genetic stability of gametophytes after cryopreservation, as well as sporophytes obtained from them, was confirmed by flow cytometry, amplified fragment length polymorphism, and inter-simple sequence repeat markers.

Using serpentine in concrete: A literature review

Concrete is the most important and extensively used building material. It is used for various functions, including shielding materials from radiation sources such as nuclear power plants. Nuclear technology is applied in numerous research institutes, enterprises, and healthcare facilities, in addition to the exposure to radiation from power plants. Concrete has been considered as a potential shielding material by a number of researchers due to its low cost, durability, and strength, as well as the fact that it can be made using readily available materials. Numerous concrete technologists have turned to materials such as Serpentine to make heavy-weight concrete for radiation shielding against different levels of gamma rays and neutron shielding. This review investigates the radiation shielding materials of Serpentine and materials containing Serpentine mineral, such as Green Marble, in the building industry. This review study is divided into two primary areas: serpentine concrete and the use of serpentine aggregates as a radiation shielding material in concrete. Concrete mixtures using Serpentine alone and in combination with other efficient materials like boric acid and other minerals were used to create radiation-shielding concrete (RSC). On the basis of experimental data, the indicator of radiation shielding performance and the unit weight of concrete was found to have a correlation with a high degree of fitting. The objective of this study is to review the use of Serpentine with concrete and to provide direction on the difficulties encountered in the research process so far regarding the use of the mining waste from serpentine rock in concrete.

Determination of linear attenuation coefficient of aggregate serpentine concrete exposed to gamma and neutron radioactive sources

This research was designed to perform linear attenuation calculations for ordinary concrete both through simulation and experiment. The linear attenuation coefficient is an essential parameter for radiation shielding design for both source transport casks and storage bunkers. The shielding properties of concrete designed with Serpentine aggregates of different granule sizes were investigated. The simulation was performed using Radpro computer Software while the experiment involved sourcing for local Serpentine rock, crushing into four different granule sizes of 5 mm, 10 mm, 15 mm and 20 mm respectively and casting the concrete samples, exposure of the samples to gamma and neutron radioactive sources and monitoring with a radiation survey meter, sample weight measurements and concrete sample crushing using a load testing machine for determination of the concrete compressive strength. The results of the linear attenuation calculations showed that there was high consistency in the values obtained by simulation with those obtained via experiment. Very high linear attenuation property was observed when the serpentine concrete samples were exposed to a neutron source, which corroborates the fact that Serpentine rock is a Boron-rich mineral and Boron is known to have high neutron absorption property. The experimentally determined linear attenuation coefficients showed that the values at 15 mm aggregate sizes were higher than those at 5 mm, 10 mm and 15 mm sizes respectively, which demonstrates that better shielding optimization, will be obtained when the concrete cask is fabricated with 15 mm aggregate size.

Karakteristik Batuan Ultrabasa Di Desa Winatu Dan Kamarora, Kabupaten Sigi, Provinsi Sulawesi Tengah

Ultramafic rocks are found in Sigi district in the Kamarora and Winatu areas but are not mentioned in the regional geology of the Poso sheet and the Pasangkayu sheet so that it is interesting to investigate further. Therefore, it is important to conduct this research to determine the characteristics and processes of ultramafic rock formation in the Kamarora and Winatu areas of Sigi district using the Petrographic and X-Ray Fluorescence (XRF) methods. The results of this study are based on petrographic analysis of two rock samples in Kamarora Village containing olivine (60-55%), omphasite (15-10%), enstatite (5%), serpentine (10%), garnet (15-10%) ) and chlorite (5%) with the rock name lherzolite, while one rock sample in Winatu Village contained serpentine minerals (75%), olivine (15%), omphasite (5%), enstasite (5%) with serpentine rock names. The chemical composition and percentage of each element of the samples analyzed by XRF stations ST01K, ST02K, ST01W are as follows: major element SiO2 (40 – 41.1 wt %), Al2O3 (2.90 – 19.6 wt %), Fe2O3 (7 – 9.98 wt %), MgO (17 – 33.7 wt %), CaO (11.30 – 12.4 wt %), Na2O (0.147–2.11 wt %), K2O (0.0558 – 0.234 wt %) and minor elements with a content range of TiO2 (0.104 – 0.965 wt %), MnO (0.102 – 0.145 wt%), SO3 (0.0719 – 0.259 wt %), Cl ( 0.0954 – 0.360 wt %), NiO (0.0272 – 0.307 wt %), Cr2O3 (0.111 – 0.403 wt %), Co2O3 (0.0246 wt %), WO3 (0.0563 – 0.0661 wt %). Rocks formed in the type of tholeiite magma, this type of magma has a low potassium content, usually formed in subduction and non-subduction areas. Based on the results of the plot on the Pearce et al (1976) diagram, it is known that the tectonic order of rock formation is on the ocean ridge and floor or the expansion of the ocean floor.

Unravelling the ultramafic rock-driven serpentine soil formation leading to the geo-accumulation of heavy metals: An impact on the resident microbiome, biogeochemical cycling and acclimatized eco-physiological profiles

In the present study, we have underpinned the serpentine rock, serpentinized ultramafic soil and rhizosphere's microbial communities, signifying their heavy metals-exposed taxa signatures and functional repertoires in comparison to non-serpentine soils. The results revealed that the serpentine rock embedded soil highlighted the geo-accumulation of higher amount of Cr and Ni impacting soil microbial diversity negatively by metal stress-driven selection. Biolog Ecoplate CLPP defined a restricted spectrum of C-utilization in the higher heavy metal-containing serpentine samples compared to non-serpentine. The linear discriminant analysis (LDA) score identified a higher abundance of Desulfobacterota, Opitutales, and Bacteroidales in low Cr and Ni-stressed non-serpentine-exposed samples. Whereas the abundance of Propionibacteriales and Actinobacteriota were significantly enriched in the serpentine niche. Further, the C, N, S, Fe, and methane biogeochemical cycles linked functional members were identified, and showing higher functional diversity in low Cr and Ni concentration-containing rhizosphere JS-soils. The Pearson correlation coefficient (r) value confirmed the abundance of functional members linked to specific biogeochemical cycle, positively correlated with relevant pathway enrichment. Ultimately, this study highlighted the heavy metal stress within a serpentine setting that could limit the resident microbial community's metabolic diversity and further select the bacteria that could thrive in the serpentine-associated heavy metal-stressed soils. These acclimatized microbes could pave the way for the future applications in the soil conservation and management.

Genomic and metabolomic profiling of endolithic Rhodococcus fascians strain S11 isolated from an arid serpentine environment.

Genomic and metabolomic studies of endolithic bacteria are essential for understanding their adaptations to extreme conditions of the rock environment and their contributions to mineralization and weathering processes. The endoliths of arid serpentine rocks are exposed to different environmental stresses, including desiccation and re-hydration, temperature fluctuations, oligotrophy, and high concentrations of heavy metals. Bacteria of the genus Rhodococcus commonly inhabit endolithic environments. Here, we describe genomic and metabolomic analyses of the non-pathogenic wild-type Rhodococcus fascians strain S11, isolated from weathered serpentine rock at the arid Khalilovsky massif, Russia. We found that strain S11 lacks the virulence plasmid that functions in the phytopathogenecity of some R. fascians strains. Phenotypic profiling revealed a high pH tolerance, phytase activity and siderophore production. A widely untargeted metabolome analysis performed using an Orbitrap LC-MS/MS method demonstrated the presence of chrysobactin-type siderophores in the culture medium of strain S11. The natural variation of secondary metabolites produced by strain S11 might provide a practical basis for revealing antibacterial, fungicide or insecticidal activities. Finally, plant infection and plant growth stimulation studies showed no observable effect of exposure strain S11 bacteria on the aerial and root parts of Arabidopsis thaliana plants. Based on our findings, R. fascians strain S11 might be promising tool for investigations of organo-mineral interactions, heavy metal bioremediation, and mechanisms of bacterial mediated weathering of plant-free serpentine rock to soil.

Comparison of bacterial communities and their functional profiling using 16S rRNA gene sequencing between the inherent serpentine-associated sites, hyper-accumulator, downgradient agricultural farmlands, and distal non-serpentine soils

This study aims to determine and compare the bacterial community and functional profiles associated with serpentine sites, innate hyper-accumulating weed, downgradient agricultural farmlands and non-serpentine sites using 16S rRNA gene sequencing. Elemental analysis revealed that the serpentine rock and weathered soil have higher magnesium, nickel, chromium, magnesium/calcium and lower calcium/magnesium ratios and agricultural farmlands have recorded elevated chromium. Proteobacteria were found predominant, except the non-serpentine site which was rich in Cyanobacteria. PCA analysis at the genus level indicates the uniqueness of different experimental groups, except the hyperaccumulators which exhibited relatively less dissimilarity. The shift analysis showed the serpentine sites were characterized by the abundance of bacteria having heavy metal effluxion. The hyper-accumulating weeds were higher in plant growth-promoting bacteria expressing tolerance against heavy metals toxicity such as nickel, chromium, cobalt and arsenic. Besides, the agricultural lands were abundant in wetland-associated methanogens and metal (manganese, iron and zinc) transporting function related bacteria. The results suggest that the inherent edaphic factors including heavy metal content, the interacting behavior of hyperaccumulator’s rhizosphere microbiota with soil and anthropogenic activities such as agricultural practices could be a major determinant of the variation in the bacterial community selection and abundance in the respective study sites.

A study of hydromagnesite and nesquehonite precipitation in indirect aqueous carbonation of thermally-activated serpentine in a batch mode

To control and decrease the amount of greenhouse gases in the environment, the process of carbonation is attracting particular attention. Via carbonation, it is possible to control carbon dioxide (CO2) emissions by using mining residues. This study focuses on the precipitation step of aqueous indirect carbonation of serpentine mining wastes using the actual carbonated solution. To our knowledge, studies of magnesium carbonate precipitation have been based on synthetic solutions only, unlike the process in the present study. Three solutions prepared from the carbonation step with different concentrations were precipitated at temperatures ranging from 25 to 90 °C. The solution contained dissolved magnesium and inorganic carbon in addition to impurities, such as calcium and silica that are initially present in serpentine rock. Nesquehonite precipitated at reaction temperatures of 25, 40 and 50 °C. Hydromagnesite was precipitated at 60, 70, 80, and 90 °C via transition from nesquehonite. The study showed that increasing temperatures accelerate precipitation kinetics and hastens the transition period from nesquehonite to hydromagnesite. The investigation of the effects of the initial supersaturation showed that higher supersaturation promotes a better reaction yield and consequently a better sequestration potential, but lower supersaturation is better for crystal growth. However, supersaturation had no effect on the transition phenomenon from nesquehonite to hydromagnesite. Also, the grain sizes of the resulting minerals had different ranges from those obtained in synthetic solutions. The average size of the nesquehonite in our experiments was around 120 μm, while nesquehonite’s size was around 25 µm when prepared from a synthetic solution under relatively comparable operating conditions. The average size of the hydromagnesite was around 50 μm, while its size was around 30 µm when prepared from a synthetic solution, under relatively comparable the same operating conditions.

Evaluation of the Compression Potential of Serpentine Rock Masses of the Bou Azzer Mining District in the Central Anti-Atlas of Morocco

Evaluation of the Compression Potential of Serpentine Rock Masses of the Bou Azzer Mining District in the Central Anti-Atlas of Morocco

Accessing the Subsurface Biosphere Within Rocks Undergoing Active Low‐Temperature Serpentinization in the Samail Ophiolite (Oman Drilling Project)

AbstractThe Oman Drilling Project established an “Active Alteration” multi‐borehole observatory in peridotites undergoing low‐temperature serpentinization in the Samail Ophiolite. The highly serpentinized rocks are in contact with strongly reducing fluids. Distinct hydrological regimes, governed by differences in rock porosity and fracture density, give rise to steep redox (Eh +200 to −750 mV) and pH (pH range 8.5–11.2) gradients within the 300–400 m deep boreholes. The serpentinites and fluids host an active subsurface ecosystem. Microbial cell abundances in serpentinite vary at least six orders of magnitude, from ≤3.5 × 101 to 2.9 × 107 cells/g. Low levels of biological sulfate reduction (2–1,000 fmol/cm3/day) can be detected in rock cores, particularly in rocks in contact with reduced groundwaters with pH < 10.5. Thermodesulfovibrio is the predominant sulfate reducer identified via metagenomic sequencing of adjacent groundwater communities. We infer that transport and reaction of microbially generated sulfide with the serpentine and brucite assemblages gives rise to optical darkening and sulfide overprinting, including the formation of tochilinite‐vallerite group minerals, potentially serving as an indicator that this system is inhabited by microbial life. Olivine mesh‐cores replaced with ferroan brucite and minor awaruite, abundant veins containing hydroandradite garnet and polyhedral serpentine, and late‐stage carbonate veins are suggested as targets for future spatially resolved life‐detection investigations. The high‐quality whole‐round core samples that have been preserved can be further probed to define how life distributes itself and functions within a system where chemical disequilibria are sustained by low‐temperature water/rock interaction, and how biosignatures of in situ microbial activity are generated.

Mechanochemically incorporating magnesium sulfate into antigorite to provide active nucleation sites for efficient precipitation of cadmium ions from weak acidic solution

Utilization of natural clay minerals for the treatment of heavy metal cadmium contamination is appealing as the affordable and readily accessible raw materials. However, the low reactivity of natural serpentine limits its practical application for Cd removal. In the present study, mechanochemical activation of antigorite-type serpentine (SP) as example was introduced to enhance its removal capacity for heavy metal of cadmium high enough for practical use. It was found ball-milling at 600 rpm for 60 min for antigorite resulted in the increased release of hydroxyl group to facilitate the precipitation of Cd2+, giving a capacity of 27.4 mg/g for the treatment of 100 mg/L Cd2+ for 120 min at room temperature, which was 10 times higher than that of the pristine antigorite (2.5 mg/g). More significantly, magnesium sulfate (MgSO4, MS) was introduced for the first time to process antigorite, thus to form MgSO4-incorporated antigorite. As a result, the removal capacity for Cd2+ was dramatically increased to 239.7 mg/g with the equal antigorite dosage (the molar ratio of SP/MS = 1:0.5), which is also much higher than the other reported clay minerals. Results showed that, MgSO4 incorporation promoted the reactivity of antigorite and provided numerous SO42− active sites, which allowed the heterogeneous nucleation of basic cadmium sulfate (CdSO4·3.5 Cd(OH)2·xH2O) precipitate on antigorite, therefore not requiring high alkalinity support as the conventional formation of cadmium hydroxide does. Correspondingly, under the new mechanism, the Cd precipitation could take place in a wide pH range, even from pH 3.0, which was a rarely reported phenomenon happening on natural minerals. Based on these findings, this study demonstrated the effectiveness of mechanochemical incorporation of sulfate for enhancing the Cd2+ removal capacity of serpentine, as well as the high efficiency of new pathway for Cd2+ precipitation. Moreover, the potential of low-cost serpentine as alternative stabilizers for the highly-effective remediation of heavy metal contamination may be expected.

Bayesian analysis of Enceladus’s plume data to assess methanogenesis

Observations from NASA’s Cassini spacecraft established that Saturn’s moon Enceladus has an internal liquid ocean. Analysis of a plume of ocean material ejected into space suggests that alkaline hydrothermal vents are present on Enceladus’s seafloor. On Earth, such deep-sea vents harbour microbial ecosystems rich in methanogenic archaea. Here we use a Bayesian statistical approach to quantify the probability that methanogenesis (biotic methane production) might explain the escape rates of molecular hydrogen and methane in Enceladus’s plume, as measured by Cassini instruments. We find that the observed escape rates (1) cannot be explained solely by the abiotic alteration of the rocky core by serpentinization; (2) are compatible with the hypothesis of habitable conditions for methanogens; and (3) score the highest likelihood under the hypothesis of methanogenesis, assuming that the probability of life emerging is high enough. If the probability of life emerging on Enceladus is low, the Cassini measurements are consistent with habitable yet uninhabited hydrothermal vents and point to unknown sources of methane (for example, primordial methane) awaiting discovery by future missions. What is the origin of the methane detected in Enceladus’s plumes? A Bayesian approach to the problem shows that abiotic serpentinization of rocks cannot explain the methane abundance by itself, and biotic methane production gets the highest likelihood—provided the probability of life emerging at Enceladus is high.

Numerical analysis of heat dissipation performance of heat sink for IGBT module depending on serpentine channel shape

Numerical analysis of heat dissipation performance of heat sink for IGBT module depending on serpentine channel shape

Multistep concentration of lizardite/antigorite from chrysotile mine tailings – case of the Carey Mine site in East-Broughton (Québec)

Abstract Revalorization of mining residues is of central concerns to the mining industry and the environment. Specifically, environmental management of residual products from the exploitation of chrysotile in the Thetford Mines region is one of the government concerns in Quebec and Canada. This work uses mining wastes in a second resource generation for production of magnesium from cheap and health-friendly mineral sources; the goal being to produce chrysotile-depleted pre-concentrates for a use as precursors in the leach off extraction of magnesium. The concentration of lizardite/antigorite from chrysotile containing serpentine rock mine tailings originating from the Carey Mine site in East-Broughton (Québec) was carried out using a suite of hydrocyclone, settling/decantation and magnetic separations. Four size classes of the mining residue, namely (−3150,+1580), (−1580, +600), (−600, +300) and (−300, +150) μm, were tested with an aim to reduce the level of objectionable asbestos fibers to allow access to the safer Mg-bearing minerals contained in the mine waste sources. The asbestos fibers clean-up consisted of subjecting the sieved fractions to two hydrocyclone steps, six settling/decantation steps and two magnetic separation steps. The best results were achieved when the hydrocyclone separators led to Mg recovery of 85% (±4) for the coarsest size fraction size. Both hydrocyclone underflow streams underwent settling/decantation separations. The settling tests lasted 30 min and led to Mg recoveries of 82.5% (±1.8) of Mg in the ultimate concentrate. SEM characterizations revealed that it was possible to reduce substantially the amount of chrysotile fibers to render the coarse-sized fraction in the mining waste usable while significantly lowering the health risk of the fibers. A two-step magnetic separation was applied to the final settling/decantation underflow to remove magnetic minerals such as magnetite from the lizardite/antigorite concentrate. The final quasi-non-magnetic chrysotile-depleted lizardite/antigorite concentrate allowed sample recovery of 62.5% (±0.9) wt. of Mg. These preliminary results are intended as a first compulsory step in support of viable restoration and sustainable development scenarios for the Thetford Mines mining sites as second-breath sources for valuable magnesium.

Минеральный состав серпентинитов Кишинского массива (Большой Кавказ)

Ряд ключевых вопросов геологии серпентинитовых массивов Большого Кавказа остается дискуссионным. К их числу относятся формационная принадлежность и геодинамическая типизация протолита апогипербазитов. Необходимым фактическим материалом для обсуждения этих вопросов служат сведения о минеральном составе. Объектом исследований являются серпентиниты Кишинского массива, залегающего в основании Кизилкольского тектонического покрова в зоне Передового хребта Большого Кавказа. Цель работы – получение данных о минеральном составе серпентинитов Кишинского массива, анализ особенностей состава зональных хромшпинелидов, получение данных об условиях формирования и преобразования апогипербазитов. Методы исследования. Рентгенофазовый анализ, электронно-зондовый микроанализ и электронная микроскопия, статистический анализ результатов измерений. Результаты работы. Изучаемые серпентиниты интенсивно дислоцированы. В целом они имеют хризотил-антигоритовый состав. В составе «тектонических окатышей» внутренние части сложены антигоритовыми (с небольшим количеством хризотила) с бруситом разновидностями, внешние части – хризотил-антигоритовыми с клинохлором. По разломам отмечается гидротермальное оталькование, окварцевание и карбонатизация. В серпентинитах присутствуют зональные хромшпинелиды, ядерные части которых представлены алюмохромитом с реликтами хромпикотита, каймы – феррихромитом – хроммагнетитом; локально отмечаются тонкие оторочки магнетита. Метасоматические замещения в хромшпинелидах сопровождались привносом Fe(замещавшего как двух-, так и трехвалентные катионы), Mn, Ni и выносом Mg, Al, Cr, V. Преобразования пород происходили в условиях высокотемпературной зоны зеленосланцевой фации с участием восстановительных флюидов при относительно пониженном отношении флюид/порода. Для ядер значения Cr# составляют ~0,5-0,7, Mg# ~0,4-0,6, что отвечает области составов первичных магматических шпинелей. Судя по составу хромшпинелидов, апогипербазиты связаны с офиолитовой ассоциаций и близки ультрамафитам островодужных обстановок, в том числе серпентинитовым диапирам фронтальных частей островных дуг. При сравнении с серпентинитами расположенного севернее Даховского выступа устанавливается формационное сходство – принадлежность к офиолитам, но в то же время проявляется отличие Р-Т параметров условий метаморфических трансформаций. Several key issues in the geology of the serpentinite massifs of the Greater Caucasus remain debatable. These include formational and geodynamic typing the protolith of apohyperbasites. The necessary factual material for discussing these issues is information about the mineral composition. The object of research is the serpentinites of the Kishinsky massif, which lies at the base of the Kizilkol tectonic cover in the zone of the Peredovoy Range of the Greater Caucasus. The aim of this study was to gather data on serpentinites of Kishinsky massif mineral composition; characteristics analysis of the zonal composition of chromespinelides; to obtain data on the formation conditions and transformation of apohyperbasites. Methods.X-ray phase analysis, electron microprobe analysis and electron microscopy, statistical analysis of measured results. Results. The studied serpentinites are intensively dislocated. Generally, they are of chrysotile-antigorite composition. As part of the "tectonic pellets", the inner parts are composed of antigorite (with a small amount of chrysotile) and brucite varieties, the outer parts are chrysotile – antigorite with clinochlore. Presence of hydrothermal talcose, silicification and carbonatization is noted in the observed faults. There are zonal chromespinelides in serpentinites where nuclear part is represented by chromohercynite with relics of chromepicotite; the edges - ferrochromium and chromemagnetite; locally observed thin rims of magnetite. Metasomatic substitutions in chromespinelides were accompanied by the addition of Fe (which replaced both di-and trivalent cations), Mn, Ni, and the removal of Mg, Al, Cr, and V. Rock transformations occurred in the high-temperature zone of the greenschist facies with reducing fluids at a relatively low fluid/rock ratio. The values of Cr# are ~0.5-0.7, Mg# ~0.4-0.6 for the cores which corresponds to the primary magmatic spinels composition area. Based on the composition of chromespinelides it is established the apohyperbasites are associated with the ophiolite’s association and close to ultramafic rocks of island-arc environments, including serpentinite diapires in the front parts of island arcs. A formational similarity is established – belonging to ophiolites, but there is a difference - in the P-T parameters of the conditions of metamorphic transformations when compared with serpentinites located to the north of the Dakhovsky shield

Pleural malignant mesotheliomas from environmental exposures to asbestos In Italy

Pleural mesothelioma clusters from outdoor environmental exposure have been highlighted also in Italy and, on the basis of epidemiological surveillance coordinated by the Italian National Mesothelioma Register, their frequency has been estimated at about 4.5%. Epidemiological studies and evaluations of some regional mesothelioma registers have made it possible to highlight that the dispersion of asbestos fibers in the outdoor environment was the only ascertained cause of mesothelioma in subjects from asbestos-cement factories, from the Balangero mine (Piedmont Region), from some serpentine rock quarries with tremolite outcrops in the Southern Apennines and in Alta Val di Susa (Piedmont Region); from chrysotile and serpentine caves in Valmalenco (Lombardy Region). Furthermore, cases of pleural mesothelioma were clearly caused by environmental pollution from fluoroedenite fibers in Biancavilla (Sicily Region). On the other hand, regional mesothelioma registers have also reported other circumstances of environmental asbestos exposure, like in the case of steel industry, shipbuilding, chemical plants, railway lines, and repair/demolition of railway carriages. However, these reports have not found confirmation on the basis of ad-hoc studies and it is likely that there is a lack of homogeneity in the assessment of individual cases. Apart from the scenarios which have been the subject of ad-hoc studies, the assessment of the causal role of environmental exposure to "in place" asbestos in the onset of pleural mesothelioma is problematic without an effort to more carefully examine the circumstances of possible exposure, harmonization of the attribution criteria used in the individual regional registers, analytical assessment of the impact of such exposure on the risk of onset of mesothelioma.