The Dependence of Durability and Deformation of Elements of Soil Cement Composite with Carbonate White Soil Mixture on Age

The results of an experimental study of changes in strength and deformability during the period of time subjected to short-term loading of elements made of a soil-cement composite based on white soil (belozems) of carbonate composition are discussed. Research was carried out in accordance with current standards, as well as a well-known method that has been repeatedly tested earlier. To assess the experimentally established data, the results of similar studies by other authors, carried out applying elements from soil-cement based on clay soils, as well as from lightweight concrete on lithoid pumice (volcanic rock), are also presented. On the basis of the comparative analyzes of the experimentally established data, conclusions are formulated. The consideration of those may be useful both for the estimation of optimal schedules of the construction of buildings from a soil-cement composite, and for the assessment of their stress-strain state.

Geochemical-Microscopical Characterization of the Deterioration of Stone Surfaces in the Cloister of Santa Maria in Vado (Ferrara, Italy)

Santa Maria in Vado is a monument in the rich artistic heritage of the city of Ferrara (north of Italy). In this paper we want to investigate the state of conservation of tombstones, cloister and the entrance to the basilica, in order to keep them in the best possible state for the future generations. From the chemical characterization, the state of conservation was determined focusing on the biodeteriogenic and non-biodeteriogenic factors, which determine a series of unwanted changes in the physical, mechanical and above all aesthetic properties of the material, often closely connected with the environment and conservation conditions. On the macroscopic observation, the state of conservation of the tombstones appeared to be very deteriorated through aesthetic and structural damage. In detail, the stereo microscope observation of samples collected from the tombstones show the presence of efflorescence probably caused by the abundant of water that bring the salts present inside the rock into solution. Relating the columns, μ-XRF analysis confirm the carbonate composition of samples and presence of iron and sulfur. Finally, SEM observation highlighted the presence of black crust on arch samples and the presence of pollen on the black crust and spheroidal particles probably related to atmospheric pollution.

CORRELATION OF THE SILURIAN SEQUENCE OF THE 25-KOTYUZHINY STRUCTURAL WELL WITH THE DNIESTER REFERENCE SECTION OF THE SILURIAN IN THE VOLYN-PODILLYA PLATE

The paper is devoted to lithostratigraphic and biostratigraphic subdivision of the Silurian deposits of 358 m total thickness in the 25-Kotyuzhiny structural well and its comparison with the stratotypic Dniester section of the Silurian system in accordance with Legend to the geological map of Ukraine, the Volyn-Podolsky series of 1: 200 000 scale, consistent with the latest modernization of Silurian stratigraphic charts. The described section is a parastratotype for Silurian litho-stratons of the Kovel-Khotyn structural and facies zone and a reference one for Silurian deposits in the central part of this zone. The Silurian in the 25-Kotyuzhiny well is represented by the lower (Llandoverian and Wenlockian stages) and upper (Ludlovian and Przhidolian stages) series. According to the lithological-facies composition and sedimetantaion conditions during Silurian times, there are 3 major completed stages of sedimentation as transgressive-regressive cycles, corresponding to the the Yarugian, Malinovetsian and Rukshinian series, which are quite clearly subdivided into 10 suites and 12 sub-suites. In correlation with the Dniester reference section, litho-stratons of the Silurian are characterized mainly by carbonate and clay-carbonate composition, relative stable thickness and facies pattren, diversity of fauna with a predominance of shallow benthic forms. The well is characterized by bituninous manifestations indicating hydrocarbon potential of the area and its prospectivity for shale gas accumualtions in the formations of the upper Silurian in particular.

Carbonatite-Like Rock in a Dike of the Aikhal Kimberlite Pipe: Comparison with Carbonatites of the Nomokhtookh Site (Anabar Area)

––A dike of rock similar in composition to carbonatites has been found in the Aikhal diamondiferous pipe of the Alakit–Markha field of the Yakutian kimberlite province (YaKP). The fine-grained rock of essentially carbonate composition (dolomite and calcite) rich in thin-platy phlogopite contains minerals typical of carbonatites: monazite, baddeleyite, and pyrochlore. In the high contents and distribution of incompatible elements the rock differs significantly from kimberlites and is transitional from kimberlites to carbonatites. The content of incompatible elements in this rock is 3–5 times lower than that in carbonatite breccias of the pipes in the Staraya Rechka kimberlite field of the YaKP (Nomokhtookh site). The compositions of accessory trace element minerals from the Aikhal dike rock and the Nomokhtookh carbonatite breccias are compared. An assumption is made that the high contents of incompatible elements in the carbonatite-like rock, which caused the crystallization of accessory minerals, are due to the differentiation of kimberlite melt/fluid. The high Sr isotope ratios indicate that the rock altered during hydrothermal and metasomatic processes. The obtained data on the composition of the carbonatite-like rock cannot serve as an argument for the genetic relationship between the Aikhal kimberlites and typical carbonatites. The genetic relationship between kimberlites and carbonatites in the northern fields of the YaKP remains an open issue.

Mineral assemblage within secondary crystallized melt inclusions in olivine of mantle xenoliths from the Bultfontein kimberlite pipe (Kaapvaal craton, South Africa)

<p>For the first time, snapshots of crystallized melts in olivine of sheared garnet peridotite xenoliths from the Bultfontein kimberlite pipe have been studied. This type of xenoliths represents the deepest mantle rocks derived from the base of lithosphere (at depths from 110 to 230 km for various ancient cratons). According to different models, such type of inclusions (secondary) in mantle minerals can be interpreted as relics of the most primitive (i.e., close-to-primary) kimberlite melt that infiltrated into sheared garnet peridotites. In general, these secondary inclusions are directly related to kimberlite magmatism that finally formed the Bultfontein diamond deposits. The primary/primitive composition of kimberlite melt is poorly constrained because kimberlites are ubiquitously contaminated by xenogenic material and altered by syn/post-emplacement hydrothermal processes. Thus, the study of these inclusions helps to significantly advance in solving numerous problems related to the kimberlite petrogenesis.</p><p>The unexposed melt inclusions were studied by using a confocal Raman spectroscopy. In total, fifteen daughter minerals within the inclusions were identified by this method. Several more phases give distinct Raman spectra, but their determination is difficult due to the lack of similar spectra in the databases. Various carbonates and carbonates with additional anions, alkali sulphates, phosphates and silicates were determined among daughter minerals in the melt inclusions: calcite CaCO<sub>3</sub>, magnesite MgCO<sub>3</sub>, dolomite CaMg(CO<sub>3</sub>)<sub>2</sub>, eitelite Na<sub>2</sub>Mg(CO<sub>3</sub>)<sub>2</sub>, nyerereite (Na,K)<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub>, gregoryite (Na,K,Ca)<sub>2</sub>CO<sub>3</sub>, K-Na-Ca-carbonate (K,Na)<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub>, northupite Na<sub>3</sub>Mg(CO<sub>3</sub>)<sub>2</sub>Cl, bradleyite Na<sub>3</sub>Mg(PO<sub>4</sub>)(CO<sub>3</sub>), burkeite Na<sub>6</sub>(CO<sub>3</sub>)(SO<sub>4</sub>)<sub>2</sub>, glauberite Na<sub>2</sub>Ca(SO<sub>4</sub>)<sub>2</sub>, thenardite Na<sub>2</sub>SO<sub>4</sub>, aphthitalite K<sub>3</sub>Na(SO<sub>4</sub>)<sub>2</sub>, apatite Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH,Cl,F) and tetraferriphlogopite KMg<sub>3</sub>FeSi<sub>3</sub>O<sub>10</sub>(F,Cl,OH). Note that carbonates are predominant among the daughter minerals in the melt inclusions. Moreover, there are quite a lot of alkali-rich daughter minerals within the inclusions as well. During the last decade, some research groups using different approaches proposed a model of carbonate/alkali‑carbonate composition of kimberlite melts in their source regions. This model contradicts to the generally accepted ultramafic silicate nature of parental kimberlite liquids. This study is a direct support of a new model of carbonatitic composition of kimberlite melts and also shows that alkali contents in kimberlite petrogenesis are usually underestimated.</p><p>This work was supported by the Russian Foundation for Basic Research (grant No. 20-35-70058).</p>

Formation of Monohydrocalcite in the Microbialites from Laguna de Los Cisnes (Isla Grande de Tierra Del Fuego, Chile)

Monohydrocalcite (CaCO3·H2O) is a mineral rarely found in natural environments. Here, we report finding of this mineral in the composition of the microbialites in Laguna de los Cisnes (Isla Grande, Chile), a saline alkaline lake with high Mg/Ca ratio. We have made a detailed structural and mineralogical description of these microbialites with the use of light and scanning electron microscopy, infrared spectroscopy and X-ray analysis. The predominantly carbonate composition of microbialites was revealed. Carbonates were represented mainly by high-magnesium calcites and monohydrocalcite. Calcite and aragonite were found in minor quantities. In addition, a small amount of silicates and amorphous hydromagnesite were found. The yellowish-brown surface layer of microbialites consists of numerous crystals within a mineralized exopolysaccharide (EPS) matrix. A large number of unicellular and filamentous algae, as well as areas of released EPS, are also seen here. Below is a slimy green layer. This layer is not mineralized; it represents an "algal-bacterial mat" consisting of algae, cyanobacteria, and diatoms developed in EPS. Chisel-shaped crystals of monohydrocalcite and its amorphous spherical precursors are numerous in these upper layers. The deeper layers are mineralized; they predominantly consist of Mg-carbonates with varying degrees of Mg. Algae and cyanobacteria are decomposed or fossilized there. Thus, monohydrocalcite occurs in the composition of the microbialites, being one of the main mineral components. As in other lacustrine localities, it is formed in the presence of algae and cyanobacteria. To our knowledge, this is the first report on the discovery of monohydrocalcite in South America. This research was funded by the Ministry of Science and Higher Education of the Russian Federation.

Mapping coral calcification strategies from in situ boron isotope and trace element measurements of the tropical coral Siderastrea siderea

Boron isotopic and elemental analysis of coral aragonite can give important insights into the calcification strategies employed in coral skeletal construction. Traditional methods of analysis have limited spatial (and thus temporal) resolution, hindering attempts to unravel skeletal heterogeneity. Laser ablation mass spectrometry allows a much more refined view, and here we employ these techniques to explore boron isotope and co-varying elemental ratios in the tropical coral Siderastrea siderea. We generate two-dimensional maps of the carbonate parameters within the calcification medium that deposited the skeleton, which reveal large heterogeneities in carbonate chemistry across the macro-structure of a coral polyp. These differences have the potential to bias proxy interpretations, and indicate that different processes facilitated precipitation of different parts of the coral skeleton: the low-density columella being precipitated from a fluid with a carbonate composition closer to seawater, compared to the high-density inter-polyp walls where aragonite saturation was ~ 5 times that of external seawater. Therefore, the skeleton does not precipitate from a spatially homogeneous fluid and its different parts may thus have varying sensitivity to environmental stress. This offers new insights into the mechanisms behind the response of the S. siderea skeletal phenotype to ocean acidification.

RESULTS OF PETROGRAPHIC ANALYSIS OF MESHOKO CERAMICS

The article presents the results of petrographic analysis of the ceramics of the Chalcolithic settlement of Meshoko. A total of 42 fragments were examined (see appendix), 10 of which belong to the upper part of the monument's sediments (layers 1 and 2a; Fig. 1), 20 refer to the middle part of the sediments (layer 2b; Fig. 2), 12 – to the lower part (layer 3; Fig. 3). Based on the analysis, 5 groups of ceramics were identified (Fig. 4). Group 1 consists of fragments with an admixture of limestone, group 2 – with an admixture of diorite, group 3 – with an admixture of biogenic carbonates and sand, group 4 – with an admixture of calcite, group 5 – with an admixture of diorite and chamotte. Clays of smectite composition predominate in groups 1 and 2, while clays of smectite-carbonate composition predominate in groups 3 and 4. Comparison of these groups with stratigraphy revealed that most of the ceramics of groups 3 and 4 are confined to the lower layer, and groups 1 and 2 to the middle and upper layer (Table 1). In addition, the ceramics of these layers differ in the nature of the external surface treatment. Significant changes in the technology of making ceramics during the transition from the lower layer to the middle layer allow us to assume corresponding changes in the composition of the population.

Raman spectroscopic analysis of the composition of the clam-shrimp carapace (Branchiopoda: Laevicaudata, Spinicaudata, Cyclestherida): a dual calcium phosphate-calcium carbonate composition

Clam shrimps constitute a paraphyletic group of bivalved branchiopod crustaceans that includes orders Laevicaudata, Spinicaudata, and Cyclestherida. The unique mineral content of the carapace, formed by molt retention in Spinicaudata and Cyclestherida, has been variously ascribed to calcium carbonate or calcium phosphate. We analyzed the composition of modern carapaces from one laevicaudatan species, thirteen spinicaudatan species (including cyzicids, leptestheriids, and limnadiids), one cyclestherid species, and two species of the notostracan TriopsSchrank, 1803 (as an outgroup comparison within Branchiopoda) via Raman spectroscopy. The results were surprisingly variable. The outgroup Triops species varied in either having no mineral content to having a slight amount of calcium phosphate. The laevicaudatans likewise had a minor calcium phosphate peak; the leptestheriid spinicaudatan had strong calcium phosphate and calcium carbonate peaks; the limnadiid spinicaudatans were variable, varying from no mineral content to strong dual calcium carbonate and calcium phosphate peaks; the cyzicid spinicaudatans tended to have strong calcium phosphate peaks with some amount of calcium carbonate; and the cyclestherid had no mineral content. The results support the conclusion that spinicaudatans primitively have a dual mineralization system in their carapace that utilizes both calcium phosphate and calcium carbonate, with the calcium phosphate ability being basal. This suggestion of a dual mineralization system is novel in branchiopods and warrants study from material scientists. Better understanding of the distribution of phosphate versus carbonate among modern spinicaudatans will help us understand the evolution of biomineralization in the group. This, in turn, will shed light on the fossilization potential of different fossil clam-shrimp lineages.