<p>Microscopic, prismatic single crystals of synchysite-(Ce) from Cuasso al Monte (typical average composition Ca<span class="inline-formula"><sub>1.01</sub></span>Ce<span class="inline-formula"><sub>0.37</sub></span>Nd<span class="inline-formula"><sub>0.20</sub></span>Y<span class="inline-formula"><sub>0.17</sub></span>La<span class="inline-formula"><sub>0.09</sub></span>Pr<span class="inline-formula"><sub>0.05</sub></span>Sm<span class="inline-formula"><sub>0.05</sub></span>Gd<span class="inline-formula"><sub>0.03</sub></span>Th<span class="inline-formula"><sub>0.03</sub></span>(CO<span class="inline-formula"><sub>3</sub>)<sub>2</sub></span>F<span class="inline-formula"><sub>0.72</sub></span>) have been investigated by a variety of techniques, including single-crystal X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and precession-assisted three-dimensional electron diffraction. The synchysite crystals are affected by an extraordinary abundance of diverse defects, such as stacking faults (polytypic disorder), core–rim chemical zoning, fluid and solid (hematite) inclusions, and metamict damage. Notwithstanding these faults, reliable X-ray crystal structure refinements have been obtained, which may enrich the currently scarce database. On the other hand, electron diffraction data, while remaining within acceptable limits, evidenced some challenges in refinement, even applying dynamical theory, potentially due to the impact of defects on data quality at the nanometre scale or absorption effects in such dense compounds, even in thin foils.</p>
<p>The apparent polytypic disorder affecting the studied synchysite actually disguises an ordered superstructure, suggesting a crystal growth by screw dislocation. The nanostructural relationships between inclusions and host suggest that the crystals trapped a large number of fluid inclusions during growth, while hematite inclusion formed later, filling voids or fractures. The studied crystals are chemically zoned, with the core enriched in Ce, La and Nd; the rim enriched in Y; and the outer rim enriched in Th. The latter, undergoing <span class="inline-formula"><i>α</i></span> decay, induced radiation damage to the outer rim structure of the crystals.</p>
This study investigates the mineral composition of the lunar Dryden Crater using Moon Mineralogy Mapper (M<sup>3</sup>) data. A RGB false-color composite reveals distinct pyroxene, anorthosite, and possibly spinel distribution patterns. Orthopyroxenes, excavated from deep crustal layers, dominate steep slopes, while plagioclase-rich materials align with magma ocean models of lunar crustal formation. Minor clinopyroxenes indicate impact melt origins. While space weathering and shock metamorphism pose analytical challenges, integrating spectral data with geological context elucidates the crater’s complex history. The resulting mineral distribution map supports targeted exploration during upcoming lunar missions, resource prospecting and resource utilization initiatives within this geologically complex region.
Mohadeseh Eskandari, Maryam Sheibi, Fardin Mousivand
et al.
The study area is situated in the northern part of the Central Iranian structural zone, northeast of the Toroud-Chah Shirin magmatic arc. In this area, late Eocene hypabyssal intrusions are emplaced within Eocene volcano-sedimentary sequences. Hydrothermal fluid activity has completely destroyed the original structure and mineralogical composition of these rocks, leading to the formation of significant amounts of fine-grained quartz (indicative of silicic alteration) and kaolinite, along with secondary iron oxides such as hematite and goethite. Mineralization in this area has developed in at least four argillic-silicic zones associated with breccia, vuggy quartz, and veins. The highest occurrences of sulfide mineralization are formed within the silicic veins. In these mineralized zones, vuggy to brecciated silicic rocks—referred to as lithocaps—are present alongside advanced argillic alteration containing pyrophyllite. Surrounding these central features, propylitic alteration is also observed. The primary ore minerals identified include pyrite, chalcopyrite, enargite, magnetite, hematite, and goethite. Results from analyses of trapped two-phase fluid inclusions (L+V) in quartz reveal that homogenization temperatures range from 160 to 362.8 °C, with salinity varying between 2.24 and 9.08 wt.% NaCl eq. Comparative investigation of structural characteristics, texture, mineralogy, alteration features, and properties of ore-forming fluids indicate that the copper-gold vein mineralizations in this area significant similarities to high-sulfidation (HS) epithermal deposits.
Introduction
The Toroud-Chah Shirin magmatic arc (TCSMA) is situated in the northern part of the Central Iran zone, as shown in the 1:250,000 geological map of Toroud (Houshmandzadeh et al., 1978) and the 1:100,000 geological map of Moalleman (Eshraghi and Jalali, 2006). The magmatic activity in this arc and surrounding regions is attributed to the subduction of the Sabzevar-Daruneh branch of the Neo-Tethys Ocean beneath Central Iran (Yousefi et al., 2017). The studied area contains a substantial volume of volcanic and pyroclastic rocks from the Eocene epoch, as well as numerous subvolcanic intrusions. Previous studies conducted within this magmatic arc have identified a range of epithermal mineralization events characterized by low to moderate sulfide content (e.g., Mehrabi and Ghasemi Siani, 2012; Roohbakhsh et al., 2018; Mahabadi and Fardoust, 2018, Eskandari et al., 2024; Tale Fazel et al., 2019). Geological investigations in the northeastern section of the Toroud-Chah Shirin magmatic arc (coordinates 54°50' to 54°51' E and 35°30' to 35°29' N) reveal a diverse array of alteration types, including propylitic, argillic, and quartz-alunite alterations, with extensive advanced argillic alteration. These investigations have also documented several silica caps and clear evidence of mineralization that has not been addressed in previous studies. Among the limited research conducted in this area, Zadsaleh et al. (2012) identified indicators of argillic alteration (kaolinite and montmorillonite) and advanced argillic alteration (pyrophyllite and alunite) based on X-ray diffraction method. Therefore, this research aims to systematically investigate the mineralogy, existing alteration types and their zoning patterns, geochemistry, microthermometry of fluid inclusions, and structural geological features, ultimately striving to achieve a comprehensive understanding of the genesis of this mineralization zone. The introduction of this mineralization system not only provides critical insights for exploration in the studied area but may also facilitate the identification of other epithermal-porphyry systems in the Toroud-Chah Shirin magmatic arc and other regions of Iran.
Material and methods
After completing field studies and processing satellite images, sampling was conducted across various silicic-argillic zones. A total of 30 polished thin sections and 20 thin sections were prepared for petrological, mineralogical, and ore microscopy studies. These samples were examined using an Olympus polarizing microscope at Clausthal University of Technology in Germany and Shahrood University of Technology. Additionally, two doubly polished sections from quartz-calcite veins were prepared to investigate the physicochemical properties of the mineralizing fluids. The temperature and salinity of the fluid inclusions were measured in the Economic Geology Laboratory at Shahrood University of Technology using a heating and freezing stage mounted on a polarized microscope with Linkam MDSG600 model. Following these procedures, X-ray diffraction (XRD) was conducted on 11 samples collected from altered sections (silicic and argillic) to identify the composition of clay minerals. The XRD was performed using a diffractometer equipped with copper tubes coated with nickel at Zarazma Laboratories in Tehran and the IELF at Clausthal University of Technology. Furthermore, several rock samples with minimal alteration, altered and mineralized ones were selected and examined at Acme Laboratories in Vancouver, Canada, using ICP-OES and ICP-MS methods to assess both major and trace elements. The analytical precision for major elements is ±1%, while most trace elements have an uncertainty of ±0.05%.
Results
The mineralized region features several argillic alteration zones and silica caps, located approximately 2 to 7 km north-northwest of the Chah Musa copper deposit (Figures 1 and 2). During field observations, several relatively intact outcrops of andesite were documented; however, many of these rocks have experienced significant silicic and argillic alterations, leading to a complete loss of their original texture and mineralogical composition.
Based on field and laboratory evidences, it appears that the mineral assemblages influenced by hydrothermal fluid activity exhibit a distinct zoning pattern. This distribution, identified solely through surface observations due to the absence of exploratory drilling, includes propylitic alteration (chlorite-epidote-albite-carbonate) at the outer margins, moderate argillic alteration (quartz-montmorillonite-smectite-illite-natrojarosite), and advanced argillic alteration (vuggy quartz, quartz-alunite, kaolinite, montmorillonite-illite) towards the center. The silica caps, vuggy quartz structures, and this zoning pattern (Figure 5) are consistent with the alteration patterns of high-sulfidation systems described by White and Hedenquist (1990), indicating the presence of hydrothermal fluids with a pH of less than 2 in this area (Stoffregen, 1987). These acidic fluids have resulted in the complete leaching of elements from the mineral-bearing rocks, forming residual silica in the silica caps or as quartz crystals filling the cavities.
Field studies and hand samples collected from the mineralized area under investigation reveal that the andesitic rocks contain silica-sulfide veins with varying thicknesses, ranging from 1 centimeter to 2 meters (Figure 3a). Mineralization is present as veins and veinlets that fill void spaces, as well as through replacement and disseminated occurrences (Figure 3a). The mineralized veins include hypogene sulfide phases such as pyrite, chalcopyrite, enargite, and galena, alongside supergene minerals like rutile, hematite, goethite, and limonite. The gangue minerals consist of variably thick quartz (both banded and vuggy), calcite, and clay minerals (Figure 6). At the surface, the hypogene sulfides have largely oxidized due to supergene processes, leading to their replacement by iron hydroxides, oxides, copper silicates (chrysocolla), copper carbonates (malachite, azurite), hematite, goethite, and limonite.
Fluid inclusion studies were conducted to investigate the nature and composition of the fluids involved in the mineralization processes observed in calcite and massive quartz crystals collected from the examined mineralized area. The results of the fluid inclusion study reveal final homogenization temperatures (Th) for the liquid phase ranging from 160 to 362.8 °C, final melting temperatures of ice (Tmice) between 1.3 and 5.9 °C, and salinity levels between 2.24 and 9.8 wt.% NaCl equivalent (Table 2 and Figure 9). These values align with those found in high-sulfidation (HS) epithermal systems (Hedenquist et al., 1998; Jannas et al., 1999).
Discussions
The studied area is situated in the northeastern section of the Toroud-Chah Shirin magmatic arc and lies within the northern margin of the structural zone of Central Iran. The mineralized veins are hosted in Eocene andesite rock and have experienced alteration due to the intrusion of hydrothermal fluids, leading to advanced silicification, argillic alteration, and propylitic alteration. Indicators such as the presence of enargite (a significant copper mineral in high-sulfidation deposits), vuggy quartz, extensive advanced argillic alteration in a hypogene form, and hypogene alunite (an indicator mineral for high-sulfidation deposits) suggest that the northeast mineralization area of Chah Musa is characteristic of high-sulfidation epithermal deposits.
The analysis indicates evidence of advanced argillic and silicic hydrothermal alterations, characterized by a silicified cap or lithocap at the center, with propylitic alteration surrounding it. Notable features in the studied area include vein texture and structure, hydrothermal breccia, vuggy quartz, and the mineralogical composition of the mineralization, which includes enargite and alunite. Mineralization occurs in two stages: hypogene stage (e.g., pyrite, chalcopyrite, enargite, galena, magnetite, and specularite) and supergene stage (e.g., goethite, limonite, malachite, and azurite). Gold concentrations in the analyzed samples are at anomalous levels. Results from the study of trapped two-phase fluid inclusions (L+V) in quartz reveal homogenization temperatures ranging from 160 to 362.8 °C, with salinity levels between 2.24 and 9.08 wt.% NaCl equivalent. Based on comparisons of structural characteristics, texture, mineralogy, alteration features, and ore-forming fluid properties, the copper-gold vein mineralizations in the studied area exhibit significant similarities to high-sulfidation epithermal deposits, which may potentially be associated with porphyry copper-gold-molybdenum deposits at depth.
Gómez Maqueo Anaya Sofía, Althausen Dietrich, Faust Matthias
et al.
A mineralogical database is included in the simulation of mineral dust atmospheric life cycle for the chemistry and transport model COSMO5.05-MUSCAT. Evaluation of the ability of the model to reproduce the atmospheric drivers and the spatial-temporal resolution of mineral dust in the atmosphere is done through comparisons with remote sensing measurements in the Sahara Desert region for January-February 2022. Results show simultaneously good agreements and suggest that discrepancies could be explained due to the methods used for calculating mineral dust in the atmosphere not considering compositional differences.
Critical minerals in coal deposits have attracted much attention in recent years because of their potential economic significance. However, these critical minerals are becoming scarce and expensive as their resources in conventional ores are exhausted. One promising source of W is coal and/or coal combustion products. The input of terrigenous materials and hydrothermal-fluid are the main factors affecting the enrichment of strategic mineral elements in coal. The origin and mode of occurrences of valuable element W in the M3 coal seam of the Puyang Mine is still unclear, although W was found significantly enriched. The X-ray difflraction analyzer (XRD), Scamning Electron Microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS), X-ray fluorescence spectrometry (XRF), Inductively Coupled PlasmaMass Spectrometer (ICP-MS) and other instruments were used to analyze the composition of minerals and elements in the M3 coal seam of the Puyang Mine. The main modes of W occurrence were established using selective leaching procedure. The content of W in humic acid and coal was compared by alkaline extraction to explore the binding ability of W and organic matter (humic acid). The influence of sedliment-source region and hydrothermal-fluid on the enrichment of critical element tungsten in M3 coal seam of the Puyang Mine was discussed based on the study of mineralogy and element geochemistry of these coal seams of the Puyang Mine. The results show that: the M3 coal is of medium-high volatile lignite rank and has a low-medium ash yield; The minerals in the M3 coal are mainly quartz, pyrite and calcite, to a lesser extent, kaolinite, illite, and siderite; The major element oxides in the M3 coal are dominated by SiO2 and Al2O3. Tungsten is significantly enriched in the M3 coal, with a weighted average of 70 μg/g (maximum content 325 μg/g), being 59 times of the world low-rank coal’s average. The average coal ash content can reach 359.76 μg/g (maximum content 1432.35 μg/g); The results of sequential leaching and correlation analysis indicate that tungsten in the M3 coal primarily occurs in organic matter, followed by silicate and aluminosilicate. A small amount of tungsten may also occur in pyrite, as well as in acid-insoluble minerals or in fine-grained minerals shielded by the organic matter of the coal. The W in the humic acid of the present study ranges from 58.8 to 123 μg/g, with a weighted average of 86.4 μg/g. The W content of humic acid is 1.37 times that of W in raw coal, indicating that W in M3 coal has a strong binding ability to organic matter (humic acid); The main provenance of coals in the Puyang Mine is the granite in the Wenshan. Due to the supply of clastic materials from the source rocks and hydrothermal-fluid, the W in the M3 coal is significantly enriched.
Andrei A. Shiryaev, Felix V. Kaminsky, Anton D. Pavlushin
et al.
Ballas is a rare polycrystalline diamond variety characterized by a radially oriented internal structure and spheroidal outer shape. The origin of natural ballases remains poorly constrained. We present the results of a comprehensive investigation of two classic ballas diamonds from Brazil. External morphology was studied using SEM, high-resolution 3D optical microscopy, and X-ray tomography. Point and extended defects were examined on polished central plates using infra-red, photo- and cathodoluminescence spectroscopies, and electron back-scattering diffraction; information about nanosized inclusions was inferred from Transmission Electron Microscopy. The results suggest that fibrous diamond crystallites comprising ballas are split with pronounced rotation, causing concentric zoning of the samples. Pervasive feather-like luminescing structural features envelop single crystalline domains and most likely represent fibers with non-crystallographic branching. These features are enriched in N3 point defects. Twinning is not common. The nitrogen content of the studied samples reaches 700 at.ppm; its concentration gradually increases from the center to the rim. Annealing of the ballases took place at relatively high temperatures of 1125–1250 °C; the annealing continued even when the samples were fully grown, as suggested by the presence of the H4 nitrogen-related defects in the outer rim. Presumably, the ballas diamond variety was formed at high supersaturation but in conditions favoring a small growth kinetic coefficient. The carbon isotopic composition of the studied ballases (δ<sup>13</sup>C = −5.42, −7.11‰) belongs to the main mode of mantle-derived diamonds.
Based on the analysis of tectonic background and coal-accumulating environment of Jungar coalfield, the coal petrological characteristics, inorganic mineral composition, distribution and occurrence regularity of coal and gangue in No.6 coal of the Junger coalfield are studied, and the genesis is determined byutilizing the research methods of coal petrology, mineralogy and geochemistry.The study shows that the average contents of the inertinite, vitrinite and exinite in the maceral of No.6 coal in the study area are 59 %, 28 % and 13 %, respectively.Compared with the Late Paleozoic coals in other areas of North China, the content of the inertinite is high, which reflects an adequate supply of surface water during the formation of No.6 coal seam.The main inorganic minerals in coal and gangue are kaolinite and boehmite, associated with quartz, calcite, siderite, pyrite, anhydrite, anatase and svanbergite.The vertical changes of the mineral composition and main chemical elements of No.6 coal indicate that the middle of the coal seam is rich in boehmite, while the upper and lower parts are rich in kaolinite.There are three origins of kaolinite: colloidal precipitation crystallization, terrestrial transport sedimentation and volcanic ash alteration.And there are two origins of boehmite: alumina colloidal precipitation crystallization and desilication alteration of kaolinite.
<p>The Paleocene–Eocene Thermal Maximum (PETM; <span class="inline-formula">∼</span> 55.9 Ma) was a
period of rapid and sustained global warming associated with significant
carbon emissions. It coincided with the North Atlantic opening and
emplacement of the North Atlantic Igneous Province (NAIP), suggesting a
possible causal relationship. Only a very limited number of PETM studies
exist from the North Sea, despite its ideal position for tracking the impact
of both changing climate and NAIP activity. Here we present
sedimentological, mineralogical, and geochemical proxy data from Denmark in
the eastern North Sea, exploring the environmental response to the PETM. An
increase in the chemical index of alteration and a kaolinite content up to
50 % of the clay fraction indicate an influx of terrestrial input shortly
after the PETM onset and during the recovery, likely due to an intensified
hydrological cycle. The volcanically derived zeolite and smectite minerals
comprise up to 36 % and 90 % of the bulk and clay mineralogy
respectively, highlighting the NAIP's importance as a sediment source for the
North Sea and in increasing the rate of silicate weathering during the PETM.
X-Ray fluorescence element core scans also reveal possible hitherto unknown
NAIP ash deposition both prior to and during the PETM. Geochemical proxies
show that an anoxic to sulfidic environment persisted during the PETM,
particularly in the upper half of the PETM body with high concentrations of
molybdenum (Mo<span class="inline-formula"><sub>EF</sub></span> <span class="inline-formula">></span> 30), uranium (U<span class="inline-formula"><sub>EF</sub></span> up to 5), sulfur
(<span class="inline-formula">∼</span> 4 wt %), and pyrite (<span class="inline-formula">∼</span> 7 % of bulk). At
the same time, export productivity and organic-matter burial reached its
maximum intensity. These new records reveal that negative feedback
mechanisms including silicate weathering and organic carbon sequestration
rapidly began to counteract the carbon cycle perturbations and temperature
increase and remained active throughout the PETM. This study highlights the
importance of shelf sections in tracking the environmental response to the
PETM climatic changes and as carbon sinks driving the PETM recovery.</p>
The pH value of plaeofluid exerts great influence on the formation of the secondary pores of sandstones.In the paper, the control of the acid and alkaline diagenetic fluid environment on the reservoir quality was analyzed in the Upper Paleozoic tight sandstones in the Ordos basin.Based on the plenty of survey of casting thin section, scanning electron microscope, X-ray diffraction, routine testing of physical properties, and high pressure mercury injection, the characteristics of petrology and mineralogy, physical properties, diagenesis, genetic types of pores, and pore-throat structure within the Upper Paleozoic tight sandstones were detailedly investigated in the Linxing and Shenfu district, eastern Ordos Basin.The identification, zonage, and distribution of the acid and alkaline diagenetic environment within tight sandstones as well as the evolution of diagenetic fluid environment and its reponse of the physical properties were investigated.Results showed that the upper strata underwent a diagenetic fluid evolution of alkaline-acid-alkaline mode during the burial process, whereas the lower strata experienced a mode of acid-alkaline.Acid diagenetic environment was characterized by feldspar dissolution, quartz overgrowth, and deposition of authigenic kaolinite, in which feldspar dissolution pores, intercrystalline pores of clay minerals developed with relatively large pore radius and better reservoir quality.Alkaline diagenetic environment was featured by quartz dissolution and deposition of authigenic chlorite, in which quartz dissolution pores and intercrystalline pores of clay minerals developed with relatively small pore radius and poor reservoir quality.The case of transitional zone of acid and alkaline zone(TZAA) falls in between acid zone(AZ) and alkaline zone(AlZ).Nevertheless, the physical properties are best in the AZ, followed by TZAA.The distribution of the AZ, AIZ and TAZZ and their responds to the physical properties are significant to the reservoir evaluation.
Geology, Engineering geology. Rock mechanics. Soil mechanics. Underground construction
Abstract The distribution of rheologically strong cratons, and their weakening by metamorphic hydration reactions, is of fundamental importance for understanding first‐order strength contrasts within the crust and the resulting controls on the tectonic evolution of the continents. In this study, the Douglas Harbor structural window within the Paleoproterozoic Trans‐Hudson orogen of Canada is used to study the hydration of the footwall Archean Superior craton basement by water released from the overlying Paleoproterozoic Cape Smith thrust‐fold belt. Phase equilibria modeling is applied to quantify the Archean and Paleoproterozoic metamorphic conditions, and to determine the effect of hydration on basement mineralogy. The amount of structurally bound water within the basement is calculated and shown to decrease as a function of distance below the basal décollement of the thrust‐fold belt. Applying a reactive fluid transport model to these results, the rate coefficient for fluid‐rock reaction is constrained to be 10−19 mol−1m3s−1, and the diffusivity of water through the grain boundary network to be 10−9 m2s−1 at the ambient metamorphic conditions of 570°C and 7.5 kbar. This newly documented rate of water diffusion is three orders of magnitude slower than thermal diffusion, implying that hydration by diffusion may be the rate‐limiting factor in the weakening of cratons, and therefore plays an important role in their geological persistence. This conclusion is consistent with field observations that Paleoproterozoic strain in the Douglas Harbor structural window is restricted to hydrated portions of the Archean Superior craton basement.
The mineralogy of slags of the Shuvakish ironworks plant is studied. The plant had been operated during the reign of Peter the Great from 1704 to 1716 years and was located within the presentday northwestern outskirts of Yekaterinburg. The slags are composed of fayalite aggregate with a significant content of hercynite and wüstite and contain spherules of iron, glass, leucite and ferromerrillite. The chemical composition of rock-forming and ore minerals is determined on a JSM-6390LV (Jeol) SEM equipped with an INCA Energy 450 X-Max 80 EDS (Oxford Instruments) (Institute of Geology and Geochemistry UB RAS, Yekaterinburg). The slags formed as a result of bloomery iron production. Their formation temperature is estimated in a range of 1177 °С on the basis of eutectic crystallization of wüstite and fayalite. The Shuvakish plant was supplied with marsh iron ore, which was most likely extracted in the nearest Moleben swamp located to the north from the plant.
BACKGROUND There are large amounts of copper-lead-zinc polymetallic sulfide ore resources in Yunnan Province, China, but the efficient separation of these resources remains a major problem. OBJECTIVES To improve the separation efficiency of valuable minerals in mixed concentrates. METHODS In this study, the major elemental content, phase composition, mineral composition, particle size characteristics, and monomer liberation degree of a mixed concentrate were analyzed using a variety of modern detection methods such as chemical analysis, X-ray diffraction, and mineral liberation analysis (MLA). RESULTS The results showed that the mixed concentrate had fine particles, and some minerals occurred as intergrowths or inclusions. The monomer liberation degree of the target minerals chalcopyrite, galena, and sphalerite was medium to low, ranging from 69.28% to 70.56%. It was preliminarily predicted that the theoretical separation efficiencies of copper, lead, and zinc in the mixed concentrate were 71.63%, 62.97% and 72.72%, respectively. CONCLUSIONS Improving the grinding fineness of mixed concentrates to promote the full liberation of metal minerals is a key way to improve the separation efficiency of copper, lead, and zinc minerals.
Mineralogical and geochemical characteristics of coals provide crucial information on their potential clean, efficient, and integrated utilization. In this paper, the mineralogical and geochemical behaviors of the No. 5 coals of the Taiyuan Formation in the Weibei Coalfield, North China, were investigated, and their geological controlling factors were subsequently discussed. The minerals in the Weibei coals mainly consist of kaolinite (8.3%), calcite (5.0%), and pyrite (3.1%), with minor proportions of tobelite (2.9%), dolomite (1.7%), quartz (1.8%), and traces of siderite (0.4%) and gypsum (0.6%). Several critical elements, including Nb (19.8 mg/kg), Ta (3.6 mg/kg), Zr (71.0 mg/kg) and Li (32.3 mg/kg), occur at concentrations higher than those averages for world hard coals, making the Weibei coals potential sources of these critical elements. Several factors, terrigenous material, seawater invasion, and hydrothermal fluids are responsible for these mineralogical and geochemical characteristics. The L-type rare earth elements and yttrium (REE-Y) enrichment in the roofs and partings, Al<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> and Zr/TiO<sub>2</sub>-Nb/Y plots, and negative Eu and weak negative Ce anomalies in the Weibei coals indicate a felsic-intermediate dominated sediment provenance primarily derived from the Qilian-Qinling Oldland on the South. Marine bioclastic limestone, negative Ce and positive Y anomalies in coals imply the influence of seawater on the Weibei coals. Last but not least, the cleat-infilling and/or fracture-infilling calcite, pyrite, barite, and tobelite as well as the positive Eu and Gd anomalies, H-type, and M-type REE-Y enrichment patterns suggest the influence of hydrothermal fluids, which lead to re-distribution of some critical elements from roof and parting to the underlying coal seam.
Roxana Bugoi, Cristina Talmaţchi, Constantin Haitǎ
et al.
Abstract Archaeometric investigations using OM (optical microscopy) and micro-PIXE (particle induced X-ray emission) were performed on 45 ceramic shards unearthed in archaeological excavations at Păcuiul lui Soare (southeastern Romania) and dated to the eleventh century AD. This study aimed to get clues about the raw materials and manufacturing techniques used by the potters from the Lower Danube area during the Byzantine period. The analyzed ceramic fragments were selected according to stylistic and archaeological criteria, trying to cover the entire palette of potteries discovered at this site. OM detailed the characteristics of the fabric (texture, microstructure and porosity), mineralogy, surface treatments and firing of the shards. Principal component analysis (PCA) of the PIXE data highlighted two main categories of shards with distinct compositional signatures, separated mainly by their aluminum and calcium content. Micro-PIXE maps of the interfaces between the glaze and the ceramic body showed that the green glaze is rich in lead oxide compared to the underlying ceramic body. The results of these investigations were compared to the ones previously obtained on coeval potteries from other Byzantine archaeological sites, i.e. Hârşova and Oltina, trying to get some hints about the consumption and circulation of pottery in the Lower Danube region at the beginning of the second millennium AD.
Jaime Antonio de Almeida, Janaina Corrêa, Catiline Schmitt
ABSTRACT A commonly accepted concept holds that highly fertile, shallow soils are predominant in the Basaltic Hillsides of Santa Catarina State, in southern Brazil, but their agricultural use is restricted, either by excessive stoniness, low effective depth or steep slopes. Information about soil properties and distribution along the slopes in this region is, however, scarce, especially regarding genesis and clay fraction mineralogy. The objective of this study was to evaluate soil properties of 12 profiles distributed in three toposequences (T) of the Basaltic Hillsides in the State of Santa Catarina, two located in the valley of the Peixe River (Luzerna - T1 and Ipira - T2) and one in Descanso, in the far West of the state (T3). The main focus was the mineralogical composition of the clay fraction, identified by X-ray diffractometry (XRD), and its relations with the soil chemical properties. The morphological, chemical, and mineralogical properties of the soils of the toposequences differed from each other. In most soils, the position of the most intense XRD reflections indicated predominance of kaolinite (K) however, for being broad and asymmetric, a participation of interstratified kaolinite-smectite (K-S) was assumed. Soils of T2 and T3, located in regions with higher temperatures, lower water surplus, and lower altitude than those of T1, were more fertile, mostly redder, and contained higher proportions of smectites (S) and interstratified K-S mineral, accounting for a higher activity of the clay fraction of most soils. The T1 soils were generally less fertile, with lower clay activity and, aside from kaolinite, contained smectites with interlayered hydroxy-Al polymers (HIS). The low estimated smectite contents of the most fertile soils of all toposequences disagree with the high values of cation exchange capacity (CEC) and clay activity related to pure kaolinite soils. The broad and asymmetric reflections of most of the supposed kaolinites identified as dominant minerals indicate the presence of K-S interlayers, most likely contributing to raise the CEC of the soils.
This wok shows the results of a valorisation study to use rice husk ash as raw material to develop glass-ceramic materials. An original glass has been formulated in the base system MgO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> with addition of B<sub>2</sub>O<sub>3</sub> and Na<sub>2</sub>O to facilitate the melting and poring processes. Glass characterization was carried out by determining its chemical composition. Sintering behaviour has been examined by Hot Stage Microscopy (HSM). Thermal stability and crystallization mechanism have been studied by Differential Thermal Analysis (DTA). Mineralogy analyses of the glass-ceramic materials were carried out using X-ray Diffraction (XRD). Results show that it is possible to use ash rice husk to produce glass-ceramic materials by a sintercrystallization process, with nepheline (Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub> · SiO<sub>2</sub>) as major crystalline phase in the temperature interval 700-950ºC and forsterite (2MgO·SiO<sub>2</sub>) at temperatures above 950ºC.<br><br>En este trabajo se muestran los resultados de un estudio de valorización de la ceniza de cáscara de arroz como materia prima en la obtención de materiales vitrocerámicos. Se ha formulado un vidrio en el sistema base MgO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> incorporando B<sub>2</sub>O<sub>3</sub> y Na<sub>2</sub>O para facilitar los procesos de fusión y colado del vidrio. El vidrio se ha caracterizado mediante la determinación de su composición química. Su comportamiento frente a la sinterización se ha llevado a cabo mediante Microscopía de Calefacción (MC). La estabilidad térmica de las muestras y el mecanismo de cristalización preferente se ha estudiado mediante Análisis Térmico Diferencial (ATD). La mineralogía de los materiales vitrocerámicos se ha llevado a cabo por Difracción de rayos-X (DRX). Los resultados obtenidos muestran que es posible utilizar ceniza de cáscara de arroz para producir materiales vitrocerámicos mediante un proceso de sinterización seguido de cristalización, con nefelina (Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub>·2SiO<sub>2</sub>) como fase cristalina mayoritaria en el intervalo de temperatura 700º-950ºC y forsterita (2MgO·SiO<sub>2</sub>) a temperaturas superiores a 950ºC.
En el artículo se muestran los elementos fundamentales de un algoritmo cuyo objetivo es establecer el contenido y el orden de los procedimientos necesarios para realizar el control del cálculo de extracciones en la mina de la empresa Ernesto Che Guevara que explota, a cielo abierto, yacimientos lateríticos ferroniquelíferos en la región de Moa, Cuba. Asimismo se presenta el diseño de los diálogos informáticos que han automatizado el algoritmo en la aplicación informática Tierra.