Hasil untuk "Mineralogy"

Karmina A. Aquino, Gretchen L. Früh‐Green, Stefano M. Bernasconi et al.

Abstract Although the serpentinite‐hosted Lost City hydrothermal field (LCHF) was discovered more than 20 years ago, it remains unclear whether and how the presence of microbes affects the mineralogy and textures of the hydrothermal chimney structures. Most chimneys have flow textures comprised of mineral walls bounding paleo‐channels, which are preserved in inactive vent structures to a varying degree. Brucite lines the internal part of these channels, while aragonite dominates the exterior. Calcite is also present locally, mostly associated with brucite. Based on a combination of microscopic and geochemical analyses, we interpret brucite, calcite, and aragonite as primary minerals that precipitate abiotically from mixing seawater and hydrothermal fluids. We also observed local brucite precipitation on microbial filaments and, in some cases, microbial filaments may affect the growth direction of brucite crystals. Brucite is more fluorescent than carbonate minerals, possibly indicating the presence of organic compounds. Our results point to brucite as an important substrate for microbial life in alkaline hydrothermal systems.

Zhengzhen An, Yue Zhao, Yue Zhao et al.

This study focuses on understanding the fractal characteristics and controlling factors of micropore structures within organic-rich shale of the Cambrian Shuijingtuo Formation in the Yichang area of Hubei Province. Mineralogy, petrology, and organogeochemical characteristics were confirmed through comprehensive testing methods, including whole-rock X-ray diffraction and organic geochemical analyses. Additional experiments included low-temperature carbon dioxide adsorption, low-temperature nitrogen adsorption, and high-pressure mercury injection. Fractal dimensions of micropores, mesopores, and macropores were calculated using the V-S, FHH, and MENGER sponge models, respectively. Results indicate that the Cambrian Shuijingtuo Formation represents a typical deposit from an alkaline water body, resulting in high-calcareous shale. Fractal dimensions were as follows: micropores (D1) ranged from 2.1138 to 2.3475 (average 2.2342), mesopores (D2) ranged from 2.5327 to 2.7162 (average 2.6171), and macropores (D3) ranged from 2.7361 to 2.9316 (average 2.82905). Correlations were observed between total organic carbon (TOC) content and Ro with D1 and D2 (positive) and D3 (negative). Shale pore volume and specific surface area exhibited positive correlations with D1 and D2 but negative correlations with D3. High bio-deposited silica positively influenced micropore and mesopore development, while clay mineral compaction and dehydration transformations favored macropore development. Carbonate minerals primarily contributed to regular macropores, with complex correlations involving fractal dimensions D1, D2, and D3. The research results provide theoretical support for analyzing pore fractal characteristics of shallow old Marine shale reservoirs and the prediction and development plan of high-quality reservoirs of the Shuijingtuo Formation in the Yichang area.

B. A. Pummell, J. B. Thomas

<p>Inclusion–host elastic thermobarometers are widely used to determine the pressure and temperature (<span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span>) histories of metamorphic rocks. Complex metamorphic <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> paths can affect the pressures that develop in host–inclusion systems. There are limited experimental studies that investigate how changing <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> conditions may re-equilibrate or “reset” residual pressures of inclusions. To evaluate re-equilibration of the quartz-in-garnet (QuiG) elastic thermobarometer, we performed single-, two-, and three-stage isothermal experiments. In the first stage of the experiments, oxide starting materials hydrothermally crystallised to grow garnet crystals with quartz inclusions between 700 and 800 °C and 1.0 and 3.2 GPa with constant <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> conditions for 48 h. In the second and third stage of the experiments, we isothermally changed pressure by 1.0 to 1.2 GPa for durations up to 38 d. We used Raman spectroscopy to measure strain-induced changes to the 128, 207, and 465 cm<span class="inline-formula">⁻¹</span> Raman bands of quartz inclusions to determine the inclusion pressures (<span class="inline-formula"><i>P</i>_inc</span>) and entrapment pressures (<span class="inline-formula"><i>P</i>_trap</span>) at the experimental temperature. The multi-stage experiments show that elasticity primarily controlled changes to <span class="inline-formula"><i>P</i>_inc</span> values that occur from <span class="inline-formula"><i>P</i>_trap</span> through quenching to room conditions and that <span class="inline-formula"><i>P</i>_inc</span> values measured at room conditions along with elastic modelling can be used to accurately calculate <span class="inline-formula"><i>P</i>_trap</span>. Quartz <span class="inline-formula"><i>P</i>_inc</span> values in two-stage experiments re-equilibrated to give <span class="inline-formula"><i>P</i>_inc</span> values between <span class="inline-formula"><i>P</i>₁</span> and <span class="inline-formula"><i>P</i>₂</span>. The three-stage isothermal experiments show that the observed changes to inclusion pressures are reversible along different <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> paths to restore the re-equilibrated <span class="inline-formula"><i>P</i>_inc</span> values back to their original entrapment isomeke at <span class="inline-formula"><i>P</i>_trap</span>. For rocks that underwent protracted metamorphism along complicated <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> paths, the re-equilibration experiments and viscoelastic calculations show that QuiG may underestimate maximum <span class="inline-formula"><i>P</i>_trap</span> conditions.</p>

Elena Agasheva, Alyona Gudimova, Elena Malygina et al.

This paper presents the reconstruction of the architecture of the lithospheric mantle, including its thermal state and thickness, as well as the scale and efficiency of its sampling by four kimberlites from the Arkhangelsk diamondiferous province: Arkhangelskaya, Lomonosovskaya, V. Grib, and TSNIGRI-Arkhangelskaya. These kimberlites differ in terms of their composition, diamond content, and location. Data presented include the major-element composition of clinopyroxene xenocrysts (>2000 grains), P–T calculations from compositionally filtered Cr-diopside grains, and the reconstruction of local paleogeotherms. Additionally, we used available data on Ni content in peridotitic garnet xenocrysts to calculate their T values and project them onto local Cr-diopside-derived geotherms to reconstruct the vertical distribution of mantle xenocrysts and assess the efficiency of lithospheric mantle sampling by different kimberlites. We identified the presence of a >200 km-thick lithospheric mantle beneath the region at the time of kimberlite emplacement. We also found that the diamond content of the studied pipes was, to some extent, dependent on the following set of factors: (1) the thermal state of the lithospheric mantle; (2) the width of the real “diamond window” marked by mantle xenocrysts, especially by diamond-associated garnets; and (3) the efficiency of lithospheric mantle sampling by kimberlite. The results of this study can be used to inform diamond exploration programs within the region.

Elena Tarakhovskaya, Andrea Marcillo, Caroline Davis et al.

Metabolite profiling using gas chromatography coupled to mass spectrometry (GC–MS) is one of the most frequently applied and standardized methods in research projects using metabolomics to analyze complex samples. However, more than 20 years after the introduction of non-targeted approaches using GC–MS, there are still unsolved challenges to accurate quantification in such investigations. One particularly difficult aspect in this respect is the occurrence of sample-dependent matrix effects. In this project, we used model compound mixtures of different compositions to simplify the study of the complex interactions between common constituents of biological samples in more detail and subjected those to a frequently applied derivatization protocol for GC–MS analysis, namely trimethylsilylation. We found matrix effects as signal suppression and enhancement of carbohydrates and organic acids not to exceed a factor of ~2, while amino acids can be more affected. Our results suggest that the main reason for our observations may be an incomplete transfer of carbohydrate and organic acid derivatives during the injection process and compound interaction at the start of the separation process. The observed effects were reduced at higher target compound concentrations and by using a more suitable injection-liner geometry.

Adekemi Ayodele, Akinropo Olajumoke, Sibel Pamucku et al.

The effective use of residual laterite soils is usually hindered because of their mineralogy and high fines content. This paper studied the potential improvement in the geotechnical and mineralogical properties of fly ash-treated residual laterite collected from Southwest Nigeria. Some physical and geotechnical properties, such as plasticity, compaction, unconfined compressive strength (UCS), and California Bearing ratio (CBR) of untreated and treated laterites were determined using ASTM standard methods. Stabilization was achieved by mixing the laterite with varying proportions (0%, 3%, 6%, 9%, 12%, and 15% by mass of dry laterite) of fly ash. Mineralogical analysis of untreated and treated laterite was done using the X-ray diffractometer (XRD). The results showed a slight initial increase at low proportions of fly ash (at 3%) in the plasticity properties and a subsequent decrease (of up to 65%) afterward. The UCS and CBR of the treated laterite increased over 100% (maximum UCS 110% and maximum CBR 183%) at 6% fly ash content. XRD analysis showed the formation of new minerals, predominantly portlandite, within the stabilized soils. This study confirmed that using fly ash for the stabilization of residual laterite soils is potentially viable for road construction.

Jun Yang, Yueqin Qiu

Abstract Because the 2D (two-dimensional) characterization analysis of mineral dissemination characteristics requires complex sample preparation, destroys the sample structure, and produces stereological errors, a new method for analyzing mineral dissemination characteristics in the ore in situ, non-destructively and stereoscopically, is required. The research object in this paper is a medium–low grade calcareous-magnesium phosphate ore in Guizhou, and XMT (X-ray microtomography) and BPMA (BGRIMM Process Mineralogy Analysis) are used to conduct a comparative study of 3D (three-dimensional) and 2D analysis of mineral dissemination characteristics. The results of grain size analysis show that fluorapatite and gangue minerals belong to equal-grain dissemination, with very little fine particle content. The results of 2D analysis are finer than those of 3D analysis, but 3D non-destructive analysis produces more accurate results. In addition to particle size analysis, the binding relationship between minerals analysis results show that, when compared to the 2D distribution of minerals, 3D visualization can more intuitively and stereoscopically observe the distribution of minerals inside the ore and the intergrowth relationship between minerals. Through comparative study, it can be seen that the application of 3D visualization has developed a new method for the study of mineral dissemination characteristics, which makes up for the shortcomings of 2D analysis.

Pelin Güngör Yeşi̇lova

Oligocene aged evaporite formations are observed in shallow sea-sabkha environments that develop in highly restricted conditions from sea in northeastern of the Muş basin. Evaporites are observed as alternated and intercalated with clastics and carbonates that developed under the control of factors such as climate, tectonism, volcanism and diagenesis. Evaporites consist of primary and secondary gypsum and minor anhydrite. In petrographic and minerologic examinations, secondary gypsum textures such as alabastrin, porphyroblastic and satin spar with anhydrite relicts, late diagenetic calcite, bitumen and bioturbation traces were detected. In SEM-EDS studies; celestine crstals, autogenic and detritic clay and quartz grains and euhedral dolomite mineral were observed. As a result of all these studies, the conditions and phases of the evaporites from the sedimentation stage to early diagenesis and late diagenesis processes of the evaporites were illuminated. Secondary gypsum consists of the origin of primary anhydrite and gypsum. From the diagenetic fluids released during the gypsum-anhydrite transformation, the late diagenetic calcite and by the interaction of the ions carried by the hydrothermal solutions to the basin with the groundwater were formed the celestite. Stream activity in the basin was determined by the presence of detritic minerals in gypsum minerals.

Vojtěch Ettler, Markéta Cihlová, Alice Jarošíková et al.

Ore mining and processing in semi-arid areas is responsible for the generation of metal(loid)-containing dust, which is easily transported by wind to the surrounding environment. To assess the human exposure to dust-derived metal(loid)s (As, Cd, Cu, Pb, Sb, Zn), as well as the potential risks related to incidental dust ingestion, we studied mine tailing dust (n = 8), slag dust (n = 5) and smelter dust (n = 4) from old mining and smelting sites in northern Namibia (Kombat, Berg Aukas, Tsumeb). In vitro bioaccessibility testing using extraction in simulated gastric fluid (SGF) was combined with determination of grain-size distributions, chemical and mineralogical characterizations and leaching tests conducted on original dust samples and separated PM10 fractions. The bulk and bioaccessible concentrations of the metal(loid)s were ranked as follows: mine tailing dusts < slag dusts ≪ smelter dusts. Extremely high As and Pb bioaccessibilities in the smelter dusts were caused by the presence of highly soluble phases such as arsenolite (As2O3) and various metal-arsenates unstable under the acidic conditions of SGF. The exposure estimates calculated for an adult person of 70 kg at a dust ingestion rate of 50 mg/day indicated that As, Pb (and also Cd to a lesser extent) grossly exceeded tolerable daily intake limits for these contaminants in the case of slag and smelter dusts. The high risk for smelter dusts has been acknowledged, and the safety measures currently adopted by the smelter operator in Tsumeb are necessary to reduce the staff's exposure to contaminated dust. The exposure risk for the local population is only important at the unfenced disposal sites at Berg Aukas, where the PM10 exhibited high levels of bioaccessible Pb. Keywords: Dust mineralogy, Bioacessibility, Metal(loid)s, Namibia, Mining, Smelting

А.B. Nemov, E.V. Medvedeva, V.A. Kotlyarov

А body of metapsevdotahylite with Th-U-Y-REE mineralization including fergusonite-(Y) (up to 7 wt. % UO2) and «thorogummite» (up to 29 wt. % UO2) was found in the central alkaline band of the Ilmeny-Vishnevogorsky polymetamorphic complex. The study of minerals with rare and rare earth elements, their assemblages, and the genesis of host rocks significantly expand the potential of prediction and evaluation of the distribution of these minerals in metamorphic complexes.

Julio Montero-Matos, José Otaño-Nogel, Diosdani Guerrero-Almeida

Con el propósito de facilitar a los concesionarios de canteras de materiales para la construcción una herramienta metodológica para efectuar el cierre de estas y garantizar una minería sostenible se propuso un procedimiento en seis etapas a partir del diagnóstico realizado en 22 canteras, ubicadas en tres regiones mineras cubanas. El procedimiento busca disminuir los impactos ambientales provocados por la explotación de las canteras y ofrecer a la industria un estándar para lograr uniformidad en la planificación y ejecución del cierre con un costo mínimo.

W. Friederich, A. Brüstle, L. Küperkoch et al.

The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini–Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW–SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE–SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east–west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW–SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except in volcanic areas, where both appear to be unrelated, and in the forearc where compressional principal stresses are very well aligned with compressional principal strain rates. This finding indicates that, except for volcanic areas, microseismic activity in the southern Aegean is not controlled by small-scale local stresses but rather reflects the regional stress field. The lateral and depth variations of the stress field reflect the various agents that influence tectonics in the Aegean: subduction of the Hellenic slab, incipient collision with continental African lithosphere, roll back of the slab in the southeast, segmentation of the slab, arc volcanism and extension of the Aegean crust.

Marcondes L. da Costa, Thais A.B.C. Sanjad, Rosildo S. Paiva

During the 19th century, the most prominent buildings of the city of Belém were faced entirely with tiles manufactured in Portugal and Germany, which now exhibit distinct degrees of degradation. The Pinho mansion is one of the most important of these buildings and was selected for the investigation of the action of the tropical Amazonian climate on the degradation of the tiles. To achieve this objective, the tiles were mapped for organic and inorganic degradation, and samples were collected for analysis. The minerals were determined by XRD, the chemical composition by classical wet methods and SEM/EDS, and the microorganisms under the microscope. The results show that the German and Portuguese tiles are quite different in their composition. While both ceramic bodies are composed of SiO2 and Al2O3, CaO was found only in the Portuguese tile. The low Na2O and K2O contents indicate the addition of materials to reduce the fusion temperature. SiO2 and PbO are the main constituents of the glaze, with CoO and FeO being added as pigment. The ceramic body of the German tiles is constituted of quartz, mullite, and cristobalite, in contrast with the Portuguese tiles, which are made of quartz, gehlenite, diopside, calcite, and feldspars. The glazes are XRD-amorphous. The chemical and mineralogical differences between the German and Portuguese tiles indicate that they were produced from different raw materials under distinct thermal processes. The most prominent weathering-related modifications are the thin layers (German tiles), oxidation stains, dark stains, the detachment of the tile (Portuguese tiles), loss of the glaze and powdering of the ceramic body (Portuguese tiles) through the establishment of Cyanophyta and Bacillariophyta.. The distinct degradation patterns of the tiles exposed to the tropical Amazon climate are a consequence of their distinct mineralogy and chemistry.<br>As proeminentes edificações da cidade de Belém foram revestidas durante o século 19 com azulejos produzidos em Portugal e Alemanha que já apresentam distintos graus de degradação. O Palacete Pinho é uma das mais importantes destas edificações e foi selecionado para se investigar a ação do clima tropical amazônico sobre a degradação destes azulejos. Para atingir estes objetivos mapearam-se os azulejos desta edificação visando identificar as modificações de origem orgânica e inorgânica e coletas de amostras para análises. Os minerais foram determinados por DRX, a composição química por métodos clássicos úmidos e MEV/SED e os micro-organismos por microscopia. Os resultados obtidos mostram que os azulejos Portugueses e Alemães são distintos entre si. Enquanto o biscoito é composto de SiO2 e Al2O3, CaO foi encontrado apenas nos Portugueses. Os baixos conteúdos de Na2O e K2O indicam adição de materiais para redução da temperatura de fusão. SiO2 e PbO compõem o vidrado, já CoO e FeO foram adicionados como pigmentos. O biscoito dos azulejos Alemães é constituído de quartzo, mullita e cristobalita, ao contrário do Português com quartzo, gehlenita, diopsídio, calcita e feldspatos. Os vidrados são amorfos ao DRX. As diferenças químicas e mineralógicas entre os azulejos Portugueses e Alemães indicam que foram produzidos por matéria prima distinta, bem como processo termal. As alterações relacionadas com o intemperismo são as finas camadas de detritos (nos Alemães), manchas de oxidação, manchas escuras, descolamento do azulejo (no Português); perda de vidrado e biscoito tornando-se pulverulento como consequência do estabelecimento de Cyanophyta e bacillariophyta (Português). As distintas feições de degradação dos azulejos refletem as suas diferenças mineralógicas e químicas expostas ao clima tropical Amazônico.

Clara L. Reynaldo-Argüelles

En las empresas mineras de la industria del níquel en Cuba la eficiencia económica se evalúa mediante dos únicos indicadores que no incluyen el análisis de la dimensión ambiental. En este artículo se realiza un estudio comparativo de los métodos internacionalmente aplicados para evaluar impactos ambientales con el fin de proponer una metodología que incluya indicadores económico-ambientales para la minería del níquel. La metodología que se propone formula nueve indicadores que, basados esencialmente en los costos, permiten medir la responsabilidad ambiental de las empresas. La aplicación de estos indicadores minimiza la incidencia de los costos de la actividad minera en el costo total de la empresa, facilita la planificación, el uso adecuado y el control de los recursos naturales, y la asunción de conductas responsables hacia el entorno.

D. Green, A. .. Ringwood

E. Anders

J. Verhoogen

M. Leinen, G. Heath

B. Wilkinson