Hasil untuk "Mineralogy"

Robert Blair Vocci

A. J. Cawood, D. A. Ferrill, K. J. Smart et al.

<p>Understanding the distribution and geometry of subsurface faults is critical for predicting fault penetration and associated leakage of fluids such as groundwater, hydrocarbons, and injected anthropogenic waste through sealing intervals. Fault dimensions are often underestimated due to the resolution limits of seismic reflection data, which only image portions of faults with sufficient displacement to offset seismic reflectors. To address this fault underestimation problem, we quantify relationships between host rock composition and fault displacement gradients using a well-exposed outcrop of normal faults in mechanically layered sedimentary rocks in the footwall to the west branch of the Moab Fault, Utah. We integrate high-resolution digital photogrammetry, structural mapping, X-ray diffraction (XRD) mineralogy, and Schmidt rebound measurements to analyze how mineralogy and mechanical properties influence fault displacement vs. height relationships. Our results indicate that normal fault displacement gradients tend to be higher in less competent beds and lower in more competent strata, and that fault displacement gradient is positively correlated with clay content and negatively correlated with strong minerals (e.g., quartz, feldspar, dolomite). Outcrop-derived relationships are used to build a predictive framework that uses fault displacement and mineralogy to predict fault height. We apply this framework to a worked seismic interpretation example and demonstrate that fault dimensions are likely substantially underestimated in conservative seismic interpretations. Our results highlight the importance of mechanical stratigraphy in controlling fault geometry and provide a data-driven approach for estimating sub-seismic fault dimensions, with implications for reservoir characterization, fluid containment, and geohazard assessment.</p>

Wenbao Liu, Rui Ding, Yonglun Wang et al.

Abstracts: In response to the challenges posed by the complex mineralogy of red mud and the low efficiency of conventional beneficiation processes, this study proposes a synergistic reduction roasting approach using sodium carbonate and coal for iron extraction. Through systematic investigation of key factors—including roasting temperature, additive dosage, grinding time, and magnetic intensity—the optimal conditions were identified as roasting at 1150 °C for 1.5 h with 7.5% sodium carbonate and 15% pulverized coal, yielding an iron concentrate grade of 90.37% and a recovery rate of 82.23%. Response surface methodology revealed a significant interactive effect between temperature and coal dosage, and a corresponding predictive model was established. XRD and SEM-EDS analyses indicated that sodium carbonate facilitates melt-phase reconstruction, enhances porosity to improve permeability for the reducing agent, and catalyzes the conversion of olivine (Fe₂SiO4) and hercynite (FeAl2O4) to metallic iron. Combined kinetic and thermodynamic analyses confirmed the reduction pathway: Fe2O3→Fe3O4→FeO→Fe. The addition of sodium carbonate significantly reduces the Gibbs free energy (ΔG) of the reaction through the formation of low-melting-point compounds, thereby promoting the spontaneous reduction of iron oxides. This study provides both theoretical insights and practical strategies for the sustainable valorization of red mud.

Xiaoyu Wang, Songqing Zheng, Yingfu He et al.

Reactive transport in porous media exists ubiquitously in natural and industrial systems—reformation of geological energy repository, carbon dioxide (CO₂) sequestration, CO₂ storage via mineralization, and soil remediation are just some examples where geo-/bio-chemical reactions play a key role. Reactive transport models are expected to provide assessments of (1) the effective property variation and (2) the reaction capability. However, the synergy among flow, solute transport, and reaction undermines the predictability of the existing model. In recent decades, the Micro-Continuum Approach (MCA) has demonstrated advantages for modeling pore-scale reactive transport and high accuracy compared with experiments. In this study, we present an MCA-based numerical framework that simulates dissolution/erosion or precipitation in digital rocks. The framework imports two- or three-dimensional digital rock samples, conducts reactive transport simulations, and evaluates dynamic changes in porosity, surface area, permeability tensor, tortuosity, mass change, and reaction rate. The results show that samples with similar effective properties, e.g., porosity or permeability, may exhibit different reaction abilities, suggesting that the pore-scale geometry has a strong impact on reactive transport. Additionally, the numerical framework demonstrates the advantage of conducting multiple reaction studies on the same sample, in contrast to reality, where there is often only one physical experiment. This advantage enables the identification of the optimal condition, quantified by the dimensionless Péclet number and Damköhler number, to reach the maximum reaction. We believe that the newly developed framework serves as a toolbox for evaluating reactivity capacity and predicting effective properties of digital samples.

J. Spence

Fátima Ruiz-Blas, Alexander Bartholomäus, Cynthia Henny et al.

Lake Towuti, Sulawesi, Indonesia is an ancient tectonic lake, exhibiting iron-rich, sulfate-poor anoxic deep waters. Temporal variations in water column stratification led to sediment accumulation under variable redox conditions. Such ferruginous settings make Lake Towuti an ideal study site to evaluate how a cryptic sulfur cycle could possibly operate under a scarcity of sulfate and abundance of iron minerals, similar to Earth’s primitive oceans. Here, we integrate downcore profiles for pore water geochemistry, reactive iron mineralogy, and bulk sediment elemental composition with microbial cell counts, sulfate reduction rates, 16S rRNA genes and metagenomes to resolve microbial sulfur transformations down to 15 m below lake floor (mblf). Sulfate concentrations and reduction rates dropped within the upper mblf, while pore water ferrous iron increased to its highest concentration down to 3 mblf. Any microbially-produced sulfide precipitated as reduced inorganic sulfur in the sediment, apparently forming authigenic millerite (NiS) during burial. The decrease in cell densities tracked the decline in electron acceptors in pore waters with depth. From 3 to 10 mblf, low but sustained sulfate reduction rates were observed with intermittent presence of nitrate in pore water and increased goethite in the sediment, both acting as potential oxidants of sulfur intermediates. A subsequent re-increase in pore water sulfate occurred in parallel with syntrophic fermentation of volatile fatty acids. Consistent with geochemical evolution, the taxonomic diversity of microbial populations shifted from a bacterial assemblage near the surface to selective but prevailing Bathyarchaeia down to 15 mblf. The corresponding metagenome-assembled genomes predicted metabolic potential for complete sulfate reduction (aprAB, dsrAB) in Thermodesulfovibrionia, whereas Desulfobacterota (incl. Geobacterales, Desulfuromonadales, Syntrophales) and Aminicenantia exhibited versatility in reducing iron, nitrate (narG, napA), nitrite (nirS, nrfA) and sulfate (dsrAB, asrA). By contrast, Bathyarchaeia were predicted to disproportionate sulfur to polysulfides and reduce ferredoxin via electron bifurcation (hyd I-II, sudA, dsrC, dsrE) to fuel a Wood-Ljungdahl pathway, defining homoacetogenesis as terminal electron sink. Together, these mineralogical, geochemical, and metagenomic features provide evidence for a spatially confined but active cryptic sulfur cycle with tight coupling between reduction of mineral ferric iron and intermittent pore water nitrate to syntrophic and lithotrophic (homo)acetogenesis.

K. Chave

Panpan WANG, Junfeng WU, Lin CHEN et al.

This is an article in the field of process mineralogy. The study objects are Lijiagou and Jiajika tailings, Sichuan Province. The samples were identified by optical microscopy, artificial heavy sand research (separation, identification, etc.), optical semi-quantitative analysis, chemical analysis, MLA automatic quantitative detection of minerals, LA-ICPMS in-situ analysis of mineral trace elements, and electron microscope energy spectrum analysis, X-ray powder crystal diffraction analysis and other work. The chemical mineral composition and lithium occurrence state of the tailings were studied. The results are as follows: 1. The Li2O grade of the tailings from Lijiagou and Jiajika is 0.44%～0.64%, both of which are near the boundary grade and can be re-enriched. The content of associated valuable elements such as niobium, tantalum, beryllium and rubidium does not meet the comprehensive recycling standard. 2. In the tailings from two different areas, the main material for reconcentration and recycling is spodumene and the associated trace useful minerals are mainly trace niobite-tantalite series minerals and beryl, while rubidium mainly exists in dispersed state in lithium Muscovite and potassium feldspar. 3. The main recovery target mineral of tailings is spodumene, the theoretical grade of Li2O in concentrate products is 7.33%, and the theoretical recovery rates of Lijiagou and Jiajika card concentrate are 86.14% and 87.87%, respectively. 4. The artificial heavy sand test of tailings shows that the content, distribution rate and yield of Li2O are high in the coarse grade, but low in the fine grade.

Kateřina Němečková, Jan Mareš, Jan Mareš et al.

In this study, we used microscopic, spectroscopic, and molecular analysis to characterize endolithic colonization in gypsum (selenites and white crystalline gypsum) from several sites in Sicily. Our results showed that the dominant microorganisms in these environments are cyanobacteria, including: Chroococcidiopsis sp., Gloeocapsopsis pleurocapsoides, Gloeocapsa compacta, and Nostoc sp., as well as orange pigmented green microalgae from the Stephanospherinia clade. Single cell and filament sequencing coupled with 16S rRNA amplicon metagenomic profiling provided new insights into the phylogenetic and taxonomic diversity of the endolithic cyanobacteria. These organisms form differently pigmented zones within the gypsum. Our metagenomic profiling also showed differences in the taxonomic composition of endoliths in different gypsum varieties. Raman spectroscopy revealed that carotenoids were the most common pigments present in the samples. Other pigments such as gloeocapsin and scytonemin were also detected in the near-surface areas, suggesting that they play a significant role in the biology of endoliths in this environment. These pigments can be used as biomarkers for basic taxonomic identification, especially in case of cyanobacteria. The findings of this study provide new insights into the diversity and distribution of phototrophic microorganisms and their pigments in gypsum in Southern Sicily. Furthemore, this study highlights the complex nature of endolithic ecosystems and the effects of gypsum varieties on these communities, providing additional information on the general bioreceptivity of these environments.

Farit Kh. Urakaev, Natalya V. Khan, Almagul I. Niyazbayeva et al.

The task of this article is to update, develop and introduce into scientific practice the method of "mechanochemical recrystallization" in solid-phase systems with small additives of the liquid phase of the solvent and solid-phase precursors to stabilize the formed nanoparticles. The essence of this method is shown using the example of mechanical activation of the S–AgNO3–NH4X system, where X = Cl, Br, I, with the addition of dimethyl sulfoxide (DMSO), and the resulting mechanochemical synthesis of sulfur-containing nanocomposites S/AgX with the controlled content of sulfur nanoparticles (nanosulfur). The predetermined content of nanosulfur in nanocomposites is ensured by a continuous process of dissolution-crystallization (recrystallization) of starting sulfur in the DMSO medium in a mechanochemical reactor. The proposed technical solution made it possible to obtain S/AgX nanocomposites by a single mechanical treatment of powder precursors – AgNO3, NH4Х, NH4NO3 (diluent), commercial sulfur and DMSO in planetary ball mills with various milling tools. The method also includes washing the water-soluble components of mechanosynthesis.

Yusuf Kağan Kadıoğlu, Ezgi Ulusoy

The Strandja Massif cropping out in NW Turkey is cut by Late Cretaceous intrusives. These are called Strandja Intrusives and they are felsic and mafic coeval intrusives. Felsic intrusives consist of granite, granodiorite, quartz monzonite and syenite, while mafic intrusives consist of diorite and gabbro composition. Main composition of felsic intrusives consists of quartz, alkali feldspar, plagioclase, biotite, amphibole ±pyroxene mineral association, while main composition of mafic ones consists of plagioclase, biotite, amphibole ±pyroxene ±olivine mineral association. Amphiboles hydrated double-chain mineral of the Strandja Intrusives observed in all rocks used as an index mineral in this study to understand the petrological evolution of the rocks. According to Confocal Raman Spectroscopy studies amphiboles were actinolite type and exhibited similar spectrum and results of mineral chemistry reveals that they were calcic/Mg-hornblende types. According to geothermobarometer calculations, amphiboles crystallize in felsic intrusives at a pressure range of 0.49-0.94 kbar and a temperature of 757.52-814.49oC temperature at a depth of approximately 1.34-4.93 km, while in mafic ones at 2.59 kbar pressure and 892.82oC temperature at 9.97 km depth. Different temperatures-depth conditions and overlaps in Raman shift obtained from amphiboles indicate that these intrusives are derived from different sources but crystallized in the same environment.

V.A. Popov, M.A. Rassomakhin, S.V. Kolisnichenko

Ontogenic modeling of the origin of coarse garnet of the Polyakov log occurrence (South Urals) in a fine-grained schist sequence allowed the authors to conclude on its metasomatic growth with the replacement of chlorite aggregates. Muscovite, ilmenite, epidote, quartz and apatite remain preserved in the primary schist orientation of individuals. Accessory andesine, cobaltite, pentlandite, pyrrhotite and zircon crystallized together with garnet. The formation of coarse garnet crystals is probably related to fluctuations of supersaturation relative to garnet in areas of schists with abundant chlorite. This allows us to expect the presence of coarse garnet areas in adjacent parts of the schist sequence.

S. Ferrero, A. Borghini, A. Borghini et al.

<p>The use of NanoSIMS on primary melt inclusions in partially melted rocks is a powerful approach to clarify the budget of volatiles at depth during crust formation and its reworking. Anatectic melt inclusions are indeed gateways to quantify H<span class="inline-formula">₂</span>O, halogens and other species (e.g. CO<span class="inline-formula">₂</span>, N) partitioned into the deep partial melts generated during metamorphism of the continental crust. Here we present new datasets of NanoSIMS measurements of H<span class="inline-formula">₂</span>O and Cl in preserved melt inclusions from metamorphic rocks with different protoliths – magmatic or sedimentary – which underwent partial melting at different pressure–temperature–fluid conditions. These new datasets are then compared with similar data on natural anatectic melts available in the literature to date. Our study provides novel, precise constraints for the H<span class="inline-formula">₂</span>O content in natural melts formed at high pressure, a field previously investigated mostly via experiments. We also show that H<span class="inline-formula">₂</span>O heterogeneities in partial melts at the microscale are common, regardless of the rock protolith. Correlations between H<span class="inline-formula">₂</span>O contents and <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> values can be identified merging new and old data on anatectic inclusions via NanoSIMS. Overall, the data acquired so far indicate that silicate melt generation in nature always requires H<span class="inline-formula">₂</span>O, even for the hottest melts found so far (<span class="inline-formula">&gt;1000</span> <span class="inline-formula">^∘</span>C). Moreover, in agreement with previous work, preserved glassy inclusions always appear to be poorer in H<span class="inline-formula">₂</span>O than crystallized ones, regardless of their chemical system and/or <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> conditions of formation. Finally, this study reports the very first NanoSIMS data on Cl (often in amounts <span class="inline-formula">&gt;1000</span> ppm) acquired in situ on natural anatectic melts, showing how anatectic melt inclusions – additionally to magmatic ones – may become a powerful tool to clarify the role of halogens in many geological processes, not only in crustal evolution but also in ore deposit formation.</p>

Victorine Ambassa Bela, Armel Zacharie Ekoa Bessa, John S. Armstrong-Altrin et al.

The provenance of clastic sediments in stream beds, river terraces, rivers, swamps, lakes and beaches from different geological settings was investigated based on their compositional and geochemical variations. The geochemistry data of 622 sediment samples from 22 sites in the Cameroon were compiled to infer the provenance. The results suggest that, their mineralogy is dominated by quartz, low amount of feldspars, clay minerals, heavy minerals, ferric minerals, and rock fragments. The SiO2/Al2O3 ratio indicate that the sediments of Cameroonian region are mostly rich in quartz and clay-minerals. The enrichment of K2O/Na2O ratio implies plagioclase disintegration as K-feldspar during weathering and/or K-reintroduction in the system during diagenesis. The sediments are rich in light rare earth elements (LREE) and classified as shale, Fe-shale, Fe-sand, wacke, arkose, litharenite, sublitharenite, and quartzarenite. The sediments are composed of detritus derived from felsic igneous rocks, which correspond to the geology of the source areas. Weathering indices such as chemical index of alteration (CIA), chemical index of weathering (CIW), plagioclase index of alteration (PIA) and, A–CN–K (A=Al2O3, CN=CaO∗ + Na2O, K=K2O) plot indicated that the source rocks are subjected to low, moderate and intense weathering.

Sibila Borojević Šoštarić, Gabriela Paszkowska, Nils Jansson et al.

Nordic and West Balkan countries are major investment regions in Europe for greenfield and brownfield mineral exploration; however, the availability of qualified technical, scientific and managerial personnel involved in the whole mineral cycle is limited, especially in West Balkan countries. The partners of the TIMREX EIT RawMaterials-labeled MSc program have developed a joint curriculum focused on innovative raw materials prospecting and exploration methods, with strong innovation and entrepreneurial components. The program incorporates new exploration techniques and methodologies, portable and more highly sensitive equipment, robotized exploration equipment and the processing and interpreting of large, multidimensional datasets. The TIMREX curriculum was built around the ideal mineral exploration program, as suggested by raw materials stakeholders and orientated to field geology, exploration techniques and data processing, and also includes elements of sustainability, transversal societal and regulatory aspects. The program also focuses on EIT Overarching Learning Outcomes (OLO-s), which are embedded as core elements of the curriculum (innovation, entrepreneurship, sustainability, creativity, leadership and intercultural competencies). Significant contributions to the OLOs also arise from cross-organizational program elements, including the Exploration Entrepreneurship course, summer field camp, the Internship and the Social and Civic internship.

Sarah Marshall, Andrew Dutterer, David R. Montgomery

R. Mitchell, S. Bergman

P. Hartlieb, F. Kuchar, P. Moser et al.

H. Dehghanpour, H. Zubair, A. Chhabra et al.

Yi Fang, D. Elsworth, Chaoyi Wang et al.