Silica Rocks Research Articles

A molecular simulation study on pore-scale behaviour of nitrogen-based fracking fluids for potential geo-energy applications

Molecular simulations are efficient tools in differentiating individual effects of fluid-fluid interactions and pore-fluid interactions on thermophysical properties of confined fluids; e.g. the molecular packing, adsorption mechanics and availability of accessible pore volume for confined fluids and therefore, indicate the rock fracturing phenomena as a function of geological conditions, fracking fluids nature, its composition and rock mineralogy. Presently, we have deployed the classical GCMC molecular simulations to quantify the adsorption of pure nitrogen and N2–H2O mixture (50%–50% and 30%–70%) inside porous silica rocks. While we found that adsorption and molecular packing of pure nitrogen inside silica slit pores are only a function of pore height, which quantifies the pore-fluid interactions; however, for N2–H2O mixture adsorption and molecular packing of N2 inside silica slit pores has been additionally affected by the water content in the equilibrium bulk mixture that as well describes fluid-fluid interactions inside pores. It is interestingly noted that water in N2–H2O mixture results in water-assisted nitrogen adsorption inside hydrophilic silica slit pores, which has been further proven through the radial distribution function data calculations inside each slit pore. Also, the hydrophilic nature of silica increases water adsorption and hence reduces N2 adsorption inside the smallest pore of H = 20 Å. Such a reduction in N2 adsorption density below its bulk density without layering effect, inside 20 Å pore, further initiates the possibility of negative excess adsorption density.

Damping and Stiffness Responses of Silica Rock under Constant Amplitude and Variable Rate Cyclic Loading

Damping and Stiffness Responses of Silica Rock under Constant Amplitude and Variable Rate Cyclic Loading

Rare Earth Elements (REE) Extraction from The Stones Hill at Padang Area by Precipitation

Rare Earth Elements (REE) are a very important element in modern life such as electronics, materials engineering, and even medicine. Gadolinium (Gd) is one of the REEs that is used as a basic material for implants as well as being used for other basic materials such as a corrosion inhibitor, control rods for nuclear reactors, and others. In this case, the elements are found along hills in the Padang area which have the potential to be produced in large quantities from six rock minerals such as granite, basalt, clay, silica, tuff, and limestone.). Based on the results of identification using the XRF spectrometer test tool, it was found that the six mineral rocks had an abundance of rare earth elements. The results of testing the extraction of Gadolinium Oxide (Gd2O3) using XRF were successfully carried out, Gd2O3 can be extracted by 0.06% - 1.84% in basalt rock, 0.47% - 0.95% in clay rock, and 0% - 0.88% in silica rock. This proves that the main rock minerals from stones have the Rare Earth Elements (REE) and can be extracted with using the Precipitation Extraction method.

Preparation of high purity silica from silica rock by leaching process: Optical application

The objective of this work is to increase the quality of silica rock from grade C (SiO2 = 98.75%) to grade A (SiO2 = 99.8%) to fulfil the requirements for high-end products. The studied raw silica rock composed of 98.75% SiO2, 0.410% Fe2O3, 0.1750% Al2O3, and 0.067% TiO2. After leaching treatment, the Fe2O3 content was reduced to less than 0.008% for class A product specification and 0.015% for class B product specification, complying with the requirements of MS701:2017. In this study, three types of acid (sulfuric acid, citric acid, and oxalic acid) were considered to study the removal of impurities from silica rock via leaching process at constant temperature and speed of agitation of 60℃ and 150 rpm, respectively. The treated samples were characterized through X-ray fluorescence (XRF) analysis and wet method, differential thermal analysis (DTA), and thermogravimetric analysis (TGA). The application of sulfuric acid (H2SO4) disclosed the highest silica recovery of 99.85% with significant reduction in the amounts of undesirable impurities present in the silica rock including Al, Cr, Ti, and Fe. Comparatively, C6H8O7 acid was also found considerably effecient in improving the purity of SiO2, where 99.53% purity was successfully achieved at 0.25 M acid concentration.

Upgrading silica rock quality by using attrition scrubbing and magnetic separation techniques

The study was carried out to produce high-purity silica sand used for glass making. Generally, all grades of silica sands are comparable in their chemical composition except for iron oxide (Fe2O3) content, which is slightly rigid and its concentration varies for different applications. The objective of this work was to increase silicon dioxide (SiO2) content to at least 99.5% and to reduce iron oxide content to less than 0.015% using attrition scrubbing and magnetic separator technique for the purification process. Gravimetric analysis was carried out on the original sample to determine SiO2 content, and minor elements of Fe2O3 quantification using ultraviolet–visible (UV–VIS). A complete chemical and phase analysis were carried out on the raw sample and post-treatment samples. Field Emission Scanning Electron Microscopy (FESEM) was also employed for morphological and mineral phase identification. In this analysis, 70% of solid percent in pulp was used. The optimization of the scrubbing process was performed by studying the effect of using distilled water and citric acid at various concentrations of 0.25 M, 0.5 M, and 0.75 M. The processing time and rotational speed were kept constant at 20 min and 1250 rpm, respectively. The scrubbed silica rocks were then deslimed and dried before being subjected to a wet high intensity magnetic separator (WHIMS) with a magnetic field intensity of 3A, 5A, and 7A. According to this research work, more than 99.5% of SiO2 content and less than 0.015% of Fe2O3 content was achieved although using only distilled water in the scrubbing process. The optimum consumption of citric acid was 0.5 M in the acidic scrubbing process.

The Miwah high sulphidation epithermal Au–Ag deposit, Aceh, Indonesia: Dynamics of hydrothermal alteration and mineralisation interpreted from principal component analysis of lithogeochemical data

The principal component analysis (PCA) of whole-rock major and trace element data has unravelled some of the dominant geochemical processes and identified the most relevant component as an exploration vector for many types of magmatic-hydrothermal ore deposits. An important exception is the high-sulphidation (HS) epithermal class of deposits. Here, the results of a PCA of different segments of the Miwah HS epithermal Au–Ag deposit in Indonesia show that the geochemical signature of the deposit varies from a tight group of Au, Ag, Cu and As in PC1 for the predominantly hypogene main zone to a moderately correlated assemblage of Au, As, Cu and Sb in PC1 for the variably oxidised rocks along the southern periphery to an association of Au, Ni, Cr, Co and Mo in PC1 for the overlying rocks in the north. PC2 in all zones represents the largest variability of Pb and Zn and has moderate contributions from Au and As in the periphery and the highest Au contribution in the north. By contrast, PC3 in the main and peripheral zones, shows a high variability of Cu. Representatives of auriferous vuggy-massive silica rocks from the periphery are in equilibrium with hydrothermal fluids with δ18O values of +6.18, +7.48 and +9.28‰, whereas oxidised, silicified rocks from the analogous northern zone are in equilibrium with hydrothermal fluids with δ18O values of +8.0 and +8.6‰. The results of the above PCA, complemented by centred-log-ratio bivariate diagrams of grade-scaled variables, mineralogical relationships and oxygen isotopes, are interpreted to indicate that PC1 in the main zone is consistent with the deposition of Au and related metals from the condensation of magmatic gas mixtures during the early-stage silicification of protoliths. By contrast, PC2 is related to late-stage Pb- and Zn-rich fluids that migrated away from the main conduits. A hybrid process, intermediary between PC1 and PC2, leached Cr, Ni and Co from the adjacent ultramafic rocks and superimposed the metals on the Au + Cu mineralised rocks. Processes related to PC3 and other smaller PC occurred at later and lower temperature stages in which steam-heated oxidation led to the local destruction of sulphide and arsenide phases and the resulting acid fluids decoupled Au-Ag alloys and enargite to produce separate Au- and Ag-based minerals and covellite. The PCA of individual alteration types shows metal associations that mimic those of the main-stage mineralisation, thereby providing a useful exploration tool. The ability of PCA to separate Au and the associated metals from the Cr + Ni + Co assemblage can be used to identify areas that have been affected by hyperacid fluids originating from epithermal systems; hence, such areas become exploration targets not only in the vicinity of Miwah but also throughout Sumatra or elsewhere.

Gd matrix effects on Eu isotope fractionation using MC-ICP-MS: Optimizing europium isotope ratio measurements in geological rock samples

Europium (Eu) has only two isotopes (151Eu and 153Eu). As sequential rare earth elements, Eu and Gd do not easily separate from each other during column chromatography, making it difficult to measure accurate and precise Eu isotope ratio during mass spectral analysis. Eu isotope ratios can be determined by MC-ICP-MS using internal Sm or Gd spikes to correct for mass discrimination. In this report, we discuss and propose optimal conditions for precise and accurate Eu isotope ratio measurements in geological materials (igneous rock samples) using MC-ICP-MS. The NIST3117a ultrapure chemical reagent showed almost no Eu isotope fractionation regardless of the kind of isotope pair used in normalization. A pure Eu fraction with almost no Gd matrix extracted from rock samples also showed nearly the same degree of Eu isotope fractionation regardless of the isotope pair used in normalization. In the case of Eu fraction extracted from highly fractionated granite and high silica volcanic rocks, when 154Gd interference relative to the internal 154Sm standard exceeded ca. 0.1% (due to incomplete Eu separation), this Gd matrix effect created artifactual variation in Eu isotope ratios during MC-ICP-MS analysis. In order to obtain the best estimates of Eu isotope fractionation in geological samples, especially high silica rocks, our analytical methods require complete Eu separation without Gd matrix during sample preparation.

Nanomaterials for subsurface application: study of particles retention in porous media

The ability to transport nanoparticles through porous media has interesting engineering applications, notably in reservoir capacity exploration and soil remediation. A series of core-flooding experiments were conducted for quantitative analysis of functionalized TiO2 nanoparticles transport through various porous media including calcite, dolomite, silica, and limestone rocks. The adsorption of surfactants on the rock surface and nanoparticle retention in pore walls were evaluated by chemical oxygen demand (COD) and UV–Vis spectroscopy. By applying TiO2 nanoparticles, 49.3 and 68.0 wt.% of surfactant adsorption reduction were observed in pore walls of dolomite and silica rock, respectively. Not surprisingly, the value of nanoparticle deposition for dolomite and silica rocks was near zero, implying that surfactant adsorption is proportional to nanoparticle deposition. On the other hand, surfactant adsorption was increased for other types of rock in presence of nanoparticles. 5.5, 13.5, and 22.4 wt.% of nanoparticle deposition was estimated for calcite, black and red limestone, respectively. By making a connection between physicochemical rock properties and nanoparticle deposition rates, we concluded that the surface roughness of rock has a significant influence on mechanical trapping and deposition of nanoparticles in pore-throats.

Simulation Study of Hydrocarbon Generation Characteristics in Siliceous Rock

Late Triassic-early Jurassic silica rocks are widely developed in Northeast China. To evaluate the silica rock hydrocarbon generating capacity, we have simulated the hydrocarbon evolution process by thermal simulation experiments and analyzed the hydrocarbon generation characteristics. The experiments were carried out at six temperature points 250, 270, 290, 310, 330, and 350°C, and the content of the gaseous and liquid products was measured. The experiments results showed that the organic-rich siliceous rocks are characterized by a relatively high hydrocarbon-generating capacity. The gaseous products are generated at different temperatures, while natural gas is mainly generated when the peak period of oil generation is completed. Natural gas includes hydrocarbon and non-hydrocarbon gases. Hydrocarbon gases include methane, ethane, propane, butane, pentane, and other heavy hydrocarbon gases. Non-hydrocarbon gases include hydrogen, nitrogen, carbon monoxide, and carbon dioxide. Carbon dioxide is the main component of the gas products, followed by hydrogen, methane, nitrogen, and other gases, but the total content of other gases is extremely low. Carbon dioxide generated during all stages of the oil generation process accounts for the vast majority, but in geological conditions, it will eventually be consumed by hydration. Nitrogen is mainly produced in the early stage. The content of hydrogen and hydrocarbon gases increases with increase in temperature, but hydrogen is usually depleted in the actual reservoir due to its strong chemical activity.

Triple oxygen isotopes of cherts through time

It has long been recognized that the stable oxygen isotope 18O/16O ratios of chemical sediments show a systematic decrease with increasing age. This continuous, 3.8 Ga long secular trend has been attributed to 80 °C hot early Earth oceans, a ~15‰ lower 18O/16O ratio of Archean seawater, or diagenetic obliteration of the original isotope signal. We demonstrate that high-precision triple oxygen isotope measurements including the rare third stable oxygen isotope 17O on silica rocks (cherts) can be used to shed light on this major problem in geochemistry. Our triple oxygen isotope data do not support 80 °C hot oceans in the Archean. The data also exclude that the 18O/16O of seawater was much lower in the Archean. Also, a simple freshwater-origin of cherts is not supported by the new data. We discuss the effects of diagenetic alteration on the triple oxygen isotope compositions of cherts and show that the Archean and Proterozoic cherts could have equilibrated with fluids with higher 18O/16O than today's oceans. For the Archean cherts, the high 18O/16O fluids required to explain the observations could reflect the composition of ambient seawater or of modified hydrothermal fluids. Oceans with higher 18O/16O ratio would be expected for an Archean “water world” without large continents. High 18O/16O fluids, however, could also have formed locally by reactions between seawater and the oceanic crust. Our study shows that high-precision triple oxygen isotope data provide new understandings of processes deep in time.

First Results on Understanding the Shiny Surfaces of Heat-Treated Chert

ABSTRACT In Europe, intentional heat treatment of silica rocks to improve their knapping quality appeared for the first time during the Solutrean (ca 25.5–23 ka cal BP). The recognition of heat-treated artefacts in assemblages is based on macroscopic criteria like shiny luster. Surface luster or gloss, however, may be prone to observer bias and calls for more objectives measures to quantify it. In this study, we use a laser scanning microscope to measure the micro-relief on surfaces knapped after heat treatment at different temperatures. Our results show the evolution of the roughness of fresh fracture surface as a function of heating temperatures. Roughness appears to be a good proxy for macroscopically observable surface gloss caused by heat treatment. Such Ra measurements even bear the potential to become a new tool for the recognition of heat treatment.

ИСКОПАЕМЫЕ НОРЫ THALASSINOIDES В ОПОКАХ СЕРОВСКОЙ СВИТЫ (СРЕДНЕЕ ЗАУРАЛЬЕ, ВЕРХНИЙ ПАЛЕОЦЕН)

Актуальность исследования. В северных районах Западной Сибири в отложениях танетского яруса отмечаются перерывы осадконакопления, масштабность проявления и диапазон которых остаются неясными. В частности, для доказательства их существования на южных окраинах бассейна требуется привлечение дополнительных палеонтологических и седиментологических данных, которые могут фиксировать кризис привноса осадочного материала. Одним из наиболее надежных источников информации о перерывах в осадконакоплении и других седиментационных событиях могут являться ископаемые ходы. Цель: ихнофациальный анализ кремнистых отложений верхнего палеоцена Западной Сибири. Объект: ископаемые норы Thalassinoides серовской свиты (среднее Зауралье, верхний палеоцен), вмещающие ходы породы (темные опоки с афанитовой структурой), заполняющие ходы породы (светлые опоки с тонкоглобулярной структурой) Методика: полевые исследования, растровая электронная микроскопия, литолого-петрографический, ихнотекстурный, ихнофациальный и седиментологический анализы Результаты. Приведены данные о находках ископаемых следов Thalassinoides в кремнистых породах серовской свиты (верхний палеоцен, среднее Зауралье), и дана характеристика особенностей их морфологии. Рассматриваются вопросы возможных условий, при которых происходило формирование нор и их сохранение в ископаемом состоянии. Микроскопические исследования кремнистых пород серовской свиты позволяют определить особенности и различия в постседиментационных изменениях вмещающих и выполняющих норы отложений. В качестве наиболее вероятных продуцентов ходов Thalassinoides в танетском бассейне определены десятиногие ракообразные. Ископаемые следы в кремнистых формациях палеогена ранее не изучались и приводятся в научной литературе впервые.

Stromatolitic digitate sinters form under wide-ranging physicochemical conditions with diversehot spring microbial communities.

Digitate siliceous hot spring deposits are a form of biomediated sinter that is relatively common in the Taupo Volcanic Zone (TVZ), New Zealand, and elsewhere on Earth. Such deposits have gained prominence recently because of their morphological similarity to opaline silica rocks of likely hot spring origin found by the Spirit rover on Mars and the consequent implications for potential biosignatures there. Here, we investigate the possible relationship between microbial community composition and morphological diversity among digitate structures from actively forming siliceous hot spring sinters depositing subaerially in shallow discharge channels and around pool rims at several physicochemically distinct geothermal fields in the TVZ. The TVZ digitate sinters range in morphologic subtype from knobby to spicular, and are shown to be microstromatolites that grow under varied pH ranges, temperatures, and water chemistries. Scanning electron microscopy and molecular analyses revealed that TVZ digitate sinters are intimately associated with a diverse array of bacterial, archaeal and eukaryotic micro-organisms, and for most digitate structures the diversity and quantity of prokaryotes was higher than that of eukaryotes. However, microbial community composition was not correlated with morphologic subtypes of digitate sinter, and observations provided limited evidence that pH (acidic versus alkali) affects morphology. Instead, results suggest hydrodynamics may be an important factor influencing variations in morphology, while water chemistry, pH, and temperature are strong drivers of microbial composition and diversity.

The Case for Ancient Hot Springs in Gusev Crater, Mars.

The origin and age of opaline silica deposits discovered by the Spirit rover adjacent to the Home Plate feature in the Columbia Hills of Gusev crater remains debated, in part because of their proximity to sulfur-rich soils. Processes related to fumarolic activity and to hot springs and/or geysers are the leading candidates. Both processes are known to produce opaline silica on Earth, but with differences in composition, morphology, texture, and stratigraphy. Here, we incorporate new and existing observations of the Home Plate region with observations from field and laboratory work to address the competing hypotheses. The results, which include new evidence for a hot spring vent mound, demonstrate that a volcanic hydrothermal system manifesting both hot spring/geyser and fumarolic activity best explains the opaline silica rocks and proximal S-rich materials, respectively. The opaline silica rocks most likely are sinter deposits derived from hot spring activity. Stratigraphic evidence indicates that their deposition occurred before the emplacement of the volcaniclastic deposits comprising Home Plate and nearby ridges. Because sinter deposits throughout geologic history on Earth preserve evidence for microbial life, they are a key target in the search for ancient life on Mars.

Insights into the Compositional Evolution of Crustal Magmatic Systems from Coupled Petrological-Geodynamical Models

AbstractThe evolution of crustal magmatic systems is incompletely understood, as most studies are limited either by their temporal or spatial resolution. Exposed plutonic rocks represent the final stage of a long-term evolution punctuated by several magmatic events with different chemistry and generated under different mechanical conditions. Although the final state can be easily described, the nature of each magmatic pulse is more difficult to retrieve. This study presents a new method to investigate the compositional evolution of plutonic systems while considering thermal and mechanical processes. A thermomechanical code (MVEP2) extended by a semi-analytical dike/sill formation algorithm, is combined with a thermodynamic modelling approach (Perple_X) to investigate the feedback between petrology and mechanics. Melt is extracted to form dikes while depleting the source region. The evolving rock compositions are tracked on markers using a different phase diagram for each discrete bulk-rock composition. The rock compositional evolution is thus tracked with a high precision by means of a database with more than 58 000 phase diagrams. This database describes how density, melt fraction, chemical composition of melt and solid fractions and mineralogical assemblages change over crustal to uppermost mantle P–T conditions for a large range of rock compositions. Each bulk rock composition is composed of the 10 major oxides (SiO2–TiO2–Al2O3–Cr2O3–MgO–FeO–CaO–Na2O–K2O–H2O) including an oxygen buffer. The combined modelling approach is applied to study the chemical evolution of the crust during arc magmatism and related melt extraction and magma mixing processes. Basaltic sills are periodically injected into the crust to model heat/magma influx from the mantle. We find that accumulated sills turn into long-lived mush chambers when using a lower rock cohesion or assuming a higher intrusion depth. Associated partial melting of crustal host rocks occurs around densely distributed dikes and sills. High silica rocks (e.g. granites) are generated by partial melting of the host rocks, melt segregation within dikes, and from fractional crystallization of basalts. Although the volume of these rocks is relatively small in our models compared to rocks with a mafic to intermediate composition, they provide important information about the processes of magma differentiation within arc continental crust.

Granulated Foam-Glass Crystal Materials Based on Silica Rocks of the Southern Urals

Granulated Foam-Glass Crystal Materials Based on Silica Rocks of the Southern Urals

Technical innovations during the recent Solutrean in the southwest of France: Recognition of heat treatment of chert and estimation of heating temperatures based on the example of Le Piage (Lot, France)

The Solutrean technocomplex is characterized by the use of innovative techniques for stone tool knapping during the Upper Palaeolithic. These processes include the development of pressure retouch and heat treatment of silica rocks. These innovations remain unprecedented at the scale of the recent European Palaeolithic. The aim of our analysis is to acquire new information on the application of heat treatment, by investigating the heating technique and the lithic chaîne opératoire in which this treatment occurs. Macroscopic observations of the material combined with an infrared spectroscopic analysis of 69 archaeological samples provide new data on heat treatment in the Solutrean lithic series of Le Piage (Fajoles, Lot). Raw materials were heated in controlled conditions and to temperatures of 250–300 °C. We also found that only leaf-shaped pieces were heat-treated at Le Piage. Part of the results obtained by infrared spectroscopy reveal discrepancies with macroscopic observations. These data raise questions concerning the validity of common macroscopic criteria used for recognising heat treatment and shed light on some of the choices made by Solutrean groups.

ФИЗИКО-МЕХАНИЧЕСКИЕ И ТЕПЛОФИЗИЧЕСКИЕ СВОЙСТВА ПЕНОСТЕКЛОКЕРАМИКИ НА ОСНОВЕ КРЕМНЕЗЕМСОДЕРЖАЩЕЙ ПОРОДЫ

Obtaining the foam-glass ceramic building materials bypassing the process of high-temperature glass melting and the use of local rocks as raw materials, which can significantly reduce the cost of the final product, is an urgent task of modern building materials science. The aim of this work is to study the physical, mechanical and thermal properties of foam- glass ceramic building materials obtained by one heating of the mixture consisting of silica-containing rock (tripoli) and soda ash. The developed heat-insulating building materials have an average density of 200 to 600 kg/m3, compressive strength of 1.2 to 9.8 MPa, thermal conductivity of 0.053 to 0.065 W/m °C. Studies establishes a rational ratio of components in the composition of foam glass ceramics based on silica rock. In the production of foam materials, the heating rate of the charge should vary from 3 to 4.5 ° C / min, and the maximum heating temperature from 800 to 850 ° C. The developed material will expand the range of thermal insulation building materials and can be used in the construction of industrial and civil facilities, nuclear power plants, in the gas and oil industry.

Lightweight Concretes Based on Glassy Aggregates are the Future of Envelope Structures

The paper discusses physical and mechanical, and heat-insulating properties of lightweight structural and insulating concretes based on various glassy aggregates – quenched cullets. Quenched cullet represents a fired aggregate that has a bulk density equal to 150-300 kg/m3 and cylinder strength of 0.5-2 MPa, which has been produced by pretreatment of silica rocks with an alkali component followed by firing in rotary kilns. It has been established that the aggregate grain’s glassy envelope has a closed, evenly distributed porosity with a high content of the glass phase and improved strength and thermal and physical characteristics. Influence of the glass phase as part of a porous aggregate on the totality of concrete properties - structural, thermal and hydrophysical - has been found. Process fundamentals and standardization support for practical application of lightweight concretes featuring density D500-800 kg/cm3 and strength grades B2.5-7.5 in envelope structures with high heat-insulating properties have been developed.

Chemical technology of cellular glass production

Cellular glass by its composition, structure and technical parameters is a high-performance multifunctional material, and its use in construction and engineering is extremely important. The problem of developing cellular glass power consumption technology on the base of natural amorphous aluminosilicates and silica rocks in a single technological process, combining the synthesis of a given glass composition and the formation of its cellular structure is solved by introduction of a nanodispersed modifier into the rock and by the mechanical activation of the charge, creating an impact possibility in the system at the atomic-molecular level. With the involvement of a complex modern theoretical and experimental methods, the processes of glass wool rock modifyed sintering and expanding were investigated, which served as a base for creating the cellular glass technology in the form of products and granules. The study of the secondary glass synthesis dynamics during sintering of volcanic glasses with sodium hydroxide solution showed that the hydrated amorphous neoplasms of sodium silicates synthesized at low temperatures and silica aluminosilicates with temperature rise gradually enriched with silica and formed hydrated secondary glasses, the dehydration of which expanded the mass upon reaching the pyroplastic state. Power consumption technologies of the new type cellular glasses based on the volcanic glass-wool and other amorphous silicate rocks, which allow to combine the processes of synthesis of low-melting glass and its expansion by sintering are challenging for the production and for application in construction and engineering.