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Producing biochar from various agricultural and industrial biowastes through pyrolysis is recognized as an eco-friendly approach for solid waste management and remediation of contaminated soils. However, it remains debatable which type of feedstock and pyrolysis temperature could create biochar with better surface functionality and more suitable specific end use. Biochars prepared from rapeseed residue and rice straw at different pyrolysis temperatures (300 and 550 °C) were characterized using various chemical, physical, and spectroscopic techniques. Rapeseed residue and rice straw biochars produced at 550 °C had high pH (9.98 and 10.85, respectively), due to the decrease in total surface acidity with increasing temperature as demonstrated by Boehm titration data, and their high ash contents (18.70% and 24.21%, respectively). The negative charge on high-temperature biochar particles increased with pH, which was confirmed by the reduced zeta potential values (− 42.33 mV for rice straw biochar and − 31.86 mV for rapeseed residue biochar). The mineral phase of both biochars was dominated by sylvite and a small amount of dolomite and calcite, whereas quartz was only found in rice straw biochars. A pyrolysis temperature of 550 °C is suggested for producing biochars that can potentially immobilize toxic elements in the soil.

China has rich phosphate rock resources, but with their continuous depletion, the rich ore resources have become increasingly scarce, which makes the exploration of collophane more important. Medium- and low-grade phosphate rock cannot be utilized until their impurities have been removed through mineral processing. However, due to the similar physical and chemical properties of dolomite and phosphorus minerals, the separation of dolomite from phosphate rock is a challenge for the beneficiation of phosphate rock. In this study, a collector that can separate dolomite from apatite by selective flotation was combined. The agent, named D12, is a new anionic surfactant that was obtained by the phosphorylation of ether-based nonionic surfactants. In order to determine the performance of the D12 collector, it was used in a flotation test. In this process, the raw ore had phosphorus oxide (P2O5) grade of 22.06 percent and magnesium oxide (MgO) content of 5.94 percent. The grinding fineness of 0.074 mm was approximately 87.33 percent. For roughing, the dosages of sulfuric acid (H2SO4), citric acid and collector were 7 kg/t, 1.5 kg/t and 0.5 kg/t, respectively. In the cleaning stage, the dosages of H2SO4 and collector were 5 kg/t and 0.3 kg/t, respectively. Concentrate grade of 31.02 percent and recovery rate of 68.64 percent with an open circuit were obtained under these conditions. Moreover, concentrate grade of 30.31 percent and recovery rate of 84.47 percent with MgO content of 0.92 percent were obtained with closed-circuit beneficiation indexes. The agent, D12, is promising to be applied to the industrial practice of mineral processing of phosphate rock.

We present a feasibility study of different adsorbent materials, namely residual fish scales biosorbent (FS), mineral dolomite (DL) and commercial resin (CR) in the heavy metals removal in multicomponent solution based on the properties of a real effluent from automotive battery recycling industry. Considering the effluent complex characteristics, the materials were assessed aiming to provide not only the heavy metals removal, but also the effluent neutralization and lower sludge generation. For this, all the studied materials were physicochemically and morphologically characterized with the aim of understanding the mechanisms involved in the process. Further, the elemental compositions of the solid and liquid phases generated from each treatment process were assessed by X-ray fluorescence spectrometry. The effluent presented highly acidic characteristics and heavy metals above the legislated limits for discharge (Fe, Zn and Pb). Each adsorbent material followed different mechanisms which led to dissimilar removal and neutralization capacities. The CR showed remarkable heavy metals removal capacity governed by an ion exchange mechanism; conversely, it did not show a neutralization effect. In contrast, FS and DL presented lower removal capacities by complex simultaneous phenomena (ion exchange, precipitation and/or complexation), but a great neutralization potential related to leaching of alkaline constituents. When sludge generation is considered as a key factor, mitigation and enhancement of treated effluent quality could alternatively be addressed by employing the materials in hybrid processes. Hence, the associated use of such materials could be viable yet very challenging for both neutralization and removal of heavy metals from the battery effluent.

Phosphate, when present in water, forms one of the basic nutrients that lead to eutrophication and its associated negative impacts. The use of raw dolomite powder as an adsorbent was found to be very effective in the removal of phosphates from various waters and wastewater matrices. Ayoub and Kalinian (Water Environ Fed 78:353–361, 2006) reported phosphate removals, amounting to 100%, over more than 300 bed volumes at inflow concentrations between 0.30 and 0.40 mg/L. This marked achievement led to the present study with the objective of defining the effects of the various parameters involved in the process and determining the optimal operating condition to achieve effective and sustainable removal efficiencies. Experimental work was conducted by passing three types of influent water and two types of wastewater jacked with a phosphate salt (KH2PO4) through a fluidized column bed of dolomite powder, where the effect of various parameters, including system operation mode, adsorbent particle size, rate of flow through the bed (contact time), initial phosphate concentration, influent pH, and the presence of competing anionic solutes on the adsorption of phosphate was evaluated. The results asserted that the most effective mode of operation for the system was the fluidized bed configuration. Results further showed that the smaller-sized dolomite powder (

Low-grade phosphate ore with impurities is becoming the primary source for phosphate; thus, more efficient methods are required for upgrading. Flotation is the predominant method for the processing of low-grade phosphate ore. The phosphate coarse particles of Kef-Eddur washing plant (southern Tunisia), having a low-grade phosphate, were studied to improve the recovery of phosphate flotation, lost during the washing process. The results of the chemical analysis of phosphate samples showed a grade of 12.51 % P2O5 with a carbonation rate of 2.9 %. Mineralogical study of a sample by X-ray diffraction showed the presence of the following minerals: the carbonate-fluorapatite, calcite, quartz, clinoptilolite (zeolite), and dolomite. Testing of dry grinding showed that the work index is of 10.39 kWh/t achieving an economical consumption of energy. Milling tests having high values of recovery are accompanied by a raised rate of carbonation, non-tolerable to enter the flotation circuits, dictated an intermediate determination of parameters simultaneously providing considerable recovery while having a tolerable rate of carbonation. Optimizing the operating parameters of flotation (3 scavengers, 320 g/t ester and 340 g/t amine), specifications of the best flow-sheet obtained are as follows: crushing 10 mm and ball milling (T = 5.5 min, Cs = 45 %, Rc = 3/1, Vbr = 60 tr/min). Attrition released during the first 10 min, second attrition of the same fraction for 20 min and reverse flotation render a grade of 26.80 % P2O5. The results of Kef-Eddur enrichment tests present an increase of 12.51 to 26.80 % P2O5. Application of flotation process is an alternative for this phosphate type.

Construction industries consume a large part of the natural resources in the production of concrete. Utilization of the waste in concrete has gained interest due to the development in the construction structure and depletion of natural resources. This article reviews the utilization of dolomite industrial waste in sustainable concrete production. Dolomite industrial waste is a by-product of the dolomite industries generated during the production of dolomite mineral. This paper provides the effect of dolomite waste on various properties (fresh, mechanical, and durability) of concrete, analyzes the crucial findings of dolomite waste based on the partial replacement of cement and aggregate, and discusses its suitability as a construction material. Available research studies showed the dominant potential of dolomite quarry waste as cement and aggregate replacement. In the current article, a large number of research papers have been reviewed. The finding of the different studies showed that using the dolomite waste as cement and aggregate up to certain extent increases the mechanical properties of concrete and influences the durability properties, but simultaneously decreases the workability of concrete. This paper suggests using dolomite waste as partial substitute of cement and aggregate for cleaner production of concrete.

Carbonate reservoirs account for 60% share in global oil reserves, and CO2-EOR process is employed in these carbonate fields for effective oil recovery and retention as well. Recent research reports that fines migration may lead to reservoir formation damage in oil bearing limestone and dolomite rocks. Although carbonate reservoirs are poor in clay minerals, some mass of clay fines existence in certain carbonate formations will cause severe damage to permeability and well productivity. This paper reports the single-phase flow of subcritical CO2 in porous limestone rock core containing kaolinite clay fines. Fines are natural reservoir minerals (example, quartz) and clay particles such as kaolinite, illite, feldspar, smectite, and montmorillonite. But, this paper explores this CO2-clay fines behavior in limestone rock as a function of kaolinite. So, two sets of core flood experiments were performed in the rock temperatures 120 °C and 160 °C. Initially, kaolinite clay has been injected into the limestone core in the form of suspension and then dried for hours in order to retain the solid fines in the internal pore chambers of the core. After that, the CO2 under subcritical condition has been injected into the porous limestone core for fines mobilization and injected gas recovery. The major observations that are reported from the experimental tests are there is an increase in gas saturation for increasing injection time. Steady rise of heat transfer coefficient and enthalpy was noted for increasing gas saturation and time. Concentration of fines linearly soars with respect to elevating PVI and permeability declines for rising time. Pressure in the limestone core shows abnormal and nonlinear variation. Finally, gas discharge rate declines for increasing injection time. Experimental data are tested against the statistical model (regression), and the outcome indicated good agreement. Overall, this paper has successfully established the CO2 effects on kaolinite clay fines behavior and its impact on oil recovery in carbonate fields.

Dolomites are well-known minerals; belonging to the Infra-Cambrian Hormuz Series lies within the salt domes of southern Iran. In this paper, the origin and alteration of dolomitic rocks of Paskhand and Deh-kuyeh salt diapirs in the area of Larestan (southern Iran) are investigated. Based on petrographic (size and fabric) studies, we recognize four dolomite types that consist of very fine-to-fine crystalline dolomite (D1), neomorphic dolomite (D2), fine-to-medium crystalline euhedral-to-subhedral dolomite (D3), and pore- and fracture-filling dolomite (D4). The dolomite samples with up to 26% iron can be called ferruginous dolomites. Some igneous rock patches to gehter with hydrothermal iron veins are observable in the salt domes of Larestan. Oxygen and carbon isotope values of black and white, and altered red dolomite of Paskhand and Deh-kuyeh salt domes, are equal to − 12.35 to − 18.78 for δ18OPDB and − 5.48 to − 8.49 for δ13CPDB; values enriched δ180 with low-temperature (~ 70 °C) conditions are related to D1 dolomites and values depleted δ180 with higher temperatures (~ 270 °C) are related to D3 and D4 dolomites. The most important source for secondary dolomites is deeper hydrothermal and catchment sources, which ascended through faults during the intrusion. Meteoric waters can be mentioned as less important sources for these types of dolomites. We reported sassolite B(OH)3 mineral in Deh-kuyeh salt diapir for the first time in this paper. This mineral is only observed in the areas which have famous riftings Fumarol. Therefore, in this paper, the existence of sassolite in the studied area could be considered one of the most important the origin of the composing elements of Hormuz rocks from fumarols which are formed in an extensional regime.

Acid-fracture conductivity has a major impact on acid-fracturing effects. In this paper, influences of acid concentration, temperature, and closure-stress loading time on conductivity under different acid-fluid systems have been researched based on experimental analysis for deep limy dolomite reservoirs. The measured conductivity showed high correlation and specific changing patterns with the above factors. Quantified relationships and equations between the conductivity and these factors were suggested in this paper. Additionally, a strong acid-etching effect caused by crosslinked acid and diverting acid has been observed during the tests. This could lead to high conductivity as well as broken rocks due to pressing with high-concentration acid. In this study, a 50-hour long-term conductivity test has been designed under the closure stress of 60 MPa which was closest to the actual reservoir conditions. The results showed that conductivity retention rate for each test group is less than 40%. By establishing assessment criteria of long-term and short-term conductivity based on the conductivity retention rate, linear relationships with high correlation and quantified equations of the conductivity retention rate in the same acid-rock reaction system could be obtained.

The Upper Permian Changhsing Formation is one of the most important gas-bearing formations in the Eastern Sichuan Basin. Nonetheless, the primary factors controlling the reef-shoal gas reservoirs of different regions are diverse. Clarifying the controlling factors for the formation of intra-platform reef-shoal reservoirs will promote the exploration and development process of the Changhsing Formation. By using outcrop data, core observation, thin section identification, scanning electron microscope analysis, physical property study, and logging interpretation, this paper analyse the characteristics and factors controlling the reef-shoal reservoir in Dianjiang area of the Eastern Sichuan Basin. The results show that the reef cap and reef base microfacies fine-to-medium crystalline dolomite reservoir have the best physical properties, and the reservoir spaces are primarily composed of intercrystalline pores, intercrystalline solution pores, karst caves, and fractures. The main lithology of reservoir formation is reef-shoal facies. The results for the carbon and oxygen isotopes show that dolomites of different particle sizes are formed in three environments. Affected by regression in the late Changhsingian Age, the reef-shoal of the Changhsing Formation were subaerially exposed to meteoric water diagenesis environments, resulting in the highly dispersed particles in rocks that formed a honeycomb karst system, which greatly improved the physical properties of the reservoirs. After reflux dolomitization, the honeycomb karst system was well preserved due to strong resistance to pressure and dissolution of dolomite. Therefore, dolomitization in the Changhsing formation contributed to reservoir porosity. Later, tectonic fracturing has adjusted and modified the reef-shoal reservoir. In summary, penecontemporaneous karstification was the key to the formation of the reef-shoal reservoir.

Recently, special attention has been drawn to the high-salt argillaceous dolomite reservoir in Jianghan basin, China due to its abundant oil resources with complex geological conditions. However, the current production methods used to develop this reservoir are not efficient with low throughput. Hence, the purpose of this paper is to explore the main possible reasons affecting the oil well productivity and determine suitable field development method for the target oilfield through experimental and numerical simulation approaches. The mercury injection capillary pressure (MICP) test results indicate that the average pore radius of samples is 0.0144 μm, and pore size distribution (PSD) results from MICP indicate that single peaks appeared in the PSD curves of the pore type samples. Permeability peaks of the samples range from 0.01 to 0.03 μm, and mesopores make most of the permeability contribution of the samples, which also reveals the low-permeability and porosity characteristics of the target oilfield. The results of core stress sensitivity tests show that the largest permeability damage rate is 98.97% with an average permeability damage rate of 98.37% while the maximum porosity damage rate is less than 10% with an average damage rate of 5.57% during the process of depressurization. The results of Non-Darcy percolation experiment indicate that threshold pressure gradient testing by water is about 0.03 MPa/m, which is close to the actual situation of the target oilfield. Numerical simulation method that considers the impact of threshold pressure gradient and stress sensitivity were established to study flooding patterns deployment for the research area. The simulation results show that performing water alternating gas flooding (WAG) by using CO2 is recommended for the development of the high-salt reservoir with inverse five-spot flooding pattern made up of 400 m well spacing in X-direction and 150 m row spacing.

Waste magnesia-carbon bricks (MCB) exhibit great potential for being reutilized as MgO additive for iron ore sintering due to their main composition of high activity magnesia and extra carbon content. In this paper, the combustion characteristics of the carbon component of waste MCB were first studied by thermogravimetric, derivative thermogravimetric and differential scanning calorimetry thermal analysis. The influence of waste MCB utilization as MgO additive on the mineralization of sinter raw materials was also systematically investigated. The main conclusions are shown as below: (1) Compared with anthracite, the carbon component of waste MCB has relatively worse flammability and combustibility, and its combustion heat per unit mass is less; (2) As the MgO content of sinter increases from 2.0 to 3.0 wt%, the advantage of using waste MCB, compared with dolomite, as MgO additive in the crystallinity degree of sinter gradually appears; (3) At the MgO content of 3.0 wt%, the sinter using the combination of waste MCB and dolomite as MgO additive has higher content of calcium ferrite, and the distributions of main mineral compositions and pores are more uniform than the sinter totally using dolomite or waste MCB as MgO additive.

Bentonite dolomite mixture composites were prepared by precipitation technique. The composition of these composite materials was established by different analytical tools; IR, XRD, TGA&DTA, XRF, and BET. X-ray peak broadening analysis was used to evaluate the crystallite size and lattice strain by Scherrer’s formula and Williamson–Hall (W‚ H) analysis. The variation of adsorption of 152+154Eu3+, La3+, Ce3+, and Sm3+ onto studied materials was carried out and the equilibrium time was carried out after 24 h. The capacity of radionuclide (152+154Eu3+) and some lanthanides (La3+, Ce3+, and Sm3+) were investigated, and all studied materials were selective for 152+154Eu3+.

The construction industry in Abu Dhabi is thriving and its coastline has some of the most ambitious structures in the world. Whilst the subsurface evaporitic and calcareous soft rocks of this region are of great geological interest, they are relatively poorly understood from a geotechnical engineering perspective, forcing foundation designs to be overly conservative. Understanding the stiffness of the underlying geology at small strains is of great importance for the accurate estimation of ground movements around excavations and foundations, and yet routine post-SI laboratory testing programmes tend to focus on basic rock mechanics tests such as UCS tests. These procedures are generally unsuitable for use with calcareous rocks due to their friable and moisture sensitive nature, and rarely obtain parameters representative of actual in situ behaviour. The calcareous mudstone investigated in this paper has mechanical and structural characteristics falling between those of a soil and those typical of a rock and, as such, requires a geotechnical testing approach that combines methods from both soil and rock mechanics disciplines. The mineralogical, micro-structural and mechanical characteristics of this lithology have been examined via a suite of testing techniques, including XRPD, SEM, advanced triaxial with bender elements, along with industry standard procedures. Shearing, tensile and consolidation behaviours have been explored. Examination of the micro- and macro-scale features of this material shows it to be highly structured, with strength and stiffness being controlled by inter-granular bonding of Dolomite grains, as well as by mean effective stress state and rate of strain. The presence of fibrous Palygorskite acts to reduce the degree of bonding, causing specimens rich in this clay mineral to have a more ductile mechanical behaviour.

Using mineral admixtures as cement replacement substance in concrete tends to increase in the future to provide greater sustainability in the construction industry. This paper aimed to study the influence of adding silica fume and fly ash as a weight of cement replacement on settlement cracking intensity of plastic concrete. Fifty-six mixtures were cast to evaluate the purpose of this study. Two types of cement (Portland cement and sulfate resistance cement) and two types of aggregates (dolomite and gravel) were considered. The cement was partially replaced by different ratios of silica fume (3%, 6%, 8%, and 10%) and different ratios of fly ash (10%, 15%, 20%, and 25%) of cement weight. In all concrete mixtures, a water-to-cementitious content ratio (w/cm) was 0.42. The results exhibited that the cracking intensity of settlement decreased as the slump decreased. Adding silica fume to the concrete significantly reduced the rate of appearance of settlement cracks. The ideal ratio for adding silica fume to the concrete mix was 8% from cement weight. Adding fly ash to mixtures did not significantly affect settlement cracking intensity, but enhanced the workability of fresh concrete.

CO2 geological storage (CGS) is a crucial strategy for meeting CO2 emission reduction targets. However, the effect of microbial action on CGS in deep saline aquifer is unclear. In this paper, numerical simulations based on previous experimental data were conducted to investigate CO2 solubility-trapping and mineral-trapping by microbial-mediated process in CGS demonstration base in Ordos, north of China. The simulation results reveal that the presence of a microbial community has a positive influence on CGS, mainly in terms of the amount of CO2 that can be injected and the manner by which it is stored. With the effect of microbial action, the amount of injected CO2 was increased by 23.33% and the CO2 mineral sequestration increased from 1.12 to 2.05%. In addition, microbial action plays different roles at different stages of CGS. In the initial stage of CO2 injection, the microbial action promotes dissolution of calcite, oligoclase and clay minerals such as chlorite and kaolinite, providing a favorable condition (more K+, Ca2+, Na+, Mg2+, Fe2+ and HCO3−) for CO2 mineral-trapping. In the following stage of CGS, microbial action accelerates the precipitation of carbon-fixing minerals such as calcite and siderite, enhancing the CO2 storage security in deep saline aquifer. As such, secondary minerals such as ferroan dolomite and dawsonite were observed in advance in microbially mediated CO2–saline–sandstone interactions, further indicating that microbes play a positive role in CO2 mineral-trapping. Consequently, the microbial action can promote mineral capture of CO2 and increase the CO2 storage security in deep saline aquifer. These conclusions can provide a reference and basis for the suitability assessment of CGS in such deep saline aquifer like Erdos, China.

The purpose of this paper was to propose a method to predict shear-wave velocities in the process of AVO (amplitude variation with offset) inversion, to interpret seismic converted-wave data, and to match reservoir engineering information with seismic data in regions without shear-wave velocities. During CO2 flooding and sequestration, the shear-wave velocity varies with the pressure that is caused by fluid injection. Predictions of how the shear-wave velocity changes with pressure can be used to interpret 4D seismic monitoring data during different stages of CO2 injection. To verify the calculations, the authors used the characteristic parameters of the Marly dolomite and Vuggy limestone units of the Weyburn Oilfield reservoir in Canada. The Digby’s model and Gassmann’s equation were used to evaluate the dependence of the shear-wave velocity on the pressure in the carbonate rock formation. The authors have developed a new method for calculating the coordination number of the model and supplement the results with a shale correction, enabling the prediction to match the measured shear-wave velocities more closely. Our method is verified by dipole sonic logging data and petrophysical test data from the Weyburn Oilfield. When applied to petrophysical test data, the average error is below 5%. When the method is applied to well log data, the average error in the porous media is 3.014% in the Marly unit and 6.288% in the Vuggy unit.

Bayan Obo ore contains mainly bastnaesite, monazite and associated iron, fluorite, calcite, dolomite, barite, and trace amount of columbite. Due to its complex mineral compositions and similar mineral properties, it is difficult to separate and obtain rare earth and fluorite concentrates with high purity by conventional magnetic separation and flotation. In this paper, a stepwise magnetic separation process comprised of wet permanent magnetic separation (PMS), wet electromagnetic separation (EMS), and superconducting magnetic separation (SCMS) was proposed to pre-concentrate iron, rare earth, and fluorite minerals from Bayan Obo ore. The results showed that iron, rare earth, and fluorite preconcentrates with high purity and low impurity content could be achieved, which might be helpful to shorten the technological process and improve the separation efficiency for the subsequent flotation of iron, rare earth, and fluorite minerals.

The present paper reports the effective utilization of marble sludge powder (MSP) for the recovery of potash values from waste mica scrap using chlorination roasting-water leaching method. Characterization studies indicated the presence of dolomite as the major mineral phase in MSP, whereas muscovite and quartz were observed in the mica sample. The acid leaching studies suggest a maximum of 22% potash recovery under conditions: 4 M H2SO4 acid, particle size of ∼100 µm, stirring speed of 600 r/min, leaching temperature of 75°C, and leaching time of 90 min. The chlorination roasting-water leaching process was adopted to achieve the lowest level of 80%–90% potash recovery. The optimum conditions for the recovery of ∼93% potash from mica (∼8.6wt% K2O) requires 900°C roasting temperature, 30 min roasting time, and 1:1:0.75 mass ratio of mica: MSP: NaCl. The roasting temperature and amount of NaCl are found to be the most important factors for the recovery process. The reaction mechanism suggests the formation of different mineral phases, including sylvite (KCl), wollastonite, kyanite, and enstatite, during roasting, which were confirmed by X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM) morphologies. The MSP-blended NaCl additive is more effective for potash recovery compared with the other reported commercial roasting additives.

In this paper, the Johnson-Holmquist II (JH-2) model with parameters for a dolomite rock was used for simulating rock fragmentation. The numerical simulations were followed by experimental tests. Blast holes were drilled in two different samples of the dolomite, and an emulsion high explosive was inserted. The first sample was used to measure acceleration histories, and the cracking pattern was analyzed to perform a detailed study of the blast-induced fracture to validate the proposed method of modelling and to analyze the capability of the JH-2 model for the dolomite. The second sample was used for further validation by scanning the fragments obtained after blasting. The geometries of the fragments were compared with numerical simulations to further validate the proposed method of modelling and the implemented material model. The outcomes are promising, and further study is planned for simulating and optimizing parallel cut-hole blasting.

Although there is an analogy between electrical and thermal conductivities, rock electrical parameters are mostly related to the pore system, whereas thermophysical properties mostly affected by the solid part. It seems that using the mentioned analogy and simultaneous consideration of the electrical and thermophysical properties lead to a better description of the rocks. In this paper, a solid part of rock was considered as a bundle of cylindrical rods. The formation thermal factor (FT) was defined as a parameter based on thermal conductivities of evacuated rock and its solid part and using the analogy with the definition of formation resistivity factor (FR). Also, a combination of electrical and thermophysical properties was used to describe rock permeability. Two datasets of dolomite and sandstone were used to confirm the analogy between FT and FR. Results revealed that there is a power relation between FT and rock solidity similar to the power relationship between FR and porosity, i.e., Archie’s equation. Determination coefficients (R2) of FT versus solidity for sandstone and dolomite samples were 0.97 and 0.99, respectively. Furthermore, it was concluded that permeability and FR × FT have a power relationship with high R2 for sandstone (R2 = 0.92) and dolomite samples (R2 = 0.93). Moreover, the relationship between permeability and FR × FT was proven using the Kozeny-Carman model. Finally, the electrical quality index (EQI) and thermal quality index (TQI) were defined based on the analogy with reservoir quality index (RQI). It is believed that simultaneous consideration of RQI, EQI, TQI, FR × FT , and their correlations with well-log data lead to a more accurate characterization of the reservoir rock.

Cement has been widely used for low- to intermediate-level radioactive waste management; however, the long-term modelling of multiple mineral transfer between the cement leachate and the host rock of a geological disposal facility remains a challenge due to the strong physical-chemical interactions within the chemically disturbed zone. This paper presents a modelling study for a 15-year experiment simulating the reaction of crystalline basement rock with evolved near-field groundwater (pH = 10.8). A mixed kinetic equilibrium (MKE) modelling approach was employed to study the dolomite-rich fracture-filling assemblage reacting with intermediate cement leachate. The study found that the mineralogical and geochemical transformation of the system was driven by the kinetically controlled dissolution of the primary minerals (dolomite, calcite, quartz, k-feldspar and muscovite). The initial high concentration of calcium ions appeared to be the main driving force initiating the dedolomitization process, which played a significant role in the precipitation of secondary talc, brucite and Mg-aluminosilicate minerals. The modelling study also showed that most of the initially precipitated calcium silicon hydrate phases redissolved and formed more stable calcium silicon aluminium hydrate phases. The findings highlight the importance of a deep and insightful understanding of the geochemical transformations based on the type and characteristics of the host rock, where the system is under out of equilibrium conditions, and the rates of mineral reactions.

This paper aims to identify the impact of the diagenesis processes on the carbonate reservoir’s characteristics (porosity and permeability) of the Mishrif Formation. A detailed investigation of available core samples and microscopic study of more than 200 thin sections of the core limestone samples were examined from two wells (Ratawi-2 and Ratawi-5) in Ratawi oilfield, which are located in the Basrah Governorate, southern Iraq which revealed that different diagenetic parameters influence the reservoir quality in Mishrif Formation. Diagenetic features and four identified diagenetic environments that have affected the carbonate rocks in the Ratawi oilfield were the meteoric vadose, meteoric phreatic, marine phreatic and mixing zone. Petrographic examinations revealed that diagenesis varies in intensity from microfacies to another, micritization, dissolution, cementation, compaction, neomorphism, dolomitization and authigenic minerals (pyrite) are the dominant diagenetic parameters which are identified in the current field of study. Among all the observed diagenetic features, dissolution and neomorphism (recrystallization) were formed as a result of subaerial exposure during the meteoric diagenesis and contribute to porosity enhancement and reservoir quality. The cementation (calcite and dolomite), compaction, dolomitization, and micritization have a negative impact on the reservoir behavior, through reducing porosity and permeability that led to reducing reservoir quality. Other processes such as authigenic minerals (pyrite) did not have strong effects on reservoir quality. Based on the genetic classification of porosity, most of the porosity within Mishrif Formation is a combination of depositional, diagenetic and fracturing. The diagenetic porosity is the far more dominant types of porosity such as vuggy, intraparticles, fractured and moldic, implying that carbonate Mishrif reservoir is the type of diagenetic reservoirs.

The unique case of carbon dioxide accumulation in the bottom layer of the acidic lake formed in the Guadiana open pit (Herrerias mine, SW Spain) led to exceptionally high dissolved gas pressures (ca. 5.0 bar at depths of 50–70 m). This CO2 has formed by carbonate (calcite, dolomite) dissolution during decades of interaction of the acidic water with the rocks of the pit walls and associated mine tunnels. The elevated dissolved gas pressures were only comparable to those found in the volcanic crater lakes of Cameroon like Nyos and Monoun, which erupted in the 1980s and sadly triggered the loss of hundreds of human lives. This gas pressure was not far from the absolute (hydrostatic plus atmospheric) pressure limiting CO2 solubility at depth, thus making this pit lake potentially dangerous for the possibility of a hypothetical limnic eruption. Following detailed field and experimental studies aimed at deciphering the source and accumulation patterns of CO2 in the lake, a degassing project started in 2014, which followed an upscaling strategy with construction and installation of progressively bigger pipelines capable of extracting increasingly higher flow rates of CO2-charged water from the deep part of the lake. As of May 2019, the degassing systems have successfully extracted most of the CO2 originally present in the lake (i.e. ≈ 123,000 m3 CO2), which has been discharged to the atmosphere in a controlled and safe way. The fountains became progressively smaller and finally stopped, due to the decreased gas pressure at depth. The larger pipes will serve as a regulating system in the future. This paper describes the main findings encountered during the degassing project, some relevant technical issues observed during the last 5 years (2014–2019), and lessons learnt from the Guadiana pit lake experience.

To find out the sedimentary microfacies evolution patterns of the 3rd member of the Yingshan Formation in the Gucheng area of Tarim Basin and provide the basis for the exploration of oil and gas from carbonates in this area, a series of research work has been carried out in this paper. Based on the analysis of cores and thin sections from 11 wells, it was revealed that the 3rd member of the Yingshan Formation mainly has three rock types, including limestone, dolomite, and siliciclastic rocks. 3D seismic data analysis shows that the 3rd member of the Yingshan Formation is a gentle slope of a carbonate platform with four sedimentary subfacies, which includes the inner gentle slope, inner zone of a shallow gentle slope, outer zone of a shallow gentle slope, and deep gentle slope. These subfacies are subdivided into 13 microfacies: tidal flat, lagoon, dolomite shoal, dolomite flat in the topmost part of the shoal, interbank dolomite flat, granular shoal, interbank sea, and storm deposit. According to sequence boundary markers such as wireline log curves (U, GR, U/Th), carbon isotope, and lithofacies associations, the 3rd member of the Yingshan Formation is divided into three fourth-order sequences (SQ1-1, SQ1-2, and SQ1-3). Isochronous sequence stratigraphic framework is established, in which dolomitization shoal and dolomite flat in the topmost part of the shoal are mainly developed at the top of the fourth-order sequence. Vertically, from SQ1-1 to SQ1-3, the area shows changing sedimentary trends from transgressive to regressive. According to the control of microfacies by the strata thickness characteristics of west-high and east-low, and the change of paleogeomorphology, combined with the analysis of seismic attributes, the plane distribution map of sedimentary microfacies in three high-frequency sequence periods is compiled to reproduce the spatial distribution relationship of sedimentary microfacies in each sequence period of the 3rd member of the Yingshan Formation. The SQ1-1 period is characterized by the development of dolomite shoal and dolomite flat in the topmost part of shoal deposits in the inner gentle slope and the inner belt of the shallow gentle slope in the west. In the eastern part, sand shoal deposits are mainly developed in the outer belt of the shallow gentle slope. During the period of the sedimentation of SQ1-1 to SQ1-3, the inner belt of the shallow gentle slope gradually decreases in the western part and the outer belt of the shallow gentle slope gradually increases in the western part. In order to guide the exploration of oil and gas in the carbonates of the 3rd member of the Yingshan Formation in the Gucheng area, it is clear that the fine-medium and medium-coarse crystalline dolomite with residual sand shoal clastic structures are the most favorable types of reservoirs in the area. The dolomite shoal and dolomite flat in the topmost part of the shoal in the inner belt of the shallow gentle slope are the most favorable sedimentary microfacies for the exploration of oil and gas in the 3rd member of the Yingshan Formation in the Gucheng area.

Many buried karst areas in Iran, and in other parts of the world have not yet been mapped using detailed geological or geophysical studies to delineate susceptibility to sinkhole development. The purpose of this paper is to investigate the possibility of using the results of hydrogeochemical analysis with routine measurements of physicochemical parameters to evaluate and detect areas prone to sinkhole develop. Sixteen spatial maps were prepared using analyzed data from 77 water samples from monitoring water wells in the Kabudar Ahang, Razan, and Qahavand (KRQ) sub-catchments of the Hamadan province, western Iran. By use of geographic information system tools 16 thematic maps for physicochemical parameters (EC, pH., TDS, and groundwater temperature), major cations (Ca2+, Mg2+, Na+, and K+), anions (HCO−3, SO42−, NO3−, and Cl−), and calcite, dolomite, gypsum, and partial pressure of CO2 saturation indices (SIC, SID, SIG, and SIpCO2) were prepared. It was hypothesized that the anomalies of each parameter concentration could be consistent with sinkhole prone areas. To evaluate this assumption, the area under the Receiver Operating Characteristic (ROC) curve was calculated by 100 points as a true sinkhole pixel (50 positive true) and non-sinkhole point (50 true negative). The areas under curve of ROC for these thematic maps were calculated for the 16 variables. Results show that the dolomite and calcite saturation indices (0.49 and 0.43, respectively) are poor indicators, whereas HCO−3 and pCO2 saturation indexes (0.83 and 0.78, respectively) are good indicators of sinkhole susceptibility in the study area. The result confirmed application of hydrogeochemical anomaly analyses and the ROC validation method in covered karst can be a useful tool for prediction of sinkhole prone zones forming in region, where sparse data are available.

Songam Cave, a magnificent dolomite cave in the Democratic People’s Republic of Korea—is also known as “A Splendid Flower Cave”—is regarded as one of the renowned natural tourist attractions with a great number of beautiful and complicated aragonitic anthodites in different forms and shapes, together with diversified underground karst features (stalactite, stalagmite, limestone columns, flowstone, rimstone dams, botryoidal forms, pool spar, concretions, underground waterfall, ponds, etc.). This paper deals with the cave formation process, the features of speleothems and other karst features in Songam Cave, which indicate that Songam Cave is a geoheritage site of high conservation significance. The geological setting of the cave and the detailed features and diversity of the speleothems provide sufficient evidence to foster an understanding of the formation and development of the karst cave. The aragonitic anthodites and the outstanding underground karst features unfolded on the ceilings and walls throughout the cave suggest that Songam Cave can also be a cave tourist attraction of high aesthetic value. Overall, Songam Cave is a geoheritage of high conservative significance because of its geological and aesthetical value.

This paper takes the thick and widely distributed crystal dolomite of Xixiangchi Formation, Upper Cambrian in Southeastern Sichuan basin as an example, the reservoir characteristics and main controlling factors of crystal dolomite have been analyzed systematically, and the genesis and reservoir formation mechanism of crystal dolomite have been discussed. It shows that the main reservoir rocks of crystal dolomite include powder crystalline dolomite and finely crystalline dolomites, and the intercrystal pores and dissolved intercrystal pores are the main reservoir spaces, with few dissolved vugs and fractures developed in the reservoir. The pore structure analysis shows that the throats of crystal dolomite reservoir are mainly lamellar, reflecting a good configuration between pores and throats, medium- low porosity and low permeability, representing typical porous-type reservoir. Dolomitization analysis indicates that the dolomitization occurred in the penecontemporaneous or early diagenetic stage. The degree of dolomitization decreased gradually from the top to the bottom in each sedimentary cycle, and distribution of dolomite in the study area shows that the content of dolomites decreases from the west to the east, which reflects the degree of dolomitization weakening eastward. Combined with the geochemical research of crystal dolomite, the C and O isotope data reflect the same characteristics of seawater during the late Cambrian. It indicates that the dolomitization might be related to the seepage-reflux of seawater in the early time. Recrystallization played an important role in the genesis of the crystal dolomite, because most of crystal dolomites remain residual granular texture. The intercrystal pores formed by seepage–reflux dolomitization acted as superior seepage channels for the reservoir transformation, and the recrystallization adjusted the previous pores and made them better, while the karstification was the key to the dissolved pore formation.

A type of carbonate-hosted lead–zinc (Pb–Zn) ore deposits, known as Mississippi Valley Type (MVT) deposits, constitutes an important category of lead–zinc ore deposits. Previous studies proposed a fluid-mixing model to account for metal precipitation mechanism of the MVT ore deposits, in which fluids with metal-chloride complexes happen to mix with fluids with reduced sulfur, producing metal sulfide deposition. In this hypothesis, however, the detailed chemical kinetic process of mixing reactions, and especially the controlling factors on the metal precipitation are not yet clearly stated. In this paper, a series of mixing experiments under ambient temperature and pressure conditions were conducted to simulate the fluid mixing process, by titrating the metal-chloride solutions, doping with or without dolomite, and using NaHS solution. Experimental results, combined with the thermodynamic calculations, suggest that H2S, rather than HS− or S2−, dominated the reactions of Pb and/or Zn precipitation during the fluid mixing process, in which metal precipitation was influenced by the stability of metal complexes and the pH. Given the constant concentrations of metal and total S in fluids, the pH was a primary factor controlling the Pb and/or Zn metal precipitation. This is because neutralizing or neutralized processes for the ore-forming fluids can cause instabilities of Pb and/or Zn chloride complexes and re-distribution of sulfur species, and thus can facilitate the hydrolysis of Pb and Zn ions and precipitation of sulfides. Therefore, a weakly acidic to neutral fluid environment is most favorable for the precipitation of Pb and Zn sulfides associated with the carbonate-hosted Pb–Zn deposits.

The depletion of good-quality phosphate resources, coupled by a need to supply acceptable products at a rapid rate, while meeting the specifications of fertilizer chemical plants, is of significant concern to the phosphate industry, particularly the production of concentrates with tolerable dolomite content. Tremendous efforts have been made in the past to develop an efficient and economical process that can effectively reject dolomite. However, dolomite removal continues to plague the phosphate industry due to several process-specific challenges being encountered with various beneficiation technologies. In this regard, detailed characterization of phosphate reserves is crucial to understand textural limitations and help design appropriate strategies to achieve quality products. In this paper, the development of procedures to establish dolomite rejection/francolite recovery curves for gravity preconcentration of pebble phosphate from Central Florida is described using high-speed X-ray computed tomography (HSXCT). The developed procedure is illustrated with the analysis of high MgO pebble phosphate samples (10.39 mm × 1 mm) received from South Pasture and Four Corners locations operated by the Mosaic company. The rejection/recovery curves were calculated for each sample for five different particle size classes to observe the trend in rejection/recovery with variation in particle size. In order to evaluate the reliability of the HSXCT data, analysis using the high-resolution X-ray computed tomography (HRXCT) technique was performed on one particular sample (FC-3-1). Finally, to assess the separation efficiency, the HSXCT and HRXCT rejection/recovery curves obtained were compared to experimental gravity preconcentration results reported in the literature. In this way, liberation limitations for gravity preconcentration in the processing of pebble phosphate have been established based on X-ray computed tomography analysis.

For the purpose of solving the problem of water prevention for a vertical shaft passing through the sinian ultra-thick dolomite (SUTD) aquifer in Southwest China, the groutability of the SUTD and the technical parameters of the surface pre-grouting (SPG) were studied by a field grouting test and numerical simulation. Firstly, the field grouting test was conducted to investigate the groutability of the SUTD. According to the results of the field test, the SUTD could be divided into two members, and the upper member has greater groutability than that of the lower member. In the upper member, special measures should be utilized to avoid the overspread phenomenon, while a high pressure should be applied to increase the grout takes for ensuring the sealing effects in the lower member. Then, the rational borehole spacing and final grouting pressure were obtained through numerical simulation and the field SPG test. Finally, the effectiveness of the SPG was verified by the water pressure test. The residual water inflow was small enough to meet the shaft sinking after the SPG was completed, and the sealing efficiency was 98.04%. The results of the present paper could provide technical references for water controlling for shaft sinking under the similar geological conditions.

The coexistence of carbonates and evaporites is common for various petroliferous basins in geological periods globally. It holds much more significance to find out the interaction of these two. This paper expounds the macroscopical and microscopic relationship from petrography, facies, and geochemical analyses from core samples. The study area is dominated by successions of evaporites and carbonates, and three sulfate, five carbonates and mudstone lithofacies have been identified. And carbonates and evaporites are commonly lateral equivalents, both resulted from the similar sedimentary environment and chemical constituents. The intergrowth relationship was mainly reflected in the factors for their formation (including sea-level, evaporation, salinity, climate and so on), sedimentary cycle (including the vertical cycle and banded distribution) and the diagenetic transitions (including TSR, dolomitization, dedolomitization and dissolution). A depositional model has been developed that reveals a bull’s-eye pattern which was dominated by restricted carbonate platform and evaporitic platform with shoal and reef facies developed around the platform margins. With gypsum salts served as the caprock, favorable dolomite reservoir which largely resulted from the diagenetic transition and source of high quality can form a large reservoir.

Polyhalite has been discovered for years in the Triassic of the Sichuan Basin. However, it is difficult to exploit and utilize such polyhalite because of its deep burial depth and its coexistence with anhydrite or dolomite. Therefore, it has always been regarded as “dead ore”. Based on slice identification, X-powder diffraction, chemical analysis, REEs analysis and strontium isotope test on halite samples from the fourth and fifth member of Jialingjiang Formation to Leikoupo Formation of Wells ZK601 and ZK001 in Xuanhan area, Northeast Sichuan Basin, this paper discovers thick layers of granular polyhalite associated with halite and the polyhalite content accounts for 10–30%. These deep polyhalites can be obtained by water-soluble mining and utilized, so they are called “new type polyhalite potash deposits”. The deposit is deep buried at 3,000 m underground, and the thickness of a single layer can be more than 30 m. It is stable in regional distribution. The discovery of the “new type polyhalite potash deposits” has “activated” polyhalite, which has been considered as deep “dead ore” and has great significance for potash prospecting in China.

Integration of the information from hydrochemical data, statistical analysis and modeling technique is crucial for extending our knowledge of hydrochemistry of karst aquifers. In this paper, conventional graphical methods, statistical analysis and PHREEQC inverse modeling were used to investigate the hydrogeochemical characteristics and evolution processes of karst groundwater in Jinci spring area. The results showed that the dominant hydrochemical types of karst groundwater determined by Piper diagram were Ca·Mg–SO4·HCO3, Ca·Mg–SO4, Ca–SO4, Ca–SO4·HCO3 and Ca–HCO3, and the main components of karst groundwater were dominated by rock–water interactions based on statistical analysis. Ca2+, Mg2+ and HCO3− originated mainly from the dissolution of calcite and dolomite; SO42− came mostly from gypsum dissolution and pyrite oxidation; and the source of Na+ and Cl− could either be major from halite dissolution or cation exchange. Moreover, PHREEQC inverse modeling indicated that calcite, gypsum and CO2 (g) were dissolved, and Ca–Mg exchange prevailed along the flow path (from recharge area to runoff area); the dissolution of gypsum, dolomite and CO2 (g), and halite precipitation, and Na–Mg and Ca–Mg exchange occurred along runoff area to discharge area; and there were the dissolution of carbonate, gypsum, halite and CO2 (g), Na–Mg and Ca–Mg exchange from deep buried area to discharge area.

Dolomite is the most important component of the prolific reservoirs in the Ma55 to Ma51 submembers of the Ordovician Majiagou Formation in the central Yishan Slope, Ordos Basin. However, the origins of the different types of dolomite are unclear because of the different diagenetic environments and complex diagenetic fluids. This paper mainly focuses on the diagenetic environment and diagenetic fluid associated with the dolomite. The petrographic features of the dolomite were studied on the basis of core observation and thin section identification. Geochemical characteristics were analyzed according to the O, C and Sr stable isotopes and major and trace elements. The results demonstrate that, petrographically, the dolomite can be divided into four types, namely, type 1, type 2, type 3 and type 4. Type 1 is mainly characterized by dolomite with gypsum and salt dissolution as well as breccia structures with no clay minerals filling between breccia clasts. Type 2 is characterized by powder-fine crystalline dolomite with apparent residual textures and residual intergranular and intercrystal pores. Type 3 is characterized by leopard limestone or dolomite with leopard textures and massive bioborings. Finally, type 4 is characterized by karst breccia dolomite with many fractures and caves filled by abundant terrigenous clay minerals. In combination with the petrographic data, analysis of the geochemical data reveals that the type 1 dolomite formed in an early near-surface diagenetic environment and the diagenetic fluid might have been early freshwater. Type 2 and type 3 dolomite formed in a shallow-burial diagenetic environment. The diagenetic fluid of type 2 dolomite might have been hypersaline brine that was influenced by freshwater, but that of type 3 dolomite might have been a mixed fluid consisting of seawater and freshwater, which was less saline than the type 2 dolomite fluid. Type 4 dolomite formed in an epidiagenetic near-surface environment and the diagenetic fluid might have been superficial freshwater carrying abundant terrigenous clay minerals. The study shows that the analysis of the diagenetic environment and fluid of dolomite has great significance for research on dolomite origins. The porosity and permeability values of the four types of dolostone reservoirs indicate that type 1 dolomite reservoirs are the best reservoir, type 2 dolomite reservoirs have good physical properties, type 4 dolomite reservoirs are relatively good reservoirs, and the worst reservoir is the type 3 dolomite reservoirs.

In this paper, two types of reinforcement agents of fibrous palygorskite (PAL) and rhombohedral dolomite (DOL) have been used together by simply mixing in order to improve the mechanical and thermal properties of waterborne polyurethane (WPU). A great synergistic effect between 1D PAL and 3D DOL on reinforcing WPU matrix has been observed. In comparison to neat WPU, the tensile strength of such three components WPU-based composite has been significantly improved by 178% with an addition of 4 wt% PAL and 6 wt% DOL. Furthermore, its initial decomposition temperature also has been increased 55 °C. The formation of 3D conjugated filler network with 1D PAL inserted into the 3D DOL network could be attributed to such synergistic reinforcement of WPU. This work provides a good example and eco-friendly pathway for the preparation of high performance polymer composites by simply using micro/nano-fillers with different dimension together.

In today’s scenario cement-concrete has become the backbone of infrastructure development. The use of concrete is increasing day by day and so does cement. One of the major concerns is that the cement manufacturing contributes 7% of total man-made CO2 emission in the environment. At the same time India being a developing country secured the second position in cement production. On the other hand solid waste management is one of the growing problems in India. As we are one of the major contributors in this situation so, the time has come to think about the sustainable alternatives. From various researches it has been observed that the low clinker cement can be suitable option. In the present paper we have tried to develop a low clinker ternary blend for Indian cement industry using the concept of synergetic behavior of fly ash–limestone reaction and formation of more stable monocarboaluminate hydrate and hemicarboaluminate hydrate. 30% fly ash and 15% limestone and 5% gypsum have been used as supplementary cementing material for replacing 50% clinker. The mechanical properties like, compressive strength, have been studied for the fly ash limestone ternary blends cements and the results have been compared with the other controlled blends and ternary blends. The effect of intergrinding of constituent materials has shown a comparable properties which can be used for various structural application. The effect of dolomitic limestone has also been studied in fly ash limestone ternary blends and the result shows the relation between compressive strength and dolomite content is inversely proportional.

Evaluation of paleo-seawater pH is an important aspect to study the paleo-ocean environment. The Paleozoic strata lack foraminiferal shells; therefore, reconstruction of paleo-seawater pH is difficult. In this paper, the Cambrian–Lower Ordovician evaporate sequence present in the Tarim Basin is used as an example to work out methods for reconstruction of paleo-seawater pH for evaporate sequences through study of boron isotopes. Analysis of diagenetically unaltered samples yields δ11B values for normal seawater in an open environment ranging from 7.5 to 12.6‰ (average = 9.4‰) and those of evaporative salt-lake facies ranging from − 4.7 to − 1.8‰ (average = − 3.3‰). With increase in the rate of evaporation of seawater, its pH decreases gradually and the δ11B values of tricoordinated and tetracoordinated compounds decrease synchronously. Using a salt-lake brine with pH 7, δ11B value in sedimentary rock of − 3.3‰ and unfractionated δ11B in tetracoordinated B(OH) 4 − in solution, the average δ11B of the Middle Cambrian–Early Ordovician paleo-seawater came to be 16.2‰. It establishes a workable relationship between δ11B in sedimentary rock and seawater pH. The Middle Cambrian–Early Ordovician normal paleo-seawater pH estimated using the δ11B value of sedimentary rock representing the weakest evaporation intensity is ~ 9.1 that is 0.9 higher than pH of modern seawater. In these calculations, it is assumed that the total dissolved inorganic carbon is unchanged between the Cambrian–Early Ordovician paleo-seawater and modern seawater and the [CO3 2−] content in the paleo-seawater is greater by a factor of 2–3 than that in modern seawater. This increase in [CO3 2−] content is inferred to be one of the main factors for the widespread development of dolomite.

WOS: 000423279600002, The Lower Pliocene lacustrine sediments of the Sakarya and Porsuk Formations in the Sivrihisar and Yunusemre-Bicer regions consist of claystone, argillaceous carbonate, carbonate, and evaporites. No detailed studies of paleoclimatic conditions have been performed previously. The present study aimed to determine the depositional environment and paleoclimatic conditions for the formation of these economically important sepiolite/palygorskite/carbonate/evaporite deposits based on detailed mineralogical, geochemical, and isotopic studies. Samples from various lacustrine sediments were examined using polarized-light microscopy, X-ray diffraction, scanning electron microscopy, and chemical and isotopic analysis methods. Dolomites are predominantly of micrite, which is partly recrystallized to dolomicrosparite/dolosparite close to desiccation fractures. The presence of ostracods and dacycladecean algae in the carbonates reflects a restricted depositional environment. The formation of sepiolite and palygorskite fibers, either as cement between/enclosing dolomite and/or as calcite crystals, reflects occasional changes in physicochemical conditions provided by fluctuations in the lake-water level and influx of groundwater in relation to climatic changes during and after dolomite precipitation. The positive correlations of Sigma REE with Al2O3, Nb, high-field-strength elements, and transition elements are due to alteration of feldspar and hornblende in the volcanic units. The high values of Ba and Sr relative to Cr, Co, Ni, and V also indicate that felsic rather than ophiolitic rocks were the parent material. The crossplot of whole-rock SiO2 vs. Al2O3+K2O+Na2O and V/Cr ratio suggests deposition of carbonate-dolomitic sepiolite-sepiolitic dolomite under arid climate and oxic conditions, whereas the Ni/Co and V/(V+Ni) ratios of the sediments indicate deposition of organic-bearing sepiolite/palygorskite under anoxic-dysoxic conditions. An enrichment in delta 13C and delta 18O values of dolomite with respect to calcite is probably due to differences in mineral fractionations. The delta 34S and delta 18O values and 87 Sr/86 Sr isotope ratios for gypsum suggest an intensely evaporitic lacustrine environment fed by an older marine evaporitic source. The Si, Al, Mg, Ca, and enhanced TOT/C required for periodic precipitation of organic-rich brown sepiolite/palygorskite characterize deposition in a swampy environment, while dolomitic sepiolite and sepiolitic dolomite formed in ponds by partial drying of the main alkaline lake., Scientific Research Projects Fund of Eskisehir Osmangazi UniversityEskisehir Osmangazi University [2014-487], The present study was supported financially by the Scientific Research Projects Fund of Eskisehir Osmangazi University under Project No 2014-487. The authors are indebted to the editors and to the anonymous reviewers for their extremely careful and constructive reviews which improved the quality of the paper significantly. Part of this work was presented during the 53rd Annual Meeting of The Clay Minerals Society, Georgia State University, Atlanta, Georgia, USA, in June 2016. Jennifer Huggett thanks the staff of the Natural History Museum, London, for assistance with the SEM work.

Enhanced oil recovery in carbonates due to wettability alteration has received much attention recently. In contrast to sandstones reservoirs, carbonates are neutral-wet or preferentially oil-wet. The use of CO2 dissolved into water has emerged as an alternative method for EOR operations in carbonates reservoirs. In the present paper, oil recovery from two carbonate outcrop rocks was evaluated with different brines containing CO2. The evaluation included a qualitative approach by spontaneous imbibition tests and a quantitative assessment by the Amott–Harvey index. The rocks tested were limestone and dolomite samples known as analogous to Brazilian pre-salt reservoirs. The testing fluids were a medium gravity crude oil, seawater concentration brine, formation equivalent brine and the carbonated version of these brines. Results shown additional oil recovery directly associated with wettability alteration driven by brine concentration switches. Oil recovery increases were observed independently if the brine concentration decreased or increased over the water replacement process. Wettability alteration took place in both carbonate types starting at oil-wet to neutral-wet conditions. Similar tests carried out with equivalent carbonated brines showed similar alterations in the wetting properties, trending no dependence on salt concentration. However, CO2 and its derived ions dissolved in the brines seem to inhibit the wettability alteration mechanism.

Investigation of drinking-water recarbonization process is the main aim of this work. Experiments aimed at increasing of Ca2+ and Mg2+ in water were carried out in laboratory scale fluidized-bed reactor. This technique offers potential for increasing of reaction surface area and overall reaction rate, and represents a new approach in drinking-water industry. Measurements of hydraulic characteristics of the fluidized bed were performed. The results of comparison of two different recarbonization agents, dolomite and half-calcined dolomite, show that half-calcined dolomite is more efficient for increasing concentration of Ca2+ and Mg2+ from value below the recommended limit to 3.4 mmol L−1. Effect of carbon dioxide on enrichment of water by calcium and magnesium was also investigated and positive effect was observed. Concentration of Ca2+ and Mg2+ with CO2 present was increased by factor 2.6 in comparison without addition of CO2 to the system at the same conditions. The use of fluidized-bed reactor resulted in significantly higher remineralization rate in comparison with static filtration column.

This paper presents an experimental and thermodynamic contribution about the role of inorganics in ash-bed material interactions during thermal conversion of miscanthus in fluidized bed. The objectives are (1) to describe the transformation of inorganics at high temperature, (2) to reveal their role in the agglomeration and (3) to provide recommendations for miscanthus gasification in fluidized bed. The main ash forming elements in miscanthus are K, Si, Ca, Mg, P, S and Cl. The ashes are composed of silica, carbonates and salts. The carbonates and salts decompose and volatilise at 700 °C. At elevated temperature, the dominant solid phases are Ca and Mg silicates. The liquid phase is composed of SiO2, K2O, CaO, MgO regardless of the atmosphere. The accuracy of thermodynamic prediction tool is evaluated with the experimental results. The ash-bed interactions show that the wetting of bed material by molten ashes is one of the key parameters of the agglomeration. The adhesion of particles increases in the order of silica sand, olivine, calcined olivine. There is no significant difference in the agglomeration mechanism in oxidizing or reductive atmosphere. However, in reductive atmosphere, two immiscible liquid phases can occur. The parametric investigation shows that the operating temperature has a significant effect on the agglomeration ratio and the addition of kaolin or dolomite is the most effective tool to reduce agglomeration risks.

This paper gives new insight into the precipitation sequences in six playa basins that host microbial mats. The study basins are distributed across two evaporitic endorheic drainage systems located in the Central part of Spain with markedly different hydrochemistry and mineralogy. One group, in the north, consists of highly alkaline, brackish to saline lakes containing a high concentration of chloride with dominant carbonate over sulphates. A second group of lakes are mesosaline to hypersaline, with sulphate the dominant anion over chloride. Mineral assemblages identified in both contain several phases that provide evidence for mixed carbonate-sulphate precipitation pathways, in the north, and sulphate-dominated pathways in the south. Regardless of their ionic composition, saline lakes support thin veneers of microbial mats which, by integrating several lines of evidence (hydrochemical and physical analyses, statistical analyses of ions, mineralogical assemblages, textural relationships among mineral phases and microbial mats) are shown to modify the chemical behavior of the evaporitic sediment and promote the formation of carbonates and sulphates from Ca-poor waters with high Mg/Ca ratios. Geochemical changes induced in the environment surrounding the microorganism favor the nucleation of hydrated Mg-carbonates (hydromagnesite and nesquehonite), calcite and dolomite. Simultaneously, the microbial mats provide nucleation sites for gypsum crystals, where they are subjected to episodic stages of growth and dissolution due to saturation indices close to zero. In addition, the bubbles produced by the metabolic activities of microorganisms are shown to promote the precipitation of hydrated Mg-sulphates, despite permanent subsaturation levels. Although common in the studied playa basins, this effect has not been previously reported and is key to understanding sulphate behavior and distribution. Modern and natural evaporitic microbial environments are important analogs for understanding brine evolution and mineral precipitation pathways in shallow water settings that have existed since the Archean on Earth and perhaps on Mars.

The dissolution of carbonate rocks has a significant control on reservoir quality under deep burial conditions, which has become a focus of studies in recent years. A series of hydrothermal minerals and combinations, such as fluorite, dickite, barite and hydrothermal dolomite, were discovered in the Ordovician strata in some exploration wells in the Tahe area. Moreover, the analysis results of carbon and oxygen isotope, REE, strontium isotope and inclusion homogenization temperature further confirmed that hydrothermal fluids existed in the Ordovician strata of Tahe areas. In this paper, the dissolution mechanism of carbonate rocks under deep burial conditions is discussed. It was considered that the hydrothermal dissolution required three conditions, i.e., the development of fault system, the presence of acidic fluids and a fall in temperature. The major theoretical foundation was the retrograde solubility of carbonate rocks that could be achieved through temperature drop and the upward migration of hydrothermal fluids. The dissolution of carbonate rocks caused by hydrothermal fluids normally occurred in the vicinity of migration pathways (faults or other pathways), which could be identified as good reservoir development zones.

The objective of the study described in this paper is to use correlation analysis and multivariate regression analysis for investigating the effect of physical and petrographic characteristics of carbonate rock on its mechanical properties. The cretaceous carbonate samples from boreholes drilled for preliminary investigations in the Koohrang’s third tunnel path, located in the western part of Shahrekord, Iran, were tested to determine the compressive strength, Young’s modulus, dry and saturated unit weight, porosity, and P-wave and S-wave velocity. Then, samples were subjected to petrographic investigation, including size and percentage of grain, matrix type, dolomitization percent, and carbonate percent. The results showed that compressive strength and Young’s modulus values were related to the dolomite percent, grain size, allochem percent, and carbonate percent. Since no single parameter determined strength and Young’s modulus, polynomial prediction equations were developed for estimating mechanical properties. Dunham’s (1962) classification system appeared to show a correlation with mechanical properties determined for the samples, for example, regarding the organic bounds; some textures such as bindstone and bafflestone indicated the lowest strength and Young’s modulus.

In the context of the harmonisation of the Swiss stratigraphic scheme (HARMOS project), the stratigraphic nomenclature of the Triassic sedimentary succession of northern Switzerland has been reorganised to six formations (from base to top): Dinkelberg, Kaiseraugst, Zeglingen, Schinznach, Bankerjoch, and Klettgau Formation. The first three are formally introduced in this paper. The Dinkelberg Formation (formerly «Buntsandstein») encompasses the siliciclastic, mainly fluvial to coastal marine sediments of Olenekian to early Anisian age. The formation is some 100 m thick in the Basel area and wedges out towards southeast. The Kaiseraugst Formation (formerly «Wellengebirge») comprises fossiliferous siliciclastic and carbonate sediments documenting a marine transgressive—regressive episode in early Anisian time. It starts with sandstone, dolomite, continues with subtidal limestone and marl and ends with bituminous shale and supratidal dolomite. Thickness decreases from approximately 50 m in the High Rhine area to 10 m in the south and east. In the Lake Constance area, a transition to the siliciclastic marginal facies of the Vindelician High (Eschenbach Formation in Germany) is documented by borehole evidence. The Zeglingen Formation (formerly «Anhydritgruppe») documents a regressive marine evaporitic megacycle during the Illyrian (late Anisian). At most places, except in far eastern Switzerland, it starts with massive halite deposits. It continues with sulfate and marl sequences and ends with littoral stromatolitic dolomite. In the WSW–ENE trending depot centre total formation thickness is 150 m and more, and thickness of salt layers reaches up to 100 m. In the High Rhine area, the thickness is reduced due to subrecent subrosion. At some places evidence points to syn- to early-post-diagenetic erosion. For practical reasons, the six formations are organised in three lithostratigraphic groups: Buntsandstein Group (with the Dinkelberg Formation), Muschelkalk Group (combining the Kaiseraugst, Zeglingen and Schinznach Formations) and Keuper Group (combining the Bankerjoch and Klettgau Formations).

The ballast layer is one of the most important components of the railway track superstructure in which angular aggregates of high strength rocks are used. Ballast degradation is one of the main sources of railway problems in which the ballast aggregates are gradually degraded due to the abrasion of the sharp corners of the angular particles and splitting each individual particle into two or several small pieces under loading. In this paper, the effects of rock type, aggregate size and particle shape on the strength of the single ballast particles are investigated. For this purpose, point load test is carried out on ballast aggregates of four rock types including basalt, marl, dolomite and trachyte. According to the obtained results, as the size of the aggregates increases, the point load strength index decreases. The influence of size on the strength is more noticeable for ballasts obtained from higher strength rocks. It is also found that the shape of ballast particles has no major effect on its strength. Furthermore, our findings show that the failure pattern for ballasts of higher strength is so that each particle commonly splits into three pieces; while the dominant failure pattern for ballast particles with less strength is breaking the particle into two pieces.

Micro-cracks induced by the coring process in rock samples retrieved from high in situ stress conditions may seriously influence the evaluation of rock properties. This paper presents work performed to study the coring damage mechanism of marble samples containing a kind of inclined grey (or brown) ribbon-like stripes, whose mineral components are calcite and dolomite. These samples were obtained from the Jin-ping Second Stage Hydropower Station (JPII) in China, and the coring site is located in the strata of the 5th layer of the Yan-tang group marble in the Middle Triassic system (T 2y 5 ). A special stress-relief coring scheme was carried out to collect rock samples under different stress levels at one position, then the coring damage in these samples was examined by sonic wave testing and acoustic emission monitoring under uniaxial loading conditions, and a numerical simulation was also conducted to investigate the stress path experienced by a rock core during sampling. The results indicate that for the specific Jin-ping Yan-tang group marble (T 2y 5 ) sample, the coring damage can be attributed to two kinds of micro-cracks: horizontal micro-cracks induced by stress redistribution, and vertical or sub-vertical micro-cracks mainly derived along the special rock structure. The horizontal cracks, generated by the tensile stress induced during coring, are mostly trans-granular ones, and can be regarded as the main reason for coring damage. In contrast, the vertical (or sub-vertical) micro-cracks are mainly caused by the combined effect of coring-induced high deviatoric stress and the inclined grey-brown ribbons, and it usually occurs along grain boundaries. At a relatively low stress level, the shear failure may preferentially occur along special rock structures. However, the impact of the micro-structure on cracking reduces significantly with the increase of stress level, and then the induced tensile stress may become the dominant factor leading to horizontal cracks or disking.

In this paper, contact angle measurements using crude oil, five carbonate rocks, and six brines were conducted to study the effect of water salinity and rock components on wettability alteration. The results showed that lowering water salinity results in wettability alteration of carbonate surfaces to more water-wet. And there exists an optimal salinity at which the maximum wettability alteration occurs. In addition, the optimal salinity tends to increase as the content of dolomite in the rock decreases gradually. When low-salinity water is kept the same, the lower dolomite content in the carbonate rock, the more water-wet the rock will tend to be.

From the perspective of economy and safety, balancing gas contained in the pore space of rocks is extremely essential, predominantly to establishments dealing with extraction of mineral resources. One of the main methods of evaluating the amount and composition of gas contained in the pore space of a rock is releasing the gas as a result of comminuting the investigated rock material. In the case of cupriferous rocks, effective comminution is a very difficult task, due to the strength properties of these rocks. The present paper discusses the results of studies into the gas content of cupriferous rocks, obtained by means of an original device named the GPR analyzer. The research was done on 41 samples of dolomites and anhydrites from various areas of two copper mines located in Poland: “Rudna” and “Polkowice-Sieroszowice.” For all samples, on the basis of microscope analyses performed on cuts and polished sections, the open porosity, closed porosity, and total porosity were determined. In the case of the dolomite samples, the total porosity variability fell in the range of 4.75–23.05%, and in the case of the anhydrite samples—in the range of 3.87–16.60%. The maximum gas content of the dolomite samples was 166.67 cm3/kg, and of the anhydrite samples—84.66 cm3/kg. In some of the studied samples, the presence of methane was confirmed. Toxic gases, such as H2S, were not found. The main gas in the pore space of the investigated rocks was nitrogen. Knowing the amount of the released gas and the value of the closed porosity in the investigated samples, the authors were able to estimate the pore pressure of the gas, whose maximum value was 0.583 MPa.