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[Display omitted] • A novel collector DDALA is developed based on dodecylamine (DDA) structure. • The reagent system composed of DDALA and xanthan gum has better flotation selectivity for apatite/quartz. • DDALA/oleic acid combined collector exhibits different competitive adsorption configurations on apatite and dolomite surfaces. • DDALA/oleic acid molecular aggregates on apatite surface dictate its weakened capturing ability. This paper introduces a novel amphoteric collector, N -dodecyl-β-alanine (DDALA), derived from the molecular structure of dodecylamine, with the incorporation of a propionic acid group. In the study, flotation experiments are undertaken to examine the selectivity of DDALA in apatite flotation. Results demonstrate that DDALA, in combination with xanthan gum (XG) depressant and oleic acid collector successfully accomplishes the reverse flotation separation of apatite from quartz and dolomite. In addition, the synergistic application of zeta potential experiments, X-ray photoelectron spectroscopic tests, and first-principles calculations has been employed to delve into the action mechanisms of DDALA collector and XG depressant. By combining the results with existing research, the paper proposes that the selective adsorption of XG between apatite and quartz surfaces facilitates the selective separation of these two minerals by DDALA collector. Moreover, the intermediate collecting ability of DDALA/oleic acid combined collector for dolomite results from the competitive adsorption of DDALA neutral molecules and oleic acid anions on dolomite surface. Furthermore, the formation of hydrophilic molecular aggregates between DDALA neutral molecules and oleic acid anions on apatite surface diminishes the collecting ability of DDALA/oleic acid combined collector for apatite compared to the individual use of each collector. [ABSTRACT FROM AUTHOR]

The deeply buried (>8 km) end-Ediacaran Qigebrak Formation dolostones in the Tarim Basin, China, have significant petroleum potential, but have experienced multi-stage dolomitization that has resulted in the occurrence of diverse dolomite phases. The features and origins of the different dolomite types were merely investigated, which hinders an in-depth understanding of the complex dolomitization processes. This paper presents an integrated petrological, geochemical (C–O–Sr isotope and in situ trace element), fluid inclusion microthermometric, and dolomite U–Pb dating study of outcrop and core samples, to investigate the dolomitization mechanisms, and the nature and evolution of the dolomitizing fluids. The results indicate the occurrence of early dolomitization triggered by seepage–reflux of mesosaline seawater, which retained the primary marine geochemical properties of most of the matrix dolomite. Subsequently, during early diagenesis, fibrous dolomite cement was precipitated from marine porewaters, which have similar geochemical characteristics to the matrix dolomites. Following this, during intermediate-depth burial diagenesis in the Ordovician, fine-to medium-crystalline dolomite cements formed at temperatures of 80–117 °C in association with dissolution–reprecipitation of the matrix and early fibrous cements or diagenetic interactions with clay minerals of the lower Cambrian Yurtus Formation shales. During deep burial diagenesis and dolomitization in the Carboniferous, coarse-crystalline dolomite cements formed at temperatures of 104–138 °C from saline brines enriched in middle rare earth elements. Saddle dolomites, formed by hydrothermal dolomitization (162–184 °C) that was closely related to Permian–Triassic volcanic activity, have positive Eu anomalies and depleted δ18O values, that resulted from the mixing of basinal brines with 87Sr-enriched hydrothermal fluids. This study provides a detailed description of multiple dolomitization events in deep time that affected deeply buried dolostones. • Multi-stage dolomitization occurred from the near-surface to deep burial depths. • The dolomitization history and diagenetic fluid evolution were determined. • Pervasive reflux dolomitization was caused by weak seawater evaporation. [ABSTRACT FROM AUTHOR]

Carbonate rocks are one of major geothermal reservoir types around the world. Understanding the thermal properties of carbonate rocks is of significance to the assessment and utilization of deep geothermal reservoirs. Different from conventional test methods, this paper introduced a new approach, molecular dynamics calculation (MDC), to studying the thermal properties of carbonate rocks. By means of MDC, the thermal properties including specific heat, thermal conductivity and thermal diffusivity of four types of carbonate rocks including calcite, dolomite, magnesite, and smithsonite were investigated. The intrinsic relationship among the Debye temperature, elastic and thermal properties of carbonate rocks was revealed. The variations of the thermal properties with the average atom weight and temperature (300–800K) were obtained and regressed as functional formulas for applications. Further, taking carbonate rock samples from North China as an example, the specific heat and thermal conductivity were tested and compared with the MDC results based on actual lattice parameters by using X-ray diffraction method (XRD). The results showed that there was a good agreement between the test and calculation results. Finally, the thermal properties of ferroan dolomite samples were predicted. The present method can provide a promising extension tool for analyzing other crystalline rocks for geothermal applications. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs), carbon, oxygen and Mg isotopes have been widely used to explain the origin of dolomite, but dolomite may undergo complex diagenetic alteration during long geological processes, and whether the geochemical signals of precursor dolomite can be preserved is still unknown. In order to further explore the formation mechanism of dolomite and the influence of diagenetic alteration processes on geochemical parameters, this paper takes the thick-layer dolomite of the Lower Qiulitage Formation of the Late Cambrian in the Tazhong uplift area as an example and divides the dolomite into two categories through petrologic observation. One category is fabric-retentive dolomite (FRD), including algal clotted dolomite, algal psammitic or psammitic grain dolomite, and aphanocrystalline dolomite; the other category is fabric-destructive dolomite (FDD), including crystalline dolomite (CD) and siliceous dolomite (SD). Cation ordering, unit cell parameters, major/trace elements, REEs as well as C–O–Mg isotopes of the pure matrix powders of different types of dolomites are further analyzed. The results show that the dolomites are near-source/far-source seepage reflux type and sabkha type eogenetic origin, and the magnesium ions mainly come from Late Cambrian seawater; dolomite crystals of different sizes are the result of the precursor dolomite suffering varying degrees of recrystallization during the early diagenesis period, inheriting the original geochemical characteristics; hydrothermal alteration occurs in the late stage of diagenesis, with limited magnesium ions in the hydrothermal fluid. Its impact on the dolomite is mainly reflected in local dolomite distortion and a large amount of aphanocrystalline silica and coarse-grained quartz cement filling, which fails to obviously reset the geochemical information of the matrix dolomite. The above results demonstrate that, under favorable conditions, early genetic marine dolomites may resist geochemical resetting over time intervals of more than 400 million years. • The eogenetic origin of dolomite of Lower Qiulitage Formation has been revealed. • Recrystallization of early diagenesis results in various crystal size. • Hydrothermal alteration occurs in late diagenesis, forming significant siliceous cement. • Eogenetic dolomite may resist geochemical resetting over long time intervals. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to investigate the mechanical properties, mainly wave velocity, strength, deformability and degradation characteristics of carbonate fault rocks in the laboratory. The investigated materials present a complex behavior, mainly controlled by their tectonic disturbance, which has not been thoroughly studied due to practical limitations in sampling preparation and execution of laboratory tests. A novel procedure to prepare samples from the studied rocks was successfully performed. Two (2) intact, parent rock types (i.e., intact limestone, intact limestone-dolomite breccia) and five (5) fault rock types (i.e., two types of limestone fault breccias, two types of fractured marly limestones and one type of tectono-diagenetic dolomite breccia) were retrieved from five locations in Lefkada Island, Greece. The mechanical properties of the intact, parent rocks were determined to define the degree of strength reduction due to the tectonic disturbance of the fault rocks. The mechanical properties of the fault rocks significantly vary, a fact that is attributed to their structural and textural properties. These properties were quantified using a novel image processing technique and two (2) discrete algorithms. The durability characteristics of the studied rocks were also assessed through freeze-thaw and slake durability tests. The specimens with a higher tectonic disturbance yielded increased degradation characteristics, in repeated freeze-thaw and slaking cycles proving that the behavior of the material can drastically change over time due to weathering and erosion processes.. The findings of this paper suggest that the behavior of fault rocks cannot be approximated by the existing rock mechanics principles and therefore, a more focused methodology to derive their mechanical properties is needed. [ABSTRACT FROM AUTHOR]

The Zhe-Min Uplift (ZMU) has undergone tectonic subsidence, which has been associated with a notable transgression in the northern marginal seas of China since the middle Pleistocene. However, its uplift history during the late Quaternary is still inadequate. The Old Red Sand (ORS) is a late Pleistocene deposit that is widely distributed along the southeastern coast of China. The ORS consists of partially-cemented fine- to medium-grained sand. In this paper, we focus on mud-rich ORS deposits of the Liushui area, Pingtan Island, Fujian Province, and report optically stimulated luminescence (OSL) ages, and new datasets of grain size, mineralogy (detrital zircon, clay and detrital minerals) and organic carbon and nitrogen isotope profiles to improve understanding of chronology, provenance, palaeoenvironmental evolution and tectonic infuence. Based on the OSL data, we hypothesize that the development of the ORS was associated with lower sea levels, with most deposition occurring within MIS4. Based on comparison of detrital zircon U Pb ages, the coarse fraction of the Liushui ORS was mainly derived from the Minjiang River, with modest input from weathering of coastal granites. The East Asian Winter Monsoon contributed some materials from the East China Sea shelf during the last glacial period, as indicated by the fine-grained nature of the Liushui ORS, low K-feldspar/plagioclase ratios, high dolomite content and the frequency of Neoproterozoic and Palaeoproterozoic detrital zircons. The deposition of the ORS was influenced by both the East Asian Winter Monsoon and sea level changes. The clay minerals in the mud layers of the Liushui ORS were dominated by kaolinite and illite, with little chlorite and no smectite, indicating that they originated from the Minjiang River. The TOC/TN ratios of the mud layers, as well as their isotope characteristics, indicate the organic matter was derived from marine sources, presumably during the transgression event in MIS5. The average uplift rate of the ORS was about 0.03 mm/yr. The uplift of the ORS provided new insights into the geological records of the ZMU, which differed from the subsidence observed in the northern region of the Minjiang River during the late Pleistocene. • The formation of the ORS was association with lower sea level, and the MIS4 was primarily the deposition stage. • During the last glacial, the more sediments from the East China Sea shelf were transported to the ORS by EAWM. • The mud layer was the transgression records during MIS5. • The distribution of the ORS was influenced by tectonic activity. [ABSTRACT FROM AUTHOR]

• Selective recovery of dolomite and calcite impurities in sedimentary phosphate ore. • Fatty acids coupled with ethoxylated alcohols provided better flotation performance. • Surface response methodology assisted in achieving satisfactory flotation outcomes. • Automated mineralogical characterization elucidated flotation performance. This paper presents a comprehensive study on the selective flotation of a multi calcium-bearing minerals ore, focusing on the efficient removal of dolomite and calcite impurities from a carbonaceous sedimentary phosphate ore. Commercial fatty acid (FA) and phosphate ester collectors were investigated in a reverse flotation process, assessing the impact of flotation pH, collector dosage, and type on the selectivity and recovery of calcite and dolomite. The efficiency of FA-based collectors was recognized as they provided higher quality concentrates with reduced carbonated-fluorapatite contents. The response surface methodology was employed to review and model the effects of pH and dosage of each fatty acid collector on flotation performance. Accurate regression models were developed, forming the basis for an optimization study to determine the optimal operating conditions for achieving selective carbonate flotation with high carbonate grade and recovery while minimizing the carbonated-fluorapatite (CFA) content. Automated mineralogical microscopy was conducted on the phosphate ore and the recovered carbonate and phosphate concentrates, confirming the success of flotation while attributing the presence of 12% CFA (≈ 4 % de P 2 O 5) in the carbonate concentrate to mineral associations and fines entrainment. [ABSTRACT FROM AUTHOR]

For successful emulsified acid treatment, it is imperative to have emulsified acid that can maintain a water-in-oil emulsion state for 24 h at room temperature and 4 h at high temperatures. As a result, a hybrid emulsified acid was developed by combining cationic and nonionic emulsifiers, guaranteeing stability at both room and high temperatures. We assessed its viscosity and explored the interaction dynamics of the emulsified acid with carbonate rock samples using rotating disk apparatus experiments. Viscosity measurements revealed a non-Newtonian shear-thinning behavior modeled using a power-law approach. We examined limestone, dolomite, and chalk disks to evaluate weight loss tendencies, dissolution rates, and diffusion coefficients when exposed to the emulsified acid and hydrochloric acid (HCl). Both the weight loss and dissolution rate demonstrated that the reactivity of HCl surpasses that of the emulsified acid by up to 2.4 times at the same rotating speed. This indicates that the emulsified acid in our study can significantly slow the rapid reaction between acid and rock due to the diffusion barrier created by the oil phase. The diffusion coefficient for the limestone sample with emulsified acid was 1.46 times greater than that of dolomite (limestone: 1.64 E–7 c m 2 / s , dolomite: 1.12 E–8 c m 2 / s , and chalk: 1.47 E–8 c m 2 / s). Consequently, understanding the rock/mineral composition of the targeted reservoir is crucial when designing matrix acidizing with emulsified acid in carbonates. In summary, it is vital to account for the impact of emulsified acid on acid-rock reaction kinetics when establishing injection parameters for carbonate acidizing. [Display omitted] • This paper presents the reaction kinetics of an emulsified acid that secures fluid stability at room and high temperatures with various carbonate disks. • It was revealed that the dissolution rate and diffusion coefficient of the emulsified acid were lower than those of hydrochloric acid. • The emulsified acid used in this study can markedly retard the rapid reaction between acid and rock because of the diffusion barrier of oil phase. • The emulsified acid used in this study can effectively stimulate carbonate reservoirs as retarded systems. [ABSTRACT FROM AUTHOR]

The positive correlation between total organic carbon and specific surface area in sediments and mudstones implies the association between sedimentary organic matter (OM) and clay minerals. However, the traditional classification of OM, including insoluble kerogen and soluble OM (SOM), ignores the role of minerals, significantly limiting the understanding of the role of mineral-OM interactions in OM preservation and evolution. This paper reviews the mineral and OM characteristics and their relationship in argillaceous sediments and rocks and classifies sedimentary OM into three forms of occurrence, namely free SOM (FSOM), mineral-bound OM (MOM), and particulate OM (POM). FSOM, dominated by non-polar compounds, is physically adsorbed on the external surface of minerals or free in pores of different sizes, so it is susceptible to oxidation. MOM includes polar SOM and insoluble amorphous OM. The former is chemically adsorbed on the external surface, sheet edge and intercalated into interlayer space, and the latter is encapsulated in the clay microfabric. MOM is preserved by mineral adsorption, physical encapsulation, and degradation-recondensation, so it is very stable. POM is predominantly insoluble structured OM in the form of discrete particles and is preserved by selective preservation at the expense of chemical reactivity. The three forms of OM occurrence result from the synergistic operation of multiple preservation mechanisms, in which mineral-OM interactions dominate long-term OM preservation. Depending on environmental conditions, the change of mineral-OM interaction leads to the OM release or cracking, thereby promoting carbon cycling. Compared to traditional OM classifications, the new model of OM occurrence incorporates mineral protection mechanisms and provides a unifying principle linking inorganic and organic processes in OM preservation and evolution. OM preservation and evolution is essentially the process of mutual transformation of OM between different forms of occurrence, so this model is very useful for understanding carbon cycling and hydrocarbon generation and should be valued. • Sedimentary organic matter is divided into three forms of occurrence. • Mineral-organic matter interaction leads to the fractionation of organic matter. • The role of mineral-organic matter interactions in carbon cycling is discussed. [ABSTRACT FROM AUTHOR]

• Dolomite powder (DP) is used for replacing clay in clay masonry units. • The effects of DP on clay bricks properties depend on DP percentage. • Use of DP can improve the thermal conductivity of clay bricks. • The compressive strength of clay bricks decreases by increasing the DP percentage. • Possibility of replacing up to 30% of clay materials with DP. This paper evaluates the influence of dolomite industrial waste (dolomite powder (DP) on the properties, structure and durability of clay bricks. Four clay samples fired at 900 °C and 1000 °C containing 0 wt%, 10 wt%, 20 wt% and 30 wt% DP were prepared and investigated to measure their properties (shrinkage, bulk density, water absorption, thermal conductivity, apparent porosity, compressive strength), structure and durability (compressive strength after freeze thaw). The results showed a decrease in bulk density, compressive strength and an increase in apparent porosity and water absorption of the clay bricks produced by mixing 70–90 wt% clay and 10–30 wt% DP compared to the control bricks. Also, a significant improvement in the thermal conductivity of clay bricks produced by 70 wt% clay and 30 wt% DP (0.407–0.420 W/(m⋅K) compared to the control clay bricks (0.839–0.845 W/(m⋅K). As clay mixtures contain DP (chemical composition: CaO-49.68%, Loi-42.80%), CO 2 emissions during the firing process are increased (decarbonation reactions). However, the thermal conductivity of the fired clay bricks is significantly reduced (to 50%). These results showed the potential of DP for the manufacturing of clay masonry units. [ABSTRACT FROM AUTHOR]

Depressive model of the LGB for flotation separation of scheelite and dolomite. [Display omitted] • Selective depressant LGB used for scheelite flotation. • Selective flotation separation of scheelite from dolomite was achieved. • LGB is selectively adsorbed on the dolomite surface by chemisorption. • The selective adsorption lies in the more active Mg sites on the dolomite surface. Dolomite is a common vein mineral in scheelite, but how to selectively suppress dolomite in flotation of scheelite has not been addressedin the past research works. In this paper, the depressive behavior of locust bean gum (LBG) in separating scheelite from dolomite is investigated and a possible inhibition mechanism is proposed. The flotation results proved that LBG (18 mg/L) could effectively inhibit dolomite in scheelite flotation at pH = 9, and the obtained grade was 65.69 % of scheelite concentrate. Moreover, combined with the results of XPS, FTIR, Zeta potential, and contact angle experiments, it was inferred that LBG would selectively accumulate on the dolomite surface due to the presence of denser and more active action sites on the surface; and LBG could be stably adsorbed on the dolomite surface based on the stable complexation reaction between the carboxyl groups in LBG molecules and Mg2+ on the dolomite surface. Notably, the preferential adsorption of LBG not only brings a large number of hydrophilic groups to dolomite but also interference with the adsorption of sodium oleate, leading to a substantial decrease of the hydrophobicity of dolomite and finally realizing the selective inhibition of dolomite in scheelite flotation. [ABSTRACT FROM AUTHOR]

Carbon dioxide storage in geological formations is one of the mature strategies developed for controlling global warming. This paper represents a comprehensive experimental and geochemical modeling study to analyze CO 2 -brine-rock interactions in a carbonate rock containing calcite and dolomite minerals. PHREEQC geochemical package has been applied for modeling the geochemical reactions in the studied porous media. Firstly, dynamic experiments are performed to calibrate the geochemical model. Then, static experiments are conducted to study the geochemical reactions in the CO 2 -brine-rock interaction system. This study contributes to analyzing the precipitation-dissolution and ion exchange mechanisms in the CO 2 -brine- carbonate rock reactions during carbon dioxide storage. The purpose of the present paper is providing a scientific basis to judge surface CO 2 loading in carbonate reservoirs. Results of the present study show that brine-rock interaction increases the dissolution of carbon dioxide gas in the aqueous phase. It is also demonstrated that carbonate ions can attach to the minerals' surface through the ion exchange mechanism. Among the surface ion exchangers, >CaHCO 3 contains the maximum amount of carbonate ion. At the high pressures, amount of the carbon dioxide stored on the minerals' surface is almost independent of the pressure variation. [Display omitted] • Analyzing the ion exchange in the CO 2 -brine-rock interaction systems. • >CaHCO 3 contains the maximum amount of carbonate ion. • Surface CO 2 loading is negligible in calcite and dolomite minerals. [ABSTRACT FROM AUTHOR]

Several laboratory studies observed wettability alteration of carbonate rocks towards a more water-wet state through modifying the composition of injected water. The change in carbonate surface charge was reported as the underlying reason behind this wettability alteration and the corresponding incremental oil recovery by engineered water injection (EWI). Although the reported results of carbonate rock sensitivity to injected water ionic strength, pH, salinity, and concentration of potential determining ions (Ca2+, Mg2+, and SO 4 2−), there is still an ambiguity on the way carbonates interact with injected water/ions. This is due to the different mineralogical compositions and electrokinetic properties of carbonates. Therefore, this paper provides more insight into the role of major rock-forming carbonate minerals (calcite and dolomite) in engineered water injection at different water compositions by utilizing surface complexation modeling (SCM). The study utilizes a geochemical simulator to highlight the effect of dolomite surface complexation reactions. After determining the total rock surface charge and surface potential, the disjoining pressure was calculated to estimate the water film thickness and consequently, infer about wettability alteration. The results showed that a successful EWI operation creates three regimes: displacement regime, surface reaction regime, and quasi-equilibrium regime. These regimes can be characterized by the proposed surface complexation technique to calculate/optimize the injection pore volumes needed for each regime, determine the location of EWI effect in the reservoir, and predict the time ranges when EWI will reach to the surface in the form of additional oil recovery. Also, it was found that the surface reaction regime is the most important one where main surface reactions and oil recovery occur. Furthermore, the study utilizes SCM for both calcite and dolomite minerals for the first time highlighting their importance in geochemical reactions of EWI when the rock has dolomite in its composition. Existing SCM considers oil-brine and rock-brine interfaces where only calcite mineral is captured in the rock-brine interface. The latter is based on assuming that the rock composition is pure calcite, which is not necessary the case. The findings of this study confirm that seawater is capable of inducing wettability alteration in carbonates under certain favorable conditions due to adsorption/desorption of the potentially determining ions. • This paper provides novel insight into the role of major rock-forming carbonate minerals (calcite and dolomite) in EWI/LSWI at different water compositions by utilizing the surface complexation reactions. • It is found that in a successful EWI operation, three regimes would be created, i.e. displacement regime, surface reaction regime, and equilibrium regime. • These regimes can be characterized by the proposed technique to calculate/optimize the injection pore volumes needed for each zone. • The developed approach can determine the location of EWI effect in the reservoir, and predict the time ranges when EWI would reach to the surface in the form of additional oil recovery. • This study utilizes SCM for both calcite and dolomite minerals for the first time highlighting their importance in geochemical reactions during EWI when the rock has dolomite as a constituent. [ABSTRACT FROM AUTHOR]

Detailed geological field measurements combined with petrographic and mineralogical analyses of the Horse Racing Club outcrop, Bahrain, revealed new insights into the composition, facies distribution, and depositional settings of the Early Eocene Rus Formation, which is poorly constrained in Bahrain. The mineralogical analysis revealed that the rock-forming units are dominated by dolomite, dolomitic marl, claystone, and minor evaporites. The integration of field data and lab measurements resulted in the identification of thirteen facies that are grouped into five facies associations comprising i) lagoonal complexes, ii) sabkha complexes, iii) transgressive lag, iv) peritidal channel complexes, and v) barrier island and washover complexes. Combined paleocurrent analysis of field-observed clinoformal structures, lateral accretion surfaces, and trough cross-bedding indicate a NNW–SSE paleoshoreline trend with tidal channels trending dominantly towards NE–SW and NW–SE directions. The depositional facies model developed for the Rus Formation in Bahrain and within the surrounding region suggests that during the Early Eocene, two landmasses existed to the north and south of Bahrain, restricting the Neo-Tethys Ocean flow through a relatively narrow strait that was influenced by periodic storms. The results of this paper challenge the role of the Rus Formation as an effective regional hydrocarbon seal and, as such, highlight the need for a critical evaluation of the associated petroleum system potential in Bahrain and neighboring countries. • Detailed geological field and lab work was performed at the Rus Formation outcrops in Bahrain. • Thirteen facies have been identified, with dolomite and dolomitic marls dominating. • Five facies associations have been developed, indicating marginal marine depositional settings. • The Rus Formation in Bahrain can be considered a reservoir, with porosity values reaching 17%. • During the Early Eocene, Bahrain was represented by a strait influenced by periodic storms. [ABSTRACT FROM AUTHOR]

• Na 3 PO 4 lowers the temperature for the partial decomposition of dolomite. • The partial decomposition of Na 3 PO 4 -doped dolomite involves multiple steps. • Magnesian calcite forms in the partial decomposition of Na 3 PO 4 -doped dolomite. • The Mg content in magnesian calcite depends on calcination conditions. Dolomite calcination is of important industrial significance in versatile scenarios. This paper reports the effect of trisodium phosphate on dolomite decomposition. The thermogravimetric tests showed that the dolomite with 1.0 wt. % Na 3 PO 4 (Na 3 PO 4 -dolomite) partially decomposed into MgO and magnesian calcite (Mg-CaCO 3) and the formed Mg-CaCO 3 then decomposed subsequently. The Na 3 PO 4 lowered the temperature and significantly enhanced the rate of partial decomposition of dolomite. The change in the apparent activation energy (178.5-104.0 kJ/mol) versus the conversion indicated that multiple steps were involved in the partial decomposition of Na 3 PO 4 -dolomite. In the partial decomposition, Mg-CaCO 3 with different Mg contents and MgO formed as final products. The Mg content of the Mg-CaCO 3 was dependent on the calcination conditions. High-magnesian calcite (>10 mol% Mg) was obtained by calcining Na 3 PO 4 -dolomite at 873 K within 60 min. [Display omitted] [ABSTRACT FROM AUTHOR]

Cleaner and value-added resourceful utilization of the tailings or natural mineral resources has gained increasingly attention under the advanced concept of green and sustainable development. To develop an environmental-friendly preparation process for cobalt blue pigments with high chroma and low cobalt consumption, a dolomite-induced mechanochemical technology was developed for fabrication of cobalt blue composite pigments with controllable high blue intensity in the presence of kaolin tailing sand without using and discharging waste liquids. It revealed that the excellent color performance (L* = 37.63, a* = 10.68, b* = −54.87, C* = 55.91) benefitted from the Ca/Mg species and the lamellar morphology of dolomite by the mechanical force, which could facilely adjust the color performance and in-situ load pigment nanoparticles, respectively. The composite pigments presented a flaky morphology decorated with about 10 nm of nanoparticles, and consisted of calcium aluminate, anorthite, quartz and spinel magnesium cobalt aluminates. It is worth mentioning that the as-prepared composite pigments exhibited excellent environmental stability and good application performance as painting ink on rice paper. Therefore, this novel and cleaner technology is expected to produce high-performance cobalt blue pigments with lower cobalt consumption, as well as simultaneously realize the resource utilization of kaolin tailing sand and dolomite. [Display omitted] • CoAl 2 O 4 composite pigments with high blueness were prepared using kaolin tailing sand and dolomite. • The activated kaolin tailing sand provided the Si source for formation of anorthite. • Dolomite was mechanochemically activated as benign substrate and Ca/Mg sources for regulating the color. • Strong blue intensity relates to synergy of CaAl 2 O 4 , MgAl 2 O 4 and substrate roles of kaolin tailing sand and dolomite. • It provided a promising strategy for cleaner and value-add utilization of kaolin tailing sand and dolomite. [ABSTRACT FROM AUTHOR]

In this paper, heavy metals (i.e., V, Cr, Co, Cu, Zn, Cd, Pb, and Sb) in soils from a tannery waste lagoon, Hebei, north China were investigated. Element concentrates were determined by a portable X-ray fluorescence in situ and an inductively coupled plasma mass spectrometry in the lab. Two sets of indexes, including geological accumulation index, contamination factor, and pollution load index, and hazard quotient and total carcinogenic risk were adopted to evaluate the pollution and health-risk of heavy metals. A scanning electron microscopy in conjunction with an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy was used to observe chromium occurrence and speciation. With an average of 6493.11 mg/kg, chromium contents in the lagoon soils reached up to 12971.19 mg/kg, 211-times higher than the threshold of Chinese soils (61.00 mg/kg). Elevated Cr contents resulted in significantly high pollution and noncarcinogenic and carcinogenic risks in the studied area. Chromium in most soils occurred predominately as Cr3+ (60–74%), and to a lesser extent, Cr6+. The mechanism responsible for decreasing Cr6+ percentages in soils with increasing depth was summarized: Cr6+ favors aqueous environment; soil moisture decreased with increasing depth; in soils especially in the lower portion, Cr6+ was reduced by Fe0 and Fe2, transforming into Cr3+ and Fe3+. In addition, the alkaline condition promoted Cr3+ to precipitate, resulting more Cr3+ absorbing in soils. The intimate association of Cr and Fe in soils (i.e., Cr mainly occurred in Fe oxides and dolomite) further confirmed our assumptions. A combined application of microorganism (e.g., Aeromonas hydrophila) and biochar (prepared from maize stalk or peanut shells) were recommended to alleviate Cr pollution in the soils. [Display omitted] • Chromium contents in lagoon soils are much higher than those of soils from the leather tanning districts worldwide. • The average I geo of Cr from studied soils is 7.59, higher than the threshold (>5) for significant pollution. • The Cr3+ percentages ranged from 60 to 74% in most soils, except for 42% in soils kb2 1–10 and kb3 1–10. • Chromium contents and Cr3+ percentages increased with the increasing depth. • Chromium occurs mainly in dolomite and Fe oxides; while no Cr was found in calcite. [ABSTRACT FROM AUTHOR]

• Three constitutive models (JH-2, JHC, KCC) of dolomite are subjected to comparative study. • Dolomite behavior is reproduced under SHPB, impact and blast testing. • Advanced modeling including failure description is reflected and verified. • The best performance of JH-2 model is confirmed for mixed compressive-tensile damage of dolomite. • The benchmark of numerical simulations of full-scale underground blasting is proposed. Understanding the behavior of rock under blast- and shock-induced loadings requires a high-fidelity constitutive model. The present paper provides a detailed comparison study of three selected material models that are available in the most popular hydrocodes: the Johnson-Holmquist II (JH-2) model, the Johnson-Holmquist Concrete (JHC) model and the Karagozian and Case concrete (KCC) model. Numerical simulations are carried out to evaluate their performance under different stress conditions and to verify their effectiveness in realistically reproducing dolomite behavior. The outcomes are compared qualitatively based on specimen failure and quantitatively based on measured characteristics. The pros and cons of each model are presented and analyzed. Based on the comparison study, the JH-2 model is selected to simulate a representative blast in a mining face. The cracking, fracturing and fragmentation are correctly captured by the JH-2 model, proving its efficiency in the simulation of drilling and blasting in a mining face. [ABSTRACT FROM AUTHOR]

South Matese, Apennines, is a hydrothermally and seismically active extensional area characterized by CO 2 outgassing and Mw ≤ 7.1 earthquakes. There, meters-sized pockets of incohesive pulverized dolostone are hosted within Mesozoic carbonates at the hanging wall of seismically active normal faults. The aim of this paper is to understand the pulverization process. The pulverized dolostone is finely comminuted (down to a few microns), but primary structures, mainly bedding, are preserved. The grain size distribution is similar to that of previously studied pulverized rocks associated with active faults and dissimilar to that of carbonate cataclasites and fault gouges. The pulverized pockets are surrounded by zones (halos), in which the loose grains are cemented, in their original position, by microcrystalline calcite, resulting in a cemented micro-mosaic breccia. Stable isotopes from the cement are compatible with calcite precipitation from rapidly CO 2 -degassing shallow waters. Comparing our observations with results of laboratory experiments on carbonate pulverization through rapid decompression of pore-hosted CO 2 , the best explanation for the pulverized dolostone may lie on local accumulations of pressurized CO 2 -rich gas, suddenly decompressed during earthquakes. The limited permeability of the gas-saturated dolostone must have prevented a prompt escape of the gas from the rock, which was therefore anhydrously pulverized by the rapid expansion of the trapped gas. The sudden decompression must have suctioned bicarbonate-rich groundwaters, from which microcrystalline calcite rapidly precipitated, fossilizing the freshly pulverized dolostone. Calcite precipitation formed an impermeable shield around the pulverized pockets, which, therefore, remained internally uncemented. This process may have occurred over multiple cycles at depths shallower than the CO 2 subcritical–supercritical boundary (ca. -800 m). Although hypothetical, the proposed mechanism is for the first time suggested for an active tectonic environment. The gas rapid decompression could have been triggered by coseismic processes (e.g., dynamic unloading or transient tensile pulses) previously proposed for the formation of other pulverized rocks. The presented case may improve our knowledge of possible chemical-physical processes connected with the subsurface storage of CO 2 in seismically active areas. • Incohesive pulverized dolostone hosted within Mesozoic carbonates are studied. • Accumulations of pressurized CO 2 must have suddenly decompressed during earthquakes. • Dolostone was anhydrously pulverized by the rapid expansion of the decompressed gas. • Sudden decompression suctioned groundwaters from which calcite rapidly precipitated. [ABSTRACT FROM AUTHOR]

Clumped isotope thermometry is an effective tool which allows to understand the post-depositional alteration, including recrystallization and solid-state reordering, of carbonate rocks. However, as both processes are controlled by elevated temperatures, it is frequently a challenge to distinguish between the relative importance of these two processes in deeply buried carbonate successions (depth > 5000 m or formation temperature > 150°C). In this paper, we have established a clumped isotopic framework of paired dolomite and calcite in order to decipher the relative influence of solid-state reordering versus recrystallization and consequently offer an improved understanding of the mechanisms involved. The material studied was derived from two deeply buried successions (Jurassic-Ediacaran) drilled in the central Sichuan Basin of South China. The calcite and dolomite minerals from these cores were separated using buffered acetic acid, and based on a two-component mixing model, the carbon, oxygen and clumped isotopic (Δ 47) compositions of the two endmembers were determined. Based on an evaluation of solid-state reordering models, we conclude that micritic carbonates (dolomite and calcite) from the Jurassic to the Cambrian have been altered during burial by the geothermal gradient as determined by vitrinite reflectance. The Ediacaran micritic dolomite records a hydrothermal event in the transition between the Ediacaran and Cambrian. In contrast, the clumped isotopic temperature of Ediacaran saddle dolomites reflects subsequent hydrothermal activity during the Silurian and Devonian and shows compositional variations controlled by cooling rates. This study highlights the utility of the theoretical framework based on paired dolomite and calcite records to untangle overprinted signals of clumped isotopes in ancient carbonate rocks and gives insight to better understand the complexity of alteration processes in deeply burial carbonate successions. [ABSTRACT FROM AUTHOR]

It is important to understand the mechanisms controlling the chemistry of the pore water in the Boom Clay, which has been studied as a reference host rock for the geological disposal of radioactive waste. The chemistry of the pore water and the related properties of the Boom Clay were investigated experimentally. This paper presents the results of equilibrium calculations and discusses the probable chemical constraints that control the concentrations of major elements in the pore water. The present-day Boom Clay pore water is a dilute NaHCO 3 solution of 10–20 mM, and the concentration increases with the depth of the Boom Clay over a thickness of 65 m around the underground laboratory at approximately 200 m below sea level. The present-day NaHCO 3 water is likely a result of freshwater infiltration, and the concentration profile observed must have been affected by waters from upper and lower aquifers. Among the minerals found in the Boom Clay, equilibrium calculations indicate that the pore water is in equilibrium with calcite, dolomite, siderite, pyrite, and quartz. Aluminium silicate minerals, kaolinite and chlorite, are also possibly in equilibrium, but their saturation states cannot be fully demonstrated mainly because of uncertainties associated with the pore-water concentration of aluminium. Cation exchange, an important property of clays, seems to be controlling only the pore-water concentration of potassium. Concentrations of other cation exchangeable elements, such as calcium and magnesium, are more likely regulated by the solubility of carbonate minerals. On clay surfaces, however, cation-exchange reactions are evidenced and control occupancies of all exchangeable cations. The cation-exchange pool on clay responds to the increase in NaHCO 3 concentration with depth, and the surface occupancies vary according to the selectivity of exchangeable cations. Equilibrium calculations allow us to propose a Boom Clay reference model that is able to explain the observed pore-water chemistry. This model is compared to other models in the literature, such as those for the Opalinus Clay in Switzerland and Callovo-Oxfordian Clay in France, which have also been studied for the purpose of radioactive waste disposal. Future studies to improve our understanding of the Boom Clay pore-water geochemistry include i) accurate determination of the pore-water concentration of aluminium, which is crucial for studying the mineral saturation state of aluminium silicates; ii) improving understanding of the mineralogical composition of dolomite in the Boom Clay and its dissolution mechanisms; iii) reassessment of magnesium cation-exchange occupancy on clay surfaces; and iv) improving pore-water sampling and analysis techniques with respect to pH and pCO 2 measurements to avoid perturbations to water samples so that the in situ conditions can be preserved to a maximum extent. • Pore-water model of the Boom Clay at the Mol site, Belgium. • Model validated by water and clay cation exchange data stratigraphically. • Model with 7 minerals buffering the pore-water composition. • Model applicable to other clays. [ABSTRACT FROM AUTHOR]

Globally many valuable karst resources are under severe threat due to anthropogenic activities. This paper presents a review of the geomorphology of karst landforms including caves, sinkholes, etc. in southern Africa. It further presents the environmental threats and challenges faced by these karst landscapes, their genesis and controlling factors, as well as their possible mitigation and remedial measures. The karst landscapes in the region are most abundant in the interior of the sub-continent, whereas coastal karst is sparsely distributed, and is mainly found in the Eastern and Western Cape, and Kwa-Zulu Natal provinces of South Africa, as well as parts of Namibia. The karst of the interior is largely limited to the Proterozoic dolomitic limestone, while coastal karst is formed in the Tertiary coastal limestone and Quaternary calcareous sandstones. The human impacts threatening karst in southern Africa include mining and mineral extraction, construction and development, agricultural activities, climate change, and changes in the local hydrogeology. Anthropogenic impacts have particularly affected the karst landscape of the Gauteng and northern Free State Provinces of South Africa due to groundwater extraction associated with mining. Changes in land use and water management, consequential to development pressures and a variety of climate change scenarios, are the most significant threats currently facing southern African karst terrain. It is argued that sustainable engineering technologies, informed by sound geomorphological research, are necessary to ensure that future development, property, and life on karst terrain are safe from avoidable environmental problems. • Karst is a landscape that has developed on soluble rocks such as carbonates, and some partially soluble non-carbonate rocks. • In southern Africa, karst is abundant in the interior of the region, while coastal karst is sparsely distributed. • Human impacts such as mining, construction, agriculture, as well as climate change threaten karst in the region. [ABSTRACT FROM AUTHOR]

Fibrous carbonate cement is a common phase in marine phreatic environments — but its origin and diagenetic history are underexplored. This paper compares two fibrous fabrics that are different in terms of their peculiarities but share important similarities regarding their essentials: upper Ediacaran fibrous dolomite cement and Upper Ordovician fibrous calcite cement, both from the Tarim Basin, China. The focus is on the significance of these fabrics as archives of their marine paleoenvironment. Upper Ediacaran fibrous dolomite cement is present as (i) a fascicular-optic and (ii) a radial-fibrous phase. Judging from the optical length-slow character and luminescent zones, radial-fibrous dolomite cement precipitated directly from early diagenetic marine porewater. Fascicular-optic dolomite cement has a length fast optical character and hence likely formed as a high-Mg calcite precursor penecontemporaneously in a reefal, shallow-marine diagenetic environment. Similarly, two types of Upper Ordovician fibrous cement are present: (i) radiaxial-fibrous and (ii) fascicular-optic calcite cement. Fascicular-optic calcite precipitated in a marine phreatic platform environment, whereas radiaxial-fibrous calcite cement formed in an early marine diagenetic porewater environment. Both fabrics arguably replace a magnesium calcite precursor. For the case of the Tarim Basin, cathodoluminescence and redox-sensitive elements indicate predominantly anoxic, upper Ediacaran marine waters (Ce anomaly = 0.8 ± 0.2), and suboxic, Upper Ordovician shallow-marine seawater (0.7 ± 0.2). Based on PHREEQC modeling, the shallow burial, upper Ediacaran porewater (5.1) yields a higher dolomite saturation index than upper Ediacaran (4.8) and Upper Ordovician seawater (3.7). The direct precipitation of radial-fibrous dolomite from Ediacaran porewaters was likely induced due to organic matter decomposition and related seawater oxygen depletion, elevated Mg2+/Ca2+ ratios, and high alkalinity values. Modeling and proxy data show significant hydrogeochemical differences between seawater and porewater in the upper meters of the sediment column. The upper Ediacaran seawater apparently favored fibrous cement formation with magnesium calcite precursors. In contrast, fibrous dolomite cement was directly precipitated in an early-diagenetic marine porewater regime. The comparability of proxy data reflecting seawater and such recording early diagenetic marine porewater is critically discussed. The Ediacaran early diagenetic marine porewater yields higher dolomite saturation index than the Ediacaran seawater and Ordovician seawater. [Display omitted] • Radial-fibrous dolomite with length-slow character and well-preserved zone is primary. • Fascicular-optic calcite and radiaxial-fibrous calcite have precursor of Mg-calcite. • Aqueous chemistry shows variation from shallow seawater to early diagenetic porewater. • Anoxic, elevated Mg2+/Ca2+ ratios and alkalinity favored the precipitation of dolomite. [ABSTRACT FROM AUTHOR]

• The structure of reaction rim formed in ACR can block the migration of alkali ions. • The thickening of the reaction rim will inhibit the dedolomitization progress. • Large particles of dolostone will not react completely when exposed to NaOH solution. • The process of dedolomitization is shown in this manuscript. Alkali-carbonate reaction (ACR) are chemical reactions in concrete which may induce significant damage in concrete structures. Researchers have mainly focused on studies of the symptoms pertaining to the reaction, namely expansion and loss of mechanical properties. Not enough attention has been paid to the processes of dedolomitization in dolomitic rocks, such as migration of alkali and hydroxide ions to the surfaces of dolomite crystals, formation of products and effect of products on further migration of alkali and hydroxide ions to newly generated surface of the reacted dolomite crystals. These processes may significantly affect dedolomitization of dolomite and the resulted expansion of ACR. This paper investigates the alkali ion migration in dolostone and the process of dedolomitization of dolomite in the aggregates. Dolostones were crushed, sieved, and graded. Chemical, physical, and microstructural analysis of dolostones and degree of dedolomitization based on X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and laser scanning confocal microscopy (LSCM) of dolostones. Three of the key outcomes of this study provide new insights on the dedolomitization under autoclave conditions: (i) the degree of dedolomitization for large dolostone particles will stop increasing after a period of autoclaving time in 1 mol/L NaOH solutions, (ii) the reaction rim forms a nanofiltration-like structure that, when thick enough, can block the migration of alkali ions and inhibits the dedolomitization process, and (iii) the mechanism of dedolomitization of dolomite is that Mg2+ ions in the dolomite gradually dissolved from dolomite to form brucite with OH− ions, while the rest of dolomite eventually converts to calcite when all Mg2+ is dissolved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption is the most effective method for heavy metal removal. • Alkaline activated materials (AAMs) have unique adsorption properties due to its zeolite like structure. • Dolomite/HAP can be new potential AAMs for adsorbent due to its environmental friendly and good mechanical properties. • Molarity of NaOH, solid/liquid ratio, alkali activator ratio, and curing conditions affect the alkaline activation process. • Thermal and mechanical processes can improve the physical properties of AAMs such as surface area and pore volume. • The use of immobilized bacteria promises simple and cost effectiveness. Hazardous pollutants, especially heavy metals in wastewater, have become a major concern due to the high potential of causing serious problems to humans and aquatic ecosystems, such as adverse health effects, environmental damage, and air pollution. The adsorption process is widely used to remove heavy metals because it is inexpensive, simple, and environmentally friendly. However, recent studies have shown that some adsorbents such as activated carbon, ion exchange resins, and carbon nanotubes are becoming more expensive due to their complex production. Considering these problems, alkali-activated materials (AAMs) can be considered as a new potential adsorbent material due to their excellent physical, chemical, and mechanical properties, which make them suitable for use in the field of civil engineering. Dolomite is one of the AAMs that is capable of adsorbing hazardous pollutants such as heavy metals in wastewater due to its unique structure. This material is also classified as a cost-effective adsorbent because it is abundant and can be found all over the world. Nevertheless, few studies have focused on the adsorption method using dolomite as a precursor material to remove heavy metals in wastewater, and currently only limited studies focus on the relationship between dolomite and hydroxyapatite (HAP). In addition, some studies have shown that the properties of geopolymers can be improved (up to 40%) when a moderate amount of calcium-containing material is added to the geopolymer. Although they have been used as a stand-alone material with excellent properties, combining them with another material could be another way to improve their properties. Therefore, this review provides an in-depth analysis on the properties of dolomite as a new potential precursor material in combination with HAP for contaminant removal. This would help to find the best parameters for the geopolymerization process between dolomite and HAP to meet the adsorption method requirements. This paper also investigated the ability of HAP as a carrier with the combination of bacterial strains via an immobilization process to improve the properties of dolomite as a geopolymer adsorbent. A microbial community can also act as an adsorbent for the removal of heavy metals and inorganic/organic contaminants from wastewater. This review can serve as a basis for understanding the ability of dolomite/HAP as a new alkali-activated material in geopolymer adsorbents in combination with immobilizing bacteria to remove heavy metals in wastewaters. [ABSTRACT FROM AUTHOR]

The tight sandstone of gravity-flow deposits in Miocene Mbr 2 of the Huangliu Fm, Ledong area is one of the focuses future exploration in the Yinggehai Basin. Reservoirs have complex sedimentary and diagenesis processes, experienced multi-stage fluid influence. However, the influence of different diagenesis on reservoir quality, and distribution patterns of different diagenetic facies in Mbr 2 of the Huangliu Fm are still short in research. In this paper, a variety of methods, such as thin sections analysis, electron microscopy (SEM), electron probe micro-analyzer (EPMA), cathode luminescence (CL), x-ray diffraction measurement (XRD), in situ carbon and oxygen isotopes composition of cements (SIMS), fluid inclusion homogenization temperature, and high-pressure mercury injection (HPMI), are used to analyze reservoir quality, diagenetic evolution stages, diagenesis, fluid filling processes, etc. Studies have shown that there are obvious differences in diagenetic evolution process, including carbonate cementation, organic acid and hydrothermal dissolution, etc. Which ultimately leads to large differences in physical properties. Although sandstone texture has an impact on reservoir quality, strong compaction and early carbonate cementation were the main reasons for reservoir densification. Early calcite was precipitated in alkaline seawater, and later ferrocalcite was formed by the recrystallization of calcite and polyframboidal pyrites and euhedral pyrites formed under organic acid charged. After hydrothermal fluid charged, dolomite, iron dolomite, cement pyrites and dispersed granular pyrites precipitated. Besides, illite filled the throat. The dissolution of organic acids and late CO 2 -rich hydrothermal fluids improved the quality of reservoirs. According to the difference of diagenetic process and the quality of the reservoirs, Mbr 2 of the Huangliu Fm is divided into 4 types of diagenetic facies. High-quality reservoirs are mostly developed in H2-Ⅰ, H2-Ⅱ, and H2-Ⅴ sand formation near faults. Early carbonate cements were less developed, which could support primary intergranular pores. Feldspar, rock fragments, and early carbonate cements were strongly dissolved. It includes two diagenetic facies, low cementation - strong dissolution reservoirs and slightly cementation - weaken dissolution reservoirs. On the contrary, tight reservoirs mostly develop in H2-Ⅲ, H2-IV, and H2–V sand formation far away from faults, including late compacted tight reservoirs and early carbonate cementation tight reservoirs. The research results are helpful to analyze the diagenetic evolution of tight sandstone reservoirs, and conducive to the study of similar gravity-flow reservoir quality with the influence of hydrothermal fluids. • The diagenesis characteristics of N 1 h 2 shows obvious heterogeneity. • The diagenetic evolution stages and genesis of carbonate cements are revealed. • Gravity flow deposition and fluid charging have effect on reservoir quality. • Diagenetic facies distribution model of Mbr 2 of the Huangliu Fm is established. [ABSTRACT FROM AUTHOR]

• Water-rich sandy dolomite formation is extremely prone to catastrophe. • Limit equilibrium analysis combining seepage flow and pressure arch characteristics. • Prediction method of sanded dolomite catastrophe under seepage action. • Construction method suitable for water-rich sandy stratum. Revealing the mechanism of sand gushing triggered by failure of tunnel face in water-rich sandy dolomite strata contributes to the safe construction of tunnels. In this paper, we find that sandy dolomite and the water environment are the key factors causing sand gushing through geophysical prospecting at the tunnel face where 12,000 m3 sand surge occurred. Through the flow-solid coupling model, the extrusion deformation at the tunnel face is the main deformation form in the tunnel of water-rich sandy dolomite strata. The influence of different factors on the deformation value of the tunnel face is from strong to weak: sandification degree, head height, and tunnel depth. Combined with the study of pressure arch characteristics of the model, the limit equilibrium theory considering seepage effects and pressure arch characteristics is proposed. We get that sand gushing will occur in the tunnel in the intensively sandy dolomite strata where the head exceeds 80 m. For the intensively sandy dolomite strata with head below 80 m, the stability of the tunnel face is controlled by the degree of seepage damage. According to the reason of sand gushing, the comprehensive control measures consisting of risk identification by over-detection, double-layer close-packed pipe shed, grouting sealing technology and dewatering technology, and Milling and blasting combined construction method are proposed, and the effective control of tunnel working face is realized in practical application. [ABSTRACT FROM AUTHOR]

Water scarcity and deficiency of trace elements (e.g., Cu and Mn) in soils of arid and semi-arid areas are major constrains to crop growth and development. The application of brackish water drip irrigation system (BWDIs), coupled with trace elements, is probably an effective way to solve this problem. However, fouling problems caused by trace elements in BWDIs were inevitable. Therefore, this paper evaluates the mechanism of different types of trace element chelated fertilizers on the fouling of emitters in BWDIs by using long-period, high-frequency periodic flow monitoring and mineral fraction analysis. The influence of chelated fertilizers such as copper (EDTA-Cu) and manganese (EDTA-Mn), and traditional micro-fertilizers copper sulfate (CuSO 4) and manganese sulfate (MnSO 4) on emitter fouling in BWDIs were investigated. Results suggested, compared with CK, the EDTA-Cu effectively alleviated the emitter fouling, increasing the average discharge ratio (Dra) and Christiansen coefficient of uniformity (CU) by 21.0%− 28.9% and 36.7%− 67.6%, respectively. Due to the strong adsorption ability, EDTA-Cu adsorb the Ca2+ and Mg2+ in BWDIs, which enhanced the structural stability, reduced the flocculation and deposition ability in the fouling, and indirectly reduced the content of calcium and silica fouling. In addition, compared with CK, the EDTA-Mn significantly aggravated the emitter fouling in BWDIs, decreasing the Dra and CU by 18.2%− 22.5% and 24.5%− 43.1% respectively. EDTA-Mn directly increased the content of Ca2+ and Mg2+ in BWDIs due to strong flocculation, which destroyed the morphology of EDTA-Mn chelates and indirectly increased the content of calcium silica fouling (calcite, muscovite, k-feldspar, dolomite and chlorite), thus reduced the anti-clogging ability of BWDIs. Considering these results, this study does not recommend the application of EDTA-Mn for manganese fertilizer in BWDIs. This study provides a new perspective on the rapid application of micronutrient fertilization in BWDIs, with potential implications for sustainable development in arid and semi-arid areas. • Effect of manganese and copper fertilizers on fouling of drip irrigation systems was analyzed. • EDTA-Cu fertilizer significantly reduced calcium and silicate fouling in the irrigator runners. • Use of EDTA-Cu fertilizer in brackish water drip irrigation is strongly recommended. [ABSTRACT FROM AUTHOR]

[Display omitted] • The formation temperature of typical borates in skarn-type deposit were between 500 °C and 700 °C. • The formation of Mg(OH) 2 would control the pH value of contact metamorphism. • Contact metamorphism was the main metallogenic mode for skarn-type and metamorphic borate deposits. • Na-Ca borate in the exogenous ores may be converted into insoluble endogenous Mg borate. Borate minerals are important industrial materials that are produced in both exogenous and endogenous borate deposits. The former includes volcanic-sedimentary and salt lake sedimentary borate or boron-rich brine, and the latter contains skarn-type and metamorphic borate deposits. In this paper, XRD and TG-DTG-DSC are used to study the thermal decomposition characteristics of three natural borates, and we find that they are ulexite, mixture of tincalconite and northupite, and mixture of szaibelyite, dolomite, magnesite and lizardite, respectively. The thermal decomposition of borates mainly contain three processes: dehydrate crystal-water under 300 °C, remove hydroxyl accompanied by the amorphous at 300∼550 °C, and crystallization at 550∼700 °C. The ulexite and tincalconite mix with calcite and magnesite respectively and react for two hours at 500∼700 °C to form kotoite and takedite, which indicates that temperature, boron-rich fluid and calcium-magnesium carbonate are the main factors to control contact metamorphism. This also provides a theoretical basis for mineral combinations and wall rock alterations of metamorphic borate deposits, which is similar to that of skarn-type borate deposits. The MgO formed by thermal decomposition of magnesite and dolomite reacts with hydrothermal fluid to form Mg(OH) 2 during skarn mineralization, which may be an important factor in controlling the pH value of hydrothermal fluid, meanwhile it provides reactants for the formation of kotoite. Mixture of szaibelyite, dolomite, magnesite and lizardite react for 2 h at 500∼700 °C to form suanite, indicating it can be produced by dehydration of szaibelyite. Therefore, it is speculated that the Liaodong borate deposits may experience at least two stages: deposition stage of the early hydrous borates (or boron-rich sediment), contact metamorphic stage is similar to skarn-type mineralization, whether there is a high temperature dehydration stage needs further research. Combined the experimental results with the relationship between the endogenous and exogenous borate deposits in ore-forming age, tectonic setting and source link, it is found that the endogenous borate deposits may be another form preserved by early exogenous borate deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pore and throat structure can be characterized separately by XCT scanning. • Chlorite and illite produced most of the intercrystalline pores in tight sandstone. • Chlorite coatings are effective in preserving the large primary pore-throat. • The densification was completed by cementation instead of compaction. • Tight sandstone with high chlorite is the best quality reservoir in the Ordos Basin. As an important part of tight sandstone, authigenic clay minerals and carbonate cements have a strong influence on the densify of tight sandstone, but the details of these effects on pores and throats need be further clarified. The Ordos Basin is the second-largest sedimentary basin in China with the highest annual oil output and is characterized by tight sandstone. In this paper, the thin section, HPMI, XCT scanning and fluid inclusion homogenization temperature were combined to study the densification process of the tight sandstone in the Ordos Basin. The results show that early chlorite coating can effectively reduce further damage to the pore-throat space. But the pore-lining chlorite and illite led to reduce of the radius of intercrystalline micropores to <1 μm. After mechanical compaction, authigenic illite and the late ferrocalcite and ferrodolomite cements continued to grow and eventually complete the densification. Authigenic clay minerals and carbonate cements played contrasting role on evolving of pores and throats: tight sandstone with high chlorite showed obvious "right peak" PSD and TSD in XCT scanning with the largest number of throats, formed the best-quality reservoir; tight sandstone with high carbonate cement suggesting flat "right peak" TSD and increased the average length of throats; tight sandstone with high illite showed flat and "left shift" PSD and obvious "bimodal" TSD with the fewest number of throats, and formed the worst-quality reservoir. [ABSTRACT FROM AUTHOR]

• Fracture parameters of dolomite are determined with Brazilian test and semicircular bending test • An improved calibration procedure of KCC model for brittle materials is proposed • Calibrated KCC parameters were validated in two static and one dynamic tests • Wide parametric study with detailed description of limitation of KCC model was performed • New calibration strategy improved the tensile crack reproduction in quasi-brittle materials This paper presents a procedure to compute the parameters of the Karagozian and Case Concrete (KCC) constitutive model for brittle materials based on dolomite rock. First, the fracture energy and fracture toughness of the dolomite rock were determined from two experimental tests: the semicircular bending test (SCBT) and Brazilian indirect tension test (BT). Next, the novel optimization-based strategy was developed for efficiently calibrating the brittle damage parameters, and a broad parametric study was performed based on dolomite rock. Finally, the optimal parameters were validated through three experimental tests: SCBT, BT and a drop-weight fragmentation test. The results were compared with those obtained using three different sets of parameters for dolomite rock that is the KCC model with automatically generated parameters, parameters that provides an instable softening behavior, and the KCC model with parameters calibrated by the authors in a previous study. A qualitative and quantitative comparison of the results confirmed that the approach presented here improves the efficiency of fracture reproduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mineralized fluids are characterized by weakly acidic, reduced, and low temperature. • W/R interaction and CO 2 degassing caused the precipitation of carbonate minerals. • Mixing of metals and BSR-originated S2− resulted in the sulfide precipitation. • The origin of the Banbanjie deposit is similar to that of the MVT deposits. This paper investigates the origin of the newly discovered Devonian carbonate-hosted Banbianjie Ge-Zn deposit in South China. This deposit is rich in Ge (>900 t @ 110 ppm Ge) and contains 7.7 Mt of sulfide ores at a mean grade of 5.1 wt% Zn. The mineralization is stratabound or veined and is structurally controlled by the E-W trending Huangsi fault. Sulfide ores are dominated by sphalerite and dolomite with subsidiary pyrite, marcasite, and calcite, and minor galena. The mineralization forms massive, veined, brecciated, and disseminated structures and the hydrothermal minerals present in the deposit have colloform, fibrous, granular, and acicular textures. The hydrothermal dolomite has positive Ce (δCe = 1.13–1.20) and negative Eu (δEu = 0.43–0.68) anomalies that are indicative of formation in a weakly acidic, reduced, and low-temperature environment. The δ13C PDB and δ18O SMOW values of the dolomite range from −0.97‰ to −0.24‰ and +13.89‰ to +21.84‰, respectively, indicating that the dissolution of carbonate wall rocks was involved in the formation of hydrothermal dolomite. Theoretical C-O isotopic calculations further suggest that the hydrothermal dolomite formed as a result of water/rock (W/R) interaction and CO 2 degassing. The δ34S values of the sulfides (−11.23‰ to −4.95‰) are markedly lower than those of the Devonian seawater sulfate and sulfate from evaporates in the Devonian strata (+21.9‰ to +25.9‰), suggesting that the reduced sulfur was derived from evaporates within the ore-hosting sedimentary rocks by bacterial sulfate reduction (BSR). The Banbianjie sulfides have an upper crustal Pb isotopic affinity, as demonstrated by their 206Pb/204Pb (18.335–18.343), 207Pb/204Pb (15.725–15.735), and 208Pb/204Pb (38.288–38.326) ratios, suggesting the metals were derived from metamorphosed basement rocks. These data suggest that: i) the Banbianjie deposit formed as a result of a combination of weakly acidic, reduced, and epigenetic low temperature mineralized fluids, trap structures, and favorable lithologies; ii) W/R interaction and CO 2 degassing caused the precipitation of hydrothermal dolomite, whereas mixing of metals and S2− was the main formation mechanism of the sulfides; and iii) the Banbianjie Ge-Zn deposit is a typical Mississippi Valley-type (MVT) deposit. [ABSTRACT FROM AUTHOR]

• The static surface acidification experiment integrating SEM microstructure mapping and micromechanical test was proposed to understand the effects of rock microstructure on the fracture etching of geothermal dolomite reservoir. • The crystal structure and pores distribution highly influence on the fracture etching and the ultimate conductivity of geothermal dolomite reservoir. Acid etching in a naturally fractured carbonate formation is one of the most significant mechanisms to enhance the fluid conductivity in fractures. In this paper, an acid dissolution experiment has been employed to understand the influence of rock microstructure on the acid etching involving reaction rate, the morphology of acid corrosion, and the embedding strength of a fracture surface. Three typical dolomite samples with almost the same mineral composition but distinct microstructures were selected from the Wumishan Geothermal carbonate formation that is composed of dolomudstone, algal dolomudstone, and silt-to-fine crystalline dolostone. A couple of measurement approaches including the thin section, SEM, 3D laser scanning, and nano indentation tests were used to observe and quantify the microstructures, reaction rate, and embedding strength of the fracture surface. Microstructure characterization indicates that the dolomudstone contains much finer crystal particles and a loose microstructure compared to other two samples. On the contrary, the silt-to-fine crystalline dolostone reserves coarse crystal particles and a tight microstructure. The structure of algal dolomudstone falls in between those two mentioned cases. Results of acid dissolving reveal that rock microstructures offer control over the acid-rock reaction of dolomite. Specifically, the loose microstructure of dolomite depicts a fast acid reaction, a rough surface, but weak embedding strength, while the compact microstructure behaves as a slow acid reaction, a uniform etching, and with a strong embedding strength. The knowledge obtained from this study is valuable to optimize the acid dissolution strategy from the view of the microstructure analysis. [ABSTRACT FROM AUTHOR]

Clay ceramic water filters impregnated with silver colloids have been used to purify water in many parts of East Africa disregarding the removal of fluoride, which is a health-threatening ion in water supplies. This paper presents a synthesis of clay ceramic materials containing in-situ generated calcium/magnesium phosphate system as an adsorbent for water de-fluoridation. The materials were prepared in varied ratios of clay (K) to heat-pretreated dolostone (R) (K:R = 0:100, 90∶10, 85∶15, 75∶25 and 100:0), sintered at temperatures between 500 °C and 900 °C, and characterized using XRF, AAS, CHNS–O analyzer and X-ray PDF analysis. The materials improved in de-fluoridation performance with increase in sintering temperature at 500–700 °C, before exhibiting a sharp drop at 800 °C. The adsorption performance of K:R = 75:25 was higher than that of K:R = 0:100, signifying the effect of clay. The adsorption data obeyed Freundlich isotherm model, suggesting multi-layer adsorption. Fluoride uptake follows pseudo-second-order and intra-particle diffusion models, which suggests a chemisorption process involving rate-limiting intra-particle diffusion. • Multi-phasic Ca/Mg phosphate system was synthesized from dolostone. • In-situ synthesis is a feasible method to incorporate phosphate systems in clay ceramics. • Phosphate systems improve de-fluoridation performance of clay ceramics. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) have been proposed as a promising agent for groundwater aquifer remediation, greenhouse geological storage, and enhanced oil recovery (EOR) applications. Nevertheless, in many of these cases, NPs applications require long transport distances, which may be limited by NPs retention in porous media, especially at high saline conditions as is the case with some oil reservoirs, causing a reduction in rock permeability and subsequent formation damage. Therefore, understanding of NPs transport through porous media and their stability behavior are significant challenges before their large-scale applications, which has been less explored in previous works. This paper investigates silica NPs transport through dolomite rocks, which are the host rocks of many sub-surface reservoirs. To this end, the stability of silica nanofluids with different concentrations in the presence of different ionic strength and ion types was explored by zeta potential measurement and particle size analysis. NPs adsorption on rock surface was examined by SEM images. The DLVO analysis was conducted to determine the interaction energies between NPs and the rock, and investigate the reversibility of NPs adsorption on the rock. Single-phase coreflooding experiments aided by NPs effluent analysis were performed to obtain breakthrough curves. Results indicated that increasing silica NPs concentration from 0.1 to 0.5 wt% leads to a reduction in nanofluid stability in which the average size of silica NPs increased from 110 to 220 nm. Higher ionic strength (50,000 ppm) decreased nanofluids stability and this negative effect was more pronounced for nanofluids containing MgCl 2 salt. It was found that less stable nanofluids showed higher NPs retention through porous media. Highly stable nanofluids exhibited a higher probability of NPs to be detached during the brine post-flushing stage. As to the results of silica nanofluid injection in dolomite rock, increase of the silica NPs concentration and decrease of their stability in suspension were two causes of the rock permeability impairment; a 10% reduction in rock permeability was observed by 0.1 wt% salt-free silica nanofluid, whereas it decreased by 87% using 0.5 wt% of saline nanofluids prepared by 50,000 ppm MgCl 2. According to the interpretations based on the deep bed filtration model, the higher salinity of nanofluid is, the higher filtration coefficient would be, meaning that the higher rate of particle capture at higher salinities. Also, no internal/external filter cake was formed and instead, the pore filling process was found to be the major mechanism of the permeability impairment by silica NPs. • The transport behavior of silica nanofluids was investigated in the dolomite rock. • Nanofluid stability decreased by increasing NPs concentration and ionic strength. • Less stable nanofluids showed higher particle retention through the porous media. • MgCl 2 led to a higher adsorption of silica particles as compared to NaCl. • Pore filling was the major mechanism of permeability impairment by silica NPs. [ABSTRACT FROM AUTHOR]

This paper focuses on celestite-carbonate-cemented veins that developed in the Jialingjiang Formation of the Lower Triassic carbonates from the Libixia anticline in eastern Sichuan Basin, China. Comparative petrography and geochemistry of the host rock and vein minerals provide clues to the nature, origin, and evolution of the vein-cementing fluids. The host rocks are composed mainly of micrite dolomite which yields δ18O, δ13C and 87Sr/86Sr ratios close to the values that characterize contemporaneous seawater. Two generations of vein-mineralization were recognized based on textural relationships, fluid inclusion data and isotope geochemistry. The early generation is dominated by celestite and saddle dolomite, formed from hypersaline, Sr-enriched, hydrothermal fluids. The later generation is represented by calcites, precipitated from less saline fluids at lower temperatures. The 87Sr/86Sr ratios of vein dolomite and celestite vary from 0.7076 to 0.7081, significantly lower than those of host carbonate counterparts (0.7078 to 0.7081; average 0.7080). This isotopic discrepancy suggests that the majority of Sr was sourced from deeper sequences of the lower Triassic carbonates, probably associated with thermochemical sulfate reduction for Sr accumulation. It is argued that the fracture systems associated with the Huayingshan fault provided the heat source and served as conduits for migration of hydrothermal fluids through several hundred meters, and the final mineralization occurred as a result of mixture of Sr-enriched brines with sulfate-bearing solutions. The large celestite ore bodies in the studied area are proposed to form related partially to these hydrothermal fluids. [ABSTRACT FROM AUTHOR]

Reefs may be formed in the middle parts of sedimentary basins and grow on tectonically uplifted substrate blocks. In this paper, the strata of the Central European reef system of the Upper Permian Zechstein Limestone (Ca1) formation located in West Poland are evaluated. The formation has produced natural gas since the early nineties of the past century. The reefs grew on an uplifted horst built of Carboniferous rocks, known as the Wolsztyn Ridge. As individual sub-blocks originally showed diversified altitudes, four zones suspected to represent initial sedimentation conditions are distinguished: (1) basin zone , located close to the margins of the WR; (2) lower reef zone; (3) transitional zone and (4) the upper reef zone. Clear diagenetic differences between particular zones are observed. The basin zone strata are characterized by a strongly recrystallized mosaic of dolomite but show a limited extent of anhydrite cementation. The lower reef zone rocks, covered by thick Zechstein evaporites have been dolomitized and anhydritized most intensively, probably by means of the downward seepage of heavy brines, as suggested by the stable isotope data. It is assumed that the process was focused on the calm-water facies due to their low primary porosity and permeability. This mechanism was also probably responsible for the dolomitization of Ca1 strata in the remaining zones, where lower δ18O values in dolomite reflect some temperature increase on the final isotopic signature of rocks. Transitional zone carbonates appear to be almost purely calcitic with only a minor dolomite admixture. They contain various types of calcite cement, including marine and meteoric-phreatic phases, reflecting an intermediate position of the substrate and optimal reef growth conditions. Marine phases are also commonly recognized in the upper reef zone. Owing to a significant elevation of the substrate in this zone, the corresponding strata might have experienced some impact of karstification, presumably taking place well before the deposition of the Zechstein evaporites. It is concluded that the morphology of the substrate in tectonically-influenced areas strongly controls the reef diagenesis, and thus can affect the distribution of hydrocarbon accumulations. • The morphology of the substrate influences reef diagenesis and should be considered in hydrocarbon exploration. • The downward seepage of brines can cause dolomitization and anhydritization of reef rocks developed on uneven substrates. • Brine seepage-related dolomitization may be intensified in mud-supported facies of small thickness, overlain by evaporites. • The carbonate build-ups of the highest topographic position may become karstified and penecontemporaneously dolomitized. • Porous reefs formed at intermediate altitudes are areas of intensive calcite cementation in marine and meteoric conditions. [ABSTRACT FROM AUTHOR]

The ultra-deep dolomite reservoir of the Permian Qixia Formation in northwest Sichuan is important for hydrocarbon reservoirs, but the mechanism of dolomite genesis is complex and has long been controversial, thus requiring further elucidation. By studying the dolomite with different types in the Permian Qixia Formation, northwest Sichuan Basin, this paper, based on outcrop sections observation and core description, seeks to find out the dolomitizing fluids' source and the dolomite's genetic mechanism by analyzing the dolomite's rock-mineral and geochemical characteristics. Various technologies are applied, including rock thin section observation, cathode luminescence, carbon and oxygen isotope analyses, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and inclusion homogenization temperature and salinity. Results show that the dolomite is mainly classified into silty-fine dolomite (Md1), fine-medium dolomite (Md2), medium-coarse dolomite (Md3), and saddle dolomite (SD) filled in the pores. Md1 is formed in the early shallow-burial stage; the dolomitizing fluids are mainly derived from the early seawater sealed in carbonate sediments; and the penesaline seawater is formed by the seepage reflux under a moderate evaporitic environment. Md2 and Md3 are formed in the middle and late shallow-burial stages. Of these two types, Md2 is formed earlier, and the dolomitizing fluids are primarily derived from the seawater sealed in the early stage and partially derived from the residual evaporated seawater and hydrothermal fluids. In contrast, Md3 is formed later, and the dolomitizing fluids are the mixture of the seawater sealed in the early stage and the hydrothermal fluids formed in the late stage. In addition, Md3 was affected by the hydrothermal process more significantly during the formation. SD is deposited and formed when the saturated hydrotherm upwells along with the fracture system in the late stage. This study provides a significant reference for understanding the source and action mechanism of multi-stage dolomitizing fluids and expands the exploration field of the deep dolomite reservoir. • The precise microanalysis is conducted on the dolomite of different grain sizes by the LA-ICP-MS technology. • The geochemical characteristics of dolomites show the trend of continuous and progressive. • Dolomite fluids come from the normal seawater, penesaline seawater. and hydrothermal fluids. [ABSTRACT FROM AUTHOR]

Due to the small difference in floatability between dolomite and fluorite, the problems of low grade of fluorite concentrate occur. It is very important to find a depressant that can selectively inhibit the floating of dolomite. As a natural polymer, starch is often used as a gangue depressant because of its low price and easy availability. In this paper, the effects of caustic cassava starch (CS) on the single mineral flotation performance of fluorite and dolomite and the flotation separation of mixed ore were studied. Its selective inhibition mechanism was investigated. The results of flotation tests with single minerals stated that the flotation of dolomite was vastly inhibited, while the fluorite was hardly affected when CS was added in flotation using sodium oleate as the collector. The concentrate grade of artificially mixed ore flotation fluorite reached 90.15%, and the recovery rate was 89.54%. The physical adsorption of CS on the surface of dolomite blocked the adsorption of hydrophobic sodium oleate on the surface of dolomite, thus depressing dolomite. The adsorption energy of dolomite and CS was much larger than that of fluorite and CS. This greatly deteriorated the flotation of dolomite and achieved flotation separation between fluorite and dolomite. The results demonstrate that CS is a promising depressant for dolomite in fluorite flotation. [Display omitted] • The inhibitory effect of CS as a carbonate depressant is studied. • The adsorption modes of CS with dolomite and fluorite are clarified. • The adsorption strength of CS on fluorite and dolomite surface is revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reflux seepage, burial and hydrothermal types of dolomite in the Cambrian Sanshanzi Formation are petrographically and geochemically identified. • Reflux seepage dolomitization was formed by high-salinity and Mg2+-enriched fluid penetrates downward into the limestone, and the dolomite has low δ 13C, high Sr and low Mn contents. • Burial dolomitization was due to the limestone deeply buried during the diagenetic stage and formed under a high-temperature and pressure environment. • Hydrothermal dolomitization occurred during Mg2+-rich hydrothermal fluid invaded, and the dolomite characterized by saddle dolomite with a positive δ Eu anomaly, and a low δ 18O value. The Cambrian Sanshanzi Formation is an important dolomite horizon in the Ordos Basin of northern China, and is well exposed in the western part of that basin. This paper focuses on the petrography and geochemistry of dolomites in this formation with an aim to provide a better understanding of their genesis. Reflux seepage, burial, and hydrothermal dolomites are identified in the Sa nshanzi Formation. Reflux seepage dolomites include dolomitic grainstone and powder crystal dolomite, and have high Sr and low Mn contents, a high CaO/MgO ratio and low δ 13 C values, and the reflux seepage dolomitization was formed by high-salinity and Mg2+-enriched fluid penetrates downward into the limestone. Burial dolomites are the main type of dolomite distributed through the Sanshanzi Formation. Burial dolomites are composed of fine- to coarse-crystal dolomite and have low Sr and high Mn contents, a low CaO/MgO ratio, and high δ 13C values. The features of high salinity, strong reducibility and negative δ 18O values indicate the burial dolomites formed under high-temperature and high-pressure conditions, the burial dolomitization was due to the limestone deeply buried during the later diagenetic stage. Hydrothermal dolomites are mainly characterized by saddle dolomite features, a positive δ Eu anomaly, and low δ 18O values, and the hydrothermal dolomitization occurred during Mg2+-rich hydrothermal fluid invaded. The reflux seepage and hydrothermal dolomite developed in local areas, with the hydrothermal dolomite affected by the distribution of faults. [ABSTRACT FROM AUTHOR]

This paper integrates major, minor, trace and rare-earth element (REE) data into C-, O-, Sr-isotopes, fluid-inclusions microthermometry of replacive matrix dolomite and vug/fracture-filling saddle dolomite and calcite of the Lower Cretaceous Qamchuqe Formation, the Kurditan Region of Iraq, in order to get further insights into the origin and geochemical evolution of their parent diagenetic fluids. Multiple generations of dolomite have been observed. These dolomites constitute replacive matrix dolomite and saddle dolomite cement, dominantly poorly ordered, non-ferroan, non-stoichiometric, with an average of 59.4 and 60 mol% CaCO 3 , respectively, and have low Sr, Fe and Mn concentrations. Replacive matrix dolomites display fairly comparable REE patterns to saddle dolomite, but with light REE (LREE) enrichment, and moderate low (∑REEs) contents (18.9–1111.5 and 16.6–593.4 ppb, respectively). Saddle dolomite has moderately positive Eu anomalies while replacive matrix dolomite has slightly less positive Eu anomalies and negative Dy, Ho and Yb anomalies. Both dolomites are characterized by slightly radiogenic 87Sr/86Sr ratios ranging from 0.707702 to 0.707839, overlapping, wide-ranging and negative δ18O values from −10.43 to −4.47 and −12.87 to −7.79 ‰ VPDB , and δ13C values ranging from 0.38 to 3.57 and −3.45 to 3.11‰ VPDB , respectively. The primary fluid inclusions microthermometry of replacive matrix and saddle dolomites yield homogenization temperatures (T h) ranging from 71.3 to 228.3 °C and 82–188 °C, respectively, and salinity values ranging between 14.4 to 25.4 and 15.6 to 27.9 wt% NaCl eq., respectively. These data suggest multiple hydrothermal fluid fluxes during and post Zagros orogeny. The geochemical data also show that these fluids derived from similar source of mixed hydrothermal and marine fluids, which caused the dolomitization of host rock and precipitation of dolomite cements. • The presence of multiple hydrothermal fluid flow events with unique geochemical footprints. • Comparable major and trace element geochemistry occur of replacement and cement dolomites. • REE, isotopes and fluid inclusions in dolomite suggest mixed marine and hydrothermal fluids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dolomite was modified by the spent ternary lithium-ion battery (LIB) material. • The modified dolomite reduced the activation energy of biomass pyrolysis. • The modified dolomite had a high catalytic activity in tar cracking. • The modified Do inhibited the production of phenols from 50% to 5.8%. This paper proposed a novel method for modification of dolomite (Do) using the leaching solution derived from the spent ternary LIBs. During catalytic pyrolysis of biomass, the modified Do showed a good performance on both reducing the activation energy and upgrading the volatile products. The apparent activation energy was decreased from 201 to 180 kJ/mol for the cellulose pyrolysis, and it was decreased from 80 to 75 kJ/mol for the lignin pyrolysis. The cellulose pyrolysis with the modified Do could significantly promote the conversion of anhydrosugars into small-molecule components (e.g., ketones). Meanwhile, the Do modified by transition-metal (e.g., Mn, Co, Ni) oxides had a high catalytic activity in cracking phenols (main tar precursors) to hydrocarbons (e.g., aromatics) during the lignin pyrolysis. The modified Do inhibited the production of phenols (from 50% to 5.8%) and enhanced the production of hydrocarbons (from 0.6% to 30.3%). [ABSTRACT FROM AUTHOR]

Centering on the mechanism of reactive acid transport in fractured two-mineral carbonate rocks, this paper established a two-mineral model for fractured media with the extended finite element method based on the two-scale continuum model. A series of examples are presented with the numerical model, the numerical results show that the variation of volume fraction of dolomite, the surface reaction constant of dolomite as well as the diffusion coefficient can alter the dissolution morphology and dissolution performance. As the volume fraction of dolomite increases or surface reaction constant of dolomite decreases, the dissolution patterns would transform form wormhole to uniform dissolution. And the bedding distribution and porphyritic distribution of dolomite will cause a fragmentation phenomenon for the dissolution morphology. Besides, the bedded dolomite can bring about an increased acid consumption. It can be inferred that the reaction rate difference between limestone and dolomite is the key factor that affects the dissolution morphology, and the retarded acid with a low reaction rate in dolomite rocks does not perform well. • A two-mineral model for simulating acid transport in carbonate reservoirs was developed. • The reaction mechanism of two minerals in carbonate rocks was analyzed. • The dissolution morphology characteristics in two mineral carbonate rocks were discussed. • The effect of dolomite distribution characteristics on acid transport was investigated. [ABSTRACT FROM AUTHOR]