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The carbonate-evaporite sequence of the Arab Formation constitutes the important reservoir unit in the Persian Gulf and adjacent area. The paper aims to present detail facies characteristics, depositional environment and sequence stratigraphic analysis of the Arab Formation in an oil field in the Persian Gulf. A total of 12 microfacies (MF) and 3 dolomitic (diagenetic) facies (DF) were identified, and are interpreted as a homoclinal carbonate ramp platform. The Arab Formation is divided into four third order sequences corresponding to main reservoir intervals (Arab-A, B, C, D). The results highly correlate with the sequences of local and regional studies in the Arabian Plate. It is probably due to the cake layer nature of the Arab Formation and high impact of the world eustatic sea-level fluctuations (global curves) on the facies stacking pattern. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the adsorption process of a new composite adsorbent prepared from chitosan (Ch) and dolomite (Do) for removal of lead ions from aqueous solutions. The adsorption process of Pb2+ions onto Ch-Do composite adsorbent as initial Pb2+ concentration, solution pH, temperature, contact time and desorption was investigated. From the results, it has been observed that the highest removal efficiency is approximately 89% at contact time of 6 h, initial Pb2+concentration of 500 mg L−1, adsorbent dosage of 100 mg and agitation speed of 150 rpm at pH 4.0. Langmuir isotherm has a better fit with the experimental isotherm data (R2 = 0.920). The maximum Pb2+adsorption capacity from the Langmuir model was found as 0.332 mol kg−1 at 25°C Also, it performs pseudo-second-order superior performance in kinetic behaviour compared to other used kinetic models (R2 = 0.904). Thermodynamic parameters showed the Pb2+adsorption onto Ch-Do was endothermic, spontaneous and possible. The desorption studies have shown that Ch-Do composite adsorbent has a good adsorption/desorption performance for Pb2+ions. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the effective use of high calcium fly ash (HCFA) and dolomite powder in geopolymer mortar (GPM) and concrete. Trail HCFA GPM mixes were made with 10%, 20%, 30% and 40% dolomite powder. The alkaline liquids used for polymerization are sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). To prepare different mixes, 8 M, 10 M, 12 M and 14 M concentration of NaOH solution, NaOH to sodium silicate ratio 2.5 and liquid to binder ratio 0.5 were selected. Ambient temperature was used to cure the specimens. Test results show that HCFA GPM mix with 20% dolomite powder and 14 M NaOH concentration yielded remarkably higher compressive strength with 41.95 MPa at 28 days than the other mixes. Further, experimental work on HCFA geopolymer concrete (GPC) using 20% dolomite powder demonstrated more excellent strength properties than those demonstrated by control mix cement concrete. [ABSTRACT FROM AUTHOR]

In this paper, we describe porosity variations in Miocene to Holocene carbonates off the west coast of Australia and assess their compaction trends. The porosity values were measured using discrete samples of Sites U1459–U1464 obtained by the International Ocean Discovery Program Expedition 356. The carbonate deposits have been influenced by a range of textures and diagenetic conditions throughout a nearly continuous sequence of geological ages from the Miocene to Holocene and at core depths from 0 to 1100 m below the seafloor. The collected samples were mostly grainstone, packstone, wackestone and mudstone textures. Dolostones and dolomitic carbonates were described at the Miocene intervals. Compaction trends were estimated exponentially and linearly based on cored sites, carbonate textures and dominant mineralogies (dolomite, calcite/aragonite). At all six sites, porosity distribution and reduction were generally depth-dependent. The porosity converged to about 30% between 750 and 1100 m, which suggests that the carbonates were close to the densest packing by mechanical compaction at a burial depth of ∼750 m. The porosity deviations are associated with textures and dominant mineralogies. Increasing mud content from grainstone to mudstone is a controlling factor for initial porosity and porosity reduction rate. Dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains cause deviations from the depth-dependent compaction trends. Reflux-related cementation generally decreases porosity in Miocene dolomitic intervals. Higher porosity values of the Quaternary wackestone and mudstone at Site U1461 resulted from the presence of aragonite needle-rich mud hosting abundant micropores and from a high sedimentation rate. The occurrence of non-skeletal grains, such as ooids and peloids, as well as occasional meteoric exposure led to porosity inversion, occluding interparticle permeability and the creation of moldic pores. Porosity variations of Miocene–Holocene carbonates off the west Australian coast are primarily depth-dependent. Mechanical compaction affected porosity reduction down to a value of ∼30% at a burial depth of ∼750 m. Differences in texture-based compaction trends were affected by increasing mud content. Major porosity deviations are associated with dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains. [ABSTRACT FROM AUTHOR]

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The number of pore volumes to breakthrough is one of the most critical indicators of wormhole characterization in the matrix acidizing process. This number is often needed for experimental work that is time-consuming and costly. In this article, an empirical model was used to evaluate the acidizing procedure in the carbonate cores, including limestone and dolomite. This empirical model measures the number of wormholes formed in the carbonate cores after acid injection by using the conservation of mass law. This approach maintained the transport relative reaction rates of core and acid within the wormhole structure during the wormhole formation procedure. In addition, this empirical model accounted for changes in acid concentration as an injected fluid flow. Also, the changes in carbonate porosity, the effect of the Damköhler number, and injection rate were included in the model. Compared to other experimental and semi-empirical works, the established model gave an excellent assessment of 95.45% for the average accuracy and 0.9933 for the average coefficient of determination. Therefore, an empirical technique to approximate this number in the carbonate formations with high accuracy using physical core and acid properties is herein proposed. [ABSTRACT FROM AUTHOR]

There is not a consistent view about the mechanism of wettability alteration during low salinity water flooding. This paper highlights extensive wettability studies to investigate the wettability alteration on mineralogically different carbonates. Contact angle measurements were conducted to characterize wettability changes quantitatively. The results clearly revealed that wettability of carbonate rock surfaces can be altered to a more water-wet condition by lowering water salinity. The trend of the maximum change of contact angle (MCCA) variation with dolomite/calcite content in the rock is fairly linear under the same salinity, which demonstrates that carbonate minerals can affect rock wettability in a way. Also, the higher calcite content in the rock, the greater MCCA, i.e. the stronger effect of LSWF. Besides, the sensitivity of rock wettability to minerals is different under different salinity conditions. When the salinity is in the range of 2384.6 ∼ 4769.2 mg/L, rock wettability is most sensitive to minerals. The analysis of the effect of ion composition showed that the effect of Ca2+ on wettability alteration is greater than that of Mg2+ at room temperature, and with the increase of the content of calcite in the rock, the effect of Ca2+ is more pronounced than that of Mg2+. [ABSTRACT FROM AUTHOR]

This paper discusses the physical simulation of aquathermolysis for heavy oil in the presence of minerals - dolomite and calcite. According to the SARA-analysis and IR-spectroscopy, the presence of calcite provides significant effects on the reduction of resins and asphaltenes, their condensability and aromaticity by destructing the least stable C-S-C bonds. Based on the results of gas chromatography, the thermal conversion of heavy oil increased the hydrocarbon content with homologous series of С19-С30. The analysis of geochemical coefficients revealed the high maturity of organic matters in thermally conversed heavy oil from model system with dolomite. [ABSTRACT FROM AUTHOR]

Gasification is a process in which biomass is decomposed into small quantities of solid char and ash and large quantities of gaseous products in the presence of one or more fluidizing agents. In this paper, a lab scale fluidized bed gasifier was used to explore the effects of different kinds of calcined dolomites (CD-1, CD-2, and CD-3) on tar conversion and composition during air-steam gasification of biomass. Results showed that all dolomites have a good performance in terms of tar reduction but CD-2 is more reactive than two other dolomites with respect to tar destruction. When the temperature was lower than 850◦C, conversion of tar was relatively low; however, with temperature increasing further (>850 ◦C), tar conversion was greatly enhanced. [ABSTRACT FROM AUTHOR]

A significant amount of the world oil reserves is held in naturally fractured carbonate reservoirs which can undergo temperature-induced changes in structural and physicochemical properties while applying thermal stimulation methods. This study reports thermo-kinetic and microstructural analyses of a fractured-carbonate rock from a Mexican reservoir exposed to high temperatures using thermogravimetry and X-ray micro-computed tomography. Activation energies and reaction mechanism kinetics involved in the thermal degradation of the rock sample were determined through iso-conversional and model-fitting methods. X-ray diffraction revealed the expected mineralogy of the rock sample: dolomite (96.5%) and quartz (3.5%). Results indicated that rock thermal-decomposition follows a first-order reaction kinetics with an average activation energy of 195.910 kJ/mol. Noteworthy microstructural changes were detected on the analyzed fractured-carbonate rock exposed to heat-treatment which resulted in percent increases of 7.47, 4.37 and 25.39% in total, effective and isolated porosity, respectively. Results presented in this work can be relevant for the exploitation through thermal stimulation methods of naturally fractured carbonate reservoirs. [ABSTRACT FROM AUTHOR]

In this paper, nanocomposites are synthesized with Tunisian natural clay which has the advantage of being cheap. In fact, it is simply a mixture of several sorts of clays (kaolinite, dolomite, calcite, illite, and quartz). This clay has been cleaned, purified, dried, and steered with different resins which are actually used in the textile field for several applications such as comfort, elasticity, or impermeability. First, the different mixtures of resin/clay were deposited with different clay percentages on a PET/cotton fabric sheet. Then samples were examined by SEM in order to see their compositions and ensure the formation of nanocomposites. Finally, different mechanical tests such as tensile, breakout, abrasion, and tear tests were performed. Furthermore, it appears that the mechanical performance of fabric is globally increased versus the amount of clay for all resins except the polyvinylacetate, which shows a decrease in the fabric tear resistance when using more than 20% clay. It has also been noticed that mechanical characteristics of the coated fabric without clay decrease significantly in comparison with the reference, but become better when clay is added to the resin. Consequently, it is obvious that the type of resin is important because the results shown are different from one resin to another. [ABSTRACT FROM AUTHOR]

The southern Cobar Superbasin includes the Mount Hope, Cobar and Rast troughs and adjacent Winduck, Mouramba and Kopyje shelves. These stratotectonic units host a range of mineral systems within deformed upper Silurian to Lower Devonian rocks. Despite the metallogenic importance of the terrane the regional metamorphic- and alteration-related mineral assemblages have not been systematically described until now. Here, we present a study using the HyLogger™ spectral scanner to systematically map changes in both background and alteration-related mineralogy for 14 mineral systems across the Nymagee area. The study found that, with the exception of the late diagenetic zone assemblages associated with the Winduck Shelf, the mineral assemblages for zones away from mineralisation are consistent with uniform sub- to lowest-greenschist facies metamorphic conditions, with no evidence for a regional, thermal field gradient across the basin. By contrast, proximal to mineralisation, there are significant changes in alteration-related mineral abundances and species reflecting elevated fluid temperatures. For several zones, including Browns Reef, Great Central, Hera, May Day, Nymagee and Shuttleton, there is a systematic change in chlorite composition from Fe- and/or Fe–Mg-chlorites to more Mg-rich varieties towards mineralisation. In addition, talc was noted for May Day, Mineral Hill and Shuttleton. The change in chlorite composition suggests that these ore-forming fluids were undersaturated with respect to iron. Furthermore, although present in discrete zones, carbonate alteration is not a dominant alteration type. However, at Manuka and Blue Mountain, the mineralisation is associated with carbonate-rich (calcite, ankerite, dolomite) units that have been dolomitised (Mg alteration) but not all dolomite-rich zones are mineralised. For Mineral Hill, there are systematic changes to mineral species/chemistry with observed data consistent with Parkers Hill being proximal to the centre of a mineralising system. The G and H Lode area (Southern Ore Zone) is slightly more distal whereas the Pearse deposit may represent a zone more distal again. [ABSTRACT FROM PUBLISHER]

In this work, the synergistic effect of hydrochloric-acid etching and inhibitors on the flotation separation of magnesite and dolomite in the sodium oleate (NaOL) system was studied. Flotation tests revealed that the synergistic effect of acid etching and sodium hexametaphosphate, sodium alginate, and sodium lignosulfonate on the separation of magnesite and dolomite was poor. Meanwhile, the synergistic effect of acid etching with sodium carboxymethyl cellulose (CMC) could regulate the flotation separation of magnesite and dolomite over a wide pH range. Moreover, the synergistic effect of acid etching and CMC increased the flotation difference between magnesite and dolomite from 15.73% to 67.17%, and the selective separation index increased from 1.38 to 2.89. Characterization by atomic force microscopy revealed that acid etching altered the surface morphology of magnesite and dolomite, roughening their surfaces. Contact angle measurements, Fourier transform infrared spectroscopy analysis, and zeta potential measurements indicated that the synergistic effect of acid etching and CMC changed the wettability, charge, and adsorption performance of dolomite, selectively inhibiting the adsorption of NaOL onto the surface of dolomite, thereby inhibiting dolomite flotation. However, it has minimal effect on the floatability of magnesite. [ABSTRACT FROM AUTHOR]

This paper presents the results of pioneer study of the most popular calcium supplements as a potential additional source of radiolead210Pb in human diet. The analyzed calcium pharmaceutics contained organic or inorganic calcium compounds; some came from natural sources as mussels' shells, fish extracts, or sedimentary rocks. The idea was to investigate the naturally occurring210Pb activity in different calcium supplements and calculate the annual effective radiation dose from radiolead210Pb decay in consumed calcium supplement. The results showed210Pb concentrations in natural origin calcium supplements (especially sedimentary rocks) were significantly higher. The highest210Pb activity concentrations were determined in mineral tablets made from dolomite – 2.97 ± 0.18 mBq g−1, while the lowest was observed in organic calcium compounds – both calcium lactate – 0.08 ± 0.01 and 0.13 ± 0.01 mBq g−1. The highest annual radiation dose from210Pb taken with 1 tablet of calcium supplement per day was calculated for soluble calcium lactate sample – 1.19 ± 0.03 µSv year−1, while the highest annual radiation dose from210Pb taken daily with 1 g of pure Ca for dolomite – 5.57 ± 0.34 µSv year−1. [ABSTRACT FROM PUBLISHER]

This paper physically and numerically models the influence of biofilms on heavy metal removal in a gravel filter. Experimental flow columns were constructed to determine the removal of Cu, Pb and Zn by gabbro and dolomite gravel lithologies with and without natural biofilm from sustainable urban drainage systems (SuDS). Breakthrough experiments showed that, whilst abiotic gravel filters removed up to 51% of metals, those with biofilms enhanced heavy metal removal by up to a further 29%, with Cu removal illustrating the greatest response to biofilm growth. An advection–diffusion equation successfully modelled metal tracer transport within biofilm columns. This model yielded a permanent loss term (k) for metal tracers of between 0.01 and 1.05, correlating well with measured data from breakthrough experiments. Additional 16S rRNA clone library analysis of the biofilm indicated strong sensitivity of bacterial community composition to the lithology of the filter medium, with gabbro filters displayingProteobacteriadominance (54%) and dolomite columns showingCyanobacteriadominance (47%). [ABSTRACT FROM AUTHOR]

To improve the magnesite flotation system with sodium oleate (NaOL), dodecyl dimethyl betaine (BS-12), an environmental-friendly surfactant, was first used in the flotation of magnesite and dolomite with NaOL. Micro-flotation tests, surface tension measurements, and contact angle experiments were carried out to evaluate the effects of BS-12 on the flotation of magnesite and dolomite with NaOL. The results demonstrated that BS-12 had little collection effect on both magnesite and dolomite, but the mixture of BS-12 and NaOL had better low-temperature resistance than NaOL, meanwhile, the mixture collector could effectively promote the flotation of magnesite to improve the separation of magnesite and dolomite, when their ratio was 3:2. The addition of BS-12 in NaOL flotation system could also enhance the surface activity and hydrophobicity of magnesite and dolomite. The effect mechanism of BS-12 on the flotation of magnesite and dolomite with NaOL was studied through zeta potential measurements, Fourier-transform infrared spectroscopy (FTIR), and molecular dynamics simulations. The results demonstrated that NaOL and the mixed collector could adsorb on the surfaces of the minerals by chemical interaction. The addition of BS-12 could weaken the electrostatic repulsion between NaOL ions and generate hydrophobic association with NaOL, which improves the adsorption of NaOL on surfaces of the minerals and enhances the flotation separation of magnesite and dolomite. [ABSTRACT FROM AUTHOR]

The development of the Mechanistic-Empirical Pavement Design Guide (MEPDG) provides an opportunity to simulate the performance of pavements. This paper considers the impact of fine aggregate on the predicted performances of pavements by simulating the performance differences between pavement mixes prepared with different sources of fine aggregate with different gradations using the MEPDG. A natural and four manufactured sands from parent material consisting of dolomite, limestone, traprock (TR) and a glacial gravel (GG), and five gradations were utilised in this study. This resulted in 19 different sand/stone combinations being tested for dynamic modulus to enable level 1 analysis in the MEPDG. The results indicate that the fine aggregate angularity (FAA) test adequately ranks aggregates from the same source, but does not appropriately rank aggregates from different sources. TR and GG were identified as the best performers within the investigated aggregate sources and that the FAA, aggregate source and gradation are not significant in determining mixture performance. [ABSTRACT FROM AUTHOR]

The cable shovel is an important primary excavator in surface mining operations. The production function of this shovel becomes more critical in the Athabasca oil sands formation with little or no pre-production blasting. The random occurrence of shales, dolomites and limestones in this formation causes a high digging resistance, mechanical wear, tear and failure, resulting in high maintenance costs. Research is currently underway to develop an intelligent navigation technology to provide smart shovel excavation in this formation. This paper contributes to this research by developing a numerical simulation model for determining the resistive force on a shovel dipper during excavation. The spatial dynamics of the dipper geometry and the loaded material weight are modelled using ordinary differential equations and solved using the Runge - Kutta algorithm. Numerical simulation results show that the depth of cut increases with an increase in crowd arm extension speed and a decrease in hoist rope retraction speed. The results also show that the dipper digging and loading rate is proportional to the speed of crowd arm extension and hoist rope retraction. For a constant hoist rope retraction speed, the optimum dipper trajectory is defined for crowd arm extension speeds and vice versa. Also, the digging time for crowd arm extension and hoist rope retraction speeds sampled from a uniform distribution between 0.15 and 0.35 m/s follows a triangular distribution with minimum 6.12 s, mode 7.26 s and maximum 13.7 s. Using these results, production engineers can parameterize shovel excavation schemes for optimum production performance. [ABSTRACT FROM AUTHOR]

Conventionally, limestones have been used in passive mine water treatment systems. Limestones with the highest proportion of calcite are recommended since they have the greatest long-term alkalinity generating potential. Manganese is present in mine waters and needs to be removed in order to comply with environmental quality standards. This paper compares seven different Permian carbonate rocks, both limestone and dolomite, in their ability to promote manganese oxidation in real mine waters over an 8-h period. The substrates are characterised using thermogravimetric analysis, X-Ray diffraction and scanning electron microscopy. Fluorescence spectrophotometry is used to monitor any changes in the dissolved organic matter concentration in the water as manganese is removed. We determine that there is no statistically significant correlation between manganese removal and the proportion of calcite or between manganese removal and substrate surface roughness. Fluorescence spectrophotometry demonstrates that there is a distinct change in the observed spectra in the water during manganese removal. There is a positive and statistically significant correlation between manganese removal and the production of a tyrosine-like substance (up to ∼150 ppb in 8 h), which fluoresces at 270-280 nm excitation wavelength and 300-310 nm emission wavelength, suggesting that microbial activity is an important factor in promoting manganese removal within dolomite passive treatment systems. It may be possible to use fluorescence spectrophotometry to monitor for microbial activity in passive treatment systems. [ABSTRACT FROM AUTHOR]

For clarifying the effect of dolomite on the volume stability of Portland dolomite cement (PDC) at high reaction degree, the length change of PDC pastes with the replacement levels of 10–30 wt% dolomite and cured in different conditions was examined, in contrast with Portland limestone cement (PLC). The hydration products and microstructure were investigated using XRD, TGA, and SEM. Results indicate that at 40 and 60 °C the PDC and PLC show similar deformation patterns, with a small expansion. At 80 °C, however, the PDC are characterized by a higher expansion than the PLC, especially at high replacement levels. The reaction process of dolomite in PDC is dependent on the availability of aluminate phases. In the presence of free alumina, dolomite would react preferentially to form carboaluminates, hydrotalcite, and calcite. When the alumina is exhausted, dedolomitization reaction takes place producing brucite and calcite. The high expansion in PDC is mainly associated with the dedolomitization, which may result in the reinforcing frame volume and crystallization pressure due to the formation of brucite and calcite in confined space. However, the expansion of PDC is too small to cause damage to hardened pastes. Therefore, the incorporation of dolomite in PDC has no adverse effect on the volume stability of cement-based materials. [ABSTRACT FROM AUTHOR]

Dolomite [CaMg(CO3)2] is used widely for soybean, Glycine max (L.) Merr. production in Japan to amend soil pH, although magnesium (Mg) in the dolomite can inhibit soybean growth and yield. The aim of this study was to determine the effect of Mg on soybean production in a paddy – upland rotation field in 2019–2020 by comparing the application of dolomite and calcite (CaCO3). The field test included three replications with three lime applications: control (no lime), dolomite, and calcite. The amounts of calcite and dolomite applied in each year were 253 and 259 g m−2, respectively. The soil pH was almost similar following the applications of calcite and dolomite, whereas the soil exchangeable Mg content was higher following the dolomite application than following the other applications. The shoot weight from the flowering stage to the harvest stage (R8) was significantly higher following the calcite application than following the other applications. However, the shoot weight at only R8 was significantly higher following the dolomite application than following the control application. In 2019–2020, the highest soybean yield was resulted from the calcite application (355 g m−2) followed by the dolomite application (312 g m−2) and the control application (260 g m−2). The severity of soil-borne diseases was lower following the dolomite application than following the control application, and even lower following the calcite application. Thus, the application of dolomite increased soybean yield by improving soil pH; however, Mg in the dolomite inhibited a further increase in soybean yield in a paddy – upland rotation field. [ABSTRACT FROM AUTHOR]

The Israelite Plain, a narrow terrace at the western edge of the Great Australian Bight, is characterised by a series of schizohaline, ephemeral lakes leeward of a marginal marine eolianite dune complex that has many similarities to the Coorong Coastal Plain (CCP). The late Pleistocene and Holocene sediments are a mixture of dominantly quartzose sand and lesser carbonate components. Paleolagoon to shallow marine MIS 5e, mollusc-rich quartzose deposits are capped by calcrete or karst and contain a biota similar to the well-documented, coeval Glanville Formation on the CCP. Holocene sands with minor carbonate are also lagoonal and resemble many modern Coorong Lagoon deposits. Both deposits are interpreted to reflect marine accumulation during sea-level highstands. Lakes today range from dry to water-filled with most floored by calcareous quartzose sand. Microbial influenced sedimentary structures in the form of pustular to laminated mats veneer lake margin bedrock and sediment. Carbonate minerals are mostly calcite with abundant accessory magnesium-calcite, aragonite and traces of magnesite, monohydrocalcite and halite. Gypsum is minor but ubiquitous and floors one of the smaller, marginal-marine lakes. Although having a similar evaporative climate and evidence of groundwater resurgence like Coorong lakes, there is no significant synsedimentary dolomite. This aspect is interpreted to reflect the narrow width of the plain, and the Mg-poor source of groundwater from the nearby karst Nullarbor Plain to the north. The Israelite Plain, together with other coeval, young successions marginal to the Southern Ocean under a semiarid climate now illustrate the depositional variations and early diagenetic differences that can occur in similar environments adjacent to a cool ocean. The Israelite Plain is a narrow, marginal marine terrace covered by Quaternary, lagoonal, eolian to lacustrine, calcareous siliciclastic sands, similar to several other calcareous terraces along the southern Australia coast. The interpreted sediment ages are late Pleistocene stage MIS 5e with the deposit sporadically overlain by similar Holocene deposits. Most 14C age dates are suspicious because of interpreted diagenesis or MIS 5e age, whereas U/Th age dates appear correct or altered by diagenesis. Pleistocene biota is dominated by the bivalve Anadara trapezia, whereas Holocene deposits contain a varied array of cooler water molluscs. The carbonates are similar to those on the Coorong Coastal Plain but do not contain any dolomite likely because of climate and lack of Mg-groundwater flow. [ABSTRACT FROM AUTHOR]

Geomechanical studies in carbonate rocks often require the use of log relations to obtain mechanical properties when laboratory measurements are not available. This study presents a new set of equations to predict the unconfined compressive strength (UCS) and Young's modulus (E) for three carbonate lithologies: limestone, dolomite, and chalk. The equations are developed based on more than 700 mechanical-physical tests of carbonate rocks across different geological settings and geographical locations. The obtained results confirmed that petrophysical properties are consistent in determining the carbonate mechanical properties. The relations are developed based on either a single parameter or multiple parameters where coefficient of determination was improved for the multiple parameter relations. Scattering in the prediction of UCS and E is expected due to the carbonate heterogeneity in mineralogy, porosity, fabric as well as testing conditions. Thus, the applicable range of each relation is investigated. To test whether improved fits are achieved in this study, the relations are compared with the literature, and they showed a higher coefficient of determination. The proposed relations can be generally used as a starting point for UCS and E estimate when carbonate mechanical properties from laboratory tests are not available. [ABSTRACT FROM AUTHOR]

The origin of dolostones from the Lei 4 Member (T2l4) of the Middle Triassic Leikoupo Formation in the Western Sichuan Depression is unclear. The occurrence and genetic evolution of dolostones in T2l4 were analysed by polarised thin-sections and cathodoluminescence, major- and trace-element, scanning electron microscope, and carbon, oxygen and strontium isotope analyses. The study results are summarised as follows. (1) The dolostones were mainly precipitated in three stages of <40 °C, 40–60 °C and 60–80 °C, corresponding with three paleodepth ranges of 167–300 m, 433–1000 m and 1067–1433 m. The micritic dolostones and the fabric-retentive dolostones (algal dolostone, granular dolostone) mainly formed in a near-surface–shallow-burial environment, and the crystalline dolostones were mainly formed under intermediate burial conditions. (2) 87Sr/86Sr ratios are equivalent to that of the Middle Triassic seawater, Sr/Ba and V/Ni ratios >1, Na notably higher than that in coexisting limestones of T2l4, and the dolostones always coexist with evaporative minerals such as gypsum, indicating that dolomitisation fluids mainly originated from evaporative concentrated seawater. (3) The dolostones mainly inherit materials from precursor limestones based on trace-element distribution patterns, and carbon and oxygen isotope values that are consistent with coexisting limestones of T2l4. (4) Mediated by micro-organisms during the syngenetic period, micritic dolostones and some algal dolostones were formed by replacing aragonites and calcites. During shallow burial, concentrated seawater rich in Mg2+ from the supratidal–intertidal zone flowed downward owing to gravity along the platform and replaced the underlying carbonate rocks, promoting continuous growth of the early dolomites. In the intermediate burial period, the Mg2+-depleted dolomitisation fluid caused the early micritic and silt-crystalline dolostones to recrystallise into silt- or fine-crystalline dolostones with larger crystals and altered the fabric-retentive dolostones into crystalline dolostones. (5) The evaporative dolostones deposited in the near-surface environment are characterised by maximal enrichment of Fe, Sr and Na, the highest δ18O values, the lowest order degree and the highest Ca/Mg ratios. The reflux dolostones formed in a shallow-burial environment characterised by the lowest Fe, medium δ18O values and the lowest order degree. The burial dolostones that developed in the intermediate burial environment are characterised by relative enrichment of Fe and Mn, minimal Na, the lowest δ18O values, the highest order degree and medium Ca/Mg ratios. The fabric-retentive dolostones mainly formed in a near-surface–shallow-burial environment, and the crystalline dolostones mainly formed under intermediate burial conditions. Dolomitisation fluids mainly originated from the evaporative concentrated seawater, and the dolostones inherit materials from the precursor limestones. Micritic dolostones were formed by evaporative dolomitisation; algal dolostone and granular dolostone were formed by evaporative dolomitisation and reflux dolomitisation; and silt-crystalline dolostone were formed by reflux dolomitisation and burial dolomitisation. [ABSTRACT FROM AUTHOR]

Significant amounts of petroleum are found in the deeply buried Cambrian Xiaoerbulake Formation in the Tarim Basin. However, limited understanding of origin of diagenetic fluids hampers petroleum exploration. In this study, petrological and high-resolution geochemical methods have been performed to understand the origin and evolution of diagenetic fluids, and their effects on the formation of dolostone reservoir. The Xiaoerbulake Formation is characterised by microbialites. The matrix is characterised by modern seawater-like rare earth element and yttrium (REY) patterns and δ18O values of −6.02 ± 2.11‰ Vienna Pee Dee Belemnite (VPDB). Fine-crystalline dolomite cements have similar δ13C values and heavy rare earth element enrichment patterns to that of matrix dolomite, yet with lower δ18O values of −7.47 ± 1.2‰ VPDB. In the deep-burial regimes, medium- to coarse-crystalline dolomite cements and saddle dolomites were precipitated at temperatures of 90–120 and 130–190 °C, respectively, lower δ18O values, distinct middle rare earth element enrichment, and high Fe and Mn contents compared with matrix and fine-crystalline dolomite cements. These imply thermochemical reduction of Fe- or Mn-rich oxides and/or hydrothermal fluids. Compared with other types of dolomite cements, calcite cements are characterised by low δ13C values (as low as −6‰ VPDB), light rare earth elements enrichment and significantly elevated Y/Ho ratios (86 ± 59.3), likely related to the oxidation of organic matter during thermochemical sulfate reduction (TSR). Consequently, diagenetic fluid may have evolved from: Cambrian seawater, meteoric water, shallow-buried seawater-dominated pore water, medium-deep-buried ferrous-rich pore water, lately high-salinity hydrothermal fluid-dominated pore water and finally to acidic fluids related to TSR dissolution. Reservoir quality is enhanced by hydrothermal pulses and TSR in deep-burial settings. This study is significant for those concerned with the formation of deep-buried carbonate reservoirs. [ABSTRACT FROM AUTHOR]

Geomorphological field surveys and mapping have been carried out in a catchment of the Dolomites (eastern Italian Alps) as part of a research project aiming at the assessment of sediment availability for mass wasting in mountain environments. The study area is the Liera catchment which was severely affected by a high-intensity, regional-scale storm named ‘Vaia’ (27–30 October 2018), which induced relevant morphological changes, caused a major flood in the main stream and triggered debris flows in many tributaries. This contribution gives a snapshot of the present-day state of the study area to improve the understanding of such a landscape by characterizing the processes that control its geomorphological spatiotemporal dynamics and evolution. [ABSTRACT FROM AUTHOR]

The rocks of the Aravalli Protocontinent of NW India are enriched in lead–zinc bearing deposits amongst which the Zawar mineralized belt is one of the famous for base metal deposits and was mined since ancient times. In the present study, an attempt has been made to identify and map the extension of the mineralized belt and base metal prognostic zones using the integration of multi-sensor remote sensing, geological and geochemical data. Remote Sensing studies were carried out using ASTER, AVIRIS-NG, and ASAR datasets to understand the extension and associated structural features of host rocks (dolomite in the present case) of lead–zinc mineralization from the Middle Aravalli Group. Relative band depth (B6 + B9/B8) was used to delineate the dolomite of the region using the ASTER imagery. Mineral map was derived using the AVIRIS-NG dataset with the help of the MTMF algorithm. Multifrequency and multipolarization ASAR datasets demarcated the structural features in the complexly deformed rocks of the extended belt. The obtained results from remote sensing were validated with the help of geological and geochemical studies. Geological studies (field surveys and petrographic studies) confirmed the presence of dolomites and associative mafics. Mineralogical, major oxides and trace elements data further substantiated the presence of dolomite, associated sulfides such as galena, sphalerite, pyrite, and chalcopyrite, and lead, zinc and copper in the Zawar–Dungarpur Belt. Presence of chromium and nickel were observed through the trace element studies of dolomite belt. The trace elements interpolated maps were superimposed by traced structural maps using ASAR datasets. The densely populated E-W lineaments are considered the suitable zones for base metal accumulation. These lineaments carried the base metal bearing fluid along with a low concentration of Chromium and Nickel. Under the finding of this study, the northern head of Hati Magra and near Keekawat are the suitable zones for Pb–Zn sulfide mineralization. [ABSTRACT FROM AUTHOR]

In this work, a mineralogical characterization by X-ray diffractometry and thermogravimetric analysis of a new Brazilian zinc ore sample was performed. The mineralogical semi-quantification, conducted by normative calculation of the identified minerals, using their theoretical chemical formulas and the contents determined in the chemical analyses was as follows: smithsonite (20.3%), goethite (49.6%), kaolinite (12%), quartz (6.2%), cerussite (3.0%), chlorite (4.0%), dolomite (0.5%) and others (4.4%). Subsequently, bench flotation tests were executed, using sodium oleate (anionic route) and amine (cationic route) as smithsonite collectors. Sodium silicate was used as a depressant of the gangue minerals in both routes tested. These studies showed that the anionic route (30.1% Zn in concentrate and 83% Zn recovery) performed better than the cationic route (17.5% Zn in concentrate and 46.3% Zn recovery). Considering the mineralogical composition of the concentrates obtained in the best flotation results, associated with physicochemical studies published in the literature with the identified minerals, it was evidenced that the difference in performance between the tested routes is due to the influence of ions from the dissolution of carbonates present in the ore on the surface properties of the main gangue minerals (goethite and silicates), especially for the cationic route. [ABSTRACT FROM AUTHOR]

This study focused on the effects of dolomite powder on the properties of C30 and C50 concretes. The microstructure, splitting tensile strength, compressive strength and fracture toughness property of concretes incorporating dolomite powder were measured by mercury intrusion porosimetry (MIP), pressure testing machine and universal testing machine. Higher splitting tensile strength, compressive strength and fracture toughness of concretes could be seen with the increase of dolomite powder dosage within 90 days. After 1 day of curing, splitting tensile strength, compressive strength and fracture toughness of C30 and C50 concretes could be improved considerably. The positive effects of dolomite powder on the splitting tensile strength, compressive strength and fracture toughness decreased with the increase of curing age. Because the nucleation effect, micro-filler effect and mix proportions design of dolomite powder were beneficial to the refinement of pore structure of concretes, and dolomite powder had less influence on the later stage of cement hydration. The splitting tensile strength equations expressed in terms of the compressive strength was proposed. The analysis of regression equation proved that the equation of relationship between compressive strength and splitting tensile strength of concretes containing dolomite powder in this study had high prediction accuracy. [ABSTRACT FROM AUTHOR]

In the Quadrilátero Ferrífero Region, located in the state of Minas Gerais – Brazil, the utilization of recycled water from the tailing dams in the reverse cationic flotation of siliceous iron ores is common practice. In such process, ore concentrates assigning dolomite (2.5% to 10%) besides quartz in the mineral gangue, do not reach the desired specification for the production of blast furnace pellets (≤2% SiO2) given the loss of selectivity occurring in the separation of quartz from the Fe-bearing minerals, which can be related to a rise in the ions Ca and Mg in an aqueous medium resulting from the dissolution of dolomite. With a view to improving the reverse cationic flotation route for this type of ore, fundamental studies (microflotation trials, zeta potential, adsorption/Fourier-transform infrared spectroscopy) into the effect of the Ca and Mg ions in the cationic flotation with the use of pure quartz and hematite mineral samples were carried out. The results attained with the Ca ions were presented in previous studies by the authors. The current investigation presents the results achieved with the Mg ions, added in water as MgCl2. In the microflotation trials carried out at pH 10.5, amine dosage for maximum recovery of quartz (2.5 ppm) and hematite (50 ppm) was applied. A strong depression of hematite by starch was confirmed, which did not occur with quartz. In the case of the Mg ions, a stronger depression effect was observed, if compared to starch, for the two minerals, starting from a dosage of 10 ppm of MgCl2. After the conditioning of both minerals with 10 ppm of MgCl2, followed by conditioning with 10 ppm of starch, the recoveries attained were negligible (3.5% to 4.4%). Based on thermodynamic data, zeta potential measurements, and infrared spectroscopy, it was concluded that the strong depression effect caused by the Mg ions on both minerals owes to the adsorption of the Mg2+ and MgOH+ species and also the precipitation of Mg(OH)2, where the starch is chemically adsorbed, preventing further amine adsorption. Only quartz recovery was reestablished after the complexation of the Mg ions in the water by ethylenediaminetetraacetic acid having close molar concentrations to the molar concentration of the Mg ions followed by starch conditioning. The results presented indicate the need for a reduction in the concentration of Mg in the water used, before flotation is conducted. [ABSTRACT FROM AUTHOR]

This study investigated the effect of the different mineral fillers and concentrations, film thicknesses on the bituminous mastic bond strength (BMBS). Moreover, the self-healing capabilities of different bituminous mastic compounds were assessed, where the effects of two types of high modulus additives of RW plast S and RW elast E on the self-healing of bituminous mastic were evaluated. It was found that filler concentration, due to the morphology of filler, has a great impact on the BMBS. Indeed, the more porosity, the more bitumen needed to fill the voids on the surface of filler particles that changes the thickness of free bitumen. Besides, the healing capability of the dense structure can be expected to be more than porous one. The change in the thickness of the free bitumen alters the healing mechanism of bituminous mastic. Exposing to the water helps the bitumen to make a strong bond that results in higher recovered bond strength in the long run. Regarding these issues, it was observed that the healing capability of River Filler (RF) is more than Dolomite Filler (DF). [ABSTRACT FROM AUTHOR]

Surface and groundwater resources in the Wonderfonteinspruit (WFS) catchment are of increasing importance as future sources of water supply to a growing population in the region. However, deep-level gold mining over more than a century has impacted adversely both the availability and quality of ground- and surface water. This paper analyses spatial patterns, mechanisms, and dynamics associated with the fluvial transport of uranium. Previous studies found elevated levels of dissolved U along the entire watercourse and also detected significant secondary accumulations of U in fluvial sediments. The degree of sediment contamination seems to be determined less by the distance to the source of U pollution than by the sorption capacity of sediments and certain site-specific mechanisms removing U from stream water. U concentrations in stream water were found to fluctuate by up to several orders of magnitude between two weekly measurements. This highly dynamic behavior of U in stream water is caused by complex interactions of natural and anthropogenic processes differing in frequency and magnitude. Such processes include diurnal and seasonal photosynthesis cycles, rain events, and pumping regimes of mines discharging uraniferous effluents. It is recommended to adjust sampling intervals of existing monitoring systems accordingly, because current protocols systematically underestimate the true extent of stream pollution. [ABSTRACT FROM AUTHOR]

Extensive karst aquifers developed in compartmentalized dolomitic strata constitute important groundwater reservoirs in semi-arid parts of South Africa. Located in the vicinity of densely populated and increasingly water-stressed metropolitan areas of Gauteng, these aquifers are of strategic importance for future water supply. However, many of the dolomitic groundwater compartments are severely affected by deep-level gold-mining operations. Apart from large-scale dewatering and associated modification of spatial and temporal water availability, gold mining also adversely impacts on the quality of remaining water resources. The focus of this paper is on uranium, a chemically toxic radioactive heavy metal identified by a number of previous studies as the contaminant of concern. Point- and non-point sources of U associated with mining activities in the Wonderfonteinspruit catchment, as an example of a dolomitic gold-mining area, as well as pathways of U pollution are discussed. Associated U loads emanating from major sources are estimated. The results suggest that detected levels of U pollution in the catchment are not only caused by century-old mining activities but also by current operations and that U pollution of water is likely to continue well beyond the closure of mines. [ABSTRACT FROM AUTHOR]

The mean annual rainfall of South Africa is only about 450 mm. The unpredictability of the rainfall as well as extremely high potential evaporation result in the country being water stressed. It is predicted that the demand for water will outstrip the supply within three decades. In order to mitigate this problem, various huge transcatchment schemes have been constructed in South Africa and some of its neighboring countries, but these schemes will only postpone the drying up of the main rivers within a few years. For this reason, the importance of groundwater as a resource is increasing. South Africa does not have significant groundwater resources, although the dolomitic aquifers in the West and Far West Rand have a huge groundwater potential. These dolomites contain (under natural conditions) at least twice the volume of water of the Vaal Dam, which is the main water resource for the economic heartland of South Africa. Alkaline and mafic-alkaline dikes of Pilanesburg age divide the dolomites into several ground water compartments, which overlie some of the richest gold mines in South Africa. The mines have had an adverse effect on the groundwater potential, because most of the compartments have been dewatered to some degree to enable mining operations. Since some of the mines have reached the end of their life span, it is expected that some of the compartments will be allowed to rewater. The rate of rewatering is unknown and the research described in this paper was an attempt to model the rewatering of one of the compartments, namely the Gemsbokfontein compartment, in order to determine the time of rewatering as well as the eventual decant volume. [ABSTRACT FROM AUTHOR]

This paper presents how high frequency Ground Penetrating Radar (GPR) can be effectively used for mapping the subsurface characterization of dolomite and limestone strata for determination if the rock is suitable for ripping. The results of the experiments conducted in the course of this project illustrated that water saturation helps in increasing the contrast between the dielectric constants of the separations, due to water escaping into cracks and clay layers. Running the survey on a dry rock will give a larger penetration depth; but during the interpretation of the results, one can omit small voids or clay layers. [ABSTRACT FROM AUTHOR]

Waterflooding is the widespread method for displacing the residual oil toward well production because of its accessibility and low cost. Currently, several oil-rich countries are investigating to untangle the current shortcomings to make waterflooding method efficacious more. On the other side, salinity composition has been considered in enhanced oil recovery (EOR) for better sweep efficiency and has captured great interest for EOR techniques. In this study, oil–water interfacial tension (IFT) was measured between acidic heavy crude oil (AHCO) and brine solutions of MgCl2, CaCl2, KCl, NaCl, and Na2SO4 in various concentrations from 0.1 to 1 M and analyzed to obtain the highest IFT reduction. Moreover, the effects of AHCO and water composition on initial wettability of carbonate rock were investigated. The variations of surface properties of dolomite rock samples were investigated by contact angle (CA) measurements after aging thin sections in oil and brine. In addition, silica nanoparticles (NPs) as the IFT reducer and wettability alteration affordable agent were examined to compare their effects on salinity. The lowest IFT value between AHCO and brine solutions was reported 6.5 mN/m by magnesium chloride at 1 M concentration. Likewise, the highest impact on wettability alteration from oil-wet system (137.37◦) to strongly water-wet system (30.79◦) was obtained by magnesium chloride at 1 M concentration as well. Moreover, the application of silica NPs based on different salinity showed an inconspicuous impact in this study. [ABSTRACT FROM AUTHOR]

Dolomites in Arctic Ocean sediments are widely attributed to erosion and transport of sediments from northern Canada and Greenland. Coarse-grained dolomite-rich ice-rafted debris is often linked to iceberg transport, but the origin of fine-grained dolomite is less well constrained. A presumed source is the Mackenzie River. In this article, we fingerprint the minerogenic and isotopic (Nd and Sr) composition of deglacial and Holocene fine-grained sediments (<38 µm) from the shallow Mackenzie Trough. Sediments from an 81.5-m borehole (MTW01) were analyzed. The borehole is composed of a progradational (deltaic), transitional (transgressive), and marine unit (<9.4 cal. ka BP). The average dolomite content (~7 percent) and ɛNd signals (-13.3) are surprisingly constant in the progradational and marine units. The isotopic signature is inherited from the Interior Platform, the major underlying bedrock region of the Mackenzie River mainstream. The transitional unit contains fluctuations in ƹNd (-11.0 and -14.6), reflecting enhanced input from the North American Cordillera and Canadian Shield that are not associated with elevated amounts of dolomite. Additional studies combining minerogenic and detrital ɛNd analyses from sites proximal to the paleo-icestreams draining the Canadian Arctic are required to ascertain the origin of dolomite enrichment in central Arctic Ocean sediments. [ABSTRACT FROM AUTHOR]

Aynak is the largest known copper deposit in Afghanistan, with indicated resources of 240 Mt grading 2.3% Cu placing it in the 'giant' category. Host rocks are Neoproterozoic metasediments comprising dolomitic marble, carbonaceous quartz schist and quartz-biotite-dolomite schist containing garnet, scapolite and apatite. Chalcopyrite and bornite dominate the hypogene ore with lesser pyrite, pyrrhotite, cobaltite and chalcocite, and rare sphalerite, molybdenite, uraninite and barite. Sulphides occur as bedding-parallel laminae, disseminations, metamorphic segregations and crosscutting veins. Sulphide δ34S ratios range –14.5 to +17.3‰ in bedded and disseminated sulphides (n = 34). This broad range favours biogenic reduction of seawater sulphate as a major source of sulphur, although thermochemical reduction processes are not precluded. The narrower δ34S range of –6 to +12.2‰ in vein and segregation sulphides (n = 21) suggests localized redistribution and partial homogenization during metamorphism. Geochemical associations suggest that Al, P, Ca, Ti and Fe were primary sedimentary constituents whereas Cu, Mg, S, Se, As, Co and Bi were introduced subsequently. We infer that Aynak originated as a shale- and carbonate-hosted stratabound replacement deposit, resembling orebodies of the Central African Copperbelt, although underlying red-beds are absent at Aynak and mafic volcanics were the probable copper source. These giant deposits formed worldwide in the Cryogenian probably due to marine enrichment in copper, magnesium and sulphate coincident with profuse basaltic volcanism and ocean oxidation. [ABSTRACT FROM AUTHOR]

The effects of dolomite powder dosage on the fracture properties and volume stability of cementbased materials were investigated by three-point bending method and corrugated tube method, respectively. The experiment results showed that the fracture toughness of cement mortar incorporating dolomite powder was raised compared to that of reference cement mortar. After dolomite powder was added into cement paste, the improvement of fracture toughness, flexure, and compressive strength was observed due to the formation of a new phase (magnesium hydroxide and calcium carbonate) combined with the nucleation and physical filling effect. Autogenous shrinkage of samples incorporating dolomite powder were higher than that of the control samples because the addition of dolomite powder increased the surface tension of water in pores and the compression on the walls of capillary pores, facilitating higher autogenous shrinkage. Drying shrinkage of cement pastes blended with dolomite powder was lower than that of the control samples. The refinement of the pore structure of samples incorporating dolomite powder decreased the internal capillary pressure, causing smaller drying shrinkage. [ABSTRACT FROM AUTHOR]

This study focused on the evolution of hydration process of cement-based material containing high volume of dolomite powder. The hydration products, microstructure, morphology and mechanical property of cement-based material blended with dolomite powder were investigated by means of isothermal calorimetry, X-ray diffractometry (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and universal testing machine. At early stage of hydration (1 day), high volume of dolomite powder accelerated cement hydration due to the fact that the surface of dolomite powder provided much more nucleation sites for C-S-H. As a result, the compressive strength of cement mortar incorporating dolomite powder increased significantly (up to 31.5%). At later stage of cement hydration (90 days), the reaction between dolomite powder and portlandite from the hydrated cement formed a small amount of magnesium hydroxide which led to the refinement of the pore structure and an increment of compressive strength. Besides, the tight packing of cement particles (D50 = 11.37 um) and finer dolomite powder (D50 = 6.45 um) contributed to the refined structure and the improvement of the compressive strength as well. [ABSTRACT FROM AUTHOR]

The Middle Jurassic terebratulide brachiopods from the Jordan Valley, northwestern Jordan, are herein revised and systematically described and new taxa are added to the faunal list. A new genus and species Jordanithyris ardainensis gen. et sp. nov., is introduced from the upper Bathonian (Hamam Formation) and lower Callovian (Mughanniyya Formation) of the Arda section. In the upper Bathonian Hamam Formation (consisting of limestone, dolomite, alternating sandstone, and marlstone beds), Ptyctothyris quillyensis occurs. The assemblage Arabatia bihinensis, Ectyphoria sinaiensis, Ptyctothyris quillyensis, Dorsoplicathyris dorsoplicata, and Tubithyris jurayfahiensis is recorded in the lower Callovian limestone beds with marlstone interbeds of the Mughanniyya Formation. Brachiopods of the Jordanian Hamam and Mughanniyya formations can be correlated with the fauna of the Aroussiah Formation in Sinai and the Zohar and Matmor formations in southern Israel. The sedimentary environment is interpreted as the protected shallow inner shelf, and nutrient rich habitat resulting in high faunal diversity. The high degree of endemism of this fauna is yet another confirmation of the representative pronounced Middle Jurassic endemism along the southern Tethyan margin of the Ethiopian Province. [ABSTRACT FROM AUTHOR]

The genesis of dolomite is a century-old mystery in sedimentology. The 'microbial dolomite model' proposed in recent years provides new insight into the study of dolomite genesis. However, the lack of research on the precipitation rate makes it difficult to judge whether the microbial dolomite can be deposited as a thick dolomite formation alone. In this review, the precipitation rates (about 10−12 to 10−9 cm · s−1) and productivity (about 1.3–7.9 × 10−7 cm · s−1) are estimated preliminarily, the results of cold seeps (10 −11.7 to 10 −12.5 cm · s−1) and previous modeling work (10−11.8 cm · s−1) were collected, and the possible precipitation rates of ancient (6.1–7.5 × 10−11 cm · s−1) and modern sabkha (5.9 × 10−10 to 1.3 × 10−9 cm · s−1) were calculated. To some extent, it does be possible that microbial dolomite can form a thick layer alone (because of the high productivity), but increasing order is a long process with the transformation of diagenesis. In terms of precipitation rate, there is less possibility in Sabkha, but more in cold seeps. The study on the precipitation rate of microbial dolomite may bring new enlightenment to the dolomite genesis and other fields, such as the reconstruction of paleoenvironment and study of the origin of life, but more elaborate culture experiments and modeling works are needed. [ABSTRACT FROM AUTHOR]

To solve the problem of multi-resulted in seismic responses brought by dual impacts of the thickness and the lithologic association for further research of seismic response characteristics of hydrothermal dolomite, significant efforts have been made, which were based on the study of dolomite, the Maokou formation in the eastern Sichuan Basin, to conduct an analysis of mineral composition, strata distribution and dolomitization in its area, to develop layered medium models in accordance with different dolomitization degrees and thicknesses, and to build standardized wedge models for the full display of that in binary changes. Moreover, an essential application of the pre-stack and post-stack seismic forward modeling have been performed for analyzing how different dolomitization degrees and thicknesses had influences on the seismic response characteristics of hydrothermal dolomite. Given this, the sensitive seismic attributes of the target interval in the study area have been selected preferentially by analyzing the seismic response characteristics of hydrothermal dolomite, which plays a critical role in the entire process. The results show that?1. The response characteristic of amplitude is greatly influenced by the dolomitization degree and bed thickness?2. The dolomitization degree constitutes a transformation of AVO response characteristics from II to IV, while the variation of thickness leads to a transformation of AVO response characteristics from IV to II. 3. The actual results indicate that the relative fluid factor FF is one of the most sensitive AVO attributes, and the predicted results are in par with the actual results. [ABSTRACT FROM AUTHOR]

A detailed palynological study was conducted in the lower Palaeozoic of the Zagros Basin (southwestern Iran) where the Mila and Ilbeyk formations are present in several areas. The Mila Formation mainly consists of dolostones, limestones and shales deposited in a shallow marine to outer ramp environment. It is conformably overlain by the Ilbeyk Formation, characterised by shales and sandstones with scattered limestone intervals deposited in a setting extending from shoreface to low-energy offshore environments. The palynological investigation of the Mila and Ilbeyk formations from the Chalisheh, Ghalikuh and Oshtorankuh areas allows the establishment of three palynozones. These can be well correlated with the palynozonations from adjacent areas and/or with middle–late Cambrian sections independently dated with trilobites. These correlations are useful for the age determination of the Cambrian successions from southern Iran. The Cambrian assemblages exhibit close affinities with microfloras from peri-Gondwana (including the countries belonging to the Avalonia microcontinent in the Early Ordovician) and Baltica, confirming that these palaeogeographical domains were part of the same large bioprovince, as shown in current palaeogeographical maps. [ABSTRACT FROM AUTHOR]

Ichnofossils from the type locality of the Famennian are here described and figured for the first time. The siliciclastic supratidal alluvial to proximal subtidal deposits of S Belgium yield a diverse ichnofauna composed of Arenicolites ispp. (two morphotypes), Chondrites intricatus, Diplocraterion isp., Dolopichnus gulosus, Gordia marina, Helminthopsis isp., Lockeia cordata, L. siliquaria, Palaeophycus tubularis, P. sulcatus, Planolites isp., Protovirgularia obliterata, P. cf. rugosa, P. isp. and Psammichnites implexus. As a whole, these 16 ichnospecies and 11 ichnogenera form the typical assemblage of the Cruziana ichnofacies where Palaeophycus is largely dominant. However, the Belgian Famennian displays a large range of lithofacies corresponding to various environments in which distinct ichnofossil assemblages are identified. Arenicolites isp. collected from sabkha-type primary dolomite indicates the probable colonisation of hypersaline environment by Arenicolites tracemakers as early as the Late Devonian. The type material of Crossochorda marioni Dewalque, 1881 is revised and attributed to Protovirgularia obliterata and P. cf. rugosa. [ABSTRACT FROM AUTHOR]

The 'rim dolomite' of South Australia's Central Flinders Ranges is a prominent ridge-forming, layered dolomitic and siliceous unit. The rim dolomite is interpreted to be a lateral caprock found exclusively at the salt–sediment interface between the Patawarta diapir and the Ediacaran-aged Bunyeroo Formation. Lateral dolomite caprock is defined by the following field relationships: (1) the rugose dolomicrite base that parallels the contact of the diapiric matrix and the bedding in the overlying stratigraphy, (2) the exclusive presence of dolomite at the salt–sediment interface, (3) the lack of sedimentary structures or fossils (cyanobacterial laminites and stromatolites), (4) the lack of interbedded Bunyeroo lithofacies, and (5) the inability to trace the rim dolomite capstone away from the diapir margin into the outboard stratigraphy. In addition to the field relationships, the rim dolomite displays the following capstone fabrics: (1) massive—microcrystalline dolomite, (2) porphyritic—two distinct crystal sizes, one forming microcrystalline dolomite groundmass and the other forming rosettes of silica, (3) banded—microcrystalline dolomite forming pressure-dissolution layers of silica and authigenic hematite, and (4) brecciated—mosaic to disorganised, forming a microcrystalline dolomite groundmass, which locally contains remnant clasts of Callanna non-evaporite lithologies, such as quartz arenite to arkosic sandstones and basalts, surrounded by an anastomosing cement-filled vein network. All capstone fabrics contain various amounts of anhydrite, quartz, feldspar and non-evaporite grains that represent the insoluble residue during halite dissolution and caprock accretion. Three different genetic models for the lateral caprock are described and tested, and that of these, only the halokinetically rotated caprock model fits the data. The field relationships and capstone fabrics of the rim dolomite match other lateral caprocks in salt basins such as the Paradox Basin and Gulf Coast, USA. [ABSTRACT FROM AUTHOR]

The Flinders and Willouran ranges of South Australia contain over 20 examples of exposed allochthonous salt sheets and canopies comprising the Callanna Group megabreccias. The identification of a given diapir or portion of a diapir as allochthonous is well documented in some cases but more speculative in others. Here we summarise most of the examples, citing the evidence and arguments supporting allochthonous origins and discussing relevant geometries and aspects of salt–sediment interaction. The allochthonous bodies are distributed over a large area, from the eastern Willouran Ranges to the Northern and Central Flinders Ranges, with fewer occurrences in the Southern Flinders Ranges. However, apparent base-salt flats are largely confined to four specific stratigraphic intervals that are in places linked by base-salt ramps. These levels are the Skillogalee Dolomite (Burra Group), the Tapley Hill Formation (Umberatana Group), and the Brachina and Bunyeroo formations (Wilpena Group), with ramps and minor flats continuing up through the Pound Subgroup and into Cambrian strata. At least three of the units with flats represent times of slow deposition, which favours lateral salt emplacement. Those in the Wilpena Group may also have been facilitated by minor contractional squeezing of feeder diapirs during early stages of the Delamerian Orogeny. The Flinders and Willouran ranges provide an exceptional natural laboratory for studies of outcropping structures analogous to those found in the subsurface of other salt basins such as the Gulf of Mexico and Atlantic margins. The diapirs and allochthonous salt sheets of the Flinders Ranges were also a key component of the basin framework in which strata containing Ediacaran fauna were deposited. [ABSTRACT FROM AUTHOR]

The low salinity water injection has become one of the most important studies in the oil industry for improving oil recovery compared to conventional seawater injection. Thus, extensive studies have been conducted in carbonate and sandstone reservoirs to investigate how the physical properties of rocks and the chemical composition of fluids influence low salinity effect, while, the carbonate reservoir rocks requires more investigation of the effect of molecular and/or ionic interactions. In this experimental work, the effectiveness of various water flooding schemes in carbonate reservoir rock samples is investigated. In this regard, the oil recovery potential of seawater (SW), reservoir formation water (RFW) and managed water salinity (MWS), with different ion compositions adjusted based on the formation water composition are used. The experiments have been performed on the dolomite core samples and crude oil from an Iranian oil reservoir. Various measurements including zeta potential, XRD, contact angle and interfacial tension have been planned. The main contribution is to investigate the effect of both brine's ionic composition and rock's initial water saturation on wettability change and oil recovery. The results show that, the concentration of SO 4 − 2 ion in the injected water must be managed over an optimum range for each case. This results in changing the wettability of carbonate rock to a less oil-wetting state by altering the brine composition and reducing the salinity. Moreover, initial water saturation plays a role in the process, so that, by increasing SO 4 − 2 content in optimum range, the oil recovery increased. [ABSTRACT FROM AUTHOR]

Thirty-eight non-tropical carbonate rock samples with subtropical affinities, from northern Zealandia, were obtained from oceanographic dredging expeditions in the Reinga-Aotea Basin (2013), and the Norfolk, Loyalty, and Three Kings ridges (2015). Samples range in age from Pleistocene to Paleocene and were petrographically classified into five depositional and one authigenic petrofacies: (1) coarse, bioclastic grainstone to packstone, (2) coarse, bioclastic packstone, (3) coated grains, (4) fine, bioclastic packstone, (5) wackestone, and, and (6) dolomite. The coarse grainstone, packstone and coated-grains petrofacies are dominated by >mm-scale bioclastic components indicating deposition in high energy continental shelf environments. These petrofacies show similarities to non-tropical carbonates such as the onshore New Zealand Oligocene Te Kuiti Group limestones. Fine bioclastic packstone and wackestone petrofacies, consistent with bathyal deposition, comprise primarily foraminfera and micrite, similar to Eocene fine-grained carbonates outcropping in New Zealand. The dolomite petrofacies comprises diagenetic dolomite similar to Paleocene and Eocene rocks of the Mead Hill and Amuri Limestone formations. Other post-depositional features are also directly comparable to onshore New Zealand limestones. Despite no clear relationship between age, lithology, or geographic location, this study shows that non-tropical shelf carbonates with subtropical affinities extend north beyond New Zealand (southern Zealandia) to at least 23.7°S latitude. [ABSTRACT FROM AUTHOR]