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Edmonds, Clive N. "Chapter 15 Dissolution – carbonates." Geological Society, London, Engineering Geology Special Publications 29, no. 1 (2020): 389–401. http://dx.doi.org/10.1144/egsp29.15.
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AbstractThe dissolution of limestone and chalk (soluble carbonates) through geological time can lead to the creation of naturally formed cavities in the rock. The cavities can be air, water, rock or soil infilled and can occur at shallow levels within the carbonate rock surface or at deeper levels below. Depending upon the geological sequence, as the cavities break down and become unstable they can cause overlying rock strata to settle and tilt and also collapse of non-cemented strata and superficial deposits as voids migrate upwards to the surface. Natural cavities can be present in a stable or potentially unstable condition. The latter may be disturbed and triggered to cause ground instability by the action of percolating water, loading or vibration. The outcrops of various limestones and chalk occur widely across the UK, posing a significant subsidence hazard to existing and new land development and people. In addition to subsidence they can also create a variety of other problems such as slope instability, generate pathways for pollutants and soil gas to travel along and impact all manner of engineering works. Knowledge of natural cavities is essential for planning, development control and the construction of safe development.
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Stockmann, G., D. Wolff-Boenisch, S. R. Gíslason, and E. H. Oelkers. "Dissolution of diopside and basaltic glass: the effect of carbonate coating." Mineralogical Magazine 72, no. 1 (February 2008): 135–39. http://dx.doi.org/10.1180/minmag.2008.072.1.135.
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AbstractFar-from-equilibrium dissolution experiments with diopside and basaltic glass in mixed-flow reactors at 70°C and pH 8.2 show that solute concentrations do not reach steady state over the experimental duration of 45—60 days. Chemical modelling indicates that during the dissolution experiments, solutions have become supersaturated with respect to carbonates in the case of diopside, and carbonates, clay minerals and zeolites in the case of the basaltic glass. Decreasing dissolution is therefore interpreted as a result of secondary surface precipitates blocking the reactive surface area. Calcite formation was supported in both experiments by a significant increase in Ca (and Sr) concentrations as pH was abruptly lowered from 8.2 to 7 because this change increased carbonate solubility and caused all potential carbonate precipitates to re-dissolve. The reduction in pH also led to an increase in Si concentration for diopside and a decrease in Si concentration for basaltic glass. This observation is in accordance with previous experiments on the pH-dependent dissolution rates of pyroxenes and basaltic glass.
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Harbar, Vladyslav, and Andriy Lisovskiy. "Carbonations and carbonate profile forming processes of rendzinas of the Podilski Tovtry." Visnyk of the Lviv University. Series Geography, no. 51 (December 27, 2017): 88–97. http://dx.doi.org/10.30970/vgg.2017.51.8741.
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The peculiarities of content and profile distribution of carbonates in rendzinas and soil-forming rocks of the Podilski Tovtry are investigated. It has been determined that the predominant process of weathering of carbonate rocks is a chemical dissolution, in which carbonates are converted into bicarbonates and, in the case of washing water regime, are applied from the soil (the process of decarbonization) and mechanical grinding and destruction of the remaining carbonate inclusions in the process of soil cultivation. The dissolution of carbonate rocks causes accumulation in the soil profile of an insoluble residue, the intensity of which depends on the composition of carbonate rocks, the rate of filtration of aqueous solutions, their aggressiveness and the concentration of destructive substances. The most intensive such accumulation occurs in acidic medium, at a low rate of infiltration of solutions and at high concentrations of CO2. It was established that the highest proportion of CaCO3 is characterized by lithotamium limestone (up to 90–93 %), and the lowest – carbonate polygenetic loams (up to 35–40 %). The feature of the profile distribution of the content of carbonates in rendzinas is its gradual growth in the upper part of the soil profile and rapid in the middle and lower parts. It is determined that the rendzinas of the Podilski Tovtry carbonates are represented predominantly in the form of wreckage of initial soil-forming rocks of different sizes and shapes, as well as amorphous solid-phase crude and finely dispersed products of weathering in the form of powdery and powdery carbonate dusting. It is established that in dense crystallized lithotamium limestones of the main strand, the carbonate mass weakly passes moisture, and the main process of weathering occurs due to surface corrosion. The accumulation of secondary carbonates in the form of mycelium and veins is characteristic on the slopes of the Tovtry (mostly in brown rendzinas and pararendzinas), due to the vertical and lateral migration flows of the dissolved forms of CaCO3. Key words: rendzinas, Podilski Tovtry, carbonates, carbonate profile.
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Kashurin, R., S. Gerasev, and A. Suslov. "Study of the Solubility of Sediments of Certain Lantanoids in Carbonate Solutions." Bulletin of the South Ural State University series "Chemistry" 12, no. 4 (2020): 63–71. http://dx.doi.org/10.14529/chem200403.
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The study examines the dissolution process for the precipitates of the rare-earth carbonates and phosphates with a change in the concentration parameters of the system. The objective of the study is to determine the nature of the dissolution process at variable composition of the studied solutions. As a result of the theoretical base analysis, the qualitative and quantitative content of rare-earth metals in red sludge and phosphogypsum is presented, which governs the interest in this problem under consideration. The available techniques for extraction of rare-earth metals from red sludge and phosphogypsum have also been considered, their advantages and disadvantages are presented. A promising carbonate-alkali method for the extraction of rare-earth metals has been considered. Thermodynamic parameters of the system have been calculated to determine the possibility of the process. During the experiment the factors affecting the dissolution process have been examined: the carbonate ion concentration, the nature of the solvent cation and rare-earth metal cation. Carbonates and phosphates of europium, holmium, and neodymium have been considered as the analyzed components. Carbonates and phosphates of neodymium, europium, and holmium have been dissolved in model solutions of K2CO3 with the concentrations of 0.2–4.5 mol/L until reaching equilibrium. The obtained results show the dependence of solubility of the precipitates of rare-earth metals on the solvent nature and concentration. The explored data are presented as solubility isotherms. On the basis of experimental data the values of the extraction degree of a rare-earth metal into the solution have been calculated. For neodymium, europium, and holmium carbonates, the maximum recovery degree αmax is 72.8 %, 81.2 %, 83.0 %, respectively. During the experiment with dissolution of lanthanide phosphates, the following results have been obtained: the maximal degree of neodymium extraction is 60.59%, while for europium it equals 51.66 % and 93.01 % for holmium
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Kamgaing, Théophile. "Précipitation de carbonates de cations divalents dans les systèmes lacustres : intérêt, état des connaissances des mécanismes et suggestions (Revue critique de la littérature)." Revue des sciences de l’eau 28, no. 2 (July 7, 2015): 81–102. http://dx.doi.org/10.7202/1032292ar.
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Les carbonates de fer, de manganèse, de calcium et de magnésium précipités en solution des lacs sont documentés. Indicateurs de climat et de variation des caractéristiques chimiques des lacs, ils sont de plus en plus recherchés dans les sédiments. Souvent incomplets, les mécanismes de leur précipitation dans la colonne d’eau du lac et dans les eaux interstitielles sont reprécisés dans cette étude. D’après la littérature, la sidérite et la rhodochrosite précipitent en milieu réducteur saturé de carbonate de fer et de carbonate de manganèse respectivement. Ces prévisions sont confirmées dans cette étude, le potentiel redox étant un paramètre déterminant pour la précipitation du carbonate de fer. Toutefois, la littérature ne décrit pas suffisamment l’origine (géochimique ou biologique) des éléments constitutifs des solides carbonatés lacustres, encore moins les phénomènes qui stabilisent ces derniers ou les rendent vulnérables (dissolution). Cette étude apporte plus de précisions à l’endogènèse de ces carbonates, l’origine de leurs éléments constitutifs étant prise en compte. Elle montre que le caractère de l’eau (agressif ou incrustant) pourrait avoir un impact considérable sur le devenir de ces carbonates. Ainsi un dégazage forcé d’un lac rendrait ses eaux incrustantes, caractère idéal pour la précipitation des carbonates, mais néfaste à la stabilité des strates qui changent de composition après précipitation d’espèces chimiques. Par conséquent, tout projet de dégazage de lac devrait prendre en considération ce paramètre (caractère de l’eau) dans sa conception, sa mise en oeuvre et son exploitation.
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Toffolo, Michael B. "Radiocarbon Dating of Anthropogenic Carbonates: What Is the Benchmark for Sample Selection?" Heritage 3, no. 4 (November 24, 2020): 1416–32. http://dx.doi.org/10.3390/heritage3040079.
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Anthropogenic carbonates are pyrotechnological products composed of calcium carbonate, and include wood ash, lime plaster/mortar, and hydraulic mortar. These synthetic materials are among the first produced by humans, and greatly influenced their biological and cultural evolution. Therefore, they are an important component of the archeological record that can provide invaluable information about past lifeways. One major aspect that has been long investigated is the possibility of obtaining accurate radiocarbon dates from the pyrogenic calcium carbonate that makes up most of these materials. This is based on the fact that anthropogenic carbonates incorporate atmospheric carbon dioxide upon the carbonation of hydrated lime, and thus bear the radiocarbon signature of the atmosphere at a given point in time. Since plaster, mortar, and ash are highly heterogeneous materials comprising several carbon contaminants, and considering that calcium carbonate is prone to dissolution and recrystallization, accurate dating depends on the effectiveness of protocols aimed at removing contaminants and on the ability to correctly identify a mineral fraction that survived unaltered through time. This article reviews the formation and dissolution processes of pyrogenic calcium carbonate, and mineralogical approaches to the definition of a ‘dateable fraction’ based on its structural properties.
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Song, Jinmin, Shugen Liu, Hairuo Qing, Luba Jansa, Zhiwu Li, Ping Luo, Di Yang, Wei Sun, Hanlin Peng, and Tong Lin. "The depositional evolution, reservoir characteristics, and controlling factors of microbial carbonates of Dengying Formation in upper Neoprotozoic, Sichuan Basin, Southwest China." Energy Exploration & Exploitation 36, no. 4 (December 9, 2017): 591–619. http://dx.doi.org/10.1177/0144598717743995.
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The Dengying Formation of Neoprotozoic age deposited in north Sichuan Basin, China, is dominated by dolomitic strata containing microbial carbonates. Thirteen cyanobacteria forms, one oncolite and two stromatolitic structures have been identified. Different microfacies may be related to different microbe forms or assemblages as well as depositional environments. Potential hydrocarbon reservoirs in microbial carbonates are of low porosity and permeability. Microbialites develop in the members Z2 dn1, Z2 dn2, and Z2 dn4. The member Z2 dn1 and Z2 dn2 lying in the lower part, dominated by thrombolitic and spongiostromata dolostone, with three reservoir intervals of overall 190 m thick. Laminite and stromatolitic dolostone are the most important in member Z2 dn4, with three reservoir intervals of 119 m thick. Microbial carbonate reservoirs in members Z2 dn1 and Z2 dn2 were effected by two stages of fresh water dissolution, three stages of burial dissolution, and one stage of hydrocarbon invasion. But one stage of fresh water dissolution, two stages of burial dissolution, and three stages of hydrocarbon invasion modified the reservoirs of member Z2 dn4. The dominant factors for microbial reservoirs were microbial textures and development of Mianyang-Changning intracratonic sag.
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Lindroos, Alf, Jan Heinemeier, Åsa Ringbom, Mats Braskén, and Ámy Sveinbjörnsdóttir. "Mortar Dating Using AMS 14C and Sequential Dissolution: Examples from Medieval, Non-Hydraulic Lime Mortars from the Åland Islands, SW Finland." Radiocarbon 49, no. 1 (2007): 47–67. http://dx.doi.org/10.1017/s0033822200041898.
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Non-hydraulic mortars contain datable binder carbonate with a direct relation to the time when it was used in a building, but they also contain contaminants that disturb radiocarbon dating attempts. The most relevant contaminants either have a geological provenance and age or they can be related to delayed carbonate formation or devitrification and recrystallization of the mortar. We studied the mortars using cathodoluminescence (CL), mass spectrometry (MS), and accelerator mass spectrometry (AMS) in order to identify, characterize, and date different generations of carbonates. The parameters—dissolution rate, 13C/12C and 18O/16O ratios, and 14C age—were measured or calculated from experiments where the mortars were dissolved in phosphoric acid and each successive CO2 increment was collected, analyzed, and dated. Consequently, mortar dating comprises a CL characterization of the sample and a CO2 evolution pressure curve, a 14C age, and stable isotope profiles from at least 5 successive dissolution increments representing nearly total dissolution. The data is used for modeling the interfering effects of the different carbonates on the binder carbonate age. The models help us to interpret the 14C age profiles and identify CO2 increments that are as uncontaminated as possible. The dating method was implemented on medieval and younger mortars from churches in the Åland Archipelago between Finland and Sweden. The results are used to develop the method for a more general and international use.
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Hadžišehović, Munevera, Nada Miljević, Vojislava Šipka, Dušan Golobočanin, and Radule Popović. "Isotopic Analysis of Groundwater and Carbonate System in the Surdulica Geothermal Aquifer." Radiocarbon 35, no. 2 (1993): 277–86. http://dx.doi.org/10.1017/s003382220006495x.
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We present here results of our investigation of the isotopic chemical composition of groundwater and carbonates in the Surdulica geothermal aquifer, Serbia. We considered the effects of carbonate dissolution and measured 13C, 14C, D, 18O, 3H, field pH, temperature, Na+, Ca2+, Mg2+, HCO−3; and other aqueous species from 30 springs and boreholes. Geothermal waters are supersaturated with calcite. Carbon isotope compositions vary with carbonate mineral dissolution. The δD and δ18O of groundwater samples fit the meteoric water line, and indicate that groundwater is recharged mainly from higher altitudes and the cold season. Different groundwater residence times point out two mechanisms for their formation: fissure flow for young waters and standard diffusion processes for old ones.
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Kasioptas, A., C. Perdikouri, C. V. Putnis, and A. Putnis. "Pseudomorphic replacement of single calcium carbonate crystals by polycrystalline apatite." Mineralogical Magazine 72, no. 1 (February 2008): 77–80. http://dx.doi.org/10.1180/minmag.2008.072.1.77.
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AbstractDuring chemical weathering and natural hydrothermal reactions, apatite can form by replacing calcium carbonates. In hydrothermal experiments in which aragonite and calcite single crystals have been reacted with phosphate solutions, the carbonates are replaced by polycrystalline hydroxylapatite (HAP). In both cases the crystals have retained their overall morphology while their compositions have changed significantly. The HAP appears to have a crystallographic relationship to the parent carbonate crystals. The textural relationships are consistent with an interface-coupled dissolution-precipitation mechanism. Structural relationships and relative molar volumes and solubilities appear to be factors that greatly affect replacement reactions.
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Ahmad, Waqar, Balwant Singh, Ram C. Dalal, and Feike A. Dijkstra. "Carbon dynamics from carbonate dissolution in Australian agricultural soils." Soil Research 53, no. 2 (2015): 144. http://dx.doi.org/10.1071/sr14060.
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Land-use and management practices on limed acidic and carbonate-bearing soils can fundamentally alter carbon (C) dynamics, creating an important feedback to atmospheric carbon dioxide (CO2) concentrations. Transformation of carbonates in such soils and its implication for C sequestration with climate change are largely unknown and there is much speculation about inorganic C sequestration via bicarbonates. Soil carbonate equilibrium is complicated, and all reactants and reaction products need to be accounted for fully to assess whether specific processes lead to a net removal of atmospheric CO2. Data are scarce on the estimates of CaCO3 stocks and the effect of land-use management practices on these stocks, and there is a lack of understanding on the fate of CO2 released from carbonates. We estimated carbonate stocks from four major soil types in Australia (Calcarosols, Vertosols, Kandosols and Chromosols). In >200-mm rainfall zone, which is important for Australian agriculture, the CaCO3-C stocks ranged from 60.7 to 2542 Mt at 0–0.3 m depth (dissolution zone), and from 260 to 15 660 Mt at 0–1.0 m depth. The combined CaCO3-C stocks in Vertosols, Kandosols and Chromosols were about 30% of those in Calcarosols. Total average CaCO3-C stocks in the dissolution zone represented 11–23% of the stocks present at 0–1.0 m depth, across the four soil types. These estimates provide a realistic picture of the current variation of CaCO3-C stocks in Australia while offering a baseline to estimate potential CO2 emission–sequestration through land-use changes for these soil types. In addition, we provide an overview of the uncertainties in accounting for CO2 emission from soil carbonate dissolution and major inorganic C transformations in soils as affected by land-use change and management practices, including liming of acidic soils and its secondary effects on the mobility of dissolved organic C. We also consider impacts of liming on mineralisation of the native soil C, and when these transformations should be considered a net atmospheric CO2 source or sink.
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Kashurin, R. R., T. E. Litvinova, I. T. Zhadovskij, and M. E. Titova. "Dissolution of Carbonates and Hydroxides of Rare-Earth Metals in Carbonate Solutions." Вестник Санкт-Петербургского государственного университета технологии и дизайна. Серия 1: Естественные и технические науки, no. 3 (2020): 98–101. http://dx.doi.org/10.46418/2079-8199_2020_3_14.
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Bathurst, R. G. C. "Conference on Precipitation, Deformation and Dissolution of Carbonates." Geological Journal 16, no. 2 (April 30, 2007): 154–55. http://dx.doi.org/10.1002/gj.3350160209.
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Gehlen, M., F. C. Bassinot, L. Chou, and D. McCorkle. "Reassessing the dissolution of marine carbonates: I. Solubility." Deep Sea Research Part I: Oceanographic Research Papers 52, no. 8 (August 2005): 1445–60. http://dx.doi.org/10.1016/j.dsr.2005.03.010.
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Henrich, Rüdiger, and Gerold Wefer. "Dissolution of biogenic carbonates: Effects of skeletal structure." Marine Geology 71, no. 3-4 (May 1986): 341–62. http://dx.doi.org/10.1016/0025-3227(86)90077-0.
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Shaheen, Robina, Paul B. Niles, Kenneth Chong, Catherine M. Corrigan, and Mark H. Thiemens. "Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere." Proceedings of the National Academy of Sciences 112, no. 2 (December 22, 2014): 336–41. http://dx.doi.org/10.1073/pnas.1315615112.
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Carbonate minerals provide critical information for defining atmosphere–hydrosphere interactions. Carbonate minerals in the Martian meteorite ALH 84001 have been dated to ∼3.9 Ga, and both C and O-triple isotopes can be used to decipher the planet’s climate history. Here we report Δ17O, δ18O, and δ13C data of ALH 84001 of at least two varieties of carbonates, using a stepped acid dissolution technique paired with ion microprobe analyses to specifically target carbonates from distinct formation events and constrain the Martian atmosphere–hydrosphere–geosphere interactions and surficial aqueous alterations. These results indicate the presence of a Ca-rich carbonate phase enriched in 18O that formed sometime after the primary aqueous event at 3.9 Ga. The phases showed excess 17O (0.7‰) that captured the atmosphere–regolith chemical reservoir transfer, as well as CO2, O3, and H2O isotopic interactions at the time of formation of each specific carbonate. The carbon isotopes preserved in the Ca-rich carbonate phase indicate that the Noachian atmosphere of Mars was substantially depleted in 13C compared with the modern atmosphere.
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Rocha, Emilia Fernandes de Medeiros, Osvair Vidal, Erika Tomie Koroishi, Janeth Alina Vidal Vargas, and Luis Fernando Lamas de Oliveira. "Porosity Alteration of Carbonates by CO2-Enriched Brine Injection." Materials Science Forum 965 (July 2019): 69–77. http://dx.doi.org/10.4028/www.scientific.net/msf.965.69.
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Carbon dioxide (CO2) is considered one of the main gases that cause global warming. In this perspective, its injection in aquifers and oil and gas reservoirs has been a possible alternative to reduce its emission in the atmosphere. An alternative strategy in which CO2 is used efficiently in the Oil Industry is the Carbonated Water Injection (CWI), where the carbon dioxide is injected through the reservoir dissolved in the brine, eliminating problems of gravitational segregation and low sweeping efficiency present in other gas injection methods. Once injected, the fluid may react with the carbonate rock and inducing their dissolution, causing changes in the petrophysical properties of the rock. This work investigated changes in the average porosity of carbonate samples from Brazilian reservoir through a dynamic flow test with enriched brine with 100% CO2 injection under high pressure and high temperature conditions and simulating a region around the face of the injector well, with an injection pressure of 8,500 psi, a temperature of 70 °C and a flow rate of 2cm3/min. The core-flooding experimental setup includes two coreholders arranged in series with samples confined in its interior, which are swept by X-ray Computed Tomography (CT), taking measurements of average porosity data. The results showed that there was dissolution in the sample assembled in the first coreholder since the porosity had increased, while in the second, no significant alterations of the porosity were observed (around 8.5% of its initial value). This observation can still be confirmed by the analysis of the dissolved moles, which exhibit behavior similar to the porosity, indicating that some minerals actually suffered dissolution from the injection of carbonated brine.
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Lopez-Aguayo, F., and J. M. Gonzalez Lopez. "Fibrous clays in the Almazan Basin (Iberian Range, Spain): genetic pattern in a calcareous lacustrine environment." Clay Minerals 30, no. 4 (December 1995): 395–406. http://dx.doi.org/10.1180/claymin.1995.030.4.11.
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AbstractThe Tertiary sediments of the southern part of Almazán basin (Province of Soria) exhibit two different facies with a sharp transition between them: (1) a coarse detrital facies; and (2) a lutite and carbonate facies. The vertical evolution of these facies in the different sections and boreholes is made up of several retrograde depositional sequences which evolve from proximal alluvial fans to carbonate lacustrine systems associated with the most distal fan sediments.The variation of the mineralogical association (carbonates, quartz, detrital clay minerals, palygorskite and, occasionally, sepiolite and smectites) allows four ‘mineralogical facies’ to be established. Each facies has a distinctive mineralogy related to the main genetic processes: (1) detrital facies; (2) transitional facies; (3) ‘chemical dolomite-palygorskite’ facies and (4) ‘chemical calcite’ facies. Although the carbonates (calcite and dolomite) are always the most abundant minerals, fibrous clay minerals are also important. The main mechanism of mineral authigenesis in this basin is chemical precipitation; the presence and distribution of carbonates and fibrous clay minerals is controlled by the relative concentrations of [Mg2+], [Ca2+], pCO2, pH and [SiO4H4]. Palygorskite occurrences, in these conditions, are related to dissolution-precipitation mechanisms of pre-existing detrital material.
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Dubiel, Stanisław, Adam Zubrzycki, Czesław Rybicki, and Michał Maruta. "Application of Dst Interpretation Results by Log – Log Method in the Pore Space Type Estimation for the Upper Jurassic Carbonate Reservoir Rocks of the Carpathian Foredeep Basement / Interpretacja Testów Wykonywanych Rurowymi Próbnikami Złoża – Rpz w Skałach Węglanowych Górnej Jury Podłoża Zapadliska Przedkarpackiego." Archives of Mining Sciences 57, no. 2 (November 12, 2012): 413–24. http://dx.doi.org/10.2478/v10267-012-0027-0.
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Abstract In the south part of the Carpathian Foredeep basement, between Bochnia and Ropczyce, the Upper Jurassic (Oxfordian, Kimmeridian and Tithonian) carbonate complex plays important role as a hydrocarbon bearing formation. It consists of shallow marine carbonates deposited in environments of the outer carbonate ramp as reef limestones (dolomites), microbial - sponge or coral biostromes and marly or micrite limestones as well. The inner pore space system of these rocks was affected by different diagenetic processes as calcite cementation, dissolution, dolomitization and most probably by tectonic fracturing as well. These phenomena have modified pore space systems within limestone / dolomite series forming more or less developed reservoir zones (horizons). According to the interpretation of DST results (analysis of pressure build up curves by log - log method) for 11 intervals (marked out previously by well logging due to porosity increase readings) within the Upper Jurassic formation 3 types of pore/fracture space systems were distinguished: - type I - fracture - vuggy porosity system in which fractures connecting voids and vugs within organogenic carbonates are of great importance for medium flow; - type II - vuggy - fracture porosity system where a pore space consists of weak connected voids and intergranular/intercrystalline pores with minor influence of fractures; - type III - cavern porosity system in which a secondary porosity is developed due to dolomitization and cement/grain dissolution processes.
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Shoesmith, D. W., M. G. Bailey, and P. Taylor. "Anodic oxidation of lead in aqueous carbonate solutions. II. Film formation and dissolution in the pH range 9 to 14." Canadian Journal of Chemistry 66, no. 11 (November 1, 1988): 2941–46. http://dx.doi.org/10.1139/v88-454.
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The anodic oxidation of lead has been studied in aqueous carbonate solutions at pH values in the range 9 ≤ pH ≤ 14. The solid films formed on the electrode surface have been identified by X-ray diffractometry. The dissolution and film formation processes have been studied by a number of electrochemical techniques at rotating disk electrodes. The anodic oxidation process can be divided into two distinct regions. In the main anodic oxidation process, a variety of surface phases is formed. The nature of the phase formed is pH-dependent. Plumbonacrite (Pb10O(OH)6(CO3)6) formation is observed at all pH values and predominates at pH ≥ 13. At pH < 11, cerussite (PbCO3) is the predominant phase, whereas at intermediate pH values, hydrocerussite (Pb3(OH)2(CO3)2) predominates. The dissolution rate of Pb2+ species from the electrode surface is directly proportional to the solubility of the predominant phase present. At more positive potentials, a reactivation, involving increased dissolution and a further stage of film formation, is observed. Litharge (PbO) is observed to grow underneath the initially formed basic lead carbonates. Dissolution occurs either by the field-assisted dissolution of the base-layer on the electrode or by metal dissolution through faults in the base-layer.
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Liu, L. H., Y. S. Ma, B. Liu, and C. L. Wang. "Hydrothermal dissolution of Ordovician carbonates rocks and its dissolution mechanism in Tarim Basin, China." Carbonates and Evaporites 32, no. 4 (July 23, 2016): 525–37. http://dx.doi.org/10.1007/s13146-016-0309-2.
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El Howayek, Alain, Antonio Bobet, and Marika Santagata. "Microstructure and cementation of two carbonatic fine-grained soils." Canadian Geotechnical Journal 56, no. 3 (March 2019): 320–34. http://dx.doi.org/10.1139/cgj-2018-0059.
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This paper presents an investigation of the microstructure and cementation of two carbonatic fine-grained soils obtained from a deposit of lacustrine origin formed during the Wisconsin glaciation. The two soils differ in the degree of cementation (with average total carbonate contents of ∼55% and ∼38%), the dominating carbonate mineral (calcite versus dolomite), and the forms of carbonates present. The study is founded on observations of the microstructure using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray (EDX) spectrometry, and examination of the effects of carbonate dissolution on Atterberg limits and particle-size distribution. In both soils, the majority of the carbonate is in the form of a coating layer on the clay and silt particles, with a thickness less than 2–3 μm, and decreasing in the sample with lower carbonate content. This coating layer “networks” particles and groups of particles. Carbonate cementation impacts the engineering properties of both soils, and the site’s overconsolidation ratio (OCR) profile clearly reflects changes in carbonate content and microstructure. One-dimensional compression tests show that cementation is associated with a moderate degree of structuring, and that the resulting structure is stable, with no complete destructuration occurring even after the effective stress exceeds 10 times the preconsolidation stress.
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Pokrovsky, O. S., and J. Schott. "Surface Chemistry and Dissolution Kinetics of Divalent Metal Carbonates." Environmental Science & Technology 36, no. 3 (February 2002): 426–32. http://dx.doi.org/10.1021/es010925u.
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Gehlen, M., F. C. Bassinot, L. Chou, and D. McCorkle. "Reassessing the dissolution of marine carbonates: II. Reaction kinetics." Deep Sea Research Part I: Oceanographic Research Papers 52, no. 8 (August 2005): 1461–76. http://dx.doi.org/10.1016/j.dsr.2005.03.011.
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Kalia, Nitika, and Vemuri Balakotaiah. "Effect of medium heterogeneities on reactive dissolution of carbonates." Chemical Engineering Science 64, no. 2 (January 2009): 376–90. http://dx.doi.org/10.1016/j.ces.2008.10.026.
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Renard, François, Anja Røyne, and Christine V. Putnis. "Timescales of interface-coupled dissolution-precipitation reactions on carbonates." Geoscience Frontiers 10, no. 1 (January 2019): 17–27. http://dx.doi.org/10.1016/j.gsf.2018.02.013.
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Castro, Diana Maria Hernandez, Janeth Alina Vidal Vargas, Erika Tomie Koroishi, Luis Fernando Lamas de Oliveira, and Osvair Vidal Trevisan. "Porosity and Permeability Alteration of Carbonates by CO2-Enriched Brine Injection." Materials Science Forum 965 (July 2019): 107–15. http://dx.doi.org/10.4028/www.scientific.net/msf.965.107.
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Some carbonate reservoirs are known for their high CO2 content in oil. One possibility to handle this gas without environmental problems is to reinject it into the reservoir. Injection of carbonated water has been drawing attention because it is an advantageous technique when compared to gaseous CO2 injection, due to its improvement in mobility in the reservoir. The objective of this study is to evaluate the phenomenon of dissolution and precipitation during carbonated water injection in carbonate rocks. These effects are identified by analyzing the porosity variations through X-ray computer tomography images and permeability profile, determined indirectly by pressure transducers that measured the differential pressure by the fluid at the inlet and outlet of the core holders. The Coreflooding test were carried out with two core holders in series to represent a near region at the reservoir by the injection of brine saturated with 25% of CO2 in reservoir samples, composed of dolomite, calcite and clay. The test were performed using the following reservoir conditions of 8,500 psi at 70°C. Based on the experimental data provided by CT images, it can be seen that the core porosity increases or decrease during carbonated water injection due to coexistence of dissolution (increase of porosity) and precipitation (decrease of porosity) along the samples. These phenomena are observed in regions with high heterogeneity in porosity. In addition, the mineralogy of the cores is composed by three minerals, which influence in the capacity of reaction with carbonated water. For the experiment, the core placed in the core holder one presented a porosity increase and the second one decreased. On the other hand, the permeability showed a significant increase for both cores, it is believed that, the injection promoted a preferential way flow (wormhole) that affected considerably the permeability of the rock. The novelty of the investigation is that the experiments were carried out using Brazilian pre-salt carbonate reservoir rocks with mineralogy composed basically by dolomite, calcite and clay. Also, experimental work was performed at reservoir operational conditions.
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Yoo, Jongchan, Heeyoung Shin, and Sangwoo Ji. "Evaluation of the Applicability of Concrete Sludge for the Removal of Cu, Pb, and Zn from Contaminated Aqueous Solutions." Metals 8, no. 9 (August 25, 2018): 666. http://dx.doi.org/10.3390/met8090666.
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In this study, the possibility of using concrete-sludge recycling as an immobilizer, including dried sludge (DS), precipitated calcium carbonate (PCC), and calcite-coated particles (CCP), was evaluated for the remediation of Cu-, Pb-, and Zn-contaminated aqueous solutions. Experimental variables characterizing immobilization, including reaction time, initial solution pH, and immobilizer dosage, were selected. After DS was applied, 98.3% of Cu, 99.9% of Pb, and 95.2% of Zn were removed via metal-hydroxide coprecipitation onto the surface of DS, which increased in pH within the shortened contact time. On the contrary, PCC and CCP removed metals (above 99.9% removal) via the formation of metal carbonates, which was highly dependent on both the pH and the carbonates released from the immobilizers. The acidic solution pH contributed to the dissolution of calcite (leading to an increase in carbonates in solution), thus enhancing the removal of metals. An increase in PCC and CCP dosage (liquid to solid ratio of 1000 to 100) was effective in removing Cu with an increasing final pH and number of carbonates in solution. Our results show that concrete sludge can be recycled to reduce environmental loads, including alkaline wastewater discharge, waste disposal, CO2 emissions, and metal-contaminated aqueous solutions.
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Prognon, François, Isabelle Cojan, Pascal Kindler, Médard Thiry, and Michel Demange. "Mineralogical evidence for a local volcanic origin of the parent material of Bermuda Quaternary paleosols." Quaternary Research 75, no. 1 (January 2011): 256–66. http://dx.doi.org/10.1016/j.yqres.2010.08.002.
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AbstractThe alternation of carbonate deposits and paleosols compose the emerged part of the Bermuda archipelago. The pedological units present a complex and diversified mineralogy. Former studies demonstrated that the paleosols are not primarily a product of the unique dissolution of the surrounding carbonates, but contain a massive input of allochthonous non-carbonate detrital material. Researchers during more than the past three decades have attributed this flux of insoluble residues (IR) to Saharan dusts. We carried out systematic field and mineralogical analyses on the Quaternary paleosols from the Bermuda archipelago. Their mineralogical assemblage predominantly includes carbonates, clay minerals (kaolinite, chlorite and chlorite/vermiculite), phosphates, and aluminium and iron oxides/hydroxides. This assemblage is strikingly close to the mineralogy of the weathered volcanic substrate of Bermuda, but noticeably different from the mineralogy of Saharan dust. Moreover, we found volcanic lithoclasts in numerous paleosol profiles all over the archipelago and in all the recorded time intervals. We thus consider the volcanic seamount underlying Bermuda as the main source of non-carbonate minerals detected in the paleosols. This hypothesis further resolves the anomalous maturity of Bermudan paleosols compared to their southern counterparts in the Bahamas and Barbados.
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Aubert, Irène, Philippe Léonide, Juliette Lamarche, and Roland Salardon. "Diagenetic evolution of fault zones in Urgonian microporous carbonates, impact on reservoir properties (Provence – southeast France)." Solid Earth 11, no. 4 (July 5, 2020): 1163–86. http://dx.doi.org/10.5194/se-11-1163-2020.
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Abstract. Microporous carbonate rocks form important reservoirs with permeability variability depending on sedimentary, structural, and diagenetic factors. Carbonates are very sensitive to fluid–rock interactions that lead to secondary diagenetic processes like cementation and dissolution capable of modifying the reservoir properties. Focusing on fault-related diagenesis, the aim of this study is to identify the impact of the fault zone on reservoir quality. This contribution focuses on two fault zones east of La Fare anticline (SE France) crosscutting Urgonian microporous carbonates. Overall, 122 collected samples along four transects orthogonal to fault strike were analyzed. Porosity values have been measured on 92 dry plugs. Diagenetic elements were determined through the observation of 92 thin sections using polarized light microscopy, cathodoluminescence, carbonate staining, SEM, and stable isotopic measurements (δ13C and δ18O). Eight different calcite cementation stages and two micrite micro-fabrics were identified. As a main result, this study highlights that the two fault zones acted as drains canalizing low-temperature fluids at their onset and induced calcite cementation, which strongly altered and modified the local reservoir properties.
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Kim, Y. J., Sung Baek Cho, Ill Yong Kim, and Chikara Ohtsuki. "Preparation of Hydroxyapatite Honeycomb through Dissolution-Precipitation Reaction under Hydrothermal Condition." Key Engineering Materials 720 (November 2016): 203–6. http://dx.doi.org/10.4028/www.scientific.net/kem.720.203.
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Hydroxyapatite (Ca10(PO4)6(OH)2) can be obtained from calcium carbonates through dissolution-precipitation reaction in a phosphate solution under a hydrothermal condition, with keeping its external shape. In this study, we assumed preparation of hydroxyapatite honeycombs from a calcite (CaCO3) honeycomb. Calcite honeycomb was hydrothermally treated in a phosphate solution. After hydrothermal processing for 24 h, calcite transformed partially to hydroxyapatite phase and its external shape was kept. Moreover, specific surface areas of the specimens were increased after the hydrothermal processing. Consequently, this processing is useful to prepare honeycomb structure of hydroxyapatite from calcium carbonates.
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Zhang, Xiaohang, Shijun Wu, and Fanrong Chen. "Nano Precipitates Formed during the Dissolution of Calcite Incorporated with Cu and Mn." Minerals 8, no. 11 (October 25, 2018): 484. http://dx.doi.org/10.3390/min8110484.
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Calcite is often doped with impurity ions that affect its dissolution behavior. In the present investigation, solid solutions of (Ca, Mn)CO3 and (Ca, Cu)CO3 were synthesized by coprecipitation to study their dissolution in an acidic solution (pH = 5) at 25 °C. The solution chemical analysis results showed that the concentrations of aqueous Cu2+ and Mn2+ first increased and then decreased with the extension of dissolution time. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations revealed that rhodochrosite (MnCO3) and malachite (Cu2(OH)2CO3) formed during the dissolution. This suggested that the impurities in calcite might impact the dissolution and precipitation of carbonates in the environment.
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Long, D. G. F. "Ella Bay Formation: Early Cambrian shelf differentiation in the Franklinian basin, central eastern Ellesmere Island, Arctic Canada." Canadian Journal of Earth Sciences 26, no. 12 (December 1, 1989): 2621–35. http://dx.doi.org/10.1139/e89-223.
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Strata of the Lower Cambrian (Atdabanian) Ella Bay Formation reflect progradation and exposure of a rimmed carbonate platform, subject to intermittent introduction of siliciclastic material from an inshore coastal sand belt or fluviodeltaic source. Initial rapid progradation of platformal carbonates was related to late rift subsidence. Stabilization of depositional sites of oolitic and stromatolitic platform marginal carbonates during middle and late Ella Bay times reflects the earliest phase of differential subsidence of the platform and deep-water basin within the Franklinian mobile belt. Carbonate strata landward of the rim accumulated in a protected shelf setting that was for the most part below effective storm wave base. Towards the end of Ella Bay times, the outer rim became emergent as a result of differential rotation along listric faults as the continental margin began to subside in response to early sea-floor spreading. Dissolution of carbonates along the outer rim during this phase led to the development of distinctive breccia-conglomerates as cave and karst fill. Carbonate production in the lagoon became highly restricted as siliciclastics derived from the inshore clastic belt flooded the area. The pronounced change in style between the Ella Bay Formation and overling clastics of the Ellesmere Group, which consists of a thick sequence of northwesterly prograding clastic wedges, may reflect a change to more rapid subsidence as the ocean began to spread. The local unconformity between the Ella Bay Formation and the Ellesmere Group is thus interpreted as a breakup unconformity.
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Huang, Tianming, and Baoqiang Ma. "The Origin of Major Ions of Groundwater in a Loess Aquifer." Water 11, no. 12 (November 23, 2019): 2464. http://dx.doi.org/10.3390/w11122464.
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When groundwater represents most of the world’s reserves of unfrozen freshwaters, water quality is commonly a limiting factor in quantifying usable fresh groundwater storage, especially in arid and semi-arid areas. Tracing the origin of major ions is important to the understanding of hydrochemical evolution and water–rock interaction. Strontium (Sr) and calcium (Ca) are geochemically similar in terms of ionic radius and ionic charge and can substitute for each other in mineral lattices such as in carbonates and silicates. This allows the use of Sr as a proxy for Ca during water–rock interaction. Geochemical mass balance and carbon and strontium isotope techniques were employed to study the origin of each major ion (such as Na, Ca, Mg, Cl, and SO4) in a loess aquifer (there is 10% to 20% of carbonate in the loess). Geochemical mass balance between atmospheric deposition and groundwater shows that the Cl (average concentration of 5.5 mg/L) and SO4 (average concentration of 6.8 mg/L) in groundwater originated from atmospheric deposition. The dissolution of loess using acetic acid was used to analyze the 87Sr/86Sr ratio of carbonate (mainly deposited in continental environments). Groundwater 87Sr/86Sr ratios (0.710677 to 0.712319) are consistent with 87Sr/86Sr ratios in carbonate (0.710329 to 0.711085) but are significantly lower than the whole-rock (0.715136 to 0.717155) and residue (0.719091 to 0.720438), suggesting that Ca and Mg mainly originated from the dissolution of carbonate in the loess aquifer. However, Na originated from the dissolution of albite, suggesting saturation controls the ability of dissolution. There are cation exchanges between Ca + Mg and Na, resulting in Na concentration increases and Ca + Mg concentration decreases in groundwater. This study is important to the understand of the origin of the major ions in groundwater and the geochemical processes in silicate-carbonate aquifers.
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van Noort, Reinier, Pål Mørkved, and Siv Dundas. "Acid Neutralization by Mining Waste Dissolution under Conditions Relevant for Agricultural Applications." Geosciences 8, no. 10 (October 16, 2018): 380. http://dx.doi.org/10.3390/geosciences8100380.
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The acidification of agricultural soils in high rainfall regions is usually countered by the application of finely ground calcite or dolomite. As this carbonate dissolves, soil pH is raised, but CO2 is released. Mining activities often produce large quantities of very fine silicate rock-derived powders that are commonly deposited in stockpiles. However, the dissolution of such powders can also result in an increase in pH, without any direct release of CO2. Of particular interest are those silicate powders that have a high reactivity and higher capacity for raising pH. In this contribution, we report experimental work addressing the dissolution of various silicate rock-derived powders that were produced during mining activities in Norway under conditions that were representative of weathering in agricultural soils. Three different powders—derived from Åheim dunite, Stjernøya nepheline syenite, or Tellnes ilmenite norite—were exposed to different acids at pH 4 in unstirred flow cells, and dissolution or leaching kinetics were determined from the changes in the fluid composition. Based on these kinetics, pH neutralization rates were determined for the individual powders and compared to expected values for carbonates. Based on this comparison, it is concluded that the application of silicate rock-derived powder dissolution to replace carbonate-based liming may not be feasible due to slower reaction rates, unless larger quantities of a finer particle size than normal are used. The application of larger volumes of slower-reacting silicates may have the additional benefit of reducing the required frequency of liming.
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Stachnik, Łukasz, Jacob C. Yde, Marta Kondracka, Dariusz Ignatiuk, and Magdalena Grzesik. "Glacier naled evolution and relation to the subglacial drainage system based on water chemistry and GPR surveys (Werenskioldbreen, SW Svalbard)." Annals of Glaciology 57, no. 72 (May 16, 2016): 19–30. http://dx.doi.org/10.1017/aog.2016.9.
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ABSTRACTGlacier naledi are extrusive ice masses that appear in front of glaciers as a consequence of refreezing of meltwater seepage during the accumulation season. These structures provide a unique opportunity to understand subglacial drainage activity during the accumulation season; however, only few detailed studies have previously focused on their characteristics. Here, we investigated glacier-derived naled assemblages in the proglacial zone of the polythermal glacier Werenskioldbreen (27.4 km2) in SW Svalbard. We determined the spatial distribution of naledi using ground penetrating radar surveys. The main subglacial drainage pattern was related to a channel under the medial moraine, and three sources are linked to a distributed subglacial drainage network. The relation between atmospherically-corrected (Ca2+ + Mg2+) and (SO42−) in sub-naled waters was closely related to sulphide oxidation coupled with carbonate dissolution (r = 0.99; slope = 1.6). This is consistent with the local lithology, which is dominated by schist containing carbonates. We also found high carbonate saturation indices in pale white ice layers within the naled. We conclude that sulphide oxidation coupled with carbonate dissolution is the dominant chemical weathering process in the subglacial drainage system of Werenskioldbreen during the accumulation season.
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Wu, Guanghui, En Xie, Yunfeng Zhang, Hairuo Qing, Xinsheng Luo, and Chong Sun. "Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China." Minerals 9, no. 6 (June 13, 2019): 360. http://dx.doi.org/10.3390/min9060360.
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The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence and their fault controls for Ordovician carbonates in the northern Tarim intracratonic basin in NW China (Halahatang area). In contrast to the uniform nature of diagenesis observed in country rocks, there is a relatively complicated style of compaction and pressure solution, multiple fracturing, and cementation and dissolution history along the carbonate fault damage zones. The relative paragenetic sequence of the structure related diagenesis suggests three cycles of fracture activities, following varied fracture enlargement and dissolution, and progressively weaker calcite cementation. These processes of structure related diagenesis are constrained to the fault damage zones, and their variation is affected by the fault activities. The results of this study suggest that the carbonate reservoir and productivity could be impacted by the structure related diagenesis locally along the fault damage zones.
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Watson, M. N., C. J. Boreham, and P. R. Tingate. "CARBON DIOXIDE AND CARBONATE CEMENTS IN THE OTWAY BASIN: IMPLICATIONS FOR GEOLOGICAL STORAGE OF CARBON DIOXIDE." APPEA Journal 44, no. 1 (2004): 703. http://dx.doi.org/10.1071/aj03035.
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Understanding CO2 source and carbonate cements in natural gas accumulations is important for predicting the behaviour of anthropogenic CO2 in a reservoir system. The Otway Basin offers an excellent opportunity to examine late CO2-derived cements as an analogue for mineralogical storage of CO2. Understanding Otway Basin diagenesis and carbonate cement distribution is also of great significance to petroleum production in the region.Elemental and textural examination of Otway Basin cements has identified five carbonates in reservoir rock from CO2-rich gas accumulations. These carbonates show an overall increase in Fe2+ and Mg2+ relative to the calcites in CO2-free reservoir rock, indicating cation derivation from CO2 interaction with labile minerals.δ13C isotopes of 2.18‰ to -6.7‰ PDB from late carbonate cements in reservoirs containing CO2, confirm an inorganic CO2 origin. 3He/4He gas isotopic ratios of R/Ra > 1 indicate a predominantly mantle input for the CO2-rich accumulations.Degassing of magma associated with Pleistocene to Recent volcanics is suggested as the dominant, CO2 source for the existing CO2 accumulations. CO2 influx from the magmatic source was rapid, and is the most analogous scenario to injection of anthropogenic CO2. Natural influx of CO2 and the opportunity for mineralisation of CO2 is variable, with CO2 dissolving some original carbonate and precipitation dependant on pH, ρCO2, and available cations. Positive mineralogical CO2 storage occurs in the Pretty Hill Formation, due to a higher content of labile lithic minerals, with ~36 kg/m3 of CO2 (~48 kg/m3 carbonate) stored in the Ladbroke Grove Field from the current CO2 phase. The Waarre Sandstone has negative mineralogical storage of CO2, with less carbonate than similar reservoir rock without CO2, and therefore more CO2 being released from dissolution of early carbonates.
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Aldhayee, Khaled, Mahmoud T. Ali, and Hisham A. Nasr-El-Din. "Modeling Wormhole Propagation During Closed-Fracture-Acidizing Stimulation in Tight-Carbonate Formations." SPE Journal 25, no. 05 (July 13, 2020): 2373–400. http://dx.doi.org/10.2118/201252-pa.
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Summary Closed-fracture acidizing (CFA) is a well-stimulation technique that can be applied to stimulate carbonate reservoirs at the end of acid-fracturing treatments. In CFA, acid is injected into the closed fracture at rates lower than the fracturing pressure to enhance the fracture conductivity. The objective of this study is to develop a robust model that can capture the dissolution process and wormhole-propagation phenomena that occur during CFA. This work develops a CFA model using computational-fluid-dynamics (CFD) techniques coupled with a two-scale continuum model that can predict accurately the reactive-flow mechanisms of hydrochloric acid (HCl) in carbonate formations. The developed CFA model is constructed and populated with the actual porosity-distribution profiles of tight carbonates. The model was tested against the experimental work performed on a fracture-conductivity apparatus. Sensitivity analysis is performed for several parameters that affect the performance of CFA in tight-carbonate formations. The developed model has successfully captured the dissolution patterns and wormhole-propagation phenomena that occur during CFA. In calcite formations, high temperatures promote acid leakoff into the formation, resulting in inefficient fracture stimulation. On the contrary, low temperatures reduce the overall reaction kinetics and attenuate the HCl reaction with calcite. Also, simulation results show that high acid concentration is favorable in treating low-conductivity fractures. In dolomite formations, it is essential to adapt a strong-acid system with an extended treatment duration to ensure efficient acid stimulation to the closed fractures. This paper provides a simulation study of the CFA process in a carbonates formation by establishing a 3D CFD model using the two-scale continuum approach. Fracture-surface etching and the associated acid-wormhole behavior during CFA are experimentally validated. This study optimizes the acid volumes and injection rates that can be used in conducting CFA.
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Karoui-Yaakoub, Narjess, Moncef Saïd Mtimet, Mohamed Hédi Negra, Chaima Grira, and Wafa Gusemi. "The Registration of the Mid-Paleocene Biotic Event (MPBE) in Tunisia." Paleontology Journal 2014 (September 18, 2014): 1–5. http://dx.doi.org/10.1155/2014/760436.
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In Tunisia, the Paleocene biomarkers are identified within the El Haria Formation shales. The Selandian is absent in most of the Paleocene outcrops and the Thanetian is unconformable to different stages of the Cretaceous. In the middle of Selandian, with the beginning of the Globanomalina pseudomenardii (P4) zone, we note that the assemblage of planktonic foraminifera becomes very poorly preserved and much less abundant than at the base. It is represented by rare species and there has been a start of the microfauna dissolution tests and an enrichment in iron oxides, silica, and gypsum crystals. The dissolution process is increasing more and more and a drop in the content of carbonates is clearly recorded at the top of Selandian. However, we note that some small benthic foraminifera belonging to the genera Lenticulina and Anomalina escape the dissolution and very few planktonic foraminifera belonging to the genera Subbotina are preserved. This dramatic and abnormal dissolution extends over a considerable thickness. These features could be an expression of the mid-Paleocene biotic event (MPBE), registered for the first time in Tunisia. This intense dissolution is caused probably by the change in the solubility of carbonates, which may be related to the changes in the deep-water circulation or to the change in the productivity of the surface waters.
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Tribollet, A., C. Godinot, M. Atkinson, and C. Langdon. "Effects of elevatedpCO2on dissolution of coral carbonates by microbial euendoliths." Global Biogeochemical Cycles 23, no. 3 (July 18, 2009): n/a. http://dx.doi.org/10.1029/2008gb003286.
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KLEIN, CARLA, and ANA MARIA PIMENTEL MIZUSAKI. "Cimentação Carbonática em Reservatórios Siliciclásticos - O Papel da Dolomita -." Pesquisas em Geociências 34, no. 1 (June 30, 2007): 91. http://dx.doi.org/10.22456/1807-9806.19465.
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Carbonates are important diagenetic cements in siliciclastic rocks thus important to determine these rocks as hydrocarbon reservoirs. The cement is the material had chemically precipitated partial or totally pore filling, affecting rock values of porosity and permeability. The acknowledgment of diagenetic patterns those are associated to the carbonatic cement precipitation and their impacts in the reservoirs quality can decrease the risks of exploration and exploitation of new reservoirs. Therefore is necessary the knowledge of origin and processes of carbonate cement’s precipitation. These cements have distribution patterns, mineralogy, textures and isotopic compositions which vary spatial and temporally, depending of perform conditions in each diagenetic environment. One of the most important diagenetic cement is dolomite and the dolomite’s group is compound by dolomite and ankerite. These minerals can be differentiated by analytical techniques such as optical petrography, staining techniques, cathodoluminescence, scanning electron microscopy and isotopes. Besides that, dolomite cement shape in a reservoir can display different forms: rhombs, poikilotopic and saddle in a variety of dimensions, pore filling, replacing detrital carbonate grains, concretions, nodules or stratified layers. Primaries calcite and aragonite replaced can promote precipitation of dolomite through increase of temperature and by presence of Mg-being fluids. The main entrance conditions to form dolomitic cement are: (i) alkaline solutions from pre-existence rocks weathering or evaporitc environments; (ii) marine waters; (iii) clay alteration; (iv) CaCO3 polymorphs dissolution; (v) dissolution of bioclasts. An interesting example of dolomitic cementation is the Carmópolis Member of the Muribeca Formation, hydrocarbon reservoir of the Camorim Field (Sergipe-Alagoas Basin, northeastern Brazil).
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Khaledialidusti, Rasoul, and Jon Kleppe. "Surface-Charge Alteration at the Carbonate/Brine Interface During Single-Well Chemical-Tracer Tests: Surface-Complexation Model." SPE Journal 23, no. 06 (August 17, 2018): 2302–15. http://dx.doi.org/10.2118/191356-pa.
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Summary Water chemistry has been shown to affect oil recovery by affecting surface charge and rock dissolution. The single-well chemical-tracer (SWCT) test is a field method to measure residual oil saturation (Sor), in which hydrolysis reaction of an ester has been known as a key process that could displace the equilibrium state of a reservoir by changing formation-water (FW) composition. Because oil mobilization during the SWCT tests causes an error in the measurement of Sor, changes in water chemistry might be a concern for the accuracy of Sor measurements. In our previous work, the extent to which different reservoir parameters might change water composition and the effect of water-chemistry changes on the calcite dissolution and the oil liberation from the carbonate-rock surfaces were extensively evaluated. In this study, the effect of water-chemistry changes on surface-charge alteration at the carbonate/brine interface has been studied by constructing and applying a surface-complexation model (SCM) that couples bulk aqueous and surface chemistry. We present how the pH drop induced by the displacement of the equilibrium state and changes in water chemistry in the formation affect surface charge in a pure-calcite carbonate rock during the SWCT tests. The results show that a pH drop during the SWCT tests while calcium concentration is held constant in the FW by ignoring calcite dissolution yields a less-positive/more-negative surface charge so that wettability of carbonate rock might be altered to a less-oil-wetting state, when the oil is negatively charged. In reality, however, calcite dissolves by water-chemistry changes during the SWCT tests, which leads to an increasing calcium concentration in the FW. Consequently, an SWCT test in carbonates is accompanied by increasing calcium concentration while pH drops, which yields an increase in the surface charge of carbonate rocks. Therefore, the pH drop does not directly affect the surface charge of carbonate rock during an SWCT test, and calcium concentration increased from calcite dissolution could control the surface charge more significantly.
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Adelinet, Mathilde, Jean-François Barthélémy, Elisabeth Bemer, and Youri Hamon. "Effective medium modeling of diagenesis impact on the petroacoustic properties of carbonate rocks." GEOPHYSICS 84, no. 4 (July 1, 2019): WA43—WA57. http://dx.doi.org/10.1190/geo2018-0559.1.
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Carbonate formations are highly heterogeneous, and the velocity-porosity relationships are controlled by various microstructural parameters, such as the types of pores and their distribution. Because diagenesis is responsible for important changes in the microstructure of carbonate rocks, we have extended the standard effective medium approach to model the impact of diagenesis on the carbonate elastic properties through a step-by-step effective medium modeling. Two different carbonate rocks deposited, respectively, in lacustrine and marine environments are considered in this study. The first key step is the characterization of the diagenesis, which affected the two studied carbonate sample sets. Effective medium models integrating all of the geologic information accessible from petrographic analysis are then built. The evolution of the microstructural parameters during diagenesis is thoroughly constrained based on an extensive experimental data set, including X-ray diffraction analysis, different porosimetry methods, and ultrasonic velocity measurements. A new theoretical approach including two sources of compliance is developed to model the specific behavior of carbonates. A compliant interface is introduced around the main carbonate grains to represent grain contacts and the different pore scales are taken into account through multiscale modeling. Finally, direct calculations with the model provide elastic wave velocities representative of the different diagenetic stages. An extrapolation to permeability evolution is also introduced. This approach allows the identification of the acoustic signature of specific diagenetic events, such as dolomitization, dissolution, or cementation, and the assessment of their impact on the elastic properties of carbonates.
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Kamali, M. R., N. M. Lemon, and S. N. Apak. "POROSITY GENERATION AND RESERVOIR POTENTIAL OF OULDBURRA FORMATION CARBONATES, OFFICER BASIN, SOUTH AUSTRALIA." APPEA Journal 35, no. 1 (1995): 106. http://dx.doi.org/10.1071/aj94007.
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Porosity generation and reservoir potential of the early Cambrian Ouldburra Formation in the eastern Officer Basin is delineated by combining petrographical, petrophysical and sedimentological studies. The shallow marine Ouldburra Formation consists of carbonates, mixed carbonates and clastics, clastics and evaporites. Detailed analysis of more than 100 samples shows that dolomitisation resulted in substantial secondary porosity development within the carbonates. Secondary porosity has also been generated within the mixed siliciclastic-carbonate zone by carbonate matrix and grain dissolution as well as by dolomitisation. Prospective reservoir units correspond to highstand shallow marine facies where short periods of subaerial exposure resulted in diagenetic changes.Sedimentary facies and rock character indicate that sabkha and brine reflux models are applied to dolomitisation within the Ouldburra Formation. Dolomite mainly occurs in two stages: common anhedral dolomites formed early by replacement of pre-existing limestone, and saddle dolomite and coarse crystalline dolomite formed during the late stages of burial diagenesis, associated with hydrocarbon shows. The dolomite reservoirs identified are ranked on the basis of their porosity distribution and texture into groups I to IV. Dolomites with rank I and II exhibit excellent to good reservoir characteristics respectively.The Ouldburra Formation shows many depositional and diagenetic similarities to the Richfield Member of the Lucas Formation in the Michigan Basin of the USA. Substantial oil and gas production from middle Devonian shallow water to sabkha dolomites makes the Richfield Member an attractive reservoir analogue to the Ouldburra Formation.
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Lukashina, N. P. "Deep water circulation in the Hunter Channel (Southwest Atlantic) in a late Pleistocene and Holocene by benthonic foraminifera." Океанология 59, no. 1 (April 18, 2019): 133–42. http://dx.doi.org/10.31857/s0030-1574591133-142.
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Was reconstructed deep-sea water circulation near the Hunter Channel (Rio Grande Rise – South-West Atlantic) in a late Pleistocene and Holocene (MIS 4-MIS 1) by benthonic foraminifera. Was studied three cores of bottom sediment. Now moves the upper North Atlantic deep water (NADW) through the Hunter Channel from the North to the South. The lower NADW in the same direction came in MIS 2 and in MIS 4. There was the lower Circumpolar deep water (CPDW), NADW and Antarctic bottom water (AnBW) in MIS 3 periodically. CPDW prevail in a near bottom layer and in Holocene and in the late Pleistocene before the Hunter Channel sidewise the Argentine Basin. So in the Hunter Channel and on the way to it from south side for all studied period AnBW was almost not. Dissolution of carbonates during the Holocene happens in the deepest east part of the Hunter Channel. In Ice Ages processes of dissolution amplified and affected east part of the channel. Dissolution happen and happened not at the expense of AnBW, and at the expense of NADW which becomes there aggressive in relation to a calcium carbonate.
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Gysi, A. P., and A. Stefánsson. "Numerical modelling of CO2-water-basalt interaction." Mineralogical Magazine 72, no. 1 (February 2008): 55–59. http://dx.doi.org/10.1180/minmag.2008.072.1.55.
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AbstractThe effects of CO2 on water-basaltic glass interaction have been simulated at 25ºC. The calculations indicate that addition of CO2 (2—30 bar) to water significantly changes the reaction path. Initially, the pH is buffered between 4 and 6 by CO2 ionization, with dissolution of basaltic glass and the formation of secondary minerals with SiO2, Mg-Fe carbonates and dolomite predominating. Upon the dissolution of additional basaltic glass and mineral fixation of CO2, the pH increases to >8 and (Ca)-Fe-Mg smectites, SiO2, Ca-Na zeolites and calcite become the dominant secondary minerals forming. The overall reaction path depends on the initial water composition, reactive surface area, and the composition of the phyllosilicates and carbonates forming. The key factors are the mobility of Mg2+, Fe2+ and Ca2+ and the competing reactions for these solutes among secondary minerals.
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Fairchild, I. J., M. J. Hambrey, B. Spiro, and T. H. Jefferson. "Late Proterozoic glacial carbonates in northeast Spitsbergen: new insights into the carbonate–tillite association." Geological Magazine 126, no. 5 (September 1989): 469–90. http://dx.doi.org/10.1017/s0016756800022809.
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AbstractCarbonate-rich glacial deposits from two discrete Vendian glacial periods are described. The older is represented by the 24–40 m thick Petrovbreen Member (E2) of the Elbobreen Formation which contains abundant detrital dolomite. Clasts in E2 and their possible source rocks have positive δ13C and negative δ18OPDBvalues. In contrast the carbonate mud-fraction of E2 sediments has different cathodoluminescence characteristics from clasts, slightly negative δ13C values, and higher Fe and Mn concentrations than clasts. Oxygen isotopes vary from −2.5 to +4.5‰PDB, thought to be related to various seawater–meltwater mixtures in the depositional environment. Preservation of information about glacial sedimentary environments is attributed to early diagenetic recrystallization forced by excess surface free energy (Ostwald's ripening) and coinciding with sulphate reduction.The younger glaciation is represented by the Wilsonbreen Formation (170 m) which has a distinctive glaciolacustrine Middle Carbonate Member (W2). W2 contains precipitated periglacial carbonates (with high Mn/Fe ratio): both limestone (rhythmitic and stromatolitic) and dolostone (rhythmites, stromatolites and dolomite-rich sandstones) which are compared with carbonates in modern Antarctic lakes. Evaporitic environments for dolomitic sandstones and stromatolitic dolostones are indicated by heavy oxygen isotope values (up to + 10.5‰PDB), high Na concentration and evidence for dissolved evaporites. High Mn concentration in detrital dolostones in W2 is suggestive of syn-sedimentary dolomite recrystallization in freshwater diamictites and haematitic siltstones.The carbonate–tillite association ultimately arises from the erosion of underlying carbonates which originated (in this case) under radically different climatic conditions. Glacial depositional waters then became carbonate-saturated as a result of dissolution of detrital carbonate. Massive recrystallization of glacially transported carbonate is proposed as a geologically significant process with considerable potential for palaeoenvironmental analysis. In glacial lakes carbonate precipitated in response to evaporation or photosynthesis. Carbonate precipitation as the result of seawater freezing, or in warm interglacial conditions, is not yet established. Oxygen isotope value are inconsistent (too heavy) with the presence of high-latitude meltwaters, implying that glaciation extended to low latitudes as proposed by Harland.
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Zhu, Dongya, Quanyou Liu, Juntao Zhang, Qian Ding, Zhiliang He, and Xuefeng Zhang. "Types of Fluid Alteration and Developing Mechanism of Deep Marine Carbonate Reservoirs." Geofluids 2019 (June 24, 2019): 1–18. http://dx.doi.org/10.1155/2019/3630915.
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Accurate recognition of the types of alteration fluid and the development mechanisms are important concerns in studying deep marine carbonate reservoirs. Major fluid types, such as seawater, meteoric water, deep burial formation water, hydrothermal fluid, and thermochemical sulfate reduction- (TSR-) derived fluid, were identified based on carbon, oxygen, and strontium isotope compositions of many samples from the Tarim, Sichuan, and Ordos basins in China. Compared with normal marine limestones, seawater calcite cement has similar isotopic compositions. Calcite cement precipitated from meteoric water has extremely light oxygen isotope compositions, and its δ18OV-PDB reaches -18.8‰. Due to the fractionation of oxygen isotopes at high temperatures (101.2~145.6°C), calcite precipitated from deep burial formation water and deep hydrothermal fluid has moderately light oxygen isotope compositions. The TSR process consumes organic matter to produce CO2/CO32-, and the calcite from TSR-derived fluid has very light carbon isotopes (δ18OV-PDB, -18.9‰) due to the incorporation of organic CO2/CO32-. Formation water and TSR-derived fluid generally originate and are confined within the carbonates and are consequently termed endogenous fluids. The 87Sr/86Sr ratios of calcite cements from endogenous fluids are basically the same as those of surrounding carbonates. Meteoric water and hydrothermal fluid originate outside the carbonate strata and are exogenous fluids. The 87Sr/86Sr ratios of calcite cements from exogenous fluids are higher than those of surrounding carbonates, up to 0.710558. For karst carbonate reservoirs developed in tectonic uplift-meteoric water environments, the reservoir spaces of karst caves and fractures occur principally under and near unconformity surfaces and megacrystalline calcite cements occur below the karst zone. In deep fault-hydrothermal fluid environments, high-quality carbonate reservoirs develop downward into ultradeep strata. In deep burial-TSR-derived fluid environments, dissolution porosity can be well preserved for a long geological time due to high CO2 and H2S concentrations.
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Xu, Hengchao, Xiaotong Peng, Shun Chen, Jiwei Li, Shamik Dasgupta, Kaiwen Ta, and Mengran Du. "Macrofaunal burrowing enhances deep-sea carbonate lithification on the Southwest Indian Ridge." Biogeosciences 15, no. 21 (October 30, 2018): 6387–97. http://dx.doi.org/10.5194/bg-15-6387-2018.
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Abstract. Deep-sea carbonates represent an important type of sedimentary rock due to their effect on the composition of the upper oceanic crust and their contribution to deep-sea geochemical cycles. However, the role of deep-sea macrofauna in carbonate lithification remains poorly understood. A large lithified carbonate area, characterized by thriving benthic faunas and a tremendous amount of burrows, was discovered in 2008, blanketing the seafloor of the ultraslowly spreading Southwest Indian Ridge (SWIR). Benthic inhabitants – including echinoids, polychaetes, gastropods and crustaceans – are abundant in this carbonate lithified area. The burrowing features within these carbonate rocks, as well as the factors that may influence deep-sea carbonate lithification, were examined. We suggest that burrowing in these carbonate rocks enhances deep-sea carbonate lithification. We propose that active bioturbation may trigger the dissolution of the original calcite and thus accelerate deep-sea carbonate lithification on mid-ocean ridges. Macrofaunal burrowing provides a novel driving force for deep-sea carbonate lithification at the seafloor, illuminating the geological and biological importance of bioturbation in global deep-sea carbonate rocks.