Amounts Of Dolomite Research Articles

Metamorphism of Dolomitic and Magnesitic Rocks in Collisional Orogens and Implications for Orogenic CO2 Degassing

Abstract Carbonate-bearing sediments, containing calcite, dolomite or magnesite as major carbonate components, are important constituents of sedimentary sequences deposited on passive margins through Earth’s history. When involved in collisional orogenic processes, these sediments are metamorphosed at variable temperatures and pressures, and undergo decarbonation reactions. While the orogenic metamorphism of some of these lithologies (i.e. impure limestones and dolostones, marls sensu stricto and calcareous pelites) is relatively well understood, very little is known about the metamorphic evolution and decarbonation history of mixed carbonate–silicate rocks in which either dolomite or magnesite is the dominant carbonate component. Here we present the results of a petrologic study of representative samples of metasediments from Central Nepal, derived from Proterozoic dolomitic and magnesitic protoliths metamorphosed during the Himalayan orogeny. The main metamorphic assemblages developed in sediments originally containing different amounts of dolomite or magnesite are characterised in detail. Forward thermodynamic modelling applied to seven samples allows constraints to be placed on (i) the main decarbonation reactions, (ii) the P–T conditions under which these reactions took place, (iii) the composition of the fluids, and (iv) the amounts of CO2 released. We conclude that the CO2 productivity of dolomitic and magnesitic pelites and marls originally containing 15–40% carbonate is significant (>5.5 ± 1.0 CO2 wt% and up to 10.5 ± 1.5 CO2 wt%), whereas for carbonate contents above 60–70%, CO2 productivity is negligible unless aqueous fluids infiltrate from the outside and trigger decarbonation reactions. Since the dolomitic and magnesitic protoliths are significantly abundant in the sedimentary sequences involved in the still active Himalayan orogen, the decarbonation processes described here could contribute to the diffuse CO2 degassing currently observed at the surface. Furthermore, we propose for the first time that the peculiar magnesium-rich assemblages investigated in this study may derive from evaporitic protoliths, and that the whole Upper Lesser Himalayan Sequence may therefore represent the metamorphic product of a Proterozoic sequence consisting of alternating layers of carbonatic, evaporitic and pelitic sediments.

Effect of Dolomite Addition on The Performance of Palm Oil Mill Fly Ash for Methylene Blue Adsorption

The use of palm oil mill fly ash (FA) as a low-cost adsorbent is one of the solutions for handling FA waste. In this study, the addition of dolomite is expected to improve the adsorbent performance. The aim of this study was to investigate the optimum FA-dolomite adsorbent composition and operating conditions for methylene blue adsorption. Different parameters were studied to optimize adsorption process such as the amount of dolomite, methylene blue flow rate, bed height and number of trays. FA-dolomite was converted into nano-adsorbent by sol-gel method which was coated on zeolite surface. Nano-adsorbents were characterized by XRF, FTIR, XRD and SEM. The adsorption capacity was tested by Spectrophotometer UV-Vis. XRF characterization showed that FA had the highest SiO2 content of 58.15%, while dolomite contained CaO of 52.72%. FTIR characterization detected the groups of Si-O-Si, Si-O-Al, Ca-O and Si-O. XRD characterization showed the average crystalline size of FA-dolomite 2% adsorbent was 28.56 nm and SEM characterization showed fine pores on the adsorbent surface. The highest adsorption efficiency obtained at FA-dolomite 2% was 97.364% and the lowest obtained at FA-dolomite 8% was 13.16% with a flow rate of 500 ml/h, adsorbent height of 9 cm and 3 trays. The greater the amount of dolomite added, the absorption efficiency decreases.

Growth and yield of soybeans at different dosages of NPK and dolomite fertilizer in ultisols of Bengkulu

Soybean cultivation in Ultisols is constrained by low soil pH and soil fertility levels. Dolomite and NPK fertilization are used to improve soil quality. The goal of this study was to find the best amounts of Dolomite and NPK fertilizer for black soybean growth and yield on Ultisols and how Dolomite and NPK fertilizers affect each other on Ultisols. This study used a completely random design (CRD) 2 factors and 3 replicates. The first factor was Dolomite with four levels: A1 = 0 ton/ha (control), A1 = 0.5 x Al-dd, A2 = 1 x Al-dd, and A3 = 1.5 x Al-dd. The second factor was NPK fertilizer with four levels: N0 = 0 kg/ha (Control), N1 = Urea 25 kg/ha, TSP 100 kg/ha, KCL 80 kg/ha, N2 = Urea 50 kg/ha, TSP 125 kg/ha, KCL 100 kg/ha, and N3 = Urea 75 kg/ha, TSP 150 kg/ha, KCL 120 kg/ha. The collected data were statistically analyzed using Analysis of Variance (ANOVA) at the 5% F level test. Research results show: 1) There is no interaction of single dose of dolomite and NPK on growth and yield of soybean Detam 4 2) Dolomite dose 1.5 times Al-dd gave the best effect on plant height and number of leaves 7 WAT and weight of 100 seeds, 3) There was no significant effect of giving NPK on soybean growth and yield except for the number of leaves 2 WAP.

Experimental Study of Diffusion and Formation Mineral Change in Supercritical CO2 Huff and Puff Process of Shale Reservoir

Abstract In order to understand the diffusion during CO2 huff and puff in the development of shale oil and its influence on the formation, expansion and viscosity reduction experiments of shale oil-CO2 system, CO2 extraction experiments, and CO2 huff and puff physical simulation experiments were conducted. The diffusion characteristics of CO2 during huff and puff and their effects on formation minerals were studied by chromatographic analysis and X-ray diffraction analysis of artificially fractured natural cores. Research indicates that CO2 huff and puff technology is an effective method to enhance the recovery of shale reservoirs after fracturing. By injecting CO2, the light components of shale oil can be effectively extracted; when the amount of injected CO2 is 50%, the saturation pressure of shale oil increases to 27.72 MPa, and the expansion coefficient increases by 27.9%, the viscosity reduction rate of shale oil can reach 58.97%, and the density reduction rate is 10.02%; under the soaking well pressure of 50 MPa, when 0.5PVCO2 was injected and the well stuffed for 8 hours, the CO2 was fully dissolved in the shale oil, and the continuous increase of the injection slug had a little effect on the CO2 diffusion. During the CO2 huff and puff process, CO2 would dissolve in the formation water and fracturing fluid and reacts with dolomite in the reservoir rock, consuming a large amount of dolomite in the reservoir, and the dolomite mineral content of core sample decreased from 30.1% to 2.6%.

The role of carbonate mineral dissolution in turbidity reduction in an oil sands end pit lake

Surface water turbidity from dispersed clay particles can hinder the development of aquatic ecosystems. One of the primary objectives for proposed oil sands end pit lakes is that they support ecological functions and lake-specific wildlife habitat. However, high surface water turbidity has been observed in the Base Mine Lake cap water, the first full-scale demonstration oil sands end pit lake. Our previous study showed that adjusting the solution pH through carbon dioxide (CO2) addition reduced surface water turbidity in oil sands tailings. Carbonate minerals such as calcite and dolomite were also previously identified in tailings, and thus the goal of this study was to determine the effect of calcite and dolomite dissolution through CO2-mediated pH reduction on turbidity and the stability of suspended clay particles. Calcite dissolution resulted in ∼99% reduction of turbidity. The suspended clay particle stability was analyzed using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory with water chemistry data from this column study. An inverse correlation was observed between the amount of dolomite and the energy barrier values on day 42 of the experiment. These results suggest CO2-mediated calcite dissolution changes the water chemistry and is the most promising treatment condition for the settlement of suspended tailings particles.

Petrological, geochemical, and microfacies analysis of the Sylhet limestone, Bengal Basin, Bangladesh: implication for depositional environment and diagenesis

The fossiliferous Sylhet limestone formation of the Eocene age in the Bengal Basin is important for scientific and geoheritage study. This formation is exposed in the two locations of Bengal Basin; however, it is least studied. In this study, petrological, geochemical, and microfacies analysis of the Sylhet limestone was carried out by analyzing twenty-eight (28) samples from the two exposed sections and two underground (boreholes) in the Bengal Basin. The microscopic and XRD analysis shows that the calcite is the most dominant mineral in the studied samples along with some amount of dolomite, siderite, ankerite, pyrite, and quartz. The presence of the crystal structure of calcite, dolomite, quartz, and pyrite was confirmed through SEM-EDX. Geochemical results show that the samples are composed of high CaO (14.296 to 53.326%) with a significant amount of Fe2O3 (0.095 to 18.482%), Al2O3 (0.664 to 7.357%), K20 (0.83 to 2.274%), MgO (0.157 to 8.109%), and SiO2 (0.08 to 0.451%). Beside the major oxides, some minor and trace elements including Sr, Mn, Zr, Zn, Sc, Co, V, Ba, Ni, and Cu were also measured. Among these, Sr, V, Mn, and Cu concentration within the Sylhet limestone directly indicates its depositional environment at a shallow continental shelf in open marine condition and its diagenetic change to convert as dolomitic limestone. Geochemical characteristics indicate that the Sylhet limestone is highly dolomitized with high Ca/Mg ratio and was deposited in a low-energy shallow continental shelf marine depositional environment. Higher values of the Ca/Mg ratio of the studied samples also confirm lower salinity during its deposition. The presence of silica in the limestone was observed with a positive/negative correlation with Ca which implies that the silica is derived either from a terrestrial source due to increases of sediment supply during the Middle Eocene for the consequences of the Indo-Asian plate Himalayan Collision or dissolution from the siliceous shells of fossils that replace the calcite. Eight (08) microfacies (MFT) types were identified based on abundance of foraminifera or calcareous algae (e.g., Nummulites sp., Discocyclina sp., Alveolina sp., Quinqueloculina sp., Cibicides sp., Lenticulina sp., Ovulites sp.) which are similar to grainstone/packstone carbonate of 18 standard microfacies types (SMF 18). The observed SMF was deposited under restricted to open marine carbonate platform of shallow water depth at different hydrodynamic conditions.

The Geochemistry of Phosphorite and Associated Rocks of Akashat Formation (Middle Paleocene) in Akashat Mine, Iraqi Western Desert. Part I: Major Oxides

The phosphatic compounds in the phosphorites of Akashat Formation (Middle Paleocene) are mainly composed of francolite. The associated rocks (phosphatic limestone) consist of calcite and francolite. As well as, there are little amounts of dolomite, palygorskite, quartz and iron oxides. Francolite is composed of Ca, P, F and O, the tetrahedron SO4 and planar CO3 as CO3+F substitute PO4. Some of Na and Mg are substituted in both sites Ca(I) and Ca(II). F occupied its sites in the channel. Some F subsititute O in CO3 to form the pseudo-tetrahedron of CO3+F. The elements Si, Al, Mg, Fe and K represent the clay minerals; montmorillonite, palygorskite and sepiolite, as well as, quartz and iron oxides. The geochemistry of phosphorite reflects the primary neoformation conditions of marine apatite (francolite) from calcium, phosphate and fluorine, in addition to the substitution of positive mono- and di- valance cations for calcium in Ca(I) in submarine mud of the oceanic floor. The phosphate deposits were exposed to winnowing and transporting by upwelling currents to the continental shelf area. This led the phosphatic deposits to be affected by early and late chemical and biochemical diagenetic processes, causing activities in substitution of cations for calcium in Ca(II) and carbonate, also, additional fluorine and sulfates for phosphate. The flow of continental water to near-shore area, whose content is magnesium leading to remineralization of clay minerals, (e.g. palygorskite and sepiolite from montmorillonite) by depleting magnesium from sea water, as well as the activity of microorganism, all that is provided by suitable growth conditions for phosphatic compounds in continental shelf area.

Multi-Isotope Investigations for Scientific Characterisation and Provenance Implication of Banded Travertines from Tripolis Antique City (Denizli–Turkey)

ABSTRACTThe coloured stones used in buildings and monuments were an indicator of power and wealth during the ancient times. In this study, Tripolis city samples have been compared with Tripolis quarry samples in order to recognise the provenance of the banded travertine blocks in the ancient city. The banded travertine samples have similar mineral compositions and mainly consist of calcite with minor amounts of dolomite, aragonite, clay and iron oxide minerals. These results are also supported by CRS studies. Calcite is in the form of needle-shaped crystals ranging between 0.163–1.418 mm (in city) and 0.303–1.270 mm (in quarry). Tripolis banded travertine samples show the similar compositional spread in terms of major oxide, trace elements. δ13CV-PDB values of banded travertines range from 1.93 to 5.25‰ (in city) and 2.99 to 3.99‰ (in quarry), δ18OV-PDB values change between (−16.93)–(−10.08) ‰ and (−15.93)–(−13.01)‰, respectively. The U–Th radiometric ages are determined between ∼267 and 9 ka in Tripolis city samples and ∼350 and 2 ka in Tripolis quarry samples. The minero-petrographic, geochemical, C–O and U–Th isotope results fairly matched with each other. It seems highly probable that the banded travertines in Tripolis city were extracted from the Tripolis quarry, which is located at the northeast of the antique city with a distance of 3 km.

Effects of a bacterivorous nematode on rice 32P uptake and root architecture in a high P-sorbing ferrallitic soil

Soil bacterivorous nematodes are key plant mutualists that increase nutrient availability for plants either by enhancing the mineralization of organic compounds (the “mineralization pathway”) or by increasing plant lateral root branching following shifts in internal plant metabolism, and subsequently leading to a higher volume of soil prospected by the roots (the “hormonal pathway”). The effects of these organisms on the nutrition of plants growing in strongly nutrient-deficient ferrallitic soils, especially in soils with limited available inorganic phosphorus (P), are poorly known, as are the pathways involved. In our study, using Oryza sativa (Poaceae) and Acrobeloides sp. (Cephalobidae), we tested the “mineralization” and “hormonal” hypotheses in an acidic P-depleted Ferralsol from the Madagascar highlands. We assessed the effect of nematode inoculation on (i) inorganic P flow from soil to plant using the 32P labelling technique and (ii) plant root architecture using a rhizobox device. We showed that the ability of Acrobeloides sp. to enhance P uptake in plants is strongly limited in Ferralsols. However, when the soil pH was corrected with dolomite, Acrobeloides sp. increased plant P uptake probably through the “mineralization” pathway (higher microbial turnover). Indeed, the L-value increased by 49% in the presence of nematodes and dolomite, suggesting the production of unlabelled plant-available P, probably through a higher net P mineralization when the nematodes were inoculated. Using the rhizobox technique, we also observed increased root length in the presence of nematodes but the specific root length, the tip number and the root branching density did not increase in the presence of nematodes, suggesting that nematodes did not increase plant P uptake and growth in this soil as proposed by the “hormonal” hypothesis. From an ecological intensification perspective, to promote agro-ecological development in tropical regions, our results suggest that amending ferrallitic soils with P-rich organic matter and correcting soil pH with an appropriate amount of dolomite may constitute suitable agronomic actionable triggers to drive the mutualistic activity of bacterivorous nematodes.

Reduction Behavior of Dolomite-Fluxed Magnetite: Coke Composite Pellets at 1573\xa0K (1300\xa0\xb0C)

High-temperature behavior of magnetite—coke composite pellet fluxed with dolomite was investigated by customized thermogravimetric analyzer (TGA) at 1573 K (1300 °C). The overall reaction was influenced by C/O ratio and dolomite content. The reduction was accelerated by increased amount of dolomite, while the samples with higher C/O ratio showed the improved reduction degree. X-ray diffraction (XRD) pattern of reduced pellet showed the phase changes of the iron oxides. Noticeable iron peaks were observed when the sample reached the final stage of reduction. CO and CO2 gases released from the reaction were measured by Infrared (IR) gas analyzer. Relation between enhanced reducibility of pellets and larger CO gas evolution from the Boudouard reaction was confirmed from the analysis. Compressive strengths were studied for the practical assessment of reduced pellets. Samples with low-reduction degree showed better physical property. Excessive amount of dolomite also deteriorated the integrity of pellets.

Statistical modeling the effect of sediment physicochemical properties on the concentration of heavy metal (case study: Musa Creek, SW Iran)

Heavy metal accumulation in sediments is important even at low levels due to their irresolvable character and harmful effects. Therefore, contamination of creeks, especially their sediments, is highly important for scientific communities. This study investigates the relationship between heavy metal accumulation and some physicochemical parameters of sediments (pH, EC, calcium carbonate, texture, specific gravity, density, porosity and percentage of organic matter) in a stretch of Musa Creek beaches. The results showed that the studied sediments are extremely salty and have slight variations in terms of pH. Although there are mostly clay-sized sediments in the studied area, their mineralogical composition contains calcite with smaller amounts of dolomite, aragonite and halite minerals. The correlation between each of the parameters and heavy metal concentration was modeled using OLS regression. Cr, Ni, Zn and Pb concentrations are positively correlated with each other and inversely correlated with Cd. The accumulation of heavy metals is directly related to parameters such as EC, organic matter, clay and silt, specific gravity and porosity; it is negatively related to calcium carbonate, sand and density parameters. Owing to slight variations, the pH parameter lacks any significant correlation with heavy metal concentrations.

Micropetrography of Hydrothermal Sediment and Synergy of Microorganisms in the Geological Environment

In the Jurihe area of Inner Mongolia, lamellar hydrothermal sediment of Permian was recognized. These rocks were inter-bedded with volcanic rocks, altered by hot water (hydrothermal fkuid) during the synsedimentary and quasi-synsedimentary stage. The lithogeochemistry of the rock components differ from typical sedimentary rocks. The particles and mineralogical components cannot be identified by microscope. By scanning electronic microscopy (SEM) observation and the rock mineral micro-district analysis (QEMSCAN), we found the mineralogical components of rocks are mainly illite and quartz, plagioclase and alkali feldspar, biotite, montmorillonite, chlorite, glauconite, apatite, hornblende, kaolinite and pyrite, zoisite, and there is a small amount of dolomite, calcite, rutile, gypsum/anhydrite, diopside, zircon, sphene, pyrophyllite, muscovite, epidote, siderite, ilmenite, sphalerite, paragonite, etc. Amongst these, biotite, epidote, zoisite are hydrothermalized alteration minerals. Total organic carbon (TOC) within sedimentary rocks is 0.41~0.27%. Crystalline minerals are generally of micro and nano-size. Amorphous minerals account for a large portion. Fineness of particles in the rock results from heat inhibiting crystallization,?regulation of organic molecules and macromolecular (Microbe-mediated mineralization). Oriented large granules are silicified organic matter from a hydrothermal source. Another form of organic matter taking shapes of clouds or clumps, distributed in layers, and rich in heavy elements, contains filamentous carbon-containing material. It is associated with microbiological activity. If, as postulated above, there are two types of organic matter, the theory of petroleum formation can be enriched to a certain extent.

Formation of fine crystalline dolomites in lacustrine carbonates of the Eocene Sikou Depression, Bohai Bay Basin, East China

The genesis of the fine crystalline dolomites that exhibit good to excellent reservoir properties in the upper fourth member of the Eocene Shahejie Formation (Es 4 s ) around the Sikou Sag, Bohai Bay Basin, is uncertain. This paper investigates the formation mechanisms of this fine crystalline dolomite using XRD, SEM, thin section analysis and geochemical data. The stratigraphy of the Sikou lacustrine carbonate is dominated by the repetition of metre-scale, high-frequency deposition cycles, and the amount of dolomite within a cycle increases upward from the cycle bottom. These dolomite crystals are 2–30 μm in length, subhedral to anhedral in shape and typically replace both grains and matrix. They also occur as rim cement and have thin lamellae within ooid cortices. Textural relations indicate that the dolomite predates equant sparry calcite cement and coarse calcite cement. The Sr concentrations of dolomites range from 900 to 1200 ppm. Dolomite δ18O values (−11.3 to −8.2 ‰ PDB) are depleted relative to calcite mudstone (−8.3 to −5.4 ‰ PDB) that precipitated from lake water, while δ13C values (0.06–1.74 ‰ PDB) are within the normal range of calcite mudstone values (−2.13 to 1.99 ‰ PDB). High 87Sr/86Sr values (0.710210–0.710844) indicate that amounts of Ca2+ and Mg2+ have been derived from the chemical weathering of Palaeozoic carbonate bedrocks. The high strontium concentration indicates that hypersaline conditions were maintained during the formation of the dolomites and that the dolomites were formed by the replacement of precursor calcite or by direct precipitation.

Gasification and pyrolysis of Posidonia oceanica in the presence of dolomite

In the present work, a very detailed study of the reforming of syngas produced in the decomposition of Posidonia oceanica is done. The effect of the presence of different amounts of dolomite is analyzed. Also pyrolysis is studied, in nitrogen atmosphere, and gasification in the presence of air, oxygen and different amounts of steam. A detailed discussion on formation and destruction of tars is done. Furthermore, the effect of the heating rate in the decomposition and the residence time of the evolved gases are discussed. Syngas with ratio H2/CO from 0.3 to ca. 3 can be obtained from this interesting material. Marine species (microalgae) are usually studied with the aim of cultivating them for gas or oil production, but in this paper we draw attention to the possibility of using a natural resource with a very small impact in the ecosystem.

The possibilities of obtaining metallic calcium from Serbian carbonate mineral raw materials

The experimental investigations defined both the technological scheme of the calcium production from limestone by aluminothermic process and the basic operating parameters of the particular technological phases. The limestone with high content of Mg, Na and K was used in the paper. X-ray analysis reveals that the samples contain mainly calcite with small amount of dolomite. At first, the influence of temperature, time and granulometry on the calcium carbonate calcination was examined. The dissociation process was completed in 10-15 min at 1200?C, and dissociation rate increases with decreasing of particle size up to 5 mm. Afterwards, the aluminothermic reduction process of calcium oxide was investigated. At the temperature 1200?C, and vacuum of at least 3 kPa, the reduction process completed within 2 hours. The chemical composition of calcium oxide and calcium showed increased content of magnesium oxide and alkaline oxides (especially sodium).

Dissolution mechanism of dolomite in converter slag at 1873 K

The mechanism of dolomite dissolution in converter slag was studied and found to proceed by two steps: decomposition of dolomite into CaO and MgO and dissolution of the product into the slag. The first step was found to be controlled by heat transfer, which was confirmed by theoretical calculation. The decomposed dolomite had many pores, which allowed easy slag penetration. A discontinuous 2CaO.SiO2 layer along with MgO.Fe2O3 particles was found on the surface of the samples. Some 2CaO.SiO2 islands were found in the vicinity of the samples in the slag, revealing that the dissolution was dominated by peeling-off of the layer of 2CaO.SiO2–MgO.Fe2O3 mixture. 2CaO.SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite samples close to the surface. 2CaO.SiO2 phase was replaced gradually by 3CaO.SiO2 towards the centre of the decomposed sample. While addition of small amounts of dolomite directly into the slag could be considered in steelmaking converter, too much would result in slow dissolution and waste of the raw materials.

Facies analysis and geochemistry of the Euphrates Formation in Central Iraq

The Euphrates Formation (Lower Miocene) in the Central Iraq consists mainly of shallow marine carbonates. Two hundred ten samples were collected from 21 wells (1E to 21ED) at Bahar Najaf area, and 18 samples were collected at Wadi Asadi in Baghdadi area, from Euphrates Formation. Four microfacies are identified, namely mudstone, wackestone, packstone, and rare grainstone with ten submicrofacies. The allochems in the Euphrates Formation are dominated by bioclasts. Peloids, ooids, and intraclasts are less abundant. The common fossils in the Euphrates Formation are miliolids, algae, ostracods, Miogypsina, and abundant shells of pelecypods and gastropods. Calcite and dolomite are the predominant mineral components of the Euphrates Formation. The carbonates of the Euphrates Formation have been affected by a variety of diagenetic processes such as micritization, dissolution, neomorphism, cementation, stylolitization, dolomitization, dedolomitization, and silicification. The Euphrates Formation was deposited in open to restricted platforms which indicated lagoonal environment with warm and restricted open circulation. In fact, prevalence and abundance of micrite provide an evidence of a shallow marine of low-energy environment and, in some places, may be approaching to be stagnant environment. The average of CaO in Najaf area (51.5 %) is slightly lower than that in Baghdadi area (53.3 %), which was reflected in calcite content found being 91 % in Najaf and 94 % in Baghdadi. Dolomite and gypsum appeared as minor minerals beside calcite, so low concentration of MgO (0.83 % in Najaf; 0.63 in Baghdadi) and SO3 (0.55 % in Najaf; 0.53 % in Baghdadi) was reflected information of small amounts of dolomite (2 % in Najaf; 1.6 % in Baghdadi) and gypsum (0.7 % in Najaf and 0.6 in Baghdadi) in the Euphrates Formation. The insoluble residue in Najaf area (4.37 %) is relatively higher than that in Baghdadi area (1.9 %), indicating that the Euphrates Formation in Najaf Area has deposited in an environment closer to the shoreline. Concentrations of the trace elements Sr, Mn, and Fe which support the conclusion that reminds the Euphrates Formation had been deposited in a shallow marine environment of quiet energy, with the likelihood that the shoreline was the nearest to Najaf rather than to Baghdadi.

Quantifying reactive chemistry along an injected CO2 flow path at the field scale using a Monte Carlo simulation approach

A Markov Chain Monte Carlo reactive transport modeling approach was applied to the problem of constraining the distribution of key reactive mineral phases along a flow path between a CO2 injector well and a monitor well at the Weyburn–Midale field in Saskatchewan. The methodology entails postulating a spatially correlated mineral distribution consisting of calcite, dolomite, anhydrite, and K-feldspar, characterized by specified volume fractions and intrinsic dissolution rates, in contact with an ambient brine composition along a one-dimensional flow path. Thousands of forward reactive transport simulations, conducted with PHREEQC, were run for the column, with simulated changes in brine chemistry compared with both synthetic test problem data as well as field data. We used a composite likelihood function to compare modeled and measured pH and concentrations of Ca2+, Mg2+, and Si. New realizations were proposed by replacing a small, contiguous section of the column with a new distribution of minerals that maintained spatial correlation with the remainder of the column. Proposed realizations were accepted/rejected using the Metropolis–Hastings acceptance criteria. If a proposal was accepted, the modified mineral distribution served as the basis for a new distribution, otherwise the modification was rejected as a non-improvement. Application of the inverse modeling approach to a synthetic problem demonstrated nearly complete recovery of a specified initial mineral distribution (i.e., “synthetic truth”) along the flow path, provided that “measurements” (synthetic data) were available across the entire column. Partial recovery of the synthetic truth was still achievable as the amount of data available for inversion was reduced to a single “measurement” collected at the column endpoint, mimicking the typical situation in the field. When applied to real brine chemistry data from a 1-km×1-km test area at the Weyburn–Midale reservoir, the inversion approach identified variations in the amounts of dolomite and calcite available for reaction along the flow path, given simplifying assumptions concerning permeability, pressure gradient, mineral specific surface, and the extent of mixing in the formation. These variations are qualitatively consistent with known compositional variability in mineralogy between the CO2 injector and the monitoring well location.

Tellurium Extraction from the Unique Independent Tellurium Ores in China by Bioleaching

This study was designed to investigate tellurium bioleaching from the unique independent low-grade tellurium ores containing tetradymite, joseite, pyrite, chalcopyrite, silica, and a minor amount of dolomite, which is the first discovered scattered element deposit in the world. For the bioleaching, the tellurium extractions from the low-grade ores by with and without the adapted bacteria of acidophilic Thiobacillus ferrooxidans were examined. The effects of pH, pulp density, and temperature for bioleaching were studied systematically. After 20 days of bioleaching at 30°C, an 80 % of the tellurium was extracted in laboratory study. Leaching kinetics indicated that diffusion through the product layer was the rate controlling process during tellurium bioleaching, and the relative activation energies during tellurium bioleaching stage was calculated to be 34.75 kJ/mol.

Early dolomitization of a Lower Cretaceous shallow water carbonate platform: was microbial activity a major controlling factor?

Early dolomitization of carbonate rocks has long been problematic as precipitation experiments at room temperature have shown that dolomite will not be precipitated chemically under Earth surface conditions. To explain the widespread occurrence of early dolomite in the geological record, bacterial mediation of dolomitization has been proposed. The strongest evidence comes from modern hypersaline environments where dolomitization was shown to take place under anoxic conditions. In this study, part of the Qatar Carbonates and Carbon Storage Research Center (QCCSRC), we investigate whether microbial mediation of early dolomitization took place on the Barremian-Berriasian carbonate platform of the Jurf Formation of Southern Oman. The sediments are characterized by a finely crystalline, poorly ordered dolomite present in various proportions. The amount of dolomite seems to be controlled by facies with tidal flats and algal/microbial facies being totally dolomitized and restricted lagoonal facies being only partially dolomitized. Results indicate that the dolomite is penecontemporaneous to sedimentation and that the dolomitizing fluids are low temperature seawater formed in an evaporative lagoon. Thus, reflux mechanisms played a role in the process of dolomitization. One of the major questions of our study is what controls the heterogeneity of the distribution of dolomite on this platform. We hypothesize that bacteria present in tidal flats and algal/microbial mats facies played an important role in controlling dolomitization. Our goal is to highlight the role of biomineralization in controlling the early diagenesis of the Jurf Formation. To test this we will use a multi-proxy approach using mineralogy, trace elements, stable and clumped isotopes, and SEM analysis, in an integrated field, petrographic and geochemical study of a Barremian-Berriasian carbonate platform exposed in the Haushi-Huqf area. A bed-by-bed sampling was done for two 15-meter thick outcrop sections separated by one kilometer. Initial results highlight the importance of considering the presence of microbial activity to build more accurate dolomitization models and in assessing the lateral heterogeneity of dolomite bodies.