Magnesium Carbonate Minerals Research Articles

Raman spectroscopic study of the magnesium carbonate mineral hydromagnesite (Mg5[(CO3)4(OH)2]· 4H2O)

AbstractMagnesium minerals are important for understanding the concept of geosequestration. One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy. A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm−1, attributed to the CO32−ν1 symmetric stretching mode. A series of infrared bands at 1387, 1413 and 1474 cm−1 are assigned to the CO32−ν3 antisymmetric stretching modes. The CO32−ν3 antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm−1. A series of Raman bands at 708, 716, 728 and 758 cm−1 are assigned to the CO32−ν2 in‐plane bending mode. The Raman spectrum in the OH stretching region is characterized by bands at 3416, 3516 and 3447 cm−1. In the infrared spectrum, a broad band is found at 2940 cm−1, which is assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm−1 are attributed to MgOH stretching modes. Copyright © 2011 John Wiley & Sons, Ltd.

Environmental benefits of using magnesium carbonate minerals as new wildfire retardants instead of commercially available, phosphate-based compounds

A serial batch leaching experiment has been carried out to evaluate the release of elements from the ash of Pinus halepensis needles burned under two test conditions-with and without treatment of the forest species with the carbonate minerals (huntite and hydromagnesite) in aqueous solution (pH 6). The ash (before and after leaching) and leachates were analyzed using atomic absorption spectroscopy and X-ray diffraction. Compared with data from samples treated with the commercially available, phosphate-based fire retardant diammonium phosphate (DAP), we found that use of huntite or hydromagnesite was much more successful in obstructing the release of the toxic elements present in the ash, probably because of the alkaline conditions resulting from decomposition of the minerals during burning. In contrast, DAP tended to be more able to facilitate the extraction of some toxic metals (e.g., Zn, Cu, Mn), probably because of the acidic conditions resulting from its decomposition to phosphoric acid. Data from this study thus lend strong support to the use of magnesium carbonate minerals as new wildfire retardants, because they were shown to be more friendly to the environment (e.g., soil, ground, and underground water streams) than those currently in use (e.g., phosphate or sulfate salt type).

The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration

Anthropogenic greenhouse gas emissions may be offset by sequestering carbon dioxide (CO2) through the carbonation of magnesium silicate minerals to form magnesium carbonate minerals. The hydromagnesite [Mg5(CO3)4(OH)2·4H2O] playas of Atlin, British Columbia, Canada provide a natural model to examine mineral carbonation on a watershed scale. At near surface conditions, CO2 is biogeochemically sequestered by microorganisms that are involved in weathering of bedrock and precipitation of carbonate minerals. The purpose of this study was to characterize the weathering regime in a groundwater recharge zone and the depositional environments in the playas in the context of a biogeochemical model for CO2 sequestration with emphasis on microbial processes that accelerate mineral carbonation.Regions with ultramafic bedrock, such as Atlin, represent the best potential sources of feedstocks for mineral carbonation. Elemental compositions of a soil profile show significant depletion of MgO and enrichment of SiO2 in comparison to underlying ultramafic parent material. Polished serpentinite cubes were placed in the organic horizon of a coniferous forest soil in a groundwater recharge zone for three years. Upon retrieval, the cube surfaces, as seen using scanning electron microscopy, had been colonized by bacteria that were associated with surface pitting. Degradation of organic matter in the soil produced chelating agents and acids that contributed to the chemical weathering of the serpentinite and would be expected to have a similar effect on the magnesium-rich bedrock at Atlin. Stable carbon isotopes of groundwater from a well, situated near a wetland in the southeastern playa, indicate that ∼12% of the dissolved inorganic carbon has a modern origin from soil CO2.The mineralogy and isotope geochemistry of the hydromagnesite playas suggest that there are three distinct depositional environments: (1) the wetland, characterized by biologically-aided precipitation of carbonate minerals from waters concentrated by evaporation, (2) isolated wetland sections that lead to the formation of consolidated aragonite sediments, and (3) the emerged grassland environment where evaporation produces mounds of hydromagnesite. Examination of sediments within the southeastern playa–wetland suggests that cyanobacteria, sulphate reducing bacteria, and diatoms aid in producing favourable geochemical conditions for precipitation of carbonate minerals.The Atlin site, as a biogeochemical model, has implications for creating carbon sinks that utilize passive microbial, geochemical and physical processes that aid in mineral carbonation of magnesium silicates. These processes could be exploited for the purposes of CO2 sequestration by creating conditions similar to those of the Atlin site in environments, artificial or natural, where the precipitation of magnesium carbonates would be suitable. Given the vast quantities of Mg-rich bedrock that exist throughout the world, this study has significant implications for reducing atmospheric CO2 concentrations and combating global climate change.

Carbon Dioxide Fixation within Mine Wastes of Ultramafic-Hosted Ore Deposits: Examples from the Clinton Creek and Cassiar Chrysotile Deposits, Canada

Abstract Carbon dioxide (CO2) is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at Clinton Creek, Yukon Territory, and Cassiar, British Columbia, Canada. Accelerated weathering is attributed to a dramatic increase in surface area, which occurs during the milling of ore. We provide a detailed account of the natural process of carbon trapping and storage as it occurs at Clinton Creek and Cassiar, including mineralogy, modes of occurrence, methods of formation for carbonate alteration, light stable isotope geochemistry, and radiocarbon analysis. Powder X-ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite [MgCO3·3H2O], dypingite [Mg5(CO3)4 (OH)2·5H2O], hydromagnesite [Mg5(CO3)4(OH)2·4H2O], and less commonly lansfordite [MgCO3·5H2O]. Textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings. Samples of efflorescent nesquehonite are characterized by δ13C values between 6.52 and 14.36 per mil, δ18O values between 20.93 and 26.62 per mil, and F14C values (fraction of modern carbon) between 1.072 and 1.114, values which are consistent with temperature-dependent fractionation of modern atmospheric CO2 during mineralization. Samples of dypingite ± hydromagnesite collected from within 0.2 m of the tailings surface give δ13C values between −1.51 and +10.02 per mil, δ18O values between +17.53 and +28.40 per mil, and F14C values between 1.026 and 1.146, which suggests precipitation from modern atmospheric CO2 in a soil-like environment. Field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments. Nesquehonite formed in an evaporative environment on the surface of tailings piles, and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate. In both cases, these minerals have been trapping and storing the greenhouse gas, CO2, directly from the atmosphere. Combined use of δ13C, δ18O, and F14C data has been applied effectively as a tool for verifying and monitoring sequestration of atmospheric CO2 within mine tailings. A number of other deposit types produce tailings suitable for CO2 sequestration, including Cu-Ni-PGE deposits, diamondiferous kimberlite pipes, and podiform chromite deposits. Our results suggest that conversion of about 10 wt percent of tailings to carbonate minerals could offset the greenhouse gas emissions from many ultramafic-hosted mining operations.

Raman and mid‐IR spectroscopic study of the magnesium carbonate minerals—brugnatellite and coalingite

AbstractTwo hydrated hydroxy magnesium carbonate minerals brugnatellite and coalingite with a hydrotalcite‐like structure were studied by Raman spectroscopy. Intense bands are observed at 1094 cm−1 for brugnatellite and at 1093 cm−1 for coalingite attributed to the CO32−ν1 symmetric stretching mode. Additional low intensity bands are observed at 1064 cm−1. The existence of two symmetric stretching modes is accounted for in terms of different anion structural arrangements. Very low intensity bands at 1377 and 1451 cm−1 are observed for brugnatellite, and the Raman spectrum of coalingite displays two bands at 1420 and 1465 cm−1 attributed to the (CO3)2−ν3 antisymmetric stretching modes. Very low intensity bands at 792 cm−1 for brugnatellite and 797 cm−1 for coalingite are assigned to the CO32− out‐of‐plane bend (ν2). X‐ray diffraction studies by other researchers have shown that these minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality and explains why the Raman spectra of these minerals have not been previously or sufficiently described. A comparison is made with the Raman spectra of other hydrated magnesium carbonate minerals. Copyright © 2008 John Wiley & Sons, Ltd.

Mid-infrared and near-infrared spectroscopic study of selected magnesium carbonate minerals containing ferric iron—Implications for the geosequestration of greenhouse gases

The proposal to remove greenhouse gases by pumping liquefied CO 2 several kilometres below the ground implies that many carbonate containing minerals will be formed. Among these minerals brugnatellite and coalingite are probable. Two ferric ion bearing minerals brugnatellite and coalingite with a hydrotalcite-like structure have been characterised by a combination of infrared and near-infrared (NIR) spectroscopy. The infrared spectra of the OH stretching region are characterised by OH and water stretching vibrations. Both the first and second fundamental overtones of these bands are observed in the NIR spectra in the 7030–7235 cm −1 and 10,490–10,570 cm −1 regions. Intense (CO 3) 2− symmetric and antisymmetric stretching vibrations support the concept that the carbonate ion is distorted. The position of the water bending vibration indicates the water is strongly hydrogen bonded in the mineral structure. Split NIR bands at around 8675 and 11,100 cm −1 indicate that some replacement of magnesium ions by ferrous ions in the mineral structure has occurred. Near-infrared spectroscopy is ideal for the assessment of the formation of carbonate minerals.

Infrared and infrared emission spectroscopic study of selected magnesium carbonate minerals containing ferric iron—Implications for the geosequestration of greenhouse gases

The proposal to remove greenhouse gases by pumping liquid carbon dioxide several kilometres below ground level implies that many carbonate containing minerals will be formed. Among these minerals, the formation of two hydrotalcite-like minerals coalingite and brugnatellite is possible, thus necessitating a study of such minerals and their thermal stability. The two such carbonate-bearing minerals brugnatellite and coalingite have been characterised by a combination of infrared and infrared emission spectroscopy. Infrared emission spectroscopy is most useful to determine the stability of these minerals. The infrared spectra of the OH stretching region are characterised by OH and water stretching vibrations. Intense (CO 3) 2− symmetric and antisymmetric stretching vibrations support the concept that the carbonate ion is distorted in these minerals. The position of the water bending vibration indicates that the water is strongly hydrogen bonded in the mineral structure. IES spectra show the temperature range of the thermal stability of these minerals.

The structure of selected magnesium carbonate minerals – A near infrared and mid-infrared spectroscopic study

The approach to remove green house gases by pumping liquid CO 2 several kilometres below the ground implies that many carbonate containing minerals will be formed. Among these minerals the formation of dypingite and artinite are possible; thus necessitating a study of such minerals. Two carbonate bearing minerals dypingite and artinite with a hydrotalcite related formulae have been characterised by a combination of infrared and near-infrared spectroscopy. The infrared spectra of both minerals are characterised by OH and water stretching vibrations. Both the first and second fundamental overtones of these bands are observed in the NIR spectra in the 7030–7235 cm −1 and 10 490–10 570 cm −1. Intense (CO 3) 2− symmetric and antisymmetric stretching vibrations confirm the distortion of the carbonate anion. The position of the water bending vibration indicates water is strongly hydrogen bonded to the carbonate anion in the mineral structure. Split NIR bands at around 8675 and 11 100 cm −1 indicates that some replacement of magnesium ions by ferrous ions in the mineral structure has occurred.

Hydromagnesite and dypingite from the Northern Pennine Orefield, Northern England

SUMMARY The rare basic hydrated magnesium carbonate minerals hydromagnesite and dypingite are reported from low temperature hydrothermal Pb–Zn deposits in the Alston Block of the Northern Pennine Orefield. Both minerals occur as very late stage constituents of deposits rich in barium carbonates. Apparently similar though uncharacterized magnesium carbonates are noted in very small amounts from elsewhere in the orefield.

Groundwater chemistry and mass transfers in the Independence aquifer, central Mexico, by using multivariate statistics and mass-balance models

In the light of progressive depletion of groundwater reservoir and water quality deterioration of the Independence aquifer, an investigation on chemical data of dissolved major and minor constituents in 246 recent groundwater samples was performed. The main objective was the detection of processes responsible for the geochemical evolution and mineralization throughout the area. Multivariate techniques revealed different sources of solutes (a) dissolution of calcium and magnesium carbonate minerals, (b) weathering of acid volcanic minerals, (c) alteration of manganese containing alkaline silicates, (d) leaching of halite deposits of meteoric origin, (e) contamination from agricultural and urban wastewaters, and (f) evaporative effects due to intensive irrigation. Although nitrate contamination is associated with pollution from intensive cultivated areas, natural contamination plays an important role in the study area. The investigation reveals that weathering of acid volcanic rocks (rhyolite) and oxidation of arsenic bearing sulfide minerals are the responsible processes for high fluorine (up to 16 mg/l) and arsenic (up to 0.12 mg/l) contents, respectively, exceeding the Mexican maximum admissible concentration for drinking water. Except for kaolinite, all recharge processes are dissolution oriented (CO2, calcite, dolomite, K-feldspar, plagioclase). Silicate precipitation (amorphous silica and chalcedony) is of growing importance in discharge zones. Cation exchange is not an important issue in the whole study area.

Carbonate mineral solubility at low temperatures in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system

Carbonate minerals have played an important role in the geochemical evolution of Earth, and may have also played an important role in the geochemical evolution of Mars and Europa. Several models have been published in recent years that describe chloride and sulfate mineral solubilities in concentrated brines using the Pitzer equations. Few of these models are parameterized for subzero temperatures, and those that are do not include carbonate chemistry. The objectives of this work are to estimate Pitzer–equation bicarbonate–carbonate parameters and carbonate mineral solubility products and to incorporate them into the FREZCHEM model to predict carbonate mineral solubilities in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system at low temperatures (≤25°C) with a special focus on subzero temperatures. Most of the Pitzer-equation parameters and equilibrium constants are taken from the literature and extrapolated into the subzero temperature range. Solubility products for 14 sodium, potassium, magnesium, and calcium bicarbonate and carbonate minerals are included in the model. Most of the experimental data are at temperatures ≥ −8°C; only for the NaHCO 3-NaCl-H 2O and Na 2CO 3-NaCl-H 2O systems are there bicarbonate and carbonate data to temperatures as low as −21.6°C. In general, the fit of the model to the experimental data is good. For example, calculated eutectic temperatures and compositions for NaHCO 3, Na 2CO 3, and their mixtures with NaCl and Na 2SO 4 salts are in good agreement with experimental data to temperatures as low as −21.6°C. Application of the model to eight saline, alkaline carbonate waters give predicted pHs ranging from 9.2 to 10.2, in comparison with measured pHs that range from 8.7 to 10.2. The model suggests that the CaCO 3 mineral that precipitates during seawater freezing is probably calcite and not ikaite. The model demonstrates that a proposed salt assemblage for the icy surface of Europa consisting of highly hydrated MgSO 4 salts and natron (Na 2CO 3 · 10H 2O) is an incompatible salt assemblage.

Geolimnology of Freefight Lake: an unusual hypersaline lake in the northern Great Plains of western Canada*

ABSTRACTFreefight Lake, Canada's deepest salt lake, is a meromictic, hypersaline lake located in the most arid part of the northern Great Plains. The lake has a distinctive basin morphology, with a large expanse of seasonally flooded mud flats and sand flats adjacent to a deep, flat bottomed perennial waterbody. The mixolimnion, dominated by magnesium, sodium and sulphate ions, has an average salinity of 110 ppt and overlies a monimolimnion of 180 ppt total dissolved salts. The entire water column is strongly supersaturated with respect to a variety of calcium and magnesium carbonate minerals; the lower water mass is also saturated or supersaturated with respect to a number of very soluble sodium, magnesium and sodium + magnesium salts.The modern sedimentary processes operating in Freefight Lake give rise to six main sedimentary facies: (i) colluvium, (ii) mud flats and sand flats, (iii) algal flats, (iv) delta, (v) slope and debris apron, and (vi) deep basin. The colluvium, mud flats and sand flats, and delta facies are dominated by physical processes and consist mainly of detrital siliciclastic sediment. The algal flats, slope and debris apron, and deep basin facies are dominated by endogenic and authigenic sediments derived mainly by physicochemical and biologically mediated carbonate and evaporite mineral precipitation. As one of very few deep water lakes in the world in which soluble evaporite minerals are forming and being preserved, Freefight Lake occupies an important position within the realm of lacustrine sedimentology. Although many of the sedimentological and geochemical processes taking place in the basin today are unusual, the delineation and evaluation of these processes is essential in order to decipher properly the stratigraphic records of Quaternary lake sediments in this large area of North America, as well as lacustrine sequences from other arid and semi‐arid regions of the world.

Thermoluminescence and Surface Correlation of Limestones

Nearly all limestones emit light when heated to a temperature below that incandescence. This thermoluminescence is a natural property of the calcium and magnesium carbonate minerals in the rock. It can also be induced artificially by irradiating specimens with gamma rays or X-rays. The natural thermoluminescence has been produced by radiation from radioactive impurities in the rock. The light emission is measured by a photomultiplier tube circuit as the temperature of the specimen is increased. Both of these variables are recorded simultaneously by means of a two-point potentiometer recorder. A plot of the light intensity as a function of temperature is termed the curve. This shows a series of light-intensity maxima which depend on the amount of radiation that the minerals have received, their impurity content, and their crystallization history. The glow curves of the artificially induced thermoluminescence of many different limestones have been measured, and the shapes of these curves have been found to be characteristic of the limestone stratum from which the specimens were obtained. Preliminary tests of the use of this property as a tool in surface correlation of limestones have shown it to be applicable under closely controlled sampling in thick limestones. It has also been indicated that certain well known Pennsylvanian limestones can be differentiated over a county-wide area by the amounts of thermoluminescence as measured from their glow curves.