Showing papers on "Silicate minerals published in 2005"
TL;DR: In this article, the authors present a compilation of chemical and physical erosion rates in small catchments and show that silicate weathering rates are not governed by any single parameter but require consideration in multiple dimensions.
817 citations
TL;DR: In this paper, the authors show that there are significant variations in the iron isotope compositions (δ57/54Fe) of mantle rocks (0.9‰) and minerals (olivines 0.6‰), with spinels showing the greatest total variation of 1.7
200 citations
TL;DR: In this article, water samples from the Fraser, Skeena and Nass River basins of the Canadian Cordillera were analyzed for dissolved major element concentrations (HCO3−, SO42−, Cl−, Ca2+, Mg2+, K+, Na+), and δ13C of dissolved inorganic carbon (δ13CDIC) to quantify chemical weathering rates and exchanges of CO2 between the atmosphere, hydrosphere, and lithosphere.
189 citations
TL;DR: The Weyburn Oil Field is a carbonate reservoir in south central Saskatchewan, Canada and is the site of a large CO 2 injection project for purposes of enhanced oil recovery as discussed by the authors.
186 citations
01 Mar 2005
TL;DR: In this paper, a double wet-alkaline method was proposed to measure biogenic silica (BSi) in all estuarine and coastal waters and correction for LSi interference.
Abstract: Measurement of biogenic silica (BSi) in the suspended matter of estuarine and coastal waters is not trivial because of the interference of lithogenic silica (LSi) that can represent up to 90% or more of the total particulate silica within the water column. Till date, no method has provided a satisfying way to correct this mineral interference when the most common wet-alkaline digestions are used. The most recently published method, Ragueneau and Treguer (Mar. Chem., 45 (1994) 43–51), presents the disadvantage to be site-specific. In this paper, we present a robust method to measure BSi in all estuarine and coastal waters and correction for LSi interference. It consists of a double wet-alkaline digestion where the filter sample is submitted to a first digestion (0.2 M NaOH, pH 13.3) at 100 °C for 40 min. At the end of this first leach, all the BSi and part of the LSi have been converted into Si(OH)4. Si and Al concentrations ([Si]1 and [Al]1) in the supernatant are analyzed. After rinsing and drying, the filter is submitted to a second digestion, exactly identical to the first one, leading to the determination of the (Si:Al)2 ratio that is characteristic of the silicate minerals present in the sample. The corrected biogenic silica concentration is thus given by [BSi]=[Si]1–[Al]1(Si:Al)2. There are three basic assumptions behind the proposed method: (1) all the Al measured during the first leach is derived from silicate minerals, (2) all the biogenic silica has been digested during the first leach, so the second leach addresses the Si:Al ratio of silicate minerals only, and (3) silicate minerals dissolve during the second digestion exactly as during the first digestion, i.e. with a similar Si:Al ratio. Theoretical considerations and field experiments demonstrate that the above assumptions are accurate. Blanks and repeatability tests indicate that the detection limit ranges from 0.6 to 1.5 nmol of BSi present on the filter and that the uncertainty is close to 10%. This method was successfully applied to more than 200 samples from five different coastal areas, demonstrating the importance of this correction, which can represent up to 92% of the apparent BSi concentration determined after the first digestion.
153 citations
TL;DR: In this article, the authors investigated the role of microbial dissimilatory Fe 3+ reduction (DIR) in low-metamorphic grade samples of Archean-Paleoproterozoic sedimentary rocks.
147 citations
TL;DR: In this paper, the overall abundance, composition and petrogenesis of accessory calcite in granitoid rocks were analyzed by analyzing a worldwide distribution of more than 100 granitic rocks and calcite occurrences include small to large isolated anhedral grains, fracture and cavity infillings, and sericitized cores of plagioclase.
137 citations
TL;DR: A suite of needle-shaped titanomagnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions' magnetic domain state as discussed by the authors.
Abstract: Submicroscopic, needle-shaped titanomagnetite inclusions exsolved in silicate minerals commonly occur in mafic intrusive rocks and are protected from alteration by their silicate hosts, making them excellent candidates for paleomagnetic studies. A suite of samples containing clinopyroxene- and plagioclase-hosted magnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions' magnetic domain state. Alternating field demagnetization experiments indicate that some inclusions are more stable recorders than others. The two factors controlling the remanence behavior of the inclusions are internal microstructures and inclusion dimensions. Magnetite-ulvospinel unmixing within an inclusion subdivides the original titanomagnetite solid solution into a boxwork structure composed of 103–105 magnetite prisms separated by thin ulvospinel lamellae. The conversion of multidomain-sized needles into assemblages of interacting single domains increases the coercivity (and hence relaxation time) of the inclusions, and results in a thermochemical magnetic remanence. In samples without this exsolution microstructure, the inclusions' diameters determine coercivity and their magnetization is thermoremanent. Both styles of high-coercivity inclusions successfully record paleomagnetic directions in Mesozoic rocks, and their ubiquity within silicate minerals (clinopyroxene and plagioclase) of mafic intrusive rocks indicates their value as chemically and magnetically stable tools for elucidating the ancient magnetic field, marine magnetic anomalies, and crustal kinematics.
128 citations
TL;DR: In this paper, two sets of experiments were conducted to test the resistance of Cs + to ion exchange and the mobility and diffusion coefficient of cancrinite, sodalite, LTA zeolite, and allophane.
111 citations
TL;DR: In this article, the authors found that 30% of the chromite grains of variable sizes in a chromitite seam at the base of the Merensky Reef of the Bushveld Complex on the farm Vlakfontein contain abundant composite mineral inclusions.
Abstract: About 30% of the chromite grains of variable sizes in a chromitite seam at the base of the Merensky Reef of the Bushveld Complex on the farm Vlakfontein contain abundant composite mineral inclusions. The inclusions are polygonal to circular with radial cracks that protrude into the enclosing chromite. They vary from a few microns to several millimeters in diameter and are concentrated in the cores and mantles of chromite crystals. Electron backscattered patterns indicate that the host chromites are single crystals and not amalgamations of multiple grains. Na-phlogopite and orthopyroxene are most abundant in the inclusions. Edenitic hornblende, K-phlogopite, oligoclase and quartz are less abundant. Cl-rich apatite, rutile, zircon and chalcopyrite are present at trace levels. Na-phlogopite is unique to the inclusions; it has not been found elsewhere in the Bushveld Complex. Other minerals in the inclusions are also present in the matrix of the chromitite seam, but their compositions are different. The Mg/(Mg+Fe2+) ratios of orthopyroxene in the inclusions are slightly higher than those of orthopyroxene in the matrix. K-phlogopite in the inclusions contains more Na than in the matrix. The average compositions of the inclusions are characterized by high MgO (26 wt%), Na2O (2.4 wt%) and H2O (2.6 wt%), and low CaO (1.1 wt%) and FeO (4.4 wt%). The δ18O value of the trapped melt, estimated by analysis of inclusion-rich and inclusion-poor chromites, is ∼7‰. This value is consistent with the previous estimates for the Bushveld magma and with the δ18O values of silicate minerals throughout the reef. The textural features and peculiar chemical compositions are consistent with entrapment of orthopyroxene with variable amounts of volatile-rich melts during chromite crystallization. The volatile-rich melts are thought to have resulted from variable degrees of mixing between the magma on the floor of the chamber and Na-K-rich fluids expelled from the underlying crystal pile. The addition of fluid to the magma is thought to have caused dissolution of orthpyroxene, leaving the system saturated only in chromite. Both oxygen and hydrogen isotopic values are consistent with the involvement of a magmatic fluid in the process of fluid addition and orthopyroxene dissolution. Most of the Cr and Al in the inclusions was contributed through wall dissolution of the host chromite. Dissolution of minor rutile trapped along with orthopyroxene provided most of the Ti in the inclusions. The Na- and K-rich hydrous silicate minerals in the inclusions were formed during cooling by reaction between pyroxene and the trapped volatile-rich melts.
83 citations
TL;DR: In this article, the authors measured the U-series disequilibria of the main basaltic rivers from the Deccan Trap region (India) and found that the deformation of carbonates, releasing dissolved U at secular equilibrium, plays a key role in the preferential release of 234U from silicate minerals.
TL;DR: In this paper, the effects of varying sulphur and oxygen contents on the dihedral angle between liquid iron-alloy and crystalline silicates up to 20 GPa were examined.
TL;DR: In this paper, the authors evaluate the effects of variable DO concentrations and mineral reactivity factors on water chemistry evolution during orpiment and realgar oxidation, and show that total As concentrations increase by ∼1.14 to 13 times and that pH values decrease by ∼0.6 to 4.2 U over a range of mineral reaction factors.
TL;DR: In this paper, the fractional enthalpy, entropy and molar volume for 35 polyhedra have been determined using weighted multiple linear regression analysis on a data set of published mineral thermodynamic properties.
Abstract: The thermodynamic properties of silicate minerals can be described as a linear combination of the fractional properties of their constituent polyhedra. In contrast, given the thermodynamic properties of these polyhedra, the thermodynamic properties of minerals can be estimated, where only the crystallography of the mineral needs to be known. Such estimates are especially powerful for hypothetical mineral end-members or for minerals where experimental determination of their thermodynamic properties is difficult. In this contribution the fractional enthalpy, entropy and molar volume for 35 polyhedra have been determined using weighted multiple linear regression analysis on a data set of published mineral thermodynamic properties. The large number of polyhedra determined, allows calculation of a much larger variety of phases than was previously possible and the larger set of minerals used provides more confident fractional properties. The OH-bearing minerals have been described by partial and total hydroxide coordinated components, which gives better results than previous models and precludes the need of a S–V term to improve estimates of entropy. However, the fractional thermodynamic properties only give adequate results for silicate minerals and double oxides, and should therefore not be used to estimate the properties of other minerals. The thermodynamic properties of ‘new’ minerals are calculated from a linear stoichiometric combination of their constituent polyhedra, resulting in estimates generally with associated uncertainty of <5%. The quality of such data appears to be of sufficient accuracy for thermodynamic modelling as shown for meta-bauxites from the Alps and the Aegean, where the effect of Zn on the P–T stability of staurolite can be both qualitatively and quantitatively reproduced.
TL;DR: In this article, the authors discuss the genesis and crystal-chemical aspects of microporous heterosilicate minerals (MHM) with mixed octahedral-tetrahedral frameworks and containing 6 or 5 coordinated transition elements.
Abstract: The chapter deals with relations between genesis and crystal-chemical aspects of microporous heterosilicate minerals (MHM) with mixed octahedral-tetrahedral frameworks and containing 6 or 5 coordinated transition elements (mainly Ti, Nb, Zr, Fe, Mn, Zn) which have been reviewed and discussed by Chukanov and Pekov (2005).
Natural occurrences of microporous silicates with transition elements are very localized: 113 out 122 known MHM (Chukanov and Pekov 2005, Tables 2⇓–4) occur in postmagmatic derivatives of peralkaline rocks. Most of them are known only in this geological setting together with zeolites and zeolite-like beryllo- and borosilicates. In alkaline pegmatites and hydrothermalites, zeolites and MHM may represent up to 90–95% of a rock. Similar diversity and concentrations of microporous silicates are unknown in other geological situations.
Almost all chemical elements present in high-alkaline systems can be incorporated in MHM as either species-forming or important components of isomorphous substitutions; these elements enter into the structure either as framework or extra-framework constituents. The following elements are known as species-forming constituents: O, H, Si, Al, Be, B, P, Zr, Ti, Nb, Sn, Fe, Mn, Zn, Mg, Li, Na, K, Cs, Ca, Sr, Ba, Y, Ce, La, Th, W, F, Cl, C; Ta, Hf, Rb; Nd, Sm, Gd, Dy, Er, Yb, U, Pb, S can be present in MHM with concentrations higher than 1 wt%. In alkaline rocks, relatively high concentrations of some rare elements can be achieved only in microporous minerals thanks to the topological and compositional variety of their structural frameworks and cavities. However, characteristics such as chemical bonds polarization and Lewis acidity of active centers play a role too. As a result, sites having high selectivity towards certain elements occur in the crystal structures of MHM and determine the important role of these minerals for the geochemistry of rare and transition elements …
TL;DR: In this paper, the authors examined the petrography of the massive sulphide mineralization at Aggeneys in the Northern Cape Province, South Africa has been subjected to peak metamorphic temperatures ranging between 670 to 690°C and pressures between 3.4 and 4.5 kbar.
Abstract: The Broken Hill-type Ph-Zn-Cu-Ag massive sulphide mineralisation at Aggeneys in the Northern Cape Province, South Africa has been subjected to peak metamorphic temperatures ranging between 670 to 690°C and pressures between 3.4 and 4.5 kbar. Due to the Ag and Bi rich nature of the ore, these conditions, based on previous experimental studies, may have been sufficient to allow partial melting of the sulphides to occur. Such features as (1) concentrations of low melting point chalcophile elements (LMCE), which include the metals Pb, Zn, Ag, Ga, As, Se, Cd, In, Sb, Te, Hg, Tl and Bi, (2) sulphide inclusions containing a number of different LMCE-bearing minerals within high temperature metamorphic gangue minerals, (3) low interfacial angles between two LMCE-bearing sulphides, such as galena and sphalerite, and LMCE-bearing sulphides and resistate minerals, particularly silicates, (4) LMCE-bearing sulphides filling fractures within metamorphic silicate minerals, (5) coarse recrystallised pegmatite bodies of galena and chalcopyrite crosscutting the regional foliation in the ore body and (6) the presence of a transgressive Mn selvage around the orebodies have all been recognised at Aggeneys and may be indicators of sulphide partial melting. The abundance of pyrrhotite in the orebodies, particularly in the lower ore body (LOB), may, in part, be due to partial melting of pre-metamorphic pyrite during peak metamorphism. Some euhedral pyrite in the LOB may similarly have been derived from desulphidation of pyrrhotite with falling temperatures. The Aggeneys ores also shows other typical features of metamorphosed sulphide ores, such as recrystallisation, remobilisation, deformation and annealing, many of which have contributed to obscuring previous textural features. The extent of sulphide partial melting is likely to have been small, and its effects obscured by later deformation, remobilisation and recrystallisation. It may, however, have played a small role in locally upgrading the ore. This study examines the petrography of the sulphides and their ore textures. Analytical techniques to examine the composition of the sulphides and of multiphase sulphide inclusions are to be undertaken. More extensive studies using numerous techniques are also required in order to clarify this topic.
Journal Article•
TL;DR: In this paper, the authors used melanocratic carbonatites of the Chagatai complex, Uzbekistan, to simulate a natural carbonate-silicate medium parental for both diamondites and their syngenetic mineral inclusions.
Abstract: To simulate a natural carbonate-silicate medium parental for both diamondites and their syngenetic mineral inclusions, melanocratic carbonatites of the Chagatai complex, Uzbekistan, were used. The carbonatites are characterized by a high percentage of silicate components and high-pressure eclogitic silicate minerals. The experiments carried out at 7.0–8.5 GPa and 1800 °C show that the diamondites formed very quickly in C-enriched carbonate-silicate melts of the Chagatai carbonatites. According to experimental evidence, the mineralogy of the Chagatai carbonatites under P-T conditions of diamondite formation is represented by grossular-almandine garnet, diopside-hedenbergite clinopyroxene, and calcite (aragonite) and resembles the mineralogy of diamond-bearing Ca-rich eclogites and grospydites found in kimberlites as mantle xenoliths. The Chagatai carbonatites are quite appropriate as a parental medium to simulate physicochemical processes for the formation of natural diamondites. The most important characteristics of these processes are as follows: quick migration of mobile low-viscosity carbonate-silicate melts into zones of diamondite formation, extremely high “snowballing” rate of diamondite crystallization from a carbonate-silicate melt oversaturated with dissolved carbon, formation of syngenetic inclusions of garnet and clinopyroxene, carbonate and sulfides, etc. inside the pores and cavities of diamondites. Experiments show that the formation of diamondites and their syngenetic inclusions is accompanied by coarse-grained crystallization of eclogitic minerals in the parental media surrounding the growing diamondites. Syngenesis of diamondites and inclusions, carbonate parental melts, experiment
TL;DR: In this article, the dissolution rate constant of basalt glass was estimated to be 10-10.2±0.5 (mole Si m-2s-1).
Abstract: Compositional and mineralogical (primary silicate minerals, volcanic glass, secondary minerals) properties of weathered basaltic ash soil ("Andisol") derived from Mt. Fuji, central Japan, with an age of ca. 6,000 y.B.P. to 240 y.B.P. were studied. X-ray fluorescence analysis indicates that the order of relative elemental mobilities during the weathering is Na, Ca > K > Mg > P > Si > Ti, Fe > Al > Mn. The trends of soil water chemistry (H4SiO4 concentration) with depth were calculated based on a dissolution (volcanic glass)-precipitation (allophane) kinetics-fluid flow coupling model. In order to calculate the trends, the data on present-day annual rainfall, solubility of basalt glass, porosity and specific gravity of the soil, deposition rate of volcanic ash and grain size of volcanic glass were used. The calculated results were compared with analytical trends of soil water chemistry. From this comparison, the dissolution rate constant of basalt glass was estimated to be 10-10.2±0.5 (mole Si m-2s-1). This value is consistent with previously determined experimental long-term dissolution rate constant of basalt glass reported in the literature (Berger et al., 1994).
TL;DR: In this article, a range of uranyl carbonate, sulphate and silicate minerals were obtained using a fibre optic-probe with an attenuated total reflectance cell in reflectance mode.
Abstract: The proposed increase in usage of nuclear power implies increased nuclear waste resulting in the formation of many uranyl secondary minerals. These minerals can translocate and a method of easy identification is required. Because many of the minerals contain water and/or OH units, the minerals lend themselves to near infrared spectroscopy. Spectra of a range of uranyl carbonate, sulphate and silicate minerals were obtained using a fibre optic-probe with an attenuated total reflectance cell in reflectance mode. The minerals include andersonite, liebigite, rutherfordine, uranopilite, zippeite, boltwoodite, soddyite, sklodowskite, uranophane and weeksite. These uranyl minerals are characterised by intense bands around 7000 cm−1 resulting from the second harmonic of the normal mode of the OH groups. Uranyl silicates show intense bands in the 4200 to 5400 cm−1 region. Two sets of bands, which are electronic in nature, are observed: one centred upon 10100 cm−1 and a second set around 8500 cm−1 in the high waven...
Journal Article•
TL;DR: In this paper, the authors focused on mineral weathering by silicate bacteria and showed that the bacteria indeed eroded the surface of the testing minerals, which were characteristic of round shapes and uneven surface.
Abstract: Interactions between microorganisms and minerals take place widely on the Earth, which lead to dissolution or precipitation of minerals and thus play an important role in the natural environment and economic development. The study of mineral weathering by microorganisms involves many fields and disciplines. Furthermore, weathering of minerals is related to the formation and evolution of soil, development of vegetation and formation of mineral deposits.This paper focuses on mineral weathering by silicate bacteria. Potassium feldspar, illite and other common minerals were selected for this study. These minerals were incubated in nitrogen-free medium containing bacteria. During incubation samples were collected from the culture and analyzed using X-ray diffraction and electron microscope. The results showed that the bacteria indeed eroded the surface of the testing minerals, which were characteristic of round shapes and uneven surface. The mineral particles were covered with numerous bacteria. Furthermore, bacteria selectively degraded different minerals due to difference in mineral crystal structure. In the Absence of bacteria, minerals remained intact, which were characterized by sharp edges and corners. The mechanisms of mineral weathering by silicate bacteria were also discussed.
TL;DR: In this article, the authors present several new diagrams that document previously unappreciated patterns and predictability in systematic mineralogy, showing that the ionic potential (charge/radius) of hard cations is proportional to that of anions (e.g., from KCl to SiC).
Abstract: This paper presents several new diagrams that document previously unappreciated patterns and predictability in systematic mineralogy. They illustrate, for example, that sulfide minerals of single cations contain only intermediate to soft cations (cations with at least some outer-shell electrons). On the other hand, hard cations (those with no outer-shell electrons) only enter into a few sulfide minerals, all of which also contain intermediate cations. Among the simple chloride, fluoride, oxide, and carbide minerals of hard cations, ionic potential (charge/radius) of cations is proportional to that of anions (e.g., from KCl to SiC). Among the simple nitrate, sulfate, carbonate, phosphate, and silicate minerals of hard cations, ionic potential of inter-radical cations is inversely proportional to the ionic potential of the cations in the oxysalt radical (e.g., from KNO 3 to ZrSiO 4 ). Across both of these sets of minerals, non-simple minerals (H 2 O- and OH - -bearing minerals or minerals with extra O 2 - ) in each group typically involve cations of higher ionic potential than those of the simple minerals. The result is predictability and pattern in the compositions of minerals.
01 Jan 2005
TL;DR: In this paper, coal combustion solid residues were analyzed by X-ray powder diffraction when firing coal and additives in a single burner furnace, moreover, the computer package F*A*C*T was used to predict the products composition of the multi-component system containing coal and additive.
Abstract: Activity of coal combustion solid residues is relevant closely to calcic minerals composition and reactions. In this paper, the solid residues were analyzed by X-ray powder diffraction when firing coal and additives in a single burner furnace, moreover, the computer package F*A*C*T was used to predict the products composition of the multi-component system containing coal and additives. The mineral composition of solid residues under different conditions has been well investigated. The results indicate that there are two types of reactions with respect to calcic minerals: desulfurization and solid state reaction. The calcic minerals generating from solid state reactions include CaO-SiO2, CaO-Al2O3, CaO-Fe2O3 and CaO-SiO2-Al2O3 group minerals. When increasing CaO content in ash, the primary mineral in the products varied following the route of mullite→anorthite→gehlenite→dicalcium silicate. Desulfurization is prior to solid state reaction when CaSO4 is stable. Due to the decomposition or further reactions of CaSO4 at high temperature, most calcium enters in silicate minerals and complicated S-containing minerals such as calcium aluminosulfate and calcium silicosulfate can be obtained.
Journal Article•
TL;DR: In this article, the effect of plants on silicate mineral dissolution and landslide preparation was investigated thoroughly and the concrete problems including identifying and dividing the lasting time of different dissolution states in natural slope water-rock systems, identifying multi-scale damage model of rockmass and transporting mechanism of fluid and chemical components in slope rockmass, and mechanical effect of multiscale preferential dissolution and so on.
Abstract: Silicates are the most important forming-rock minerals of earth crust rock and in exogenous environments,and the dissolution of silicate minerals is universal. In most laboratory experiments,there is an initial period during which nonlinear dissolution behavior is observed and steady-state dissolution rates range from 10-12 to 10-8 mol/(m2·s). Dissolution is nonstoichiometric in most experiments. Bulk dissolution rates are not directly proportional to the surface areas of the minerals studied,but when grains are large compared with the distance among adjacent defects,they will vary linearly with the specific surface areas. Under acidic conditions, dissolution rates are positively proportional to the concentration of hydrogen ion. Organic ligands deriving from organic soluble matter can complex metal ions in solutions and at solid-solution interface,and promote dissolution of silicate minerals. The effect of temperature on dissolution rates follows the Arrhenius equation. In view of the coincidence between the promoting factors of silicate dissolution and landslide occurrence,concentrations of chemical components in watershed surface water may be taken into account in regional evaluation of landslide hazard. Plants can raise the acidity of groundwater and content of organic mater in soil and groundwater runoff rate. The effect of plants on silicate mineral dissolution and landslide preparation is conspicuous. The nonlinear dissolution on slope rockmass scale and the multi-scale preferential dissolution of rock mass are necessary to investigate thoroughly. The concrete problems include identifying and dividing the lasting time of different dissolution states in natural slope water-rock systems,identifying multi-scale damage model of rockmass and transporting mechanism of fluid and chemical components in slope rockmass,and mechanical effect of multi-scale preferential dissolution and so on.
01 Jan 2005
01 Mar 2005
TL;DR: In this article, the spectral differences between plausible lunar analog opaque mineral powders and their respective quenched glasses were examined, and independent fits to the data were made to find the titanium abundances more consistent with Lunar Prospector epithermal and thermal neutron values.
Abstract: Introduction: The dominant cause for lunar visible color differences is variations in the degree of soil maturity and the abundance of FeO and opaque minerals, such as ilmenite. The addition of opaque minerals to a lunar soil tends to decrease the overall reflectance and continuum slope (darkens and decreases “redness”). As a soil weathers its reflectance is also lowered but its slope increases (darkens and increases “redness”). By exploiting these color trends numerous studies have attempted to correlate the abundance of TiO2 in the form of ilmenite to variations in blue to red ratios (i.e. 415 to 750 nm Clementine bandpasses) with varying degrees of success. Discrepancies between independent methods have been attributed to: unknown opaque phases in the lunar soil; overcorrection of thorium values in Lunar Prospector epithermal and thermal neutron data; mixing of highlands and mare basalt materials; and uncorrected scattered light effects. To investigate this problem we are examining the spectral differences between plausible lunar analog opaque mineral powders and their respective quenched glasses. Background: Lunar ilmenite (FeTiO3) is a potential ISRU source of oxygen and titanium metal. Additionally, ilmenite-rich soils preferentially retain solar wind volatiles H and He, that are also potential lunar resources. Understanding the distribution and abundance of ilmenite also serves to elucidate the Moon’s thermal history and formation of the crust. Additionally, titanium concentration is one of the most useful discriminators in classifying lunar mare basalts due to its substantial variation ( 14 wt. % TiO2) [1]. The prevalence of titanium in mare basalts, relative to the terrestrial basalts, is curious and not yet satisfactorily explained. The Hapke model [2] of lunar reflectance attributes the spectral properties of lunar soil to four components of the regolith: the ferrous iron (Fe) in silicate minerals and glasses; submicroscopic metallic iron (SMFe) grains produced in the maturation process; titanium in silicate minerals and glasses; and opaque phases (in the case of the Moon, often assumed to be mostly ilmenite). The presence of opaque phases causes an overall decrease in reflectance and spectral slope (less red, titanium rich basalts are sometimes referred to as “blue”). Increased maturation and added FeO cause a decrease in reflectance and an increase spectral slope (redder). Lucey et al. [3] developed a method for estimating titanium abundance using the Clementine 415/750 nm ratio versus 750nm reflectance to define a Ti spectral parameter. Lucey notes that this method relies on the spectral properties of opaque minerals and the assumption that ilmenite is the dominant opaque mineral everywhere on the Moon. The titanium abundances estimated by Lucey et al. are higher, by up to a factor of 2, than values from Lunar Prospector epithermal and thermal neutron data in some areas, as shown in Figure 1 [4]. Gillis et al. [5] modified the algorithm of Lucey et al. after observing spectral similarities of landing sites corresponding to outliers on the plot of Ti spectral parameter versus measured TiO2 content of returned samples. By separating the two trends and applying independent fits to the data they found TiO2 abundances more consistent with Lunar Prospector epithermal and thermal neutron values.
01 Jan 2005
TL;DR: In this article, the mineralogy and geochemical trapping possibilities of five acid-gas injection sites in the vicinity of Edmonton in central Alberta were investigated using the geochemical mass transfer program GAMSPATH.
Abstract: Publisher Summary This chapter introduces the mineralogy and geochemical trapping possibilities of five acid-gas (CO2, H2S) injection sites in the vicinity of Edmonton in central Alberta. Five acid-gas injection sites in the Edmonton area form closed geological containers to ensure the containment of the injected gas. Three injection targets are in Devonian carbonates and two are in Cretaceous elastics. Using the geochemical mass transfer program, GAMSPATH, the potential reactions between the formation mineralogy, the formation waters, and the injected gas resulted in the carbonate units; the majority of the acid-gas trapping is through solubility trapping, which may be augmented by the buffering reactions with the reservoir mineralogy. In the elastic units, mineralogical trapping of CO2 is significant over a long time span, and is the result of reactions between calcium silicate minerals and fluids. For both elastic and carbonate units, mineral trapping of H2S is limited by the amount of iron present as oxides or in the silicate minerals.
01 Jan 2005
TL;DR: A review of the results of complementary use of vibrational spectroscopy (infrared and Raman) and powder X-ray diffraction in the process of identification and detection of some carbonate, sulfide, oxide and silicate minerals originating from the Republic of Macedonia is presented in this article.
Abstract: A review of the results of complementary use of vibrational spectroscopy (infrared and Raman) and powder X-ray diffraction in the process of identification and detection of some carbonate, sulfide, oxide and silicate minerals originating from the Republic of Macedonia is presented. Studied are the following minerals: calcite, CaC03; aragonite, CaC03; siderite, FeC03;
magnesite, MgC03; dolomite, CaMg(C03)2; kutnahorite, galena, PbS; sphalerite/wurtzite, (Zn,Fe)S; hematite, Fe203; magnetite, Fe304; limonite, FeOOH; goethite, a-FeOOH; corundum, AI2O3..
01 Jan 2005
Journal Article•
TL;DR: In this paper, the dominant minerals in the composite cement are silicate minerals-alite, belite, and sulphoaluminate minerals, and the development trends of a new type cement based on minerals of C_3S C(B)_4A_3(S) and C(C(B)-4A-4A+3(s) are prospected.
Abstract: Silicate minerals were characterized by the stable and long-term mechanical performance, while the sulphoaluminate minerals have an excellent early strength. The constituent design, synthesizing technology at low temperature, performances and application of the composite cement are expatriated. The dominant minerals in the composite cement are silicate minerals-alite (C_3S), belite (C_2S) and sulphoaluminate mineralscalcium sulphoaluminate (C_4A_3(S) ), calcium barium sulphoaluminate \. The performances of C(B)_4A_3(S) and C(B)_4A_3(S) -based cements are discussed in detail. The development trends of a new type cement based on minerals of C_3S C(B)_4A_3(S) are prospected.
TL;DR: In this paper, the authors used IR spectroscopy, chemical analysis, x-ray diffraction, and thermal analysis to determine the amount of absorbed CO2 and to elucidate the mechanism of its incorporation into the aluminosilicates during grinding.
Abstract: Data are presented on CO2 sorption by natural Na- and Ca-containing aluminosilicates (plagio-clases) during mechanical activation in an AGO-2 centrifugal planetary mill filled with CO2. IR spectroscopy, chemical analysis, x-ray diffraction, and thermal analysis are used to determine the amount of absorbed CO2 and to elucidate the mechanism of its incorporation into the aluminosilicates during grinding. The results, similar in a number of aspects to those reported for Ca- and Mg-containing silicates, lend support to the conclusion made earlier that CO2 absorption by silicate minerals during mechanical activation and CO2 dissolution in silicate melts have many features in common.