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Showing papers on "Silicate minerals published in 2012"


Journal ArticleDOI
01 Oct 2012-Geology
TL;DR: In this paper, an in situ atomic force microscopy (AFM) study of the dissolution of wollastonite, CaSiO 3, as an example of surface leached layer formation during dissolution is presented.
Abstract: The dissolution of most common multicomponent silicate minerals and glasses is typically incongruent, as shown by the nonstoichiometric release of the solid phase components. This results in the formation of so-called surface leached layers. Due to the important effects these leached layers may have on mineral dissolution rates and secondary mineral formation, they have attracted a great deal of research. However, the mechanism of leached layer formation is a matter of vigorous debate. Here we report on an in situ atomic force microscopy (AFM) study of the dissolution of wollastonite, CaSiO 3 , as an example of leached layer formation during dissolution. Our in situ AFM results provide, for the first time, clear direct experimental evidence that leached layers are formed in a tight interface-coupled two-step process: stoichiometric dissolution of the pristine mineral surfaces and subsequent precipitation of a secondary phase (most likely amorphous silica) from a supersaturated boundary layer of fluid in contact with the mineral surface. This occurs despite the fact that the bulk solution is undersaturated with respect to the secondary phase. Our results differ significantly from the concept of preferential leaching of cations, as postulated by most currently accepted incongruent dissolution models. This interface-coupled dissolution-precipitation model has important implications in understanding and evaluating dissolution kinetics of major rock-forming minerals.

127 citations


Journal ArticleDOI
TL;DR: The surface characteristics, including surface charge and wettability, of layered silicates are reviewed and the wetting characteristics of the silica tetrahedral surface are examined with different experimental techniques and results are discussed.

108 citations


Journal ArticleDOI
TL;DR: In this paper, Li and B isotope signatures in soil and waters vary seasonally, depending on the vegetation growth cycle and rain events, and are mainly controlled by the degree of mineral leaching and the amount of clay mineral formation.

89 citations


Journal ArticleDOI
TL;DR: The Lac des Iles Complex hosts Pd deposits with unusually high Pd/Pt and pd/Ir ratios, which have been attributed to the introduction of Pd by late magmatic-hydrothermal fluids.
Abstract: The Lac des Iles Complex hosts Pd deposits with unusually high Pd/Pt and Pd/Ir ratios. These high ratios have been attributed to the introduction of Pd by late magmatic–hydrothermal fluids. The presence of hydrous silicates and low-temperature sulfide mineral assemblages has been advanced as evidence for fluid overprint. This idea has been investigated by documenting the change in silicate, sulfide, and platinum-group mineralogy and texture in samples from the deposit ranging from fresh gabbronorite to extensively altered chlorite–actinolite schist. In addition, whole-rock analysis combined with laser ablation analysis of the sulfides was used to determine which phase controlled each of the PGE. In fresh gabbronorite the sulfide assemblage is igneous (pyrrhotite–pentlandite–chalcopyrite) and Pd is present mainly in pentlandite and kotulskite (PdTe) inclusions associated with the sulfide minerals. All other PGE (except Pt) are present in solid solution in pyrrhotite and pentlandite. Platinum is present as sperrylite (PtAs2) and montcheite (PtTe2) inclusions associated with the sulfide minerals. These observations suggest that the PGE in the fresh gabbronorite were all collected by magmatic sulfide liquid. In the chlorite–actinolite schist the sulfide assemblage is a low-temperature assemblage consisting of chalcopyrite, pyrite ± millerite. A minor amount of palladium is present in millerite, but most is present as bismuth-rich kotulskite and Pd arsenides both of which are associated with hydrous silicate. All other PGE (except Pt) are hosted by pyrite. A minor amount of Pt is present in pyrite, but most is found as sperrylite and montcheite associated with hydrous silicate minerals. The pyrite could have formed by Fe-loss from pyrrhotite (resulting in the pyrite inheriting Os, Ir, Ru, and Rh) and Fe-loss from pentlandite to form millerite (resulting in the millerite inheriting some Pd). The PGE concentrations of the whole rock show there is no direct correlation between the sulfide assemblage, the degree of alteration of the silicate minerals and ore grade. Thus, although fluids have clearly altered the sulfide-, silicate-, and platinum-group mineralogy and their textures, it is not clear that these fluids have changed the PGE content of the rocks.

76 citations


Journal ArticleDOI
TL;DR: In this paper, the major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow (25 m) in the Varanasi area.
Abstract: Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow ( 25 m) in the Varanasi area. Hydrochemical facies, Mg-HCO3 dominated in the largest part of shallow groundwater followed by Na-HCO3 and Ca-HCO3 whereas Ca-HCO3 is dominated in deep groundwater followed by Mg-HCO3 and Na-HCO3. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump) within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals.

68 citations


Journal ArticleDOI
TL;DR: In this article, an ultraviolet (200 nm) femtosecond laser ablation (200FsLA) sector-field inductively coupled plasma mass spectrometry (SF-ICPMS) system was used for major and trace element analyses in anhydrous silicate glasses and minerals.
Abstract: We have tested an ultraviolet (200 nm) femtosecond laser ablation (200FsLA) sector-field inductively coupled plasma mass spectrometry (SF-ICPMS) system for major and trace element analyses in anhydrous silicate glasses and minerals. Use of the 200FsLA minimized the matrix effect by 50% compared to that of a 193 nm nanosecond excimer LA. The origin of this improvement was identified as the suppression of ‘melting point (MP)-induced’ element fractionation at the LA site due to a decreased thermal effect of the 200FsLA. Sensitivity enhancement in elements with high first ionization energy remained for the basalt aerosols relative to silica-rich aerosols. This is interpreted as being due to the higher thermal conductivity of the basalt aerosols in the inductively coupled plasma enhanced ionization, which is essentially controlled by the first ionization energy of an element. This was confirmed by simulation using Saha's equation and by the analytical data after reduction of the MP-induced fractionation at the LA site. Accurate determination of trace elements (within 5% of accepted values) was achieved for MPI-DING glasses ranging from komatiite to rhyolite, using a single basalt glass BHVO-2G as the calibration standard. This method is also applicable to anhydrous silicate minerals such as plagioclase, pyroxenes, and garnet. However, SRM610 glass, which has a very different matrix compared to BHVO-2G, is preferred for zircon. Apart from this exception, the proposed method requires no external analytical techniques when the amounts of unmeasured elements in the materials, such as halogens or water, are negligibly low, which is the case for many geological materials.

65 citations


Journal ArticleDOI
TL;DR: Wan et al. as mentioned in this paper investigated the history of long-term silicate weathering in the Himalaya and Tibetan Plateau (HTP) during the late Cenozoic by reconstructing 5 m.y. of silicate sedimentary records at Ocean Drilling Program (ODP) Site 1143 in the South China Sea to explore the weathering history of the Mekong River basin.
Abstract: Determining the interplay between tectonic deformation, climate, atmospheric CO2 concentrations and continental weathering and erosion is key to understanding the mechanisms that forced Cenozoic global cooling. In contrast with studies of paleo-climate and pCO(2), the history of long-term silicate weathering in the Himalaya and Tibetan Plateau (HTP) during the late Cenozoic remains unclear. We reconstruct 5 m.y. of silicate sedimentary records at Ocean Drilling Program (ODP) Site 1143 in the South China Sea to explore the weathering history of the Mekong River basin that supplied the sediment. Coherent variation of weathering proxies from the South China Sea, Bay of Bengal, Loess Plateau, as well as the Yangtze and Yellow Rivers, indicates weakening chemical weathering intensity since the late Pliocene, as the climate cooled. This cooling, coupled with tectonic activity, shifted the dominant weathering regime from more transport-limited to more weathering-limited, causing less chemical depletion of silicate minerals. While silicate weathering rates became strongly correlated to erosion rates, they were decoupled from chemical weathering intensity. Physical denudation and associated silicate weathering rates in the HTP area increased in the Pliocene, driven by both rock uplift and stronger monsoon precipitation, decreasing atmospheric CO2 concentrations, and so contributing to Northern Hemisphere Glaciation (NHG). Citation: Wan, S., P. D. Clift, A. Li, Z. Yu, T. Li, and D. Hu (2012), Tectonic and climatic controls on long-term silicate weathering in Asia since 5 Ma, Geophys. Res. Lett., 39, L15611, doi:10.1029/2012GL052377.

53 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used suppression subtractive hybridization (SSH) technology to determine the mechanisms by which fungi weather potassium-bearing minerals on a molecular level, and they found that the factors that could accelerate weathering of Kbearing minerals involved organic acids, carbonic acid, and redox participant molecules.

48 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the model suggested by Norman et al. (1995) is the most appropriate for the origin of the troilite veining and low-Ca pyroxene pseudomorphs after olivine.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the formation of metal-sulfate-rich layers on the interfaces between the atmosphere and the silica-rich coating (atmosphere-coating interface, ACI) and between the surface of the coating and the underlying rock (rock-covering interface, RCI).

40 citations


Journal ArticleDOI
TL;DR: In this article, the most abundant defect in clay minerals is oriented perpendicular to the silicate layer and thermal annealing indicates this defect in kaolinite (A-center) to be stable over geological periods at ambient temperature.
Abstract: Extensive information has been collected on radiation effects on clay minerals over the last 35 years, providing a wealth of information on environmental and geological processes. The fields of applications include the reconstruction of past radioelement migrations, the dating of clay minerals or the evolution of the physico-chemical properties under irradiation. The investigation of several clay minerals, namely kaolinite, dickite, montmorillonite, illite and sudoite, by Electron Paramagnetic Resonance Spectroscopy has shown the presence of defects produced by natural or artificial radiations. These defects consist mostly of electron holes located on oxygen atoms of the structure. The various radiation-induced defects are differentiated through their nature and their thermal stability. Most of them are associated with a π orbital on a Si–O bond. The most abundant defect in clay minerals is oriented perpendicular to the silicate layer. Thermal annealing indicates this defect in kaolinite (A-center) to be stable over geological periods at ambient temperature. Besides, electron or heavy ion irradiation easily leads to an amorphization in smectites, depending on the type of interlayer cation. The amorphization dose exhibits a bell-shaped variation as a function of temperature, with a decreasing part that indicates the influence of thermal dehydroxylation. Two main applications of the knowledge of radiation-induced defects in clay minerals are derived: (i) The use of defects as tracers of past radioactivity. In geological systems where the age of the clay can be constrained, ancient migrations of radioelements can be reconstructed in natural analogues of high level nuclear waste repositories. When the dose rate may be assumed constant over time, the paleodose is used to date clay populations, an approach applied to fault gouges or laterites of the Amazon basin. (ii) The influence of irradiation over physico-chemical properties of clay minerals. An environmental application concerns the performance assessment of the engineered barrier of nuclear waste disposals. In case of a leakage of transuranic elements from the radioactive waste form, alpha recoil nuclei can amorphize smectite after periods of the order of 1000 years according to a worst case scenario, whereas amorphization from ionizing radiation is unlikely. As amorphization greatly enhances the dissolution kinetics of smectite, the sensitivity of the smectites must be taken into account in the prediction of the long term behavior of engineered barriers.

Journal ArticleDOI
TL;DR: The Middle Eocene ironstone succession is located in the northeastern part of El Bahariya Depression, Western Desert, Egypt as mentioned in this paper and consists of two main shallow marine ironstone facies associations.

Journal ArticleDOI
01 Jul 2012-Fuel
TL;DR: In this paper, the catalytic steam reforming activity of two naturally-occurring iron-bearing mineral silicate ores containing chrysotile and lizardite, was probed using benzene model-tar compound co-mixed with simulated syngas at varying H 2, CO, CO 2, CH 4 and steam compositions.

Journal ArticleDOI
TL;DR: In this paper, the degradation process of silicate minerals to understand the weathering processes occurring at the change temperature in the subsurface environment with organic input was investigated with psychrotrophic heterotrophic bacteria.
Abstract: The bio-weathering of basalt, granite and gneiss was experimentally investigated in this study These rock-forming minerals weathered more rapidly via the ubiquitous psychrotrophic heterotrophic bacteria With indigenous bacteria of Bacillus spp from sediments of Lake Baikal, we traced the degradation process of silicate minerals to understand the weathering processes occurring at the change temperature in the subsurface environment with organic input The bacteria mediated dissolution of minerals was monitored with solution and solid chemistry, X-ray analyses as well as microscopic techniques We determined the impact of the bacteria on the mineral surface and leaching of K, Ca, Mg, Si, Fe, and Al from silicate minerals In the samples the release of major structural elements of silicates was used as an overall indicator of silicate mineral degradation at 4°C and 18°C from five medium exchanges over 255 days of rock bioleaching The increase of temperature importantly affected the efficiency of Fe extraction from granite and basalt as well as Si extraction from granite and gneiss In comparison with elemental extraction order at 4°C, Ca was substituted first by Fe or Si It is evident that temperature influences rock microbial weathering and results in a change of elements extraction

Journal ArticleDOI
TL;DR: In this article, the authors evaluated a novel approach for buffering subsurface pH that relies on the use of silicate minerals as a long-term source of alkalinity.
Abstract: Accurate control of groundwater pH is of critical importance for in situ biological treatment of chlorinated solvents This study evaluated a novel approach for buffering subsurface pH that relies on the use of silicate minerals as a long-term source of alkalinity A screening methodology based on thermodynamic considerations and numerical simulations was developed to rank silicate minerals according to their buffering efficiency A geochemical model including the main microbial processes driving groundwater acidification and silicate mineral dissolution was developed Kinetic and thermodynamic data for silicate minerals dissolution were compiled Results indicated that eight minerals (nepheline, fayalite, glaucophane, lizardite, grossular, almandine, cordierite, and andradite) could potentially be used as buffering agents for the case considered A sensitivity analysis was conducted to identify the dominant model parameters and processes This showed that accurate characterization of mineral kinetic rate constants and solubility are crucial for reliable prediction of the acid-neutralizing capacity In addition, the model can be used as a design tool to estimate the amount of mineral (total mass and specific surface area) required in field applications

Journal ArticleDOI
TL;DR: In this paper, the influence of petrographic characteristics on the engineering properties of ultrabasic rocks from the Pindos, Vourinos and Koziakas ophiolites was investigated.
Abstract: This paper investigates the influence of petrographic characteristics on the engineering properties of ultrabasic rocks from the Pindos, Vourinos and Koziakas ophiolites. The studied lithologies include dunites, olivine-rich harzburgites, typical harzburgites and plagioclase-bearing lherzolites. Quantitative petrographic analysis indicates that the samples display various percentages of secondary minerals. The peridotites are tested to determine the following engineering parameters: water absorption, apparent density, total porosity, point load index, Schmidt hammer value, aggregate abrasion value and polished stone value. The relationships between the petrographic features and the engineering parameters are determined using regression analysis. The micropetrographic index I rep and the ratios of secondary to primary ( S e / P ) and soft to hard ( S o / H ) minerals provide significant information about the impact of ocean-floor metamorphism on the strength and durability of peridotites. The correlations indicate that the formation of secondary minerals results in mechanically weaker rocks. The polished stone value is the only engineering parameter that is positively affected by the presence of low contents of alteration products. The results also imply that Cr-spinel grains are a major determinant for the preservation of the microroughness of aggregate particles owing to their very hard nature and different mechanical behaviour compared with the surrounding silicate minerals.

Journal ArticleDOI
TL;DR: The Idaho cobalt belt is a 60 km-long alignment of deposits composed of cobaltite, Co pyrite, chalcopyrite and gold with anomalous Nb, Y, Be, and rare-earth elements (REEs) in Mesoproterozoic metasedimentary rocks of the Lemhi Group as discussed by the authors.
Abstract: The Idaho cobalt belt is a 60-km-long alignment of deposits composed of cobaltite, Co pyrite, chalcopyrite, and gold with anomalous Nb, Y, Be, and rare-earth elements (REEs) in a quartz-biotite-tourmaline gangue hosted in Mesoproterozoic metasedimentary rocks of the Lemhi Group. It is the largest cobalt resource in the United States with historic production from the Blackbird Mine. All of the deposits were deformed and metamorphosed to upper greenschist-lower amphibolite grade in the Cretaceous. They occur near a 1377 Ma anorogenic bimodal plutonic complex. The enhanced solubility of Fe, Co, Cu, and Au as chloride complexes together with gangue biotite rich in Fe and Cl and gangue quartz containing hypersaline inclusions allows that hot saline fluids were involved. The isotopes of B in gangue tourmaline are suggestive of a marine source, whereas those of Pb in ore suggest a U ± Th-enriched source. The ore and gangue minerals in this belt may have trapped components in fluid inclusions that are distinct from those in post-ore minerals and metamorphic minerals. Such components can potentially be identified and distinguished by their relative abundances in contrasting samples. Therefore, we obtained samples of Co and Cu sulfides, gangue quartz, biotite, and tourmaline and post-ore quartz veins as well as Cretaceous metamorphic garnet and determined the gas, noble gas isotope, and ion ratios of fluid inclusion extracts by mass spectrometry and ion chromatography. The most abundant gases present in extracts from each sample type are biased toward the gas-rich population of inclusions trapped during maximum burial and metamorphism. All have CO 2 /CH 4 and N 2 /Ar ratios of evolved crustal fluids, and many yield a range of H 2 -CH 4 -CO 2 -H 2 S equilibration temperatures consistent with the metamorphic grade. Cretaceous garnet and post-ore minerals have high R H and R S values suggestive of reduced sulfidic conditions. Most extracts have anomalous 4 He produced by decay of U and Th and 38 Ar produced by nucleogenic production from 41 K. In contrast, some ore and gangue minerals yield significant SO 2 and have low R H and R S values of a more oxidized fluid. Three extracts from gangue quartz have high helium R/R A values indicative of a mantle source and neon isotope compositions that require nucleogenic production of 22 Ne in fluorite from U ± Th decay. Two extracts from gangue quartz have estimated 40 K/ 40 Ar that permit a Precambrian age. Extracts from gangue quartz in three different ore zones are biased toward the hypersaline population of inclusions and have a tight range of ion ratios (Na, K, NH 4 , Cl, Br, F) suggestive of a single fluid. Their Na, Cl, Br ratios suggest this fluid was a mixture of magmatic and basinal brine. Na-K-Ca temperatures (279°–347°C) are similar to homogenization temperatures of hypersaline inclusions. The high K/Na of the brine may be due to albitization of K silicate minerals in country rocks. Influx of K-rich brines is consistent with the K metasomatism necessary to form gangue biotite with high Cl. An extract from a post-ore quartz vein is distinct and has Na, Cl, Br ratios that resemble metamorphic fluids in Cretaceous silver veins of the Coeur d’Alene district in the Belt Basin. The results show that in some samples, for certain components, it is possible to “see through” the Cretaceous metamorphic overprint. Of great import for genetic models, the volatiles trapped in gangue quartz have 3 He derived from a mantle source and 22 Ne derived from fluorite, both of which may be attributed to nearby ~1377 Ma basalt-rhyolite magmatism. The brine trapped in gangue quartz is a mixture of magmatic fluid and evaporated seawater. The former requires a granitic intrusion that is present in the bimodal intrusive complex, and the latter equatorial paleolatitudes that existed in the Mesoproterozoic. The results permit genetic models involving heat and fluids from the neighboring bimodal plutonic complex and convection of basinal brine in the Lemhi Group. While the inferred fluid sources in the Idaho cobalt belt are similar in many respects to those in iron oxide copper-gold deposits, the fluids were more reduced such that iron was fixed in biotite and tourmaline instead of iron oxides.

Journal ArticleDOI
TL;DR: In this paper, major, trace and rare earth elements of phosphatic rocks around Sonrai block of Paleo-Mesoproterozoic age have been determined to evaluate their correlation, relationship with the phosphorus content, the nature of possible substitution of various elements and regional distribution pattern over the area.
Abstract: Major, trace and rare earth elements of phosphatic rocks around Sonrai block of Paleo-Mesoproterozoic age having phosphatic breccia, quartzite, shale, sandstone, limestone and ironstone, have been determined to evaluate their correlation, relationship with the phosphorus content, the nature of possible substitution of various elements and regional distribution pattern over the area. The study indicates that the number of elements is substituted in the apatite structures; few of them are associated with phosphate and carbonate minerals. The variable concentration of major, trace and rare earth elements in the phosphatic rocks has been influenced by various physico-chemical processes involved during weathering and leaching of the source rocks. The distribution of the major, trace and rare earth elements is controlled by the environmental variations in the sediment water interface. The majority of trace elements were mainly influenced by the principle adsorbents like the phosphate minerals in addition to clay, iron oxides and silicate minerals. The PAAS normalized REE patterns of Sonrai block of phosphorites are characterized by negative Ce anomalies and Positive Eu anomalies. It is inferred from the distribution and interrelationship of major, trace and rare earth elements that the deposition of phosphate minerals might have occurred in highly oxidizing to slightly reducing conditions in supratidal to intertidal continental margins and shallow marine environment. The deposition was controlled by marine upwelling leading to excess charge of phosphate in certain zones of phosphogenic basins, lithologic facies variations in restricted circulations of basinal waters and electrochemical factors such as negative Eh, pH and other factors, which influenced the deposition of phosphates. The replacement, precipitation in voids and fissures and diagenesis were also important mechanisms of phosphate generation in Sonrai basin. The main source for various elements may be the minerals of cratonic mass of Bundelkhand Granitic Complex, a basement of Bijawar Basin, which also provided land derived phosphorus through weathering of the terrestrial cover.

Journal ArticleDOI
TL;DR: Analysis of the reported heat-capacity data presented here provides a new self-consistent set of heat capacities for both cations and anions that is compatible (and thus may be combined) with an extensive set developed by Spencer.
Abstract: Single-ion heat capacities, Cp(298)ion, are additive values for the estimation of room-temperature (298 K) heat capacities of ionic solids. They may be used for inferring the heat capacities of ionic solids for which values are unavailable and for checking reported values, thus complementing our independent method of estimation from formula unit volumes (termed volume-based thermodynamics, VBT). Analysis of the reported heat-capacity data presented here provides a new self-consistent set of heat capacities for both cations and anions that is compatible (and thus may be combined) with an extensive set developed by Spencer. The addition of a large range of silicate species permits the estimation of the heat capacities of many silicate minerals. The single-ion heat capacities of individual silicate anions are observed to be strictly proportional to the total number of atoms (Si plus O), n, contained within the silicate anion complex itself (e.g., for the anion Si2O72–, n = 9, for SiO42–, n = 5), Cp(silicate ...

Journal ArticleDOI
TL;DR: In this article, X-ray diffraction studies on a sub-set of the analysed stream sediments showed that Zr is predominantly found in detrital zircon grains.

Journal ArticleDOI
TL;DR: In this article, the authors dealt with the general character of the heavy minerals of Indian beach placer sand deposits with special emphasis on the characters of ilmenite and found that these are mineralogically very complex.
Abstract: Indian beach placer sand deposits are, in general, ilmenite-rich. However, some concentrations are dominated by pyriboles. The Chavakkad-Ponnani (CP) area along the northern Kerala coast is one such deposit. This paper deals with the general character of the heavy minerals of CP with special emphasis on the characters of ilmenite. Most Indian beach sand ilmenites are of good quality. However, our observations on the ilmenites of CP using Optical Microscope, SEM and EPMA reveals that these are mineralogically very complex. The CP ilmenite varies from pure ilmenite to highly impure variety having intergrowths and inclusions of other oxide and silicate minerals. Ilmenite occurs as mixcrystals and forms intergrowth structure with hematite and Ti-hematite/ulvospinel; contains inclusions of hematite, quartz, and monazite. On the other hand ilmenite also occurs as inclusions within hematite and garnet. The pyriboles are dominantly amphiboles with hornblende-composition. Interestingly an inclusion of gold has been recorded within amphibole of hornblende composition. Garnets are mostly of almandine and pyrope type. Subordinate heavy minerals are sillimanite, zircon and rutile. Characteristic morphology, mineralogy and chemistry of amphibole, garnet and ilmenite together indicate that the placer sands of CP area are derived from the amphibolites, granite gneisses and basic igneous rocks lying in the hinterland towards the eastern border of Kerala. Though the overall quality of ilmenite is poor, highgrade ilmenite concentrate can be generated (of course with lower yield), by adopting precise mineral processing techniques. The CP deposit can be considered as a second-grade deposit but it has potential for future exploitation.

Journal ArticleDOI
TL;DR: In this paper, the authors focused on titanosilicate mineral with excellent phololuminescent activity, e.g., benitoite and fresnoite, and introduced a brief review of the synthesis of mineral-related Ti-including silicates and their PL property.
Abstract: Usually, phosphor is composed by host crystal and doped rare-earth ion which is an efficient luminescent centre. However, rare-earth elements have considerably small Clarke number and are produced from specific area. Since titanate and silicate minerals are relatively deposited in the earth’s crust, we focused on titanosilicate mineral with excellent phololuminescent activity, e.g., benitoite and fresnoite. In this article, our recent results about synthesis of mineral-related Ti-including silicates and their PL property are introduced as a brief review. The origin and mechanism of the phololuminescent properties are also described (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

BookDOI
01 Jan 2012
TL;DR: In this paper, the authors focused on the petrological and chemical features of high-Al chromitites associated with serpentinized ultramafi c rocks of mantle origin in the Jordanów-Gogołów and the Braszowice-Brzeźnica massifs, the Sudetes.
Abstract: Abstract: The presented study was focused on the petrological and chemical features of high-Al chromitites associated with serpentinized ultramafi c rocks of mantle origin in the Jordanów-Gogołów and the Braszowice-Brzeźnica massifs, the Sudetes. These massifs are the fragments of the so-called Central Sudetic ophiolite and are located along the edge of the Góry Sowie massif. The studied chromitites form small, lens-like bodies, hosted by serpentinized harzburgites and dunites. They were exploited on the turn of the19th century and at the beginning of the 20th century; after that they fell into obscurity and no reliable geological data is available on them.

Journal ArticleDOI
TL;DR: In this paper, the authors assess the solubilization of silicates during the chemical and bacterial leaching of finely ground black schist in shake flasks and show that the dissolution of main constituent elements from silicate minerals was a function of the pH of the leach solution and no direct role of bacterial action on the solusability of the silicates was evident.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the crystallization products of K-rich silicate and carbonate melts trapped as melt inclusions in clinopyroxene phenocrysts from the Dunkeldyk alkaline igneous complex in the Tajik Republic.
Abstract: This paper reports an investigation of the crystallization products of K-rich silicate and carbonate melts trapped as melt inclusions in clinopyroxene phenocrysts from the Dunkeldyk alkaline igneous complex in the Tajik Republic. Heating experiments on the melt inclusions suggest that the carbonate melt was formed by liquid immiscibility at 1180°C and ~0.5 GPa. The carbonate-rich inclusions are dominated by Sr-bearing calcite, and rich in incompatible elements. Most of the silicate minerals are SiO 2 -poor and rich in K, Ba and Ti. Leucite, kalsilite and aegirine are the earliest magmatic minerals. High Ba and Ti contents in the melt resulted in the crystallization of Ba-rich K-feldspar, titanite, perovskite and Ti-bearing garnet, and the rare Ba-Ti silicates fresnoite and delindeite. The last minerals to crystallize from volatile-rich melts and fluids were aegirine, gotzenite, K-Ba- and Ca-Sr-bearing zeolites, fluorite and strontium-rich baryte. Interaction of the early minerals with residual melts and fluids produced Ba-rich phlogopite and Sr-rich apatite.

01 Dec 2012
TL;DR: In this paper, the authors measured synchrotron Mossbauer spectra (SMS) of the high-spin Fe2+ in Fe-bearing pyrope garnet with two distinct compositions, (Mg0.8Fe0.2)3Al2Si3O12 (py80alm20) and Fe3Al 2Si3 O12 (alm100), up to 30 GPa and 750 K.
Abstract: Iron-bearing pyrope, an abundant silicate mineral in the Earth’s upper mantle, exhibits the largest quadrupole splitting (QS) in Mossbauer spectra among all common Fe-bearing rock-forming silicate minerals at ambient conditions, with a value of ~3.5 mm/s. Knowledge regarding the hyperfine QS of mantle minerals at relevant pressures and temperatures ( P-T ) is needed to aid our understanding of the electronic spin and valence states of iron and local site distortion in major mantle silicate minerals. The latter, in turn, is relevant for coherent model of electronic and mechanical properties of the Earth’s mantle. Here we have measured synchrotron Mossbauer spectra (SMS) of the high-spin Fe2+ in Fe-bearing pyrope garnet with two distinct compositions, (Mg0.8Fe0.2)3Al2Si3O12 (py80alm20) and Fe3Al2Si3O12 (alm100), up to 30 GPa and 750 K. Analyses of the SMS spectra revealed that the high-spin Fe2+ ions in the distorted dodecahedral site exhibit extremely high QS of ~3.4–3.6 mm/s and relatively high chemical shifts (CS) of ~1.2–1.3 mm/s at high P-T , indicating that the Fe2+ ions remain in the high-spin state. An increase in the Fe content in the pyrope-almandine series only slightly decreases the QS and CS of the Fe2+ ions. To decipher the energy separation (Δ) between the two lowest energy levels of the 3 d electrons of the Fe2+ ions in the sample, the d xy and d z 2 orbitals, the QS values of py80alm20 at high P-T were further evaluated using Huggins model. Our modeled results show that the Δ of the Fe2+ ions in py80alm20 is ~156 meV at high P-T , and may be correlated to the change of the crystal-field energy splitting (ΔC). Comparison of the QS, Δ, and ΔC values of Fe2+ ions in the distorted dodecahedral sites of pyrope and silicate perovskite indicates that the high-spin Fe2+ with the extremely high QS can remain stable at high P-T conditions, consistent with recent theoretical predictions. Our results thus contribute to our current understanding of the hyperfine parameters and spin and valence states of iron in the mantle silicate minerals at high P-T .

Journal ArticleDOI
TL;DR: In this paper, practical temperature ranges were established by using well-characterized lithium fluoride (LiF, TLD-100®) at 4 different research institutes in Korea.
Abstract: EN 1788:2001 suggests defining the temperature range for the thermoluminescence (TL) heating unit to calculate the TL ratio (TL1/TL2). In the present study, practical temperature ranges were established by using well-characterized lithium fluoride (LiF, TLD-100®) at 4 different research institutes in Korea. Temperature ranges differed according to models of TLD heating unit, which were wide in the case of RISO (160–249°C) as compared with Harshaw (155–232°C) TLD readers. The silicate minerals separated from irradiated turmeric samples were measured to check these intervals on a practical basis. The X-ray diffraction (XRD) analysis of separated minerals showed that quartz and feldspar minerals were the main source of well-characterized TL glow curve following irradiation. The TL glow peaks from the separated minerals were narrower in Harshaw than RISO TLD readers. The TL ratios determined after re-irradiation (1 kGy) for the tested minerals, using the pre-defined temperature intervals, provided the satisfactory results.

01 Jan 2012
TL;DR: X-ray diffraction is commonly employed in many branches of experimental science, such as physics, chemistry, biochemistry, and geology among others as discussed by the authors, which explains the important role played by X-ray crystallography in their study.
Abstract: Minerals are geological resources of major economic importance. Most of them are crystalline which explains the important role played by crystallography in their study. Minerals may occur either massive or forming characteristic geometric forms known as crystals. In 1912, Max von Laue discov- ered the diffraction of X-rays by crystals and almost immediately diffraction methods were applied to the structural characterization of minerals. One early success of X-ray crystallography was the structural classification of silicate minerals. However, application of X-ray diffraction was not limited to miner- als. It was soon used for the structural characterization of molecular crystals as well and, later on, even of proteins. Nowadays, crystallography is commonly employed in many branches of experimental sci- ences such as physics, chemistry, biochemistry, and geology among others.

Journal ArticleDOI
TL;DR: In this article, the authors examined the USGS spectral library of common silicate minerals and found that some showing these absorption features are not hydroxylated and/or hydrated but with slight alteration or impurities.
Abstract: Hyperspectral imaging is broadly used in the identification of hydroxylated and hydrated silicate minerals, especially at the wavelengths of 1.0 to 2.5 µm. The vibrations of the hydroxyl (OH) molecule, water molecule (H−O−H), and metal−OH bonds, or their combinations, produce prominent absorption features at ∼ 1.40, ∼ 1.91, and 2.20 to 2.40 μm wavelengths. In remote sensing applications, minerals showing one or two of these absorption features are usually categorized as hydroxylated and/or hydrated, and minerals showing all three absorption features are usually categorized as hydrated phyllosilicates. We examine the USGS spectral library of common silicate minerals and find that some showing these absorption features are not hydroxylated and/or hydrated but with slight alteration or impurities. This implies that the identification of hydroxylated and/or hydrated silicate minerals may not be merely based on these absorption features. Rather, incorporation of geological and environmental background is also important. We further calculate the absorption depths and silicate mineral ratios in these absorption features as references for discrimination. This study provides a cautionary perspective on the identification of hydrated phyllosilicate minerals with respect to mineralogical interpretations of Mars and other planets.

Journal Article
TL;DR: In this paper, the effect of composition and structure of modified steel slag on its hydration activity was investigated with X-ray diffraction, optical microscopy, determination of compressive strength and isothermal calorimeter.
Abstract: The process that steel slag from electric arc furnace(EAFSS) and fly ash(FA) were incorporated into ordenary oxygen furnace steel slag(BOFSS) to reheat and modify its mineralogical composition and structure at high temperature was simulated in laboratory.The effect of composition and structure of modified BOFSS on its hydration activity was investigated.The mineralogical composition,microstructure and hydration activity of both BOFSS and modified steel slag(MSS) were investigated with X-ray diffraction(XRD),optical microscopy,determination of compressive strength and isothermal calorimeter.The results show that after modification,the amount of silicate minerals in MSS is decreased with increasing use level of FA,whereas the amount of silicate minerals is increased with increasing use level of EAFSS.As a result,the crystal size of alite in MSS becomes bigger with low alkalinity,however,amount of alite in MSS with high alkalinity is increased,and morphology of alite in MSS is regular with much less free CaO.The cumulative hydration heat for sample GB40-1350 is greater than that for BOFSS by 1.9 times at 3 days,and the compressive strength of cement paste incorporating 30%(by mass) of ground sample GB40-1350 to replace cement reaches 99.9% of that for pure cement pastes at 28 days.