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Showing papers on "Silicate minerals published in 1989"


Journal ArticleDOI
01 Jun 1989-Geology
TL;DR: In this paper, it was shown that up to 34% of the sodium in the total dissolved stream load may be due to cation exchange rather than sodium production via silicate dissolution weathering reactions.
Abstract: Unpolluted rivers and streams that drain marine shales show an excess of sodium compared to chloride and a deficiency of calcium and magnesium compared to sulfate and alkalinity. This is due in part to cation exchange of sodium for divalent cations on clay minerals. Consideration of the global weathering budget suggests that up to 34% of the sodium in the total dissolved stream load may be due to cation exchange rather than sodium production via silicate dissolution weathering reactions. These results suggest that the weathering budgets for sodium and calcium are in need of revision because of the inclusion of cation-exchange processes in the weathering cycle. This implies that silicate dissolution is less important in determining the composition of global river water than was previously thought.

223 citations


Journal ArticleDOI
29 Sep 1989-Science
TL;DR: Limited data for the diffusion of argon in silicates suggest that the model describes this system as well, and may be used to predict diffusion coefficients.
Abstract: An empirical model describing the diffusion kinetics of oxygen in silicate minerals under hydrothermal conditions has been established for temperatures between 773 and 1073 Kelvin at 100 megapascals of water pressure. The equation, log D = α + (β/T) + [(γ + (δ/T))Z], where D is the diffusion coefficient, α, β, γ, and δ are constants, T is the Kelvin temperature, and Z is the total ionic porosity, may be used to predict diffusion coefficients, in most cases to within the reported experimental reproducibility of a factor of 2. For oxygen diffusion, α = -2, β = -3.4 x 104K, γ = -0.13, and δ = 6.4 x 102K, for D in square centimeters per second. Limited data for the diffusion of argon in silicates suggest that the model describes this system as well.

185 citations



Journal ArticleDOI
TL;DR: Local saturation is an attractive mechanism for enhancing fractionation during crystallization differentiation as discussed by the authors, but it is not a process that applies to all cases and some inconsistencies remain in local saturation origin for accessory phases that cannot be evaluated without additional information.

183 citations




Journal ArticleDOI
TL;DR: In this paper, the electrostatic potentials of approximately 500 anion sites in 165 rock-forming mineral endmembers have been computed and presented along with coordination numbers, coordinating cations, and mean cation-anion distances.

78 citations


Journal ArticleDOI
TL;DR: In this paper, a complete thermodynamically consistent equation of state which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to reverse phase transition kinetics from those due to material strength.
Abstract: Shock and unloading experiments on quartz and silicate rocks indicate that the release adiabats lie below the Hugoniot. The hysteresis and energy dissipation inherent in this situation have important wave propagation implications. On loading, there is a pressure‐induced transition to the stishovite phase which does not occur under conditions of thermodynamic equilibrium, in that the Hugoniot passes through a metastable mixed‐phase region for several tens of GPa. One interpretation of the unloading data is that the transition is not reversible, and the phase mixture remains frozen on unloading. However, material strength may also play a role. A complete thermodynamically consistent equation of state which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to reverse phase transition kinetics from those due to material strength. The model allows quantitative determination of the effect of reverse transition kinetics on ground shock propagation in silicate materials.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the partitioning behavior of rare earth elements (REE) between immiscible silicate liquids and found that REE preferentially partition into the end-member liquids that are rich in network-modifying cations.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of lattice strain on mineral dissolution rates was examined by comparing the dissolution rates of shocked and unshocked minerals, and the results suggest that surface dislocations produced by the shock treatment are not the primary sites for dissolution reactions.

44 citations


Journal ArticleDOI
TL;DR: The lower Neogene unit of the Karlovassi basin, Samos island, Greece, was deposited in a continental basin during Miocene times and consists of four successions overlying a basal conglomerate as discussed by the authors.
Abstract: The lower Neogene unit of the Karlovassi basin, Samos island, Greece, was deposited in a continental basin during Miocene times and consists of four successions overlying a basal conglomerate. The four successions are, from the base upward, carbonates, tuffaceous rocks, claystones, and porcelanites.Volcanic glass was originally abundant in the tuffaceous succession but is now represented by its diagenetic products, including boron-bearing K-feldspar; the zeolites clinoptilolite, analcite, and mordenite; smectite; opal (disordered tridymite-cristobalite); cristobalite; and minor amounts of the zeolites erionite, phillipsite, and chabasite; and tridymite.Evaporite minerals such as gypsum, celestite, and thenardite are present along with authigenic silicates in tuffaceous intervals into the claystone succession. Authigenic silica polymorphs represented by opal and chalcedony were identified in the uppermost succession of porcelaneous limestones to chert.Five irregular concentric zones related to the presence and kind of zeolites and K-feldspar are recognized in the lower Neogene unit: (1) a marginal zone of carbonate and detrital silicate minerals (nonauthigenic silicates), (2) a clinoptilolite zone, (3) a mixed clinoptilolite-analcite zone, (4) an analcite zone, and (5) a central boron-bearing K-feldspar zone.The general pattern of zonation and distribution of authigenic silicates as well as their chemical characteristics indicates the presence of a saline-alkaline lake during Miocene times. This lake is analogous to those of the same age which existed in southern Yugoslavia and western Turkey, where borate, sulfate, and double carbonate deposits were formed along with authigenic silicates. It is possible that a large continental area in the eastern Mediterranean underwent large-scale dessication which took place during the Miocene (Messinian salinity crisis), resulting in the development of highly saline-alkaline lacustrine environments.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the magnetism and mineralogy of the titanohematite and the inclusion-bearing augites in one granulite sample using transmission electron microscopy (TEM) and magnetic experiments to understand better the remanence properties of naturally occurring Fe-Ti oxides and their relationships to silicate minerals.
Abstract: Granulites from southwest Lofoten, Norway, often carry intense and stable components of natural remanent magnetization (NRM). Coercivities in excess of 100 mT and blocking temperatures up to 580°–645°C are common. Several phases in these rocks can carry stable components of NRM. Clinopyroxenes (augite with exsolved pigeonite and orthopyroxene) usually contain abundant Fe-Ti oxides, the majority of which are too small to be studied conclusively with visible light. Additionally, these rocks typically contain coarse-grained (∼100–1000 μm) exsolution intergrowths of rhombohedral Fe-Ti oxides and coarse-grained magnetite. We have studied the magnetism and mineralogy of the titanohematite and the inclusion-bearing augites in one granulite sample using transmission electron microscopy (TEM) and magnetic experiments to understand better the remanence properties of naturally occurring Fe-Ti oxides and their relationships to silicate minerals. The coarse-grained titanohematite has a coercivity of 350 mT and a laboratory saturation remanence that unblocks at 570°–600°C. The hysteresis characteristics of this titanohematite are typical of much smaller ∼10μm-sized single domains, which apparently reflects the presence of exsolved ilmenite lamellae, as small as <10 nm in thickness. These lamellae presumably inhibit (1) domain wall nucleation and (2) movement of walls that manage to nucleate. The inclusions in the augites serve as carriers of lower coercivity remanence with blocking temperatures less than about 560°C. Magnetite, hematite, and ilmenite are present in the augite, and intergrowth of the rhombohedral phases, revealed by TEM, persists down to the 20-nm scale. The distribution of the magnetite inclusions in the augite appears to be unrelated to any silicate microstructure, while that of the rhombohedral Fe-Ti oxides is strongly controlled by silicate microstructure, with intergrowths of these oxides commonly decorating lamellae of pigeonite, orthopyroxene, and clinoamphibole within the augite. The NRM of this sample possibly dates from the amphibolite facies metamorphism that the region experienced about 1000 m.y. ago. Paleomagnetic studies of these rocks could readily recover virtual geomagnetic poles dating from this event. In addition to the included oxides, the augites display a number of unusual features that probably result from the protracted polymetamorphic history of these granulites: pigeonite lamellae are not parallel to the b-crystallographic axis, pigeonite lamellae cut across those of orthopyroxene and numerous included minerals occur. Rare earth elements are concentrated within inclusions that reside in the augite.


Patent
30 Oct 1989
TL;DR: In this article, a monomolecular film is formed on the surface of the silica-containing minerals and silicates by coating them with an aqueous solution containing a compatible silane coupling agent.
Abstract: Cytotoxic effects associated with ground fractured silica-containing minerals and silicates, including asbestos, are prevented by coating the silica-containing minerals and silicates with an aqueous solution containing an aqueously compatible silane coupling agent so that a monomolecular film is formed on the surface of the silica-containing minerals and silicates.

Journal ArticleDOI
TL;DR: In this article, an early Cretaceous age of 114±4 Ma for the same molybdenite deposit was reported, and a rather large discrepancy was found between the Re-Os ages for molydenite and the K-Ar and Rb-Sr ages for silicate minerals from the same ore deposits of Mesozoic-Cenozoic ages in the Circum-Pacific region.
Abstract: Three K-Ar ages were determined on rocks and minerals from the mineralized areas in the east-central part of the Kitakami Cretaceous granitic terrain, where a Paleogene mineralization age was reported recently on molybdenite by the Re-Os method. The present result showed an early Cretaceous age of 114±4 Ma for the same molybdenite deposit. A rather large discrepancy was found between the Re-Os ages for molybdenite and the K-Ar and Rb-Sr ages for silicate minerals from the same ore deposits of Mesozoic-Cenozoic ages in the Circum-Pacific region, indicating that the Re-Os method needs further examination.

Journal ArticleDOI
TL;DR: The characteristics of ferromanganese concretion samples of various morpho-chemistries at elevated temperatures have been investigated in this article, where four unique physical properties such as high porosity, large surface area, high water content and ultrafine particle size were investigated.

Journal ArticleDOI
TL;DR: In this article, MeV ion beam techniques (resonant nuclear reactions and Rutherford backscattering spectrometry) are used to study the dissolution of various silicate minerals (quartz, albite, olivine).

Book ChapterDOI
TL;DR: The Miocene Chalk Hills Formation of southwestern Idaho consists mainly of interbedded mudstone, siltstone, diatomite, and vitric tuffs that were deposited in a chiefly freshwater lake as discussed by the authors.
Abstract: The Miocene Chalk Hills Formation of southwestern Idaho consists mainly of interbedded mudstone, siltstone, diatomite, and vitric tuffs that were deposited in a chiefly freshwater lake. Throughout most of the outcrop belt, the tuffs are unaltered, but south of Oreana, the tuffs are completely altered to clinoptilolite with or without smectite and opal-CT. The zeolitic zone extends parallel to the southern margin of the Snake River Plain for about 21 km. The zeolites and associated silicate minerals undoubtedly formed during diagenesis by hydrolysis and dissolution of rhyolitic glass by pore water that was trapped in the tuffs during lacustrine sedimentation.

Book ChapterDOI
01 Jan 1989
TL;DR: Polytypism is a crystallographic property of a large number of crystallized, organic as well as inorganic, substances as discussed by the authors and it is also found in silicate minerals like chain-, ribbon-, and sheet-silicates.
Abstract: Polytypism is a crystallographic property of now a large number of crystallized, organic as well as inorganic, substances. Among inorganic substances, this property is displayed by crystals of some metals, metallic alloys, semiconducting compounds of the III-V, II-VI, I-VII and ternary types as well. It is also found in silicate minerals like chain-, ribbon-, and sheet-silicates but also among non-silicate minerals like diamond, graphite, molybdenite, pyrrhotite, perovskites, for instance.

Book Chapter
01 Jan 1989
TL;DR: The analytical electron microscope (AEM) has rapidly become a versatile instrument for qualitative and quantitative elemental analyses of many materials, including minerals as discussed by the authors, and it is possible to obtain high spatial resolution (~20nm diameter) and precise elemental analyses from many silicate minerals.
Abstract: The Analytical Electron Microscope (AEM), with which secondary X-ray emission from a thin (<150nm), electron-transparent material is measured, has rapidly become a versatile instrument for qualitative and quantitative elemental analyses of many materials, including minerals. With due regard for sources of error in experimental procedures, it is possible to obtain high spatial resolution (~20nm diameter) and precise elemental analyses (~3% to 5% relative) from many silicate minerals. In addition, by utilizing the orientational dependence of X-ray emission for certain multi-substituted crystal structures, site occupancies for individual elements within a unit cell can be determined though with lower spatial resolution. The relative ease with which many of these compositional data may be obtained depends in part on the nature of the sample, but, in general, is comparable to other solid state analytical techniques such as X-ray diffraction and electron microprobe analysis. However, the improvement in spatial resolution obtained with the AEM (up to two orders of magnitude in analysis diameter) significantly enhances interpretation of fine-grained assemblages in many terrestrial or extraterrestrial rocks.

01 Dec 1989
TL;DR: In this article, the authors measured the mass absorption coefficients of ground samples of olivine, diopside, and serpentine and also smoke samples that were prepared from these minerals using pulsed laser radiation in air.
Abstract: The infrared spectra of crystalline minerals predicted in theoretical condensation sequences do not match the astronomical observations Since the astronomical spectra are a closer match to glassy silicates, the authors undertook a study to measure the infrared spectra of glassy silicates that have compositions similar to silicate minerals predicted in theoretical condensation sequences The data should support observations aimed at elucidating condensation chemistry in dust forming regions The authors measured the mass absorption coefficients, from 25 to 25 microns, of ground samples of olivine, diopside, and serpentine and also smoke samples that were prepared from these minerals The smoke samples prepared in this way are predominantly glassy with nearly the same composition as the parent minerals The crystalline samples consisted of pure olivine ((Fe(01)Mg(09))(2)SiO(4)), serpentine, diopside Sample purity was confirmed by x ray diffraction Each mineral was ground for 10 hours and a measured mass of the powder was mixed with KBr powder for absorption measurements using the method of Borghesi et a (1985) The smoke samples were prepared from the same samples used for grinding by vaporizing the minerals using pulsed laser radiation in air The smoke samples formed by condensation of the resulting vapor The smoke settled onto infrared transparent KRS-5 substrates and onto a quartz crystal microbalance used to obtain mass measurements A description of the preparation method is given in Stephens (1980) The glassy diopside showed only diffuse electron diffraction peaks and hence was nearly amorphous, while the serpentine smoke showed a weak diffraction pattern corresponding to MgO The smoke from olivine showed a weak diffraction pattern corresponding to Fe2O3 and/or Fe3O4 The mass absorption coefficients, from 25 to 25 microns, of crystalline diopside, olivine, and serpentine and their corresponding smoke samples are shown in figures


Journal Article
TL;DR: In this paper, the authors describe new and improved beneficiation techniques available to allow the production of clay minerals of exceptionally high purity, particularly for kaolins and smectites.
Abstract: The author describes new and improved beneficiation techniques available to allow the production of clay minerals of exceptionally high purity. This is particularly true for kaolins and smectites. Wet processing techniques include particle size separation, high intensity magnetic separation, chemical leaching, flotation, and selective flocculation. The blending of clay minerals with other minerals provides opportunities to make special ceramic materials such as cordierite and other minerals that have very special ceramic properties including low heat expansion, high fired strength, low absorption, and other desired qualities.

Journal ArticleDOI
TL;DR: In this article, the surface properties of silicate minerals, such as zeta-potential, flocculation dispersion characteristics and floatability, are influenced by acid pretreatment.
Abstract: It is not clear that the surface properties of silicate minerals, such as zeta-potential, flocculation dispersion characteristics and floatability, are influenced by acid pretreatment.In this paper, the surface property changes of quartz, albite and forsterite which show the typical changes among some silicate minerals with HCl treatment and aging time in the water are investigated.The results obtained are summarized as follows.(1) Results of zeta-potential measurement showed that:a) Quartz-water system could be regarded as a system without specifically adsorbed ions.b) In albite-water system, the first hydroxy complexes of multivalent cations which are dissolved from the mineral surface could re-adsorb onto the mineral surface.c) In forsterite-water system, the readsorption of the complexes and changes in the surface structure of the mineral by acid pretreatment could considerably affect the zeta-potential.(2) Flocculation dispersion characteristics depends dominantly on the absolute value of zeta-potential, that is, on the electrostatic interaction among mineral particles in solution regardless of the causes for the potential generation.(3) Flotation behavior of quartz and albite with. DAC as a collector could be explained in terms of its electrostatic adsorption on their surfaces. In the case of forsterite, additional factors such as crystallinity and smoothness of mineral surface must be considered. That is, the increasing degree of perfection and homogeneity in surface structure of the mineral by acid pretreatment has a tendency to enhance its floatability.

Journal Article
TL;DR: In this paper, the authors reported that the sulfate and carbonate-bearing minerals are contained in the same particles of airborne dust as the dominant silicate minerals, and that the dust optical depth is about 0.6 at a reference wavelength of 0.3 micron over the area of the observed spots.
Abstract: Spectra of the Martian thermal emission in the 5.4-10.5 micron region are reported. Emission features at 7.8 and 9.7 microns are attributed to surface silicates, and an emission feature at 6.1 micron is attributed to a molecular water component of the surface material. An absorption band at 8.7 micron and a possible one at 9.8 microns is attributed to sulfate or bisulfate anions probably located at a distorted crystalline site, and an absorption band at 6.7 microns is attributed to carbonate or bicarbonate anions located in a distorted crystalline site. Spectral simulations indicate that the sulfate- and carbonate-bearing minerals are contained in the same particles of airborne dust as the dominant silicate minerals, that the dust optical depth is about 0.6 at a reference wavelength of 0.3 micron over the area of the observed spots, and that sulfates and carbonates constitute 10-15 percent and 1-3 percent by volume of the airborne dust, respectively.

Journal ArticleDOI
TL;DR: In this article, the chemical compositions of silicate minerals, sulphide minerals and metal Fe-Ni in the Qinzhen meteorite were measured by the microprobe analyses, and the cosmochemical behaviour and characteristics of the existing forms of themajor elements in Qinzen meteorite have been discussed.
Abstract: The chemical compositions of silicate minerals, sulphide minerals and metal Fe-Ni in theQingzhen meteorite were measured by the microprobe analyses. Based upon these chemicalcompositions, the cosmochemical behaviour and characteristics of the existing forms of themajor elements in the Qinzhen meteorite have been discussed. These characteristics show thatunder the S-rich, O-poor, and strongly reducing conditions, the light metal elements, such asCa, Mg, K, Na may form sulphide, and metal Fe-Ni may contain Si and P. However, we con-sider that the light metal-sulphide can be stable in the lower mantle and there are some Siand P in the Fe-Ni core. Finally, an earth core-mantle model is established, where the Fe-Ni core contains some Si and P; the lower mantle is composed of Mg-rich silicate, SiO_2 andsulphide; the upper mantle, of silicate and oxide.


Dissertation
01 Jan 1989
TL;DR: In this article, the authors describe the use of both solid and solution-state NMR techniques to investigate the properties of a wide variety of silicon-containing materials, and demonstrate that where structural information can be obtained from these systems using other techniques (e.g. X-ray diffraction) NMR proves to be a valuable adjunct.
Abstract: The purpose of this thesis is to describe research, using both solid and solution-state NMR techniques, to investigate the properties of a wide variety of silicon-containing materials. One solid-state (^29)Si NMR technique ((^29)Si-(^1)H cross-polarisation), and the experimental aspects important when using it, has been discussed in detail, and later used together with single pulse (^29)Si NMR techniques, to obtain information concerning geometry and local site symmetry of silicon sites in organo silicon compounds and silicate minerals. These techniques, together with a range of h CRAMPS experiments have also proved to be powerful tools for investigating the structure and properties of porous silicate gels (i.e. xero gels). (^29)Si and (^23)Na NMR measurements have been used to acquire evidence for the relaxation mechanisms of silicate species present in aqueous alkaline silicate solutions, and a technique for investigating the properties of sodium ions in colloidal silica solutions is tentatively proposed. Conclusions are drawn from the results obtained, demonstrating that where structural information can be obtained from these systems using other techniques (e.g. X-ray diffraction) NMR proves to be a valuable adjunct. However, in situations where this information is unknown or difficult to obtain using other techniques, NMR may yield new insights into the structural properties of the materials.

Journal ArticleDOI
TL;DR: Two mica schists and three talc minerals from Jhabua and Dhar districts of Madhya Pradesh hare been studied using DTA and TGA techniques Structural changes accompanying dehydration and thermal transformations in different silicate minerals have been studied Suitability of these minerals as additive for filling and reinforcement in polymer and in alloys has been assessed SEM micrographs of the heat treated minerals are presented as mentioned in this paper.
Abstract: Two mica schists and three talc minerals from Jhabua and Dhar districts of Madhya Pradesh hare been studied using DTA and TGA techniques Structural changes accompanying dehydration and thermal transformations in different silicate minerals have been studied Suitability of these minerals as additive for filling and reinforcement in polymer and in Al-alloy has been assessed SEM micrographs of the heat treated minerals are presented

Journal ArticleDOI
Li Yan1, Wang Xuchen1
TL;DR: The presence of SO4 and K at stations H14 and H15 were found most likely to be due to the addition and removal processes, that of the other major consituents may be mainly controlled by physical mixing in this estuary as mentioned in this paper.
Abstract: 1. The nonanthropogenic SO4 in the Changjiang River stems from weathering and oxidation of sulphate and sulphite minerals, while the anthropogenic SO4 here is attributed to acid rain containing H2SO4 formed by atmospheric sulphur oxides derived from the burning of fossil fuels in the region of the lower reaches. Ca and Mg are probably derived from weathering of carbonate minerals, but possibly less from weathering of silicate minerals. 2. The Changjiang River estuary is characterized by two—layer flow based on the salinity section of the estuary, so a model of two—layer exchange of water—body in the Changjiang River estuary can be advanced. 3. The presence of SO4 and K at stations H14 and H15 were found most likely to be due to the addition and removal processes, that of the other major consituents may be mainly controlled by physical mixing in this estuary.