Layer-lattice Silicates Research Articles

Effect of excess pore pressure on the long runout of debris flows over low gradient channels: A case study of the Dongyuege debris flow in Nu River, China

Debris flows with long reaches are one of the major natural hazards to human life and property on alluvial fans, as shown by the debris flow that occurred in the Dongyuege (DYG) Gully in August 18, 2010, and caused 96 deaths. The travel distance and the runout distance of the DYG large-scale tragic debris flow were 11km and 9km, respectively. In particular, the runout distance over the low gradient channel (channel slope<5°) upstream of the depositional fan apex reached up to 3.3km. The build-up and maintenance of excess pore pressure in the debris-flow mass might have played a crucial role in the persistence and long runout of the bouldery viscous debris flow.Experiments to measure pore pressure and pore water escape have been carried out by reconstituting the debris flow bodies with the DYG debris flow deposit. The slurrying of the debris is governed by solid volumetric concentration (SVC), and the difference between the lower SVC limit and the upper SVC limit can be defined as debris flow index (Id). Peak value (Kp) and rate of dissipation (R) of relative excess pore pressure are dependent on SVC. Further, the SVC that gives the lowest rate of dissipation is regarded as the optimum SVC (Cvo). The dissipation response of excess pore pressure can be characterized by the R value under Cvo at a given moment (i.e., 0.5h, 1h or 2h later after peak time). The results reveal that a relatively high level of excess pore pressure developed within the DYG debris-flow mass and had a strong persistence capability.Further research shows that the development, peak value and dissipation of excess pore pressure in a mixture of sediment and water are related to the maximum grain size (MGS), gradation and mineralogy of clay-size particles of the sediment. The layer-lattice silicates in clay particles can be the typical clay minerals, including kaolinite, montmorillonite and illite, and also the unrepresentative clay minerals such as muscovite and chlorite. Moreover, small woody debris can also contribute to the slurrying of sediments and maintenance of debris flows in well vegetated mountainous areas and the boulders suspended in debris flows can elevate excess pore pressure and extend debris-flow mobility.The parameters, including Id, Kp, R and etc., are affected by the intrinsic properties of debris. They, therefore, can reflect the slurrying susceptibility of sediments, and can also be applied to the research on the occurrence mechanisms and risk assessment of other debris flows.

Observations with the Visual and Infrared Mapping Spectrometer (VIMS) during Cassini's flyby of Jupiter

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer covering the wavelength range 0.3–5.2 μm in 352 spectral channels, with a nominal instantaneous field of view of 0.5 mrad. The Cassini flyby of Jupiter represented a unique opportunity to accomplish two important goals: scientific observations of the jovian system and functional tests of the VIMS instrument under conditions similar to those expected to obtain during Cassini's 4-year tour of the saturnian system. Results acquired over a complete range of visual to near-infrared wavelengths from 0.3 to 5.2 μm are presented. First detections include methane fluorescence on Jupiter, a surprisingly high opposition surge on Europa, the first visual-near-IR spectra of Himalia and Jupiter's optically-thin ring system, and the first near-infrared observations of the rings over an extensive range of phase angles (0–120°). Similarities in the center-to-limb profiles of H + 3 and CH 4 emissions indicate that the H + 3 ionospheric density is solar-controlled outside of the auroral regions. The existence of jovian NH 3 absorption at 0.93 μm is confirmed. Himalia has a slightly reddish spectrum, an apparent absorption near 3 μm, and a geometric albedo of 0.06±0.01 at 2.2 μm (assuming an 85-km radius). If the 3-μm feature in Himalia's spectrum is eventually confirmed, it would be suggestive of the presence of water in some form, either free, bound, or incorporated in layer-lattice silicates. Finally, a mean ring-particle radius of 10 μm is found to be consistent with Mie-scattering models fit to VIMS near-infrared observations acquired over 0–120° phase angle.

Mg-Rich Silicate Crystals in Comet Hale–Bopp: ISM Relics or Solar Nebula Condensates?

We compare the HIFOGS 10-μm spectra of Comet C/1995 (O1) (Hale–Bopp) to the mid-IR spectra of interplanetary dust particles (IDPs). The four epochs of Hale–Bopp silicate features, at 2.8 AU (pre-perihelion), 1.2 AU (pre-perihelion), 0.93 AU (10 days after perihelion), and 1.7 AU (post-perihelion) have different spectral shapes. At smaller heliocentric distances, r h≤1.7 AU, there appears to be enhanced mid-IR emission (i.e., 9.3- and 10.5-μm peaks) from Mg-rich pyroxene crystals. A two-temperature model of warm amorphous and crystalline olivines, warm amorphous pyroxenes, and ∼165 K cooler pyroxene crystals is successful with laboratory silicate minerals (D. H. Wooden et al. 1999, Astrophys. J. 517, 1034–1058). A two-temperature model using IDPs as cometary dust particle analogs also fits Comet Hale–Bopp's silicate features, with the pyroxene IDP ∼50 K cooler than the olivine and layer–lattice silicate IDPs. The warm layer–lattice silicate IDP contributes a broad 20-μm feature which is not in the Infrared Space Observatory Short Wavelength Spectrometer (ISO SWS) spectrum of Hale–Bopp at 2.8 AU, making it a questionable cometary component. On the other hand, members of the ``cluster IDP" subclass of pyroxene IDPs fit Hale–Bopp's 10-μm spectra better than other pyroxene IDPs. Cluster IDPs are highly fragile and contain significant deuterium enrichments, indicating their presolar origin. By spectroscopic analogy, Comet Hale–Bopp's Mg-rich pyroxene crystals may also be relic interstellar grains. The IDP and mineral models for Comet Hale–Bopp indicate the importance of multiple grain components at different temperatures to explaining the temporal evolution of the observed infrared features. Relative abundances of minerals depend on their relative temperatures. Cooler grains may be more abundant than warmer grains and yet may remain hidden from detection in the 10-μm silicate feature because of their cooler temperatures. The deduced larger abundance of cooler, pyroxene-dominated grains in Comet Hale–Bopp affects the interpretation of the origin of cometary dust, and dust evolution during protoplanetesimal accumulation and disk dissipation.

Electrolyte-Induced Aggregation of Gold Particles on Solid Surfaces

An electron microscope study has been made of the aggregation of small particles of gold (ca. 2-nm radius) supported on the surfaces of different solid materials (amorphous carbon, silicon monoxide, and layer-lattice silicates) when immersed in aqueous electrolyte solutions. Particle aggregation on relatively rough surfaces of carbon and silicon monoxide, where weak particle-substrate adhesion allows reasonably high particle migration rates, occurs by a primary minimum interaction. On the smooth surfaces of silicate minerals, particle aggregates formed at room temperature in solutions of sodium chloride having concentrations ⩾ ca. 5 × 10-2 mol dm-3 and pH values within the range 8-10 were found to exhibit a reasonably uniform particle separation distance (1.7 ± 0.7 nm), indicating a secondary minimum interaction. Similar dispersions immersed in aqueous sodium nitrate under comparable conditions remained colloidally stable, even at electrolyte concentrations in the region of 4 mol dm-3. Secondary minimum aggregation was, however, found to occur in these latter systems at elevated temperatures (≥40°C). In the case of silicate-supported dispersions, lowering the pH of the electrolyte solution within the range of pH 7-2 was found to be accompanied by an increasing tendency toward particle coalescence. This effect became dominant in the region of the pH (PZC) of the gold surface. Whilst the aggregation behavior of particles supported on the surfaces of carbon and silicon monoxide can be described reasonably well in terms of the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO), this theory is entirely inadequate to account for particle aggregation on the surfaces of the silicate minerals. In these latter cases, particle aggregation behavior can be modeled satisfactorily by including an interparticle repulsive force, attributed to the structuring of solvent molecules at the particle surfaces, which decays in a simple exponential manner with increasing distance of separation. The observed effects of surface electrical potential, pH, and temperature on the colloid stability of these systems support the view that counterion hydration plays a major role in the development of structural interactions between electrically charged particles dispersed in aqueous media.

Constraints on the Parent Bodies of Collected Interplanetary Dust Particles

AbstractSamples of interplanetary dust particles (IDPs) have now been collected from the stratosphere, from the Earth’s ocean beds, and from the ice caps of Greenland and Antarctica The most likely candidates for the sources of these particles are comets and asteroids. Comparison of the infrared spectra, elemental compositions, and mineralogy of the collected dust with atmospheric entry models and data obtained from cometary probes and telescopic observations has provided important constraints on the possible sources of the various types of collected dust. These constraints lead to the following conclusions. First, most of the deep sea, Greenland, and Antarctic spherules larger than 100 μm are derived from asteroids. Second, the stratospheric IDPs dominated by hydrated layer-lattice silicate minerals are also most likely derived from asteroids. Finally, the stratospheric IDPs dominated by the anhydrous minerals olivine and pyroxene are most likely from comets. The consequences of these parent body assignments are discussed.

Interplanetary dust particles collected in the stratosphere: Observations of atmospheric heating and constraints on their interrelationship and sources

The majority of the interplanetary dust particles (IDPs) collected in the stratosphere belong to one of three major classes, the first two dominated by the anhydrous minerals olivine and pyroxene, and the third by hydrous layer-lattice silicates. Infrared spectroscopy and transmission electron microscopy studies show that the different IDP classes represent different types of dust that exist as individual particles in interplanetary space. The majority of the collected IDPs smaller than 30 μm in diameter in the layer-lattice silicate and pyroxene classes appear not to have been heated to temperatures above 600°C during atmospheric entry. The relatively low maximum temperatures experienced by these IDPs during atmospheric entry imply that they arrive at the top of the atmosphere with low geocentric encounter velocities. This limits the possible encounter trajectories for these particles to relatively circular, prograde orbits. As a result, it is unlikely that these IDPs are from Earth-crossing comets or asteroids. Asteroids, and comets having low inclinations and perihelia outside 1.2 UA, appear to be the best candidates for the parent bodies of the pyroxene and layer-lattice silicate particles. Chemical and mineralogical information suggests that the pyroxene-rich IDPs are from comets and layer-lattice silicate-rich IDPs are from asteroids. The collected IDPs dominated by olivine appear to include a larger fraction of particles heating above 600°C, suggesting that these particles were captured from more eccentric orbits. This, and the observation of the infrared spectral features of olivine in several comets suggest these particles have a cometary origin. Since much of the collected dust has apparently been captured from nearly circular, prograde orbits and since there are no appropriate parent bodies presently in such orbits, these results provide an experimental confirmation that the Poynting-Robertson effect exists as a nongravitational force important in the orbital evolution of dust in the Solar System.

Micro-FTIR measurements on individual interplanetary dust particles

The unique characteristics of micro-FTIR spectroscopy for the study of individual interplanetary dust particles (IDPs) are discussed: (1) quick and nondestructive identification of dominant silicate phases (pyroxenes, olivines, layer lattice silicates) and selection of unique IDPs for subsequent intensive study by complementary analytical techniques; (2) identification of potential carbonaceous carrier phases of isotopic anomalies; (3) measurement of IR absorption features in IDPs that can be compared with IR emission features obtained by telescopic observations from comets and protostars.

A simple device for the preparation of embedded materials science specimens for ultramicrotomy.

A simple hand-held grinding fixture is discussed which can produce microtome mounts of hard materials, oriented interfaces, and powders embedded in a 5/16-in plastic rod. The device has been used for the ultramicrotomy of meteorite samples, 10-50 micron interplanetary dust particles, and thin films on plastic. Results are presented for a layer lattice silicate from the Murchison carbonaceous chondrite, illustrating the resolution and structural detail that can be obtained with the method.

Acid Dissolution Experiments: Carbonates and the 6.8-Micrometer Bands in Interplanetary Dust Particles

A chemical dissolution experiment on an interplanetary dust particle (IDP) showed that carbonates, not acid-insoluble organic compounds, were responsible for virtually all the absorption at 6.8 micrometers seen in the infrared spectra of this particle. The IDP examined had an infrared spectrum characteristic of layer-lattice silicates and belongs to a class of IDP's whose spectra resemble those of protostellar objects like W33 A, which also exhibit a band at 6.8 micrometers.

Laboratory infrared transmission spectra of individual interplanetary dust particles from 2.5 to 25 microns

view Abstract Citations (224) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Laboratory infrared transmission spectra of individual interplanetary dust particles from 2.5 to 25 microns. Sandford, S. A. ; Walker, R. M. Abstract Dust particles collected in the stratosphere that have chondritic elemental abundances provide a new form of extraterrestrial matter for laboratory study. Spectral transmission measurements from 2.5 to 25 μm of 26 such particles show that almost all have a dominant 10 μm silicate absorption feature. Twenty-two of the particles can be grouped into one of three spectral classes referred to as olivines, layer-lattice silicates, and pyroxenes after the minerals that provide the best match to the dust spectra. Measurements of large D/H enrichments and solar flare nuclear tracks confirm that at least some particles are interplanetary dust particles. The layer-lattice silicates have additional bands at 3.0, 6.0, 6.8, and 11.4 μm. A comparison of these spectral features with the infrared spectra of comets and interstellar grains is presented. Publication: The Astrophysical Journal Pub Date: April 1985 DOI: 10.1086/163120 Bibcode: 1985ApJ...291..838S Keywords: Absorption Spectra; Abundance; Infrared Spectra; Interplanetary Dust; Interstellar Matter; Stratosphere; Cosmic Dust; Olivine; Pyroxenes; Silicates; X Ray Spectra; Astrophysics full text sources ADS | data products SIMBAD (1)

Complementary Laboratory Measurements of Individual Interplanetary Dust Particles

AbstractComplementary analysis techniques including electron microscopy (SEM/EDX and TEM), molecular spectroscopy (FTIR and Raman), and secondary ion mass spectrometry (SIMS), are used to study individual dust particles collected in the stratosphere. Large deuterium enrichments and solar flare tracks show that most particles in the “chondritic” class are interplanetary dust particles (IDPs). Infrared transmission spectra of most IDPs fall into three major classes (layer-lattice silicates, pyroxenes and olivines). TEM and Raman measurements confirm this classification. The IR spectra show certain similarities to spectra observed in comets and protostars. In particular the 6.8 μm features observed in protostars and IDPs may have a common origin. Large D excesses are observed in IDPs of the first two IR classes. The correlation of D/H ratios with the C concentration indicates a carbonaceous carrier of the excess D. The D enrichments and IR spectra provide links to interstellar molecular cloud material.

Infrared transmission spectra from 2.5 to 25 μm of various meteorite classes

Infrared transmission spectra from 53 meteorites in the spectral range from 2.5 to 25 μm were measured to permit comparisons with data of astronomical objects that are potential meteorite sources. Data were taken for 14 carbonaceous chondrites, 5 LL ordinary chondrites, 6 L ordinary chondrites, 10 H ordinary chondrites, 1 enstatite chondrite, 4 aubrites, 3 eucrites, 4 howardites, 1 diogenite, 1 mesosiderite, 2 nakhlites, 1 shergottite, and the anomalous achondrite Angra dos Reis. The CO and CV carbonaceous chondrites have spectra similar to each other, with 10-μm features characteristic of olivine. The CM carbonaceous chondrites have distinctive 10-μm features that are attributed to layer lattice silicates. Members of both the CI and CR classes have spectra distinct from those of other carbonaceous chondrites. The LL, L, and H ordinary chondrites have spectra that match those of olivine and pyroxene mixtures. The enstatite chondrites and enstatite achondrites (aubrites) all exhibit spectra diagnostic of the pyroxene enstatite. The angrite, howardites, aucrites, nakhlites, shergottite, and diogenite all have similar spectra also dominated by pyroxene. The single mesosiderite examined had a spectrum distinct from all the other meteorites.

Utilization of a cationic ligand for the intercalation of catalytically active rhodium complexes in swelling, layer-lattice silicates

Utilization of a cationic ligand for the intercalation of catalytically active rhodium complexes in swelling, layer-lattice silicates

Aspects of the Condensation of Primordial Silicates

WE introduce in this article two ad hoc hypotheses about the condensation of mafic silicates in the primordial solar nebula. From the distribution of trace elements, meteoritic abundance patterns can be largely explained1–3 using a two component model based on elemental volatility. The low temperature component, A, contains primordial volatile material accreted and separated from the solar gas at temperatures ≲530 K whereas component B separated from its volatiles at temperatures in the range 1,100 to 1,300 K. Component A has been identified with the matrix material of carbonaceous meteorites and it was concluded that the trace element abundances in this material have not been significantly altered since accretion. It seems probable, therefore, that the principal element composition of the hydrous layer-lattice silicate—by far the dominant matrix mineral—was established before accretion.

Primordial noble gases in separated meteoritic minerals—I

Magnetite and a layer-lattice silicate from the Orgueil carbonaceous chondrite show strikingly different noble gas patterns. Magnetite contains He, Ne and Ar in essentially solar proportions, with some excess Kr and Xe. Isotopic ratios are typically solar: Ne 20 Ne 22 = 12.5 , He 3 He 4 = (3.8 ± 0.4) × 10 −4 ; but Xe 129 Xe 132 is quite high, 2.0 to 6.6. He 4 Ne 20 is 730, which is probably close to the true solar ratio. Silicate contains planetary gas, with Ne 20 Ne 22 = 8.2 , He 3 He 4 = (1.4 ± 0.4) × 10 −4 , and Xe 129 Xe 132 = 1.018 ± 0.003 . The Ne 21 radiation age of the magnetite, 10.7 m.y., is higher than that of the bulk meteorite, 4.5 m.y., which implies substantial loss of cosmogonic Ne 21 from silicate. Presumably the radiation ages of other Cl chondrites are too low by similar factors. The primordial component in magnetite is loosely bound, and may represent trapped solar wind. The gas in silicate is more tightly held and was probably absorbed from the solar nebula at 350 ± 50° K. Data on low-temperature solubilities of He, Ne and Ar suggest that the observed amounts and elemental fractionations of planetary gas can probably be explained by equilibrium solubility. The isotopic features of planetary gas require an additional process, such as production of Na 22 by charged-particle irradiation.

The A and B mica layers and the crystal structure of sheet silicates

A discussion of the transition from the “ideal hexagonal” mica structure to the “ideal ditrigonal” one, leads to the conclusion that the single mica layer may have two different structures (labelled A and B). The recent literature data show that both the A and B structures have been detected in some triocahedral layer lattice silicates found in nature. An examination of the structural stability of the A and B structures suggests that the last one may not be realized by dioctahedral layer lattice silicates. The concept of two structurally different mica layers, which however have the same lattice constants, greatly improves the understanding of polymorphism and twin laws in layer lattice silicates.

Observations on Quick Clay

Certain glacial and postglacial clay strata, long static in almost flat terrain, with little or no warning may flow spontaneously with destructive consequences. Samples of such clays, known as “quick clays,” have been examined from Scandinavia, Canada, and the northeastern United States. These have been compared with similar clays in areas where quick-clay movement has not been reported. The principal minerals in the clay-size fraction of the quick clays observed are sheet-layer silicates. Illite (hydromica) and chlorite occur most frequently, interlayered illite-montmorillonite is common, interlayered chlorite-montmorillonite occurs occasionally, and interlayered illite-vermiculite was found in one sample. Quartz, feldspar, hornblende, and calcite predominate in the coarser-size fractions and are found to some extent in the clay-size fractions. Most of the clays examined are of marine origin, but one of established fresh-water origin was included. The quick clays contain an average by weight of 57.3 per cent less than 2-μ. material, and the nonquick clays average 31.6 per cent less than 2-μ material. Chlorinity tests indicate that pore-water salinity of marine quick clays, about 35 g per 1 when deposited, becomes 0.2–15 g per 1 at flowage. The pore-water content of quick clays noted exceeds 44 per cent and in some clays may be as high as 80 per cent. Major critical conditions which contribute to quick-clay movement appear to be: substantial quantities of layer-lattice silicates of colloidal size (about 40 per cent or more by dry weight), substantial pore water (44 per cent), a reduction in electrolyte concentration below 5 g of salt per 1, and the addition of a dispersant. Under such conditions a clay becomes critically sensitive and may flow spontaneously or as the result of a shock. In quick clay of marine origin it has been suggested that a random orientation of clay particles is probably induced by coagulation during deposition. This orientation appears to provide stability to such clay strata. Removal of an electrolyte by natural leaching with fresh water appears to render the clay unstable. When the clay structure undergoes collapse, flowage is believed to result. Field conditions suggest that flowage of non-marine quick clay may be attributed to the action of a dispersant such as humic acid.

Early Reaction Determination in Two Hydroxide-Kaolinite Systems by Electron Microscopy and Diffraction

Abstract Results of the study of the kaolinite-sodium hydroxide interaction showed extensive dissolution of the kaolinite structure at particle edges, with some production of “silicate relicts” as a secondary effect. The method of specimen preparation for electron micro-scopy precluded electron-diffraction study of soluble reaction products. The study of the kaolinite-calcium hydroxide interaction revealed a similar attack on particle edges and formation of “silicate relics” and, in addition, formation of an insoluble reaction product that was tentatively identified by electron diffraction as prehnite, Ca2Al2Si3O10(OH)2. Both studies showed an ephemeral phase that, by selected area elec- tron diffraction, appeared to be a layer lattice silicate in (001) orientation. In the calcium hydroxide-treated kaolinite, formation of the reaction product was followed from nucleation along particle edges, after 24 hr, to growth of particles about 0.5 to 1 μ in size after 15 days. The combination of electron microscopy of surface replicas to detect changes in morphology with selected area electron diffraction of parallel pseudoreplicas for identification shows promise as a tool for study of the early stages in mineral- chemical interaction.

WEATHERING OF SOME SCOTTISH BASIC IGNEOUS ROCKS WITH REFERENCE TO SOIL FORMATION

SummaryThe weathering of several basic igneous rocks of Lower Carboniferous age has been studied by optical microscopy and X‐ray techniques. Although similar in mineralogy, the rocks have different textures and the fine‐grained ones are most resistant to physical disintegration. In every rock, olivine has been affected by hydrothermal alteration to produce layer lattice silicates. The weathering of these products and the other mineral constituents of the rocks is described.The fine‐sand fraction (0·2‐0·02 mm.) was selected for the purpose of determining relative stabilities of the primary minerals under weathering conditions. In order of increasing stability, the arrangement is labradorite, augite, magnetite, ilmenite, and hematite. The silt (0·02‐0·002 mm.) and clay (&lt; 1.4 μ) fractions contain saponite and/or vermiculite depending mainly on the weathering conditions of augite and felspar. Kaolin is present in both size fractions but illite is scarce. The cation‐exchange capacity (c.e.c.) of both silt and clay fractions is consistent in most cases with the layer lattice silicate contents.

Cell Dimensions and Interatomic Forces in Layer Lattice Silicates

THE factors which control the sheet dimensions of the layer lattice silicates have been carefully re-examined recently1, both from a structural point of view2, and by the methods of multiple regression analysis3. This has led to a new, more explicit geometrical model4 for the octahedral layers of these minerals, and thence to a detailed study of the balance of forces which must be involved. The results of the latter are outlined here.