Interpretation of the auger electron spectra (AES) of sulfide minerals

Auger electron spectra (AES) of sulfides are interpreted using published photoelectron spectra, sulfurK _β X-ray emission spectra (XES) and Multiple ScatteringX _α calculations on metal-sulfide molecular clusters and using newly measured spectra for ZnS, Cu₂S and MoS₂. For compounds without appreciable metald-sulfur 3p interactions, only one sulfur LVV peak or a closely spaced doublet is observed. For those with substantial metald-sulfur 3p interactions additional peaks occur, with peaks at lower electron kinetic energy arising from ejection of electrons from orbitals more tightly bound than theS3p, and those with higher kinetic energy arising from electrons in less tightly bound orbitals. Thus, for many sulfide minerals, the sulfur LVV Auger Spectrum is essentially a self-convolution of the valence band density of states weighted by the amount of S3p character, and can be predicted from a knowledge of the sulfurK _β X-ray emission spectra and the X-ray photoelectron spectra.     

Anisotropic growth in the olivine-spinel transformation of Mg2GeO4 under nonhydrostatic stress

The olivine-spinel phase transformation in Mg₂GeO₄ does not occur by a martensitic mechanism. The evidence, from samples transformed in a Griggs-type solid medium deformation apparatus, are:

1. (1) lack of microstructural features in the olivine phase which can be specifically associated with a martensitic mechanism

2. (2) the orientation relationship between the two phases that is predicted by the martensitic mechanism does not occur nor is there any apparent consistency of relative orientations

3. (3) application of a differential stress to the transforming sample resulted in an anisotropic growth rate for the spinel phase indicating that growth was externally controlled rather than crystallographically controlled.

Anisotropic growth of the spinel phase results in elongation of the residual olivine phase grains in the plane normal to the direction of maximum principal compressive stress. A velocity ratio of 1.7_−0.7^+5.4 has been determined for the growth rate of the spinel from measurements on residual olivine grains. The interphase grain boundary in samples transformed under stress has cusp-shaped fingers of spinel with a blunt end separated by thin spikes of olivine. Samples transformed isostatically do not exhibit this feature providing further confirmation of anisotropic growth of the spinel. The preferred growth of the spinel is consistent with a theory of phase transformation under nonhydrostatic stress. The predicted spinel finger shape based on this theory is generally consistent with observed shapes except for the blunt end. The discrepancy may be due to surface energy which has not been considered here, or to local deviations of the applied macroscopic stress.     

The generation and preservation of multiple hurricane beds in the northern Gulf of Mexico

Cores collected from Mississippi Sound and the inner shelf of the northeast Gulf of Mexico have been examined using ²¹⁰Pb and ¹³⁷Cs geochronology, X-radiography, granulometry, and a multi-sensor core logger. The results indicate that widespread event layers were probably produced by an unnamed hurricane in 1947 and by Hurricane Camille in 1969. Physical and biological post-depositional processes have reworked the event layers, producing regional discontinuities and localized truncation, and resulting in an imperfect and biased record of sedimentary processes during the storms. The oceanographic and sedimentological processes that produced these event beds have been simulated using a suite of numerical models: (1) a parametric cyclone wind model; (2) the SWAN third-generation wave model; (3) the ADCIRC 2D finite-element hydrodynamic model; (4) the Princeton Ocean Model; (5) a coupled wave–current bottom boundary layer-sedimentation model; and (6) a model for bed preservation potential as a function of burial rate and bioturbation rate. Simulated cores from the Mississippi Sound region are consistent with the observed stratigraphy and geochronology on both the landward and seaward sides of the barrier islands.     

Reactions of the feldspar surface with metal ions: Sorption of Pb(II), U(VI) and Np(V), and surface analytical studies of reaction with Pb(II) and U(VI)

Feldspar minerals are thermodynamically unstable in the near-surface environment and their surfaces are well known to react readily with aqueous solutions, leading to incongruent dissolution at low pH values, but congruent dissolution at neutral and high pH values. Interactions with mineral surfaces are an important control on the environmental transport of trace elements and detrital feldspars are abundant in soils and sediments. However, the interactions of metal ions in solution with the reacting feldspar surface have not been widely explored. The interactions of Pb(II), U(VI) and Np(V) ions with the feldspar surface have therefore been studied. Lead is taken up by the microcline surface at pH 6 and 10, but no uptake could be measured at pH 2. There was measurable uptake of Pb(II) on the plagioclase surface at pH 2, 6 and 10. Uptake always increased with pH. In most conditions, Pb(II) reacts through cation exchange process although, at high pH, a discrete phase, probably hydrocerrusite, is observed by atomic force microscopy (AFM) to precipitate on the plagioclase surface. Supersaturation with hydrocerrusite in these conditions is expected from thermodynamic calculations. Uptake of uranyl ion , generally through surface complex formation, could only be measured at pH 6 and 10. At pH 6 and an initial U(VI) concentration above 21.0 μM, precipitation of becquerelite (Ca[(UO₂)₃O₂(OH)₃]₂·8H₂O), identified by AFM and characterised by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy, is observed on plagioclase. The U(VI) concentration range in which becquerelite precipitation begins (dissolved U(VI) 1-5 μM) is consistent with that predicted from thermodynamic modelling. On plagioclase feldspar, secondary ion mass spectrometry showed diffusion of uranium into the altered surface layer. Uptake of the neptunyl ion (Np(V)) was found at pH 6 and 10 for microcline and at pH 2, 6 and 10 for plagioclase, and was generally lower than uptake of U(VI). By combining batch sorption experiments with imaging and surface analysis, and thermodynamic modelling, it has been possible to gain a mechanistic insight into the reactions of the feldspar surface with metal ions in solution.     

Kāhuli: Uncovering Indigenous Ecological Knowledge to Conserve Endangered Hawaiian Land Snails

Indigenous knowledge is a multilayered knowledge system that can inform contemporary management in both natural observations and cultural value. Centuries old observations preserved within song, chant, and story has been globally recognized as a resource to integrate with conservation efforts for endangered species. In the case of the endemic land snails, kāhuli, of the Hawaiian archipelago, there is a prominent cultural presence preserved in oral tradition and written records in 19th and early 20th century’s Hawaiian language newspapers. As we witness the dramatic decimation of one of the greatest models of species radiation, the unveiling of the repositories of indigenous knowledge is crucial for conservation of these endemic land snails. This paper reports on indigenous knowledge that informs about the cultural significance (i.e., poetic device, metaphorical role, importance to hula) and ecology of kāhuli, and how indigenous knowledge can contribute to conservation efforts of rare and endangered species.     

Multi-instrument remote and in situ observations of the Erebus Volcano (Antarctica) lava lake in 2005: A comparison with the Pele lava lake on the jovian moon Io

The stable, persistent, active lava lake at Erebus volcano (Ross Island, Antarctica) provides an excellent thermal target for analysis of spacecraft observations, and for testing new technology. In the austral summer of 2005 visible and infrared observations of the Erebus lava lake were obtained with sensors on three space vehicles Terra (ASTER, MODIS), Aqua (MODIS) and EO-1 (Hyperion, ALI). Contemporaneous ground-based observations were obtained with hand-held infrared cameras. This allowed a quantitative comparison of the thermal data obtained from different instruments, and of the analytical techniques used to analyze the data, both with and without the constraints imposed by ground-truth. From the thermal camera data, in December 2005 the main Erebus lava lake (Ray Lake) had an area of ≈ 820 m². Surface colour temperatures ranged from 575 K to 1090 K, with a broad peak in the distribution from 730 K to 850 K. Total heat loss was estimated at 23.5 MW. The flux density was ≈ 29 kW m^− 2. Mass flux was estimated at 64 to 93 kg s^− 1. The best correlation between thermal emission and emitting area was obtained with ASTER, which has the best combination of spatial resolution and wavelength coverage, especially in the thermal infrared. The high surface temperature of the lava lake means that Hyperion data are for the most part saturated. Uncertainties, introduced by the need to remove incident sunlight cause the thermal emission from the Hyperion data to be a factor of about two greater than that measured by hand-held thermal camera. MODIS also over-estimated thermal output from the lava lake by the same factor of two because it was detecting reflected sunlight from the rest of the pixel area. The measurement of the detailed temperature distribution on the surface of an active terrestrial lava lake will allow testing of thermal emission models used to interpret remote-sensing data of volcanism on Io, where no such ground-truth exists. Although the Erebus lava lake is four orders of magnitude smaller than the lava lake at Pele on Io, the shape of the integrated thermal emission spectra are similar. Thermal emission from this style of effusive volcanism appears to be invariant. Excess thermal emission in most Pele spectra (compared to Erebus) at short wavelengths (< 3 μm) is most likely due to disruption of the surface on the lava lake by escaping volatiles.