Exsolution intergrowths of titanian ferrocolumbite and niobian rutile from the Weinebene Spodumene Pegmatites,Carinthia, Austria

Summary Titanian ferrocolumbite is a rare accessory mineral in the spodumene-bearing pegmatites at Weinebene, Carinthia, Austria. It contains abundant exsolved niobian rutile and scarce inclusions of cassiterite that may be primary. The titanian ferrocolumbite is relatively homogeneous with Mn/(Mn + Fe) 0.24–0.33, Ta/(Ta + Nb) 0.09–0.13 (atomic ratios) and 0.47–0.88 Ti per 12 cations (2.7–5.0 wt.% TiO₂). Natural specimens are considerably disordered but become more ordered on heating. Niobian rutile has Mn/(Mn + Fe) 0.00–0.04 and Ta/(Ta + Nb) 0.26–0.38; it concentrates Fe, Ta, Ti and Sn relative to the Mn- and Nb-enriched ferrocolumbite. The overall scarcity of Nb, Ta-oxide minerals in the spodumene-bearing pegmatites of southern Ostalpen conforms to their general features ranking them with the albite-spodumene type of rare-element pegmatites.With 4 Figures     

Burying response of an intertidal gastropod to freshwater and copper contamination

The effects of sublethal concentrations of freshwater and copper on the burying responses of the intertidal marine gastropod, Polinices incei, are presented. Such responses are inhibited by both pollutants and the two also act additively. Behavioural responses obtained in a 30 min assay were found to be good predictors of the results of 96 h lethal assays. The results are discussed in light of previous work.     

Acute toxicity of mine tailings to four marine species

Acute toxicity bioassays were conducted on mine tailings produced by pilot plant testing for the proposed Quartz Hill molybdenum mine, which will be situated near Ketchikan, Alaska. Tailings bioassays were conducted in seawater with juvenile coho salmon (Oncorhynchus kisutch), mussel larvae (Mytilus edulis), infaunal amphipods (Rhepoxynius abronius), and euphausiids (Euphausia pacifica). The same general range of mine tailings concentrations was acutely toxic to all four test species with acute effects observed between 61 000 to 277 000 mg l^?1 (wet wt) tailings solids (range of 95% confidence limits for LC₅₀ and EC₅₀ values). Chemical analyses of bioassay test solutions and leaching test solutions were conducted for metals (including Cd, Cu, Pb, Zn, Mn and Mo), EPA Priority Pollutant base/neutral organics, and more general parameters such as sulphate, nitrate/nitrite, cyanides, phosphate and ammonia. Parameters possibly contributing to the observed toxicity were complex contaminant mixtures including total suspended solids and heavy metals. The present study provides information related to the marine disposal of mine tailings and shows that these mine tailings present a relatively low level of acutely toxic effects.     

Strains developed in the hangingwalls of thrusts due to their slip/propagation rate: a dislocation model: reply

Folding related to the propagation of thrusts is common in thrust belts, including the Rocky Mountains. The rare development of such folds in the southern Rockies, due to lithological control, is a special case of the dislocation/ductile bead model, which, it is argued, is of general applicability.     

Time and the crystallization of apatite in seawater

Carbonate fluorapatite has been synthesized in seawater in an experiment of nearly 10-years duration. The addition of phosphate to seawater whose fluoride concentration had been increased to 7.6 mg/l brought about an initial amorphous phosphate precipitate. After 20 months, a crystalline magnesium phosphate phase developed within the amorphous phosphate. Crystallization of apatite, which occurred during the last 3 years of the experiment, was accompanied by dissolution of the crystalline magnesium phosphate phase.The MgO content of the apatite (1.9 percent) is high in comparison to Tertiary and older apatite but similar to some young apatite; the CO₂ content (3.6 percent) is medium, and the fluorine content (2.2 percent) is low but again similar to some young apatite. The hydroxyl ion (OH^?) likely fills the need for additional fluorine-position atoms. The mole ratio of Ca plus substituent elements to P plus substituent elements (1.50) is low in comparison to the expected ratio of 1.67. The substitution of the hydronium ion (H₃O⁺) for Ca may account for this difference.The synthesis of apatite in seawater demonstrates that the factor of time overcomes the well known inhibiting effect of magnesium upon the crystallization of apatite. It also implies that given an adequate supply of phosphate, apatite can form in most ocean environments and likely plays a major pan in the control of the phosphate content of seawater.     

HAZMAP: A REMOTE DIGITAL MEASUREMENT SYSTEM FOR WORK IN HAZARDOUS ENVIRONMENTS

In a continuing drive to reduce the radiation exposure of nuclear workers, many routine aspects of nuclear plant maintenance and refurbishment are increasingly undertaken by robotic or remote handling tools. Accurate “as built” documentation of plant records is vital to the successful planning and execution of such operations since an unexpected obstruction or undocumented site modification may result in a costly disruption or even failure of the intervention. In recognition of the importance of such documentation, a recent European Community ? ? Teleman-Robotics and remote sensing operations in hazardous nuclear environments
sponsored project has been directed towards the development of techniques for cost effective survey and modelling of such plant. This paper will detail the rationale behind the design of such a system and will describe typical results from a number of pilot projects.     

Infrared imaging and spectroscopy with arrays at the University of Montreal

The Montreal Infrared Camera (MONICA) consists of a LN₂ cryostat enclosing a NICMOS3 array, re-imaging optics and a filter wheel mechanism containing broad-band and circular variable filters. A polarimetry mode with a warm half wave plate and a cold polarizer/filter combination is also supported. At the CFHT 0.5 (FWHM) images are routinely obtained with limiting magnitudes of 22.8 at J and 21.7 at K (S/N=3 in 1hr).The Spectrometre Infrarouge de Montréal (SIMON) is a versatile grating spectrometer with spectral resolutions ranging from 300 to 5000. Presently under construction, this spectrometer will initially contain a 512×512 HgCdTe array. Use of reflective optics will allow a future upgrade to a similar format InSb array, extending the wavelength coverage to 5m. SIMON will also have an imaging mode to facilitate the centering of objects within interchangeable slits.     

Solar irradiance from Nimbus-7 compared with ground-based photometry

We have compared total solar irradiance from Nimbus-7 with ground-based photometry from the San Fernando Observatory (SFO) for 109 days between June 1 and December 31, 1988. We have also included in some analyses NOAA-9 SBUV2 data orF10.7 radio flux. The Nimbus-7 data are from orbital samples, averaged to the mean time of observation at SFO. Using the same parameters as in Chapmanet al. (1992), the multiple regression gives anR ² = 0.9131 and a solar minimum irradiance,S ₀, = 1371.76 ± 0.18 W m^–2 for the best fit.     

Taxonomy of asteroids

A taxonomic system was introduced by C. R. Chapman, D. Morrison, and B. Zellner [Icarus25, 104–130 (1975)], in which minor planets are classified according to a few readily observable optical properties, independent of specific mineralogical interpretations. That taxonomy is here augmented to five classes, now precisely defined in terms of seven parameters obtained from polarimetry, spectrophotometry, radiometry, and UBV photometry of 523 objects. We classify 190 asteroids as type C, 141 as type S, 13 as type M, 3 as type E, and 3 as type R; 55 objects are shown to fall outside these five classes and are designated U (unclassifiable). For the remaining 118, the data exclude two or more types but are insufficient for unambiguous classification. Reliable diameters, from radiometry or polarimetry or else from albedos adopted as typical of the types, are listed for 396 objects. We also compare our taxonomy with other ones and discuss how classification efforts are related to the interpretation of asteroid mineralogies.     

Modelling frequency-dependent seismic anisotropy in fluid-saturated rock with aligned fractures: implication of fracture size estimation from anisotropic measurements

Measurements of seismic anisotropy in fractured rock are used at present to deduce information about the fracture orientation and the spatial distribution of fracture intensity. Analysis of the data is based upon equivalent-medium theories that describe the elastic response of a rock containing cracks or fractures in the long-wavelength limit. Conventional models assume frequency independence and cannot distinguish between microcracks and macrofractures. The latter, however, control the fluid flow in many subsurface reservoirs. Therefore, the fracture size is essential information for reservoir engineers. In this study we apply a new equivalent-medium theory that models frequency-dependent anisotropy and is sensitive to the length scale of fractures. The model considers velocity dispersion and attenuation due to a squirt-flow mechanism at two different scales: the grain scale (microcracks and equant matrix porosity) and formation-scale fractures. The theory is first tested and calibrated against published laboratory data. Then we present the analysis and modelling of frequency-dependent shear-wave splitting in multicomponent VSP data from a tight gas reservoir. We invert for fracture density and fracture size from the frequency dependence of the time delay between split shear waves. The derived fracture length matches independent observations from borehole data.