The thermal expansion of anhydrite to 1000° C

The thermal expansion of anhydrite, CaSO₄, has been measured from 22° to 1,000° C by X-ray diffraction, using the Guinier-Lenné heating powder camera. The heating patterns were calibrated with Guinier-Hägg patterns at 25° C, using quartz as internal standard. Heating experiments were run on natural anhydrite (Bancroft, Ontario), which at room temperature has lattice constants in close agreement with those of synthetic material. The orthorhombic unit cell at 22° C (space group Amma) has a=7.003 (1) Å, b=6.996 (2) Å and c=6.242 (1) Å, V=305.9 (2) ų. At room temperature, the thermal expansion coefficients α and β (α in °C^?1×10⁴, β in °C^?2×10⁸) are for a, 0.10, ?0.69; for b, 0.08, 0.19; for c, 0.18, 1.60; for V, 0.37, 1.14. Second-order coefficients provide an excellent fit over the whole range to 1,000° C.     

NICMOS observations of luminous & ultraluminous infrared galaxies

HST NICMOS observations of a sample of 24 luminous (LIGs: L _IR[8-1000 m] = 10^11.0-11.99 L) and ultraluminous (ULIGs:L _IR 10^12.0 L) infrared galaxies are presented.The observations provide, for the first time, high resolution HST imagingof the imbedded 1.1 - 2.2 m nuclear regions of these mergers. Allbut one of the ULIGs are observed to have at least one compact (50-200 pc)nucleus, and more than half contain what appear to be blue star clusters.The warm infrared galaxies (i.e., the transition sources) are observed tohave bright nuclei which account for most of the light of the galaxy.This, combined with the tendency for the light of ULIGs to become morecentrally concentrated as a function of increasing wavelength, impliesthat most of their energy is generated within a region 50-200 pcacross.     

Structures in the Iranides of South-eastern Turkey

The effects of two phases of deformation in Cretaceous rocks of the Alpine Orogenic Zone of south-eastern Turkey are described. These can be correlated with the late Cretaceous and Tertiary phases of deformation already known from the zone of foreland folding to the south. Some details of the stratigraphical succession are given and a previously unrecorded development of Oligocene rocks is described. The upper Cretaceous sediments are dominantly marine carbonates but include a red bed formation. Basic volcanics are intercalated with the lower carbonate beds. A profound unconformity separates the Eocene from the Upper Cretaceous. This unconformity results from uplift consequent upon the first phase of deformation which produced north-westward plunging folds and related thrusts. Some of these north-westerly folds have been considerably modified by the superposition of younger east-north-easterly trending Alpine folds and thrusts.

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Zusammenfassung Die Effekte zweier Verformungsphasen im Kreidegestein der alpidischen orogenetischen Zone im Südosten der Türkei werden beschrieben. Diese können mit den schon bekannten Verformungsphasen der Oberkreide und des Tertiärs in der Vorlandfaltungszone im Süden zusammen betrachtet werden. Einzelheiten über die Stratigraphie werden angegeben, und die Ausbildung oligozäner Gesteine wird zum ersten Mal beschrieben. Die Sedimente der Oberkreide bestehen zum größten Teil aus marinen Karbonaten, enthalten aber eine rote Formation. In den unteren Karbonatschichten ist basisches vulkanisches Gestein zwischengelagert. Eine erhebliche stratigraphische Diskordanz stammt aus einer Hebung, die der ersten Verformungsphase folgte, in der nach Nordwesten abtauchende Falten und verwandte Aufschiebungen entstanden. Diese Falten sind zum Teil überprägt von jüngeren ostnordöstlich streichenden alpidischen Falten und Aufschiebungen, die sie wesentlich veränderten.

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Résumé Les auteurs décrivent les effets des deux phases de déformation des roches crétaciques de la zone orogénique alpine du sud-est de la Turquie. On peut les mettre en corrélation avec les phases de déformation, déjà connues, du Crétacique supérieur et du Tertiaire dans la zone de plissement de l'avant-pays au sud. Les auteurs donnent quelques détails sur la succession stratigraphique et décrit pour la première fois le développement des roches oligocènes. Les sédiments du Crétacique supérieur sont surtout des carbonates marins, mais comprennent toutefois une formation rouge. Des roches volcaniques basiques sont intercalées dans les couches carbonatées inférieures. Une discordance nette sépare l'Eocène du Crétacique supérieur; elle résulte du soulèvement succédant à la première phase de déformation qui produisit les plis plongeant au nord-ouest et les chevauchements apparentés. Ces plis ont été en partie remaniés par des plis et des chevauchements alpins plus jeunes, de direction est-nord-est, qui les ont fortement modifiés.

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Widespread occurrence of magnesiocummingtonite in ultramafic schists,Cima di Gagnone,Ticino, Switzerland

Abundant magnesiocummingtonite (space group P2₁/m) with Mg/(Mg+Fe) ratios between 0.85 and 0.89 occurs in lenses of schistose metaperidotite enclosed in kyanite-zone rocks of the Lepontine Alps, Ticino, Switzerland. It forms prisms and needles that extend homoaxially from cores of tremolite. Coexisting magnesian phases are olivine, orthopyroxene, talc, magnesite, and chlorite. Except for γ∶z, optical and structural properties of one example fall on extrapolations of existing determinative curves. Analogous to synthetic F-clinoamphiboles, zz∶z has a maximum at approximately 0.7 Mg/(Mg+Fe). Anthophyllite, of almost identical composition, occurs in the same region, often intergrown with cummingtonite along lamellae ‖(010) and ‖(100). Cummingtonite is believed to have partially inverted to anthophyllite during cooling.     

Reductive deposition of graphite at lithological margins in East Central Vermont: a Sr, C and O isotope study

O, Sr and C isotopes from east‐central Vermont are used to provide information on the timing and volume of metamorphic fluid flow. The results are then used to assess the evidence for redox transformations between C species. Oxygen profiles are homogenised on a metre scale; comparison with Sr isotopes suggest that O alteration may have occurred over a significantly larger timescale than that of Sr, possibly because O was modified during dewatering and diagenesis in addition to the high temperature alteration recorded by strontium. Sr isotope distributions are consistent with cross‐layer fluid fluxes of 10⁴?10⁶ moles m^?2; absolute values depend on the Sr fluid‐rock distribution coefficient which is poorly known; however, reaction progress constraints suggest that fluxes were towards the lower end of this range. High δ¹³C values observed at lithological boundaries cannot be explained by volume loss or closed system processes and are taken to indicate reductive precipitation of graphite as a result of mixing between CO₂ and CH₄‐bearing fluids. Mass balance calculations indicate that redox reactions occurring under metamorphic conditions convert a minimum of 10% of the CO₂ released from limestones into graphite, thus providing a potentially important control on the average residence time of C within the crust with implications for C cycling models.     

Mechanical re-equilibration of fluid inclusions in San Carlos olivine by power-law creep

Fluid inclusions in San Carlos olivine stretch via plastic mechanisms when heat-treated at 1400° C and 0.1 MPa in controlled atmospheres for several days. Measurable changes in both inclusion dimensions and fluid densities occur; densities decrease from 1.0 to 0.7 g/cc. Stretching is fastest along 100, and slower along 001 and 010. The dislocation microstructure around the inclusions suggests that creep mechanisms operate. Uncertainties in the experimental determinations of stretching rates result from optical resolution limits, errors inherent in measuring homogenization temperatures, uncertainties in the fluid equation of state, and changes in fluid chemistry during the heat-treatment. Inclusion stretching by dislocation creep can be treated using a model developed for hot isostatic pressing. In this model, we assume spherical symmetry of plastic flow, that the material yields by steady-state power-law creep, and that the parameters for the constitutive law and fluid equation of state are known. Stretching rates are predicted to depend on the difference between the fluid pressure and the external pressure, the temperature, the constitutive law governing power-law creep, and geometry. Predicted stretching rates show fair, but not exact, agreement with experimentally measured rates. The amount of stretching predicted by the model is in rough agreement with estimates based on dislocation microstructures around natural inclusions, if xenolith ascent rates are of the order of 1 cm/s or faster.Now at: L-201, Lawrence Livermore Laboratory, P.O. Box 808 Livermore, CA 94550, USA     

Intercomparison of remote measurements of stratospheric NO and NO2

During the 1982 and 1983 Balloon Intercomparison Campaigns, the vertical profile of stratospheric NO₂ was measured remotely by nine instruments and that of NO by two. Total overhead columns were measured by two more instruments. Between 30 and 35km, where measurements overlapped, agreement between NO profiles was within ±30%, which is better than the accuracies claimed by the experimenters. Between 35 and 40km there was similarly good agreement between NO₂ profiles, but below 30km, differences of greater than a factor three were found. In the second Campaign, NO₂ values from most instruments agreed within their quoted errors, except that the Oxford radiometer gave much lower values; but the first Campaign and the column measurements show a more uniform spread of results.These differences below 30km could not be resolved, but new laboratory measurements are planned which should do so.