The Arunta Inlier: a complex ensialic mobile belt in central Australia. Part 1: Stratigraphy,correlations and origin

The Arunta Inlier is a 200 000 km² region of mainly Precambrian metamorphosed sedimentary and igneous rock in central Australia. To the N it merges with similar rocks of lower metamorphic grade in the Tennant Creek Inlier, and to the NW it merges with schist and gneiss of The Granites‐Tanami Province. It is characterized by mafic and felsic meta‐igneous rocks, abundant silicic and aluminous metasediments and carbonate, and low‐ to medium‐pressure metamorphism. Hence, the Arunta Inlier is interpreted as a Proterozoic ensialic mobile belt floored by continental crust. The belt evolved over about 1500 Ma, and began with mafic and felsic volcanism and mafic intrusion in a latitudinal rift, followed by shale and limestone deposition, deformation, metamorphism and emergence. Flysch sedimentation and volcanism then continued in geosynclinal troughs flanking the ridge of meta‐igneous rocks, and were followed by platform deposition of thin shallow‐marine sediments, further deformation, and episodes of metamorphism and granite intrusion.     

Institutional forces and retail change: a case study of Metropolitan Toronto

There is a growing interest in the development of purpose-built shopping centres, which now dominate the retail environments of many cities. Much of the past research has been directed at the impact of shopping centres on more traditional retail structures. More recently, however, there has been a recognition of the importance of those institutional forces that shape the internal character of shopping centres and ultimately determine their economic impact. This paper draws attention to these factors and discusses the control that leasing agreements and corporate policy have on shopping centre development. The whole discussion is set within the framework of metropolitan Toronto, which has for some time experienced the full impact of these institutional forces.     

R-mode factor analysis on enstatite chondrite analyses

R-mode factor analysis on 11 specimens of 9 enstatite chondrites, analysed for Ga, Se, Te, Zn, Cd, Bi, Tl, In, Sb, As, Co, showed three factors (rotated) to account for 92 per cent of the elemental variations (variance).Factor 1 dominates the first 8 elements listed, all volatile and mostly chalcophile: factors 2 and 3 express Sb and As variations, respectively, probably dependent on siderophile and less volatile behaviour; factors 1 and 2 contribute to Co.Factor-scores for individual meteorites indicate compositional differences (for these elements) between the E4 as against E5 and E6 stones (which are indistinguishable).Factor analysis of a second suite of 10 specimens analysed for Zn, Cd, Bi, Tl, In, Ag, Rb, Cs showed one factor to account for 93 per cent of the elemental variance. This expresses the association of Ag, Rb, Cs with the volatile-chalcophile factor.     

Climate disaster resilience of the education sector in Thua Thien Hue Province, Central Vietnam

Recognizing the importance of building disaster resilience for education sector, this study aims to develop a methodology to measure the level of educational resilience to cope with natural disasters and is then applied in Central Vietnam. The assessment tool in this paper is developed through a combination of climate disaster resilience indexes and the 16 tasks of Hyogo framework for action designed for education sector. It looks at five dimensions namely physical conditions, human resources, institutional issues, external relationships, and natural conditions, with each dimension characterized by three parameters and five variables. Findings from this study provide important insights into enhancing resilience of the education system in Thua Thien Hue at the provincial, local, and school levels. By giving the overall resilience situation, it can help policy-makers and practitioners in developing an effective plan to increase the level of educational resilience. In addition, it provides the School Management Board with a means to assess the school??s resilience level and set out priorities that need to be focused on with regard to the improvement of school safety and disaster risk reduction education.     

The origin of reaction textures in mantle peridotite xenoliths from Sal Island, Cape Verde: the case for “metasomatism” by the host lava

Reaction zones around minerals in mantle xenoliths have been reported from many localities worldwide. Interpretations of the origins of these textures fall into two groups: mantle metasomatic reaction or reaction during transport of the xenoliths to the surface. A suite of harzburgitic mantle xenoliths from Sal, Cape Verde show clear evidence of reaction during transport. The reactions resulted in the formation of olivine–clinopyroxene and Si- and alkali-rich glass reaction zones around orthopyroxene and sieve-textured clinopyroxene and sieve textured spinel, both of which are associated with a Si- and alkali-rich glass similar to that in the orthopyroxene reaction zones. Reaction occurred at pressures less than the mantle equilibration pressure and at temperatures close to the liquidus temperature of the host magma. In addition, there is a clear spatial relation of reaction with the host lava: reaction is most intense near the lava/xenolith contact. The residence time of the xenoliths in the host magma, determined from Fe–Mg interdiffusion profiles in olivine, was approximately 4 years. Our results cannot be reconciled with a recent model for the evolution of the mantle below the Cape Verde Archipelago involving mantle metasomatism by kimberlitic melt. We contend that alkali-rich glasses in the Sal xenoliths are not remnants of a kimberlitic melt, but rather they are the result of reaction between the host lava or a similar magma and xenolith minerals, in particular orthopyroxene. The formation of a Si- and alkali-rich glass by host magma–orthopyroxene reaction appears to be a necessary precursor to formation of sieve textured spinel and clinopyroxene.     

Zircon Hf Isotopic Evidence for Mixing of Crustal and Silicic Mantle-derived Magmas in a Zoned Granite Pluton, Eastern Australia

Zircon Hf isotopic data from a zoned pluton of the Moonbi supersuite,New England batholith, eastern Australia, are consistent withmagma mixing between two silicic melts, each derived from isotopicallydistinct sources. Although zircons from three zones within theWalcha Road pluton give a U–Pb crystallization age of249 ± 3 Ma, zircon populations from each zone have arange in _Hf. Zircons from the mafic hornblende–biotitemonzogranite pluton margin and intermediate zones have _Hf +5to +11, whereas those from the more felsic centre of the plutonhave _Hf +7 to +16, representing a total variation of 11 _Hfunits. The Lu–Hf depleted mantle model ages range from650 to 250 Ma, with the younger zircons present only in thefelsic pluton centre. The variation in _Hf indicates the involvementof silicic melts from at least two sources, one a crustal componentwith a Neoproterozoic model age and the other a primitive mantle-derivedcomponent with model ages similar to the U–Pb crystallizationage of the pluton. The zircons reflect the isotopic compositionsof the different proportions of crustal-derived silicic melt,relative to mantle-derived silicic melt, between melt generationand final pluton construction. The Walcha Road pluton is consideredto have formed by incremental assembly of progressively morefelsic melt batches resulting from mixing, replenishment andcrystal–melt separation, with final pluton constructioninvolving mechanical concentration as zones of crystal mush.The zoned pluton and, more broadly, the Moonbi supersuite provideexamples of magma mixing by which the more silicic units havemore juvenile isotopic compositions as a result of increasingproportions of residual melt from basalt fractionation, relativeto crustal partial melt. KEY WORDS: Australia; granite magma mixing; zircon; zoned pluton; Hf isotopes     

Effects of melt viscosity and silica activity on the rate and mechanism of quartz dissolution in melts of the CMAS and CAS systems

The dissolution rate of quartz in melts of the CMAS and CAS systems at 1,600°C and 1.5 GPa is a function of both the silica activity of the melt and its viscosity. In melts with low silica activity quartz dissolves more quickly than in higher aSiO₂ melts regardless of viscosity. For melts with equal aSiO₂, dissolution is faster in the low viscosity melt. Quartz dissolution is controlled by interface kinetics in three of the four melts used in this study for times much greater than predicted by the model of Zhang et al. (in Contrib Mineral Petrol 102:492–513 1989). One melt which was previously shown to adhere to the predicted behaviour at lower temperature shows a significant activation time at higher temperature. All the dissolution data indicate that there are likely to be three distinct domains of dissolution behaviour, although the details of why a particular melt falls in any one domain require further study. Although the current database is small, the relationship between quartz solubility and the dissolution constant indicate that solubility may be a useful parameter for predicting dissolution rates, particularly if silica activity and melt viscosity are also known.     

Application of particle dynamics to derive a general circulation in low latitudes

Summary In Section 1 are set out the reasons for the use of particle dynamics in this investigation. In Section 2 are solved the equations of motion for particles constrained to move along a horizontal surface under the action of a constant meridional pressure gradient force to obtain (a) velocities in spherical polar co-ordinates with naturally varying Coriolis terms, and (b) velocities and trajectories in plane cartesian co-ordinates in which the Coriolis parameter is assumed constant. Results obtained in each system are compared, showing that the plane co-ordinates as used are not significantly inaccurate, and trajectories of air particles obtained by application significantly inaccurate, and trajectories of air particles obtained by application of this system in steps of 5° of latitude are plotted to show the production of belts of convergence at some distance from the equator under the action of meridional pressure gradient forces.The approximation of these idealised particle trajectories to actual streamlines of the air flow are discussed in Section 3, and the concept of the production of belts of convergence is used to formulate a theory of formation and maintenance of the sub-tropical anticyclones. In Section 4 this theory is applied to observed average temperature data and the calculated results compared with observed average pressure data. A possible synoptic application of the theory is then indicated in Section 5.

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Zusammenfassung Im ersten Abschnitt werden Gründe für die Anwendung der Dynamik von Massenteilchen in der vorliegenden Arbeit dargelegt. Abschnitt 2 enthält die Lösungen der Gleichungen für die Bewegung von Massenteilchen auf horizontalen Flächen unter der Einwirkung eines konstanten meridionalen Druckgradienten. Die Lösungen ergeben a) die Geschwindigkeiten in sphärischen Polarkoordinaten mit variablem Coriolis-Term (entsprechend natürlichen Verhältnissen) und b) Geschwindigkeiten und Trajektorien in ebenen kartesischen Koodinaten in denen der Coriolis-Parameter als konstant angenommen wird. Die Ergebnisse für beide Koordinatensysteme werden verglichen und es zeigt sich, daß bei Verwendung der ebenen Koordinaten keine wesentlichen Ungenauigkeiten auftreten. Zeichnet man schrittweise von 5 zu 5° (Fig. 1) die Trajektorien der Luftteilchen, so ergeben sich als Folge der meridionalen Druckgradienten Konvergenzzonen in einigem Abstand vom Äquator.Die Annäherung dieser idealisierten Trajektorien an tatsächliche Stromlinien der Luft wird in Abschnitt3 diskutiert. An Hand der Vorstellungen von der Entstehung der Konvergenzzonen wird eine Theorie der Entstehung und Erhaltung subtropischer Antizyklonen gegeben. Im vierten Abschnitt wird diese Theorie auf beobachtete Mitteltemperaturen angewendet und die Ergebnisse der Berechnung werden mit beobachteten mittleren Luftdruckwerten verglichen. Auf eine mögliche synoptische Anwendung der vorliegenden Ergebnisse wird in Abschnitt 5 hingewiesen.

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Résumé La première partie contient les motifs de l'emploi de la dynamique de points pesants dans la présente étude. La deuxième partie donne les solutions des équations du mouvement de points pesants sur des surfaces horizontales sous l'effet d'un gradient méridien constant. Ces solutions fournissent les vitesses en coordonnées polaires sphériques avec un terme Coriolis variable, ainsi que les vitesses et les trajectoires en coordonnées cartésiennes planes en admettant un paramètre de Coriolis constant. On compare les résultats pour les deux systèmes de coordonnées et l'on constate que l'emploi des coordonnées planes n'introduit pas d'erreurs appréciables. Si l'on dessine les trajectoires de 5 en 5 degrés on voit apparaître des zones de convergence à quelque distance de l'équateur par suite des gradients méridiens.Dans la troisième partie on discute la similitude plus ou moins grande de ces trajectoires idéalisées avec les lignes de courant réelles. Parant de l'origine possible des zones de convergence, on établit une théorie de l'origine et du maintien des anticyclones subtropicaux. Dans la quatrième partie on applique cette théorie aux températures moyennes observées et l'on compare les résultats avec les valeurs moyennes observées de la pression. Dans la cinquième partie enfin on montre l'application possible des résultats obtenus à la synoptique.

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This paper is published with the permission of the Director of the meteorological Office.     

Arctic haze: Perturbation to the radiation field

Summary A model of the polluted arctic troposphere is constructed to estimate the magnitude and seasonal variation of the climate forcing function of arctic haze. Using a pill-box bathtub model for the Arctic and envisioning it to be filled with pollution from industrial sources in Eurasia, we estimate that maximum climate perturbation from arctic contamination occurs in the spring months. The major perturbation to the radiation budget is a lowering of the albedo (heating) of the earth-atmosphere system around the vernal equinox and is due to a trace amount (about 5% by mass) of black carbon associated with the removal-resistant submicron mode of aerosols. The black carbon over the reflecting polar ice/snow introduces a heating of about 1.5 degree per day into the haze layer.With 8 Figures