Abundance Gradients in the Outer Galactic Disk

Radial abundance gradients of the element ratios O/H, Ne/H, S/H, and Ar/H are determined for a sample of disk planetary nebulae, emphasizing the behaviour of the gradients at large galactocentric distances. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Galactic Thick Disk – Status

The status of the Galactic thick disk is reviewed. Consideration of the recent literature suggests that its vertical scale height and normalisation with respect to the thin disk remain uncertain to within a factor two, with values reported in the ranges 750–1500 pc, and 0.02–0.13, respectively. The bulk of the thick disk has kinematics (σ_U, σ_V, σ_W) = (65, 54, 38 km s^-1), and lags the thin disk by some 40 km s^-1; differences of opinion exists as to whether kinematics change with distance from the Galactic plane. The bulk of the thick disk has [Fe/H] ∼ −0.6, with little or no evidence for a vertical gradient. The question of gradients is critical for an understanding of thick disk cosmogony and needs closer attention. The reality of the so-called metal-weak thick disk (material having disklike kinematics and [Fe/H] ≤ −1.0) is also considered. The case for such material seems to be steadily growing: in the range −1.6 ≤ [Fe/H] ≤ −1.0, recent estimates suggest ρ_MWTD/ρ_Halo ∼ 0.1-0.3. While many workers regard the thick disk as a discrete entity, the caveat is made that this is a sufficient condition, but not one necessarily required by the observations. Best practice requires that both the discrete model and the alternative extended configuration be compared with observational data to examine the relative likelihood of their relevance. Recent theoretical advances are also discussed, together with the need for in situ measurements of the thick disk away from the Galactic plane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution and accumulation rate of ore elements in Holocene and Late Glacial Sediments of the Deryugin Basin,Sea of Okhotsk

Results of the study of contents and accumulation rates of Fe, Mn, and a number of trace elements in Upper Quaternary sediments of the Deryugin Basin are presented. Maps of the average contents and accumulation rates of excess Fe, Mn, Zn, Ba, Ni, Pb, Cu, and Mo in sediments of the first oxygen isotope stage (OIS) have been plotted. Anomalous contents and accumulation rates are confined to peripheral zones of the Deryugin sedimentary basin and large fracture zones. Different mechanisms of the influence of fluid-dynamic processes on the rate of hydrogenic and biogenic accumulation of ore elements are assumed.Translated from Litologiya i Poleznye Iskopaemye, No. 2, 2005, pp. 115–132.Original Russian Text Copyright © 2005 by Astakhov, Gorbarenko, Bakhareva, Gretskaya, Sattarova.     

A Simple Model for the Movement of Fire Smoke in a Confined Tunnel

Fires in tunnels are unfortunately frequent occurrences often with tragic outcomes. A recent example is the fire on the funicular train at the ski resort in Kaprun (Austria), which caused nearly 160 deaths. Design engineers and risk analysts require knowledge of the fluid dynamics of the fire and smoke movement to answer questions such as how much oxygen can access and feed the fire, and what concentration of smoke will the people be exposed to. As an example in the Austrian accident the geometry was a long tunnel with fire doors closed at one end, and with a fire initiated near the closed (lower) end. The hot smoke from the fire is a source of buoyancy; the smoke reaches the ceiling of the tunnel, and then develops along the ceiling as a wall-bounded plume. The motion of the smoke is driven by a buoyancy force, but at the same time, mechanisms of turbulent heat and mass transfer act as a brake to this motion. In this paper we present how a generic model describing a semi-enclosed buoyancy-driven flow can be interpreted and used in the modelling of fire smoke movement in a confined tunnel. A consideration of the net pollutant volume flux through the tunnel leads to predictions for the variation of concentrations along the tunnel. The smoke concentrations near the fire smoke source scale linearly with the length of the tunnel, with higher concentrations at the lower section of the tunnel, as could be expected. Similarly the concentration of oxygen making its way through to the fire source decreases linearly with the length of the tunnel. A lower bound estimate of the smoke residence time can be obtained based on smoke concentration predictions from the model.     

Lang Trang Cave (Northern Vietnam): Pleistocene Mammalian Locality with Gigantopithecus Finds

Doklady Earth Sciences - Speleological, geological and paleontological characteristics of the Lang Trang cave in northern Vietnam are presented. Primates Gigantopithecus blacki von Koenigswald,...     

Die stratiforme Sulfidlagerstätte Walchen,Steiermark, Österreich: Geochemie und Genese

Zusammenfassung Die Neubearbeitung derstratiformen Sulfidlagerstätte Walchen bei Öblarn, Steiermark, offen-bart eine eisenbetonte submarin-exhalative Metallkonzentration in einem vulkano-sedimentären Rahmen. Dieser liegt heute in Form metamorpher Gesteine der untersten Grünschieferfazies vor. Mineralchemische Untersuchungen zeigen, daß die ehemalige intensivste metamorphe Überprägung der Lagerstätte im Bereich von 450°–500°C oberhalb 4 kb stattgefunden hat. Metavulkanite, vertreten durch Grünschiefer, lassen alkalibasaltische Affinität erkennen. Die vulkano-tektonische Position der Lagerstätte ist in einem intrakontinentalen Riftsystem zu sehen.

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The stratiform sulphide deposit at walchen, styria, austria: Geochemistry and genesis

Summary The Walchen deposit consists of a 1–2 m thick layer of massive to disseminated pyrite-pyrrhotite-chalcopyrite ore with an average grade of 1% Cu. It has been mined intermittently in the past. The ore horizon occurs within sericitic and quartzitic phyllites which carry intercalations with significant carbonate, garnet and graphite contents. The succession is of lower Paleozoic age and forms part of the Grauwackenzone, a volcano-sedimentary unit which separates the Central Alps from the Northern Calcareous Alps.The precursor rocks of the ore environment have been pelites and sandstones; greenschists occur in the hanging wall of the mineralization. Major and trace element analyses of greenschists reveal them as low-grade metamorphic equivalents of continental alkali basalts. Hydrothermal systems generated by volcanic activity were responsible for deposition of stratiform sulphides. The predominance of clastic sediments and the absence of stringer zones point towards a shallow depositional basin.Microprobe analyses of garnets from the ore environment reveal an increase in spessartine contents from 7 mol% in phyllites to 20 mol% in the vicinity of the ore horizon. Similar data have been reported from other stratabound base metal deposits (Broken Hill, N.S.W.; Kreuzeck Mountains, Austria; Gamsberg, South Africa); the manganese concentrations represent fossil manganese haloes.Pyrite carries minor Ni and Co (up to 0.03, respectively 0.3%), pyrrhotite averages 0.8% Ni and 0.1% Co, Fe-contents of sphalerite vary from 6.41–9.33%; Cd, In and Mn have not been recorded.Garnet-biotite pairs suggest maximum metamorphic temperatures of 450°–500°C: pressures of 4 to 5 kb have been estimated. The Walchen deposit is interpreted as the product of submarine exhalative processes in an incipient rift. It was affected by prograde metamorphism during the Variscan orogeny, and by retrograde affects during a later event. Isochemical metamorphism resulted in the preservation of a primary manganese halo.

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