Shock-effects on the K-Ar system of plagioclase feldspar and the age of anorthosite inclusions from North-Eastern Minnesota

Artificial shock pressures up to 52.5 GPa have no influence on the K-Ar system of plagioclase feldspar. The ⁴⁰Ar-³⁹Ar analysis of feldspar (labradorite An₆₇ from anorthosite of North-Eastern Minnesota) shocked up to 45 GPa—in vacuo, to prevent massive entrapment of atmospheric argon-shows that the age spectra and the argon diffusion properties remain unaltered. Similar feldspar samples (labradorite An₅₁ from Nain, Labrador), shocked in air up to 52.5 GPa and dated by the conventional K-Ar method, also yield the same age as unshocked samples but with a higher atmospheric argon contribution. The Minnesota anorthosite has an ⁴⁰Ar-³⁹Ar age of 1075 ± 10 m.y. No information on a possible previous history of the anorthosite became apparent.     

A Unifying Scheme for Low-Luminosity XRBs and AGN

In recent years, significant evidence for the similar nature of active galactic nuclei (AGN) and X-ray binaries (XRBs) has been gathered. We describe a unification scheme for accreting black holes following the idea that weakly accreting systems may be jet dominated. This is tested with the radio/X-ray correlation of XRBs and AGN. The established correlation is further used to diagnose ultra-luminous X-ray sources. For higher accretion rates, we explore high-power jets and the effect of Compton cooling of the jet by the accretion disk.     

Soil Cd,Cu, Pb and Zn contaminants around Mount Isa city,Queensland, Australia: Potential sources and risks to human health

This article investigates the relationship between soil Cd, Cu, Pb and Zn contaminants and the location and activities of the Pb–Zn–Ag and Cu mines at Mount Isa, Queensland, Australia. Analysis of the data focuses primarily on soil Pb distributions and concentrations because of their potential impact on children’s health. The Xstrata Mount Isa Mines lease (XMIM) is Australia’s leading emitter of numerous contaminants to the environment, including Cu and Pb, and the mining-related activities have been linked causally to the findings of a 2008 study that showed 11.3% of local children (12–60 months) have blood Pb levels >10 μg/dL. Queensland government authorities and Xstrata Mount Isa Mines Pty Ltd maintain that contaminants within environmental systems around Mount Isa are largely the result of near-surface mineralization. The evidence for whether the contamination is derived from XMIM or other possible sources, such as the natural weathering of ore-rich bedrock, is investigated using data from surface and subsurface soil chemistry, atmospheric modelling of metal contaminants from mining and smelting operations and local geological and associated geochemical studies. Sixty surface soil samples collected from sites adjacent to houses, parks and schools throughout Mount Isa city were analyzed for their total extractable Cd, Cu, Pb and Zn concentrations in the <2 mm to >180 μm (coarser) and <180 μm (finer) grain size fractions. Concentrations in the finer size fraction reveal a range of values: Cd – 0.7–12.5 ppm; Cu – 31–12,100 ppm; Pb – 8–5770 ppm; Zn – 26–11,100 ppm, with several samples exceeding Australian residential health investigation guidelines. Spatial analysis shows that surface soil metal concentrations are significantly higher within 2 km of XMIM compared to more distant samples, and that more than 1000 property lots are at risk of having detrimentally high soil Pb levels. Determination of metal concentrations in 49 samples from eight soil pits shows that surface samples (0–2 cm) are enriched significantly relative to those at depth (10–20 cm), suggesting an atmospheric depositional origin. AUSPLUME air dispersal modelling of Pb originating from the Cu and Pb smelter stacks and mine site fugitive sources confirms that Pb is deposited across the urban area, during periods of the year (∼20%/a) when the wind blows from the direction of XMIM towards the urban area and disperses dusts from the uncovered spoil and road surfaces, as well as from stack emission sources. Although there are some spatially restricted outcrops of Pb close to the surface in parts of the urban area, the Cu-ore body is ∼244 m below the surface. However, enriched and significantly correlated surface soil concentrations of Cu and Pb (Pearson correlation 0.879, p = 0.000) in and around the urban area of Mount Isa can only be explained by atmospheric transport and deposition of metals from the adjoining mining and smelting operations. The results from this study provide unequivocal evidence that both historic and ongoing emissions from XMIM are contaminating the urban environment. Given the ongoing Pb poisoning issues in Mount Isa children, it is clear that remediation, reductions in mine emissions and more stringent regulatory actions are warranted.     

The behavior of jet streams in potential fallout situations

Summary It is shown from a case study that the splitting of jet streams into several branches, which is frequently observed over the United States on the leading edges of intense maxima, may be explained by conservation of potential vorticity within an atmospheric layer moving over an obstacle. Such an obstacle may be a large mountain barrier, such as the Rocky Mountains, or a slowmoving dome of cold air in the lower troposphere, as is typical for cold outbreaks associated with strong jet streams.

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Zusammenfassung An Hand eines konkreten Falles wird gezeigt, daß die Aufspaltung des Jet Streams in mehrere Äste, wie dies häufig über den Vereinigten Staaten an der Vorderseite intensiver Jet Maxima beobachtet wird, mit der Erhaltung der potentiellen Vorticity innerhalb einer Luftschicht, die sich über ein Hindernis bewegt, erklärt werden kann. Ein derartiges Hindernis kann einerseits durch ein Gebirge gegeben sein, wie etwa die Rocky Mountains, andererseits aber auch durch eine sich nur langsam fortbewegende Kaltluftmasse in der unteren Troposphäre. Eine solche ist für Kaltluftausbrüche im Zusammenhang mit intensiven Strahlströmen charakteristisch.

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Résumé En se basant sur un cas particulier, on montre que la subdivision d'un courant jet en plusieurs bras distincts — fait souvent observé au dessus des Etats Unis d'Amérique à l'avant de la zone d'intensité maximum — peut s'expliquer par la conservation de l'énergie tourbillonnaire potentielle d'une couche d'air se déplaçant sur un obstacle. Un tel obstacle peut être soit une importante chaîne de montagnes telles que les Rocheuses, soit une masse d'air froid se déplaçant lentement dans la basse troposphère, comme c'est typiquement le cas lorsqu'une invasion d'air froid est liée à un fort courant jet.

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With 3 Figures     

Parallel tracks in infrared versus X-ray emission in black hole X-ray transient outbursts: a hysteresis effect?

We report the discovery of a new hysteresis effect in black hole X-ray binary state transitions, that of the near-infrared (NIR) flux (which most likely originates in the jets) versus X-ray flux. We find, looking at existing data sets, that the IR emission of black hole X-ray transients appears to be weaker in the low/hard state rise of an outburst than the low/hard state decline of an outburst at a given X-ray luminosity. We discuss how this effect may be caused by a shift in the radiative efficiency of the inflowing or outflowing matter, or variations in the disc viscosity or the spectrum/power of the jet. In addition we show that there is a correlation (in slope but not in normalization) between IR and X-ray luminosities on the rise and decline, for all three low-mass black hole X-ray binaries with well-sampled IR and X-ray coverage:   L _NIR∝ L ^0.5–0.7_X  . In the high/soft state this slope is much shallower;   L _NIR∝ L ^0.1–0.2_X  , and we find that the NIR emission in this state is most likely dominated by the viscously heated (as opposed to X-ray heated) accretion disc in all three sources.     

Common disc-jet coupling in accreting objects

The “fundamental plane of accreting black holes” and an empirical connection between X-ray binaries (XRBs) and active galactic nuclei (AGN) based on variability properties is presented. Following these connections we construct disc-fraction luminosity diagrams (DFLD), a generalisation of hardness-intensity diagrams used for XRBs. We show that the radio-loudness of AGN depends on the position in the DFLD similar to what is observed in XRBs. For those XRBs and AGN on the right side of the diagram (hard state XRBs, LLAGN and many radio-loud quasars) we show that the jet power and accretion rate can be estimated from the core radio emission. This accretion measure is used to explore the dependence of the bolometric luminosity on the accretion rate.     

Steinheim suevite—A first report of melt‐bearing impactites from the Steinheim Basin (SW Germany)

Abstract– The 3.8 km Steinheim Basin in SW Germany is a complex impact crater with central uplift hosted by a sequence of Triassic to Jurassic sedimentary rocks. It exhibits a well‐preserved crater morphology, intensely brecciated limestone blocks that form the crater rim, as well as distinct shatter cones in limestones. In addition, an impact breccia mainly composed of Middle to Upper Jurassic limestones, marls, mudstones, and sandstones is known from drilling into the impact crater. No impact melt lithologies, however, have so far been reported from the Steinheim Basin. In samples of the breccia that were taken from the B‐26 drill core, we discovered small particles (up to millimeters in size) that are rich in SiO₂ (～50 wt%) and Al₂O₃ (～28 wt%), and contain particles of Fe‐Ni‐Co sulfides, as well as target rock clasts (shocked and unshocked quartz, feldspar, limestone) and droplet‐shaped particles of calcite. The particles exhibit distinct flow structures and relicts of schlieren and vesicles. From the geochemical composition and the textural properties, we interpret these particles as mixed silicate melt fragments widely recrystallized, altered, and/or transformed into hydrous phyllosilicates. Furthermore, we detected schlieren of lechatelierite and recrystallized carbonate melt. On the basis of impactite nomenclature, the melt‐bearing impact breccia in the Steinheim Basin can be denominated as Steinheim suevite. The geochemical character of the mixed melt particles points to Middle Jurassic sandstones (“Eisensandstein” Formation) that crop out at the center of the central uplift as the source for the melt fragments.     

Loading fractures and Liesegang laminae: new sedimentary structures found in the north-western North Alpine Foreland Basin (Oligocene–Miocene, south-west Germany)

Abstract Spectacular sedimentary structures recently found in the Molasse Basin (Oligocene–Miocene) in southern Germany were produced by soft‐sediment deformation under highly unusual conditions. These large, apparently wedge‐like structures –‘loading fractures’– cut down into beds of marl and are filled with coarse sand and intraclasts of shale. Wrapping the sides of the structures is a thin, continuous bed of layered dark claystone – the ‘DCB’. The upper and lower layers of this bed are an organic‐rich clay; the middle layer is a laminated quartzite. The precursor of the DCB was a lacustrine gyttja rich in diatom frustules. It was supersaturated in silica as it was buried. Subsequent diffusion of oxygen into this gyttja at a burial depth of only a few metres resulted in the formation of Liesegang laminae of quartz. These laminae grew and amalgamated, forming the layer of laminated quartzite. The sediments overlying the DCB were eventually removed by erosion, probably in a high‐energy marine environment. This erosion cut down to the DCB but was unable to penetrate it. The DCB remained exposed on the sea floor until a sudden depositional event occurred – the deposition of a 2·5 metre thick bed of coarse sand with shale intraclasts. Although the DCB had been able to resist the submarine erosion, it could not support the load of this new bed. The quartzite layer in it therefore fractured, transferring that load down onto the underlying, still‐unconsolidated marl. The intraclast‐rich sands were forced down into this marl, carrying ahead of them the partly broken remains of the DCB.