60Fe–60Ni systematics in the eucrite parent body: A case study of Bouvante and Juvinas

Eucrites are basaltic meteorites that cooled rapidly but are in many instances thermally metamorphosed and impact brecciated. The exact timing of these events remains unclear. In this study, Ni isotopic compositions and Fe/Ni elemental ratios are presented for two non-cumulate eucrites, Bouvante and Juvinas, including mineral separates from the latter. The samples are characterized by variable, well-resolved ⁶⁰Ni-excesses consistent with the former presence of live ⁶⁰Fe (t_1/2 = 2.62 Ma) at the time of eucrite crystallization. A significant fraction of Ni with a terrestrial-like composition appears to be surface correlated. This Ni may be the product of terrestrial contamination or was introduced by a chondritic impactor during brecciation. Altogether, the data provide evidence for a complex and probably multi-stage history of Fe and/or Ni redistribution, which impedes the interpretation of the chronological data.     

Vegetation response to obliquity and precession forcing during the Mid-Pleistocene Transition in Western Mediterranean region (ODP site 976)

The ODP leg 161 Site 976 (Alboran Sea) is a deep-sea section sampled at a water depth of 1108 m in the Western Mediterranean Sea. Pollen analysis provides a vegetation and climate record of the Mid Pleistocene Transition (MPT), roughly one million years ago. The age-model tied to biostratigraphic events was revised by aligning the pollen climate index (PCI) to Mediterranean (KC01b) and global (LR04) oxygen isotope records. The studied time slice spans the interval ～1.09 Ma (MIS 31) to ～0.90 Ma (MIS 23).Across this interval, past phytogeography of nowadays extinct taxa, which were rare, allows a successful application of the modern analogues technique (MAT) to quantitative climate reconstructions for the MPT. Five, long-term, obliquity-related vegetation successions (O1 to O5), and eight short-term, precession-related vegetation successions (P1 to P8) are observed within the studied interval. These vegetation successions, regardless of their duration, show the same pattern: the progressive replacement of temperate trees by mountainous taxa, and then by herbs and steppe maxima. Precession-related successions correspond, therefore, to as dramatic vegetation changes as those driven by obliquity, including a final steppe phase under deteriorated climate conditions.Wavelet analysis of the PCI record shows that the Western Mediterranean experienced a shift at 1.01 Ma from precession-dominated frequencies (1.05–1.01 Ma) to obliquity-dominated frequencies (1.01–0.9 Ma). There is, therefore, an apparent discrepancy between wavelet analysis results and vegetation dynamic analysis (which suggests that obliquity and precession are recorded throughout the entire studied interval). This discrepancy could result from the fact that the PCI record sums, somehow, similar vegetation changes (wet to dry) occurring at different periodicities. Such a complex vegetation dynamics is mathematically rendered through a single parameter (i.e. principal component), which does not successfully catch the subtle combinations of variability occurring at two close periodicities. Furthermore, the pollen-inferred Early Pleistocene vegetation dynamic (and climate) of the Western Mediterranean region does not show a decrease of the obliquity response relative to the precession response at the onset of the MPT.     

La theorie des deux magmas fondamentaux dans le volcanisme intracontinental et l'evolution geochimique des laves du Mont-Dore (France)

Résumé Les auteurs utilisent toutes les données chimiques, volcanologiques, chronologiques et tectonophysiques fournies pour un certain nombre de massif continentaux (Mont-Dore et autres). La synthèse de toutes ces études montre qu'il existe deux magmas continentaux indépendants: le magma basaltique venant du manteau (sima) et le magma rhyolitique fourni par la croûte supérieure (sial). Le mélange de ces deux magmas et l'action secondaire de la' gravité et de la pneumatolyse expliquent logiquement la totalité des phénomènes géochimiques des volcans continentaux.

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The authors used all the chemical, volcanological, chronological and tectonophysical data supplied for a certain number of continental mountain massifs (Mont-Dore and others). The synthesis of these studies shows that there are two independent continental magmas: the basaltic magma coming from the mantle (sima) and the rhyolitic magma supplied by the upper crust (sial). The mixing of these two magmas, with the secondary action of gravity and pneumatolysis logically explains the totality of the geochemical phenomena in continental volcanoes.

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Zusammenfassung Die Autoren benutzten alle chemischen, vulkanologischen, chronologischen und tektonisch-physikalischen Daten, die von einer bestimmten Anzahl von kontinentalen Massiven (Mont-Dore und andere) entnommen wurden.Das Ergebnis dieser Studien zeigt, daß es zwei voneinander unabhängige kontinentale Magmen gibt.Das basaltische Magma, vom Sima stammend, und das rhyolitische Magma aus der oberen Sial-Kruste. Die Vermischung dieser beiden Magmen und die zusätzliche Wirkung der Gravitation und Pneumatolyse erklären auf natürliche Weise die Gesamtheit der geochemischen Phänomene des kontinentalen Vulkanismus.

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A study of Gd,Ce and Eu impurities in fluorite deposits by electron paramagnetic resonance and neutron activation analysis

In order to obtain a better understanding of fluorite deposits, rare earth impurities have been analyzed for a large number of samples taken from cross-sections of several low temperature hydrothermal veins. Two types of measurements have been used: Electron Paramagnetic Resonance (EPR) and Neutron Activation Analysis (NAA). For Gd, the ratio of spin concentrations to total concentration [Gd³⁺]/[Gd_total] is close to 1 in all the samples; on the other hand, the ratios [Eu²⁺]/[Eu_total] and [Ce³⁺ -F _? ⁱ ]/[Ce_total] exhibit large variations. The first result suggests that the major part of the lanthanides in the samples is incorporated in the crystal lattice and that clustering of lanthanides ions is not important. The behaviour of Eu and Ce is ascribed to charge state changes and symmetry state changes respectively.     

Channel response to an extreme flood and sediment pulse in a mixed bedrock and gravel‐bed river

We exploit a natural experiment caused by an extreme flood (~500 year recurrence interval) and sediment pulse derived from more than 2500 concurrent landslides to explore the influence of valley‐scale geomorphic controls on sediment slug evolution and the impact of sediment pulse passage and slug deposition and dispersion on channel stability and channel form. Sediment slug movement is a crucial process that shapes gravel‐bed rivers and alluvial valleys and is an important mechanism of downstream bed material transport. Further, increased bed material transport rates during slug deposition can trigger channel responses including increases in lateral mobility, channel width, and alluvial bar dominance. Pre‐ and post‐flood LiDAR and aerial photographs bracketing the 2007 flood on the Chehalis River in south‐western Washington State, USA, document the channel response with high spatial and temporal definition. The sediment slug behaved as a Gilbert Wave, with both channel aggradation and sequestration of large volumes of material in floodplains of headwaters' reaches and reaches where confined valleys enter into broad alluvial valleys. Differences between the valley form of two separate sub‐basins impacted by the pulse highlight the important role channel and channel‐floodplain connectivity play in governing downstream movement of sediment slug material. Finally, channel response to the extreme flood and sediment pulse illustrate the connection between bed material transport and channel form. Specifically, the channel widened, lateral channel mobility increased, and the proportion of the active channel covered by bars increased in all reaches in the study area. The response scaled tightly with the relative amount of bed material sediment transport through individual reaches, indicating that the amount of morphological change caused by the flood was conditioned by the simultaneous introduction of a sediment pulse to the channel network. Copyright © 2015 John Wiley & Sons, Ltd.     

Wesen,Ursachen und Arten der Schichtung

Ohne Zusammenfassung     

On hierarchical cosmology

Progress in laboratory studies of plasmas and in the methods of transferring the results to cosmic conditions, together within situ measurements in the magnetospheres, are now causing a ‘paradigm transition’ in cosmic plasma physics. This involves an introduction ofinhomogeneous models with double layers, filaments, ‘cell walls’, etc. Independently, it has been discovered that the mass distribution in the universe is highly inhomogeneous; indeed,hierarchical. According to de Vaucouleurs, the escape velocity of cosmic structures is 10²–10³ times below the Laplace-Schwarzschild limit, leaving avoid region which is identified as a key problem in cosmology. It is shown that a plasma instability in the dispersed medium of the structures may produce this void and, hence, explain the hierarchical structure. The energy which is necessary may derive either from gravitation or from annihilation caused by a breakdown of cell walls. The latter alternative is discussed in detail. It leads to a ‘Fireworks Model’ of the evolution of the metagalaxy. It is questioned whether the homogeneous four-dimensional big bang model can survive in an universe which is inhomogeneous and three-dimensional.     

Multiple Random Walk Simulation: A Fast Method to Map Grade Uncertainty with Large Datasets

Multiple Random Walk Simulation consists of a methodology adapted to run fast simulations if close-spaced data are abundant (e.g., short-term mining models). Combining kriging with the simulation of random walks attempts to approximate traditional simulation algorithm results but at a computationally faster way when there is a large amount of conditioning samples. This paper presents this new algorithm illustrating the situations where the method can be used properly. A synthetic study case is presented in order to illustrate the Multiple Random Walk Simulation and to analyze the speed and goodness of its results against the ones from using Turning Bands Simulation and Sequential Gaussian Simulation.     

Tremblements de terre et anomalies magnétiques

Résumé On a déjà souvent signalé que le champ magné ique terrestre s'est trouvé modifié de fa?on durable à la suile de mouvements séismiques. L'auteur rappelle plusieurs exemples récents d'anomalies magnétiques mesurées au Japon à la suite d'importants séismes (Kato). L'anomalie magnélique duBassin de Paris se déforme dans le temps en liaison possible avec des déplacements magmatiques et une activité séismique avortée. Le séisme du 11 juin 1938 en Belgique montre d'intéressants rapports avec l'anomalie magnétique belge. Les cartes isoporiques mondiales présentent des relations avec les cartes de séismicité (Omer). L'auteur pense que séismes et déformations du champ magnétique terrestre sont plus ou moins étroitement liés et que peut être une réaction atomiqueen chaine peut expliquer les séismes orogéniques et leurs répliques.

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Summary It was yet often noted that the earth's magnetic field has been steadily modified on the result of seismic earth movements. The author cites many recent examples of magnetic anomalies measured in Japan after major earthquakes (Kato). The ?Bassin de Paris?'s magnetic anomaly is modified during a certain time in a possible connection with magmatic removals and with some seismic activity. The earthquake of June 11 th., 1938 in Belgium shows some very interesting connections with the belgian magnetic anomaly. Suggestive relationships are noted between changes in the earth's secular magnetic field and areas of seismicity (Omer). The author thinks that the earthquakes and the deformations of the earth's magnetic field are more or less closely connected one with another, and it may perhaps be that the atomic energy (chain reactions) may explain some orogenic earthquakes and their aftershocks.