Structural analysis of the Subbriançonnais and Valais units in the area of Moûtiers (Savoy, Western Alps): paleogeographic and tectonic consequences

Valais and Subbriançonnais units of the Western Alps of Savoie underwent a common structural evolution, postdating peak pressure conditions associated with high-pressure metamorphism of internal parts of the Valais units. The first two phases, due to roughly north/south-directed shortening, are interpreted to be related to a NNE/SSW-striking corridor of sinistral transpression between the internal Western Alps and the European foreland. Both phases led to nappe formation, isoclinal folding and north–south elongation. Only the third phase of deformation is related to WNW-directed orogen-perpendicular shortening, thus far regarded as the predominant thrusting direction in the Western Alps. Late (post 5?Ma) normal faulting, evidenced by fission-track dating, reactivated the Houiller Front in the north and the Penninic Front in the south. Kinematics of movement, observed along the present-day Houiller Front and Penninic Front, change from north to south. In the north the Houiller Front indicates post-D3 normal faulting while the Penninic Front preserved WNW-directed thrusting (D3). In the south the Houiller Front preserves syn-D2 north-directed thrusting, whereas the Penninic Front is partly reactivated by post-D3 normal faulting. Our observations clearly favor tectonic reasons for the disappearance of the Valais units south of Moûtiers in present-day map view.     

A time-minimizing hybrid method for fitting complex Mössbauer spectra

The present study includes results of the application of a program consisting of a genetic algorithm routine and a conventional refinement part (“hybrid method”) for the evaluation of Mössbauer spectra published elsewhere. It is shown that the saving of total evaluation time compared with conventional refinement routines is very high due to the rapid finding of adequate starting parameters. Contrary to a recently published work on a similar topic our algorithm provides solutions of the combined interaction Hamiltonian with a minimum of conventional input data.     

2-[2′-(6-甲氧基-苯并噻唑)-偶氮]-1,8-二羟基萘-3,6-二磺酸的合成及其与钛的显色反应

合成了新的杂环偶氮变色酸类试剂———２［２′（６甲氧基苯并噻唑）偶氮］１,８二羟基萘３,６二磺酸,并系统探讨了在ｐＨ４．５的邻苯二甲酸氢钾ＮａＯＨ介质中显色试剂与钛的显色反应特性。结果表明,在溴化十六烷基吡啶存在下,试剂与Ｔｉ（Ⅳ）形成２∶１的络合物,显色反应１５ｍｉｎ完全并至少稳定４ｈ,最大吸收波长为６７０ｎｍ,表观摩尔吸光系数达１．６７×１０５Ｌ·ｍｏｌ－１·ｃｍ－１,钛的质量浓度在０～４００μｇ／Ｌ时符合比尔定律。用拟定的方法测定了硅砖等标准物质中的Ｔｉ（Ⅳ）,所得结果与标准值的相对误差均小于４％,ＲＳＤ（ｎ＝５）小于３．５％。     

Optical spectroscopy study of natural Fe, Ti-bearing calcic amphiboles

Over thirty samples of natural Ti-bearing amphiboles with Ti- and Fe-contents ranging from 0.111 to 0.729 atom per formula unit (a.p.f.u.) and from 0.479 to 2.045 a.p.f.u., respectively, were studied by means of optical absorption spectroscopy and microprobe analysis. Thirteen samples were also studied by Mössbauer spectroscopy. A strong pleochroic absorption edge, causing the dark brown colours of Ti-bearing amphiboles, is attributed to ligand-metal and metal-metal charge transfer transitions involving both iron and titanium ions (O^2?→ Fe³⁺, Fe²⁺, O^2?→ Ti⁴⁺ and Fe²⁺ + Ti⁴⁺→ Fe³⁺ + Ti³⁺). A broad intense Y-polarized band ～22?000?cm^?1 (ν_1/2?≈?3700?cm^?1) in spectra of two low iron amphiboles with a relatively low Fe³⁺/Fe_total ratio, both from eclogite-like rocks in kimberlite xenoliths, was attributed to electronic Fe²⁺(M3) + Ti⁴⁺(M2)→Fe³⁺(M3)+Ti³⁺(M2) IVCT transitions. The IVCT bands of other possible ion pairs, involving Ti⁴⁺ and Fe²⁺ in M2 and M1, M4 sites, respectively, are presumed to be at higher energies, being obscured by the absorption edge.     

Instability in the 3rd Dimension of the Extended Störmer Problem

The problem of motions of charged particles or charged grains of matter in the field of two magnetic dipoles in rotation about a common center are studied by means of computing families of periodic solutions and their stability. Ten such families are found and their stability study shows that only two out of the ten have short arcs of stable members, all with low inclination to the plane of the two dipoles, while the rest of the families consist exclusively of unstable solutions. Hence the impact of adding one dipole to the configuration of the Störmer problem, leads to the conclusion that in the modified system the three-dimensional motions are basically unstable unlike those of the one-dipole case. The model magnetic field used in this study is a first approximation of the Z3model of the magnetic field of Saturn as computed from the Pioneer 11 and Voyager 1 and 2 measurements.     

A Tenth Order Symplectic Runge–Kutta–Nyström Method

A tenth order explicit symmetric and in consequence symplectic Runge–Kutta–Nyström method is presented here. We derive the order conditions needed and solve them for the parameters of the method. Numerical results indicate the superiority of the new method compared to the other high order symplectic methods appeared in the literature until now.     

The Relationship Between the Interannual Variation of Earth’s Rotation and El Niño Events

We analyzed the relationship between the earth’s rotational variation and sea-surface temperature anomaly. By means of using Fast Fourier Transform (FFT) bandpass filter on the change of length-of-day (ΔLOD) data, the interannual variation series having time periods greater than 1.5-year and less than 8-year was obtained. Time series analyses of the interannual variation, which corresponds to the El Niño period, reveal a close linkage between the earth’s rotation and El Niño. A detailed comparison suggests, that six of seven El Niño events are nearly synchronous with the interannual variation of the earth’s rotation, and all ΔLOD peak are in El Niño years except 1991–92, which means the interannual variation of the earth’s rotation in these years is relatively slow. The correlation between ΔLOD and sea-surface temperature is about 0.517 (1 month-lag), which far exceeds the 99% significance level.     

Interpretation of Low Seismicity in the Eastern Anatolian Collisional Zone Using Geophysical (Seismicity and Aeromagnetic) and Geological Data

The eastern Anatolia is a continental collisional zone between the Arabia-Eurasia plates and is currently being accompanied by the westward escape of the Anatolian crustal block to the west-southwest along two major strike-slip fault zones, the NATF and the EATF. Although these major fault zones have experienced historical earthquakes with moderate to high magnitude, notably there is a low seismicity zone on the active EATF between the Bitlis and Pötürge massifs. The low seismicity zone is characterized by thinner crustal structure relative to its environs, the shallow Curie Point Depth (SCPD, ca 12–14 km in between 39–40°E and 38.5–39°N in the easternmost part of the Anatolian plate) and moderate to high b values (more than 0.7). We consider that the shallow CPD and moderate to high b values in the low seismicity zone characterized by thinner crustal area are closely related with the higher thermal structure of the crust, which most probably resulted from crust-hot asthenospheric mantle interactions.     

Imprints of sub-glacial volcanic activity on a glacier surface—SAR study of Katla volcano,Iceland

The Katla central volcano, covered by the fourth largest Icelandic glacier Mýrdalsjökull, is among the most dangerous and active volcanoes in Iceland. Due to the ice cover, several indicators of its volcanic activity can only be identified indirectly. We analysed a total of 30 synthetic aperture radar (SAR) images with special focus on identifying circular and linear depressions in the glacier surface. Such features are indicative of sub-glacial geothermal heat sources and the adjacent sub-glacial tunnel (melt water drainage) system. The time series comprises images from five different SAR sensors (ERS-1, ERS-2, JERS-1/SAR, RADARSAT and ENVISAT-ASAR) covering a time period of 12 years, starting in 1994. Individual SAR scenes only partly map the glacier surface morphology due to the environmental influences on the SAR backscatter intensity. Thus, only surface features detectable in several SAR scenes at the same location were considered and merged to form an overall picture of the surface morphology of Mýrdalsjökull and its modification by sub-glacial volcanic activity between 1994 and 2006. Twenty permanent and 4 semi-permanent ice cauldrons could be identified on the surface of Mýrdalsjökull indicating geothermally active areas in the underlying caldera. An analysis of their size was not possible due to the indistinct outline in the SAR images. The spatial distribution of the geothermally active areas led to a new, piecemeal caldera model of Katla volcano. All cauldrons are connected to tunnel systems for melt water drainage. More than 100 km of the sub-glacial drainage system could be identified under the Mýrdalsjökull in the SAR time series. It has been found that the tunnel systems are not in agreement with estimated water divides. Our results allow improved assessment of areas of potential Jökulhlaup hazard accompanying a sub-glacial eruption.     

Ferrous iron in post-perovskite from first-principles calculations

We investigate by first-principles calculations the effect of ferrous iron, Fe²⁺, on the structure and the equation of state of MgSiO₃ post-perovskite. We find that ferrous iron is high-spin over the pressure range of the mantle assuming a ferromagnetic structure. The bulk modulus and the specific volume increase with the addition of ferrous iron to MgSiO₃. We find that Fe partitions preferentially to post-perovskite and broadens the two-phase pressure range.