Present-day stress orientations and tectonic provinces of the NW Borneo collisional margin

Extent: 15p.Borehole failure observed on image and dipmeter logs from 55 petroleum wells across the NW Borneo collisional margin were used to determine maximum horizontal stress (σH) orientations; combined with seismic and outcrop data, they define seven tectonic provinces. The Baram Delta–Deepwater Fold-Thrust Belt exhibits three tectonic provinces: its inner shelf inverted province (σH is NW-SE, margin-normal), its outer shelf extension province (σH is NE-SW, margin-parallel), and its slope to basin floor compression province (σH is NW-SE, margin-normal). In the inverted province, σH reflects inversion of deltaic normal faults. The σH orientations in the extension and compression provinces reflect deltaic gravitational tectonics. The shale and minibasin provinces have been recognized in offshore Sabah. In the shale province, σH is N010°E, which aligns around the boundary of a massif of mobile shale. Currently, no data are available to determine σH in the minibasin province. In the Balingian province, σH is ESE-WNW, reflecting ESE absolute Sunda plate motions due to the absence of a thick detachment seen elsewhere in NW Borneo. The Central Luconia province demonstrates poorly constrained and variable σH orientations. These seven provinces result from the heterogeneous structural and stratigraphic development of the NW Borneo margin and formed due to complex collisional tectonics and the varied distribution and thicknesses of stratigraphic packages.Rosalind C. King, Mark R. P. Tingay, Richard R. Hillis, Christopher K. Morley, and James Clar

Un modèle de dislocations pour la transition aragonite ↔ calcite

A dislocation model for aragonite-calcite transition is suggested. A dislocation splitting in the calcite basal plane (0001) and aragonite basal plane (001), whose first partial is dragging a stacking fault, is responsible for the transition (or for the nucleation stage). This mechanism accounts for experimentally observed topotactic relations.On propose un modèle pour la transition aragonite-calcite fondé sur un mécanisme de dislocations. Nous envisageons une dissociation de dislocation dans les plans (0001) de la calcite et (001) de l'aragonite, la première partielle traînant une faute d'empilement responsable de la transition (ou du stade de germination). Ce mécanisme conduit à des relations topotactiques reconnues expérimentalement.Gillet Philippe, Madon Michel. Un modèle de dislocations pour la transition aragonite ↔ calcite. In: Bulletin de Minéralogie, volume 105, 6, 1982. pp. 590-597

Un modèle de dislocations pour la transition aragonite ↔ calcite

A dislocation model for aragonite-calcite transition is suggested. A dislocation splitting in the calcite basal plane (0001) and aragonite basal plane (001), whose first partial is dragging a stacking fault, is responsible for the transition (or for the nucleation stage). This mechanism accounts for experimentally observed topotactic relations.On propose un modèle pour la transition aragonite-calcite fondé sur un mécanisme de dislocations. Nous envisageons une dissociation de dislocation dans les plans (0001) de la calcite et (001) de l'aragonite, la première partielle traînant une faute d'empilement responsable de la transition (ou du stade de germination). Ce mécanisme conduit à des relations topotactiques reconnues expérimentalement.Gillet Philippe, Madon Michel. Un modèle de dislocations pour la transition aragonite ↔ calcite. In: Bulletin de Minéralogie, volume 105, 6, 1982. pp. 590-597

Étude de la localisation dans le manteau terrestre de l'uranium et du thorium (principales sources de chaleur de la Terre)

La Terre est une planète vivante dont l intense activité interne se traduit par les tremblements de Terre, les éruptions volcaniques, la dérive des continents, etc Ces manifestations sont liées énergétiquement au flux de chaleur mesuré à la surface de la Terre (44 TW). On estime que la moitié de l énergie requise par cette activité est générée par la désintégration radioactive de l uranium, du thorium et du potassium, dont 80% de cette énergie vient de U et Th. La localisation des sources de chaleur du globe dans le manteau terrestre est essentielle à la compréhension de la géodynamique et du comportement thermique de notre planète. Dans cette étude, nous montrons que l uranium et le thorium du manteau inférieur sont principalement concentrés dans la perovskite calcique alumineuse Al-CaSiO3, qui est la 3ème phase en abondance du manteau inférieur. Nous avons réalisé des expériences à HP-HT dans le système (U,Th)-Ca-Al-Si-O, en presse multi-enclumes jusqu à 26 GPa et en cellule à enclumes de diamant jusqu à 54 GPa. L analyse des échantillonssynthétisés à HP-HT par microsonde électronique et diffraction des rayons X, a permis de mettre en évidence une structure tétragonale pour la pérovskite (U,Th)-Al-CaSiO3 (groupe d espace P4/mmm). La spectroscopie d absorption des rayons X a permis de connaître l état d oxydoréduction de U et nous a donné des pistes sur la spéciation de U et Th dans cette pérovskite. Des calculs ab initio par simulation de densité fonctionnelle avec l approximation de gradient généralisé (GGA) et les ondes de projection augmentées (PWA), ont été réalisés afin de valider nos expériences et déterminer le scénario le plus favorable énergétiquement à l incorporation de U dans la Ca-pv. Les résultats obtenus dans un système simple ont été par la suite confirmés dans un système plus complexe, de composition pyrolitique, représentatif de la composition du manteau terrestre. Cette étude propose de concentrer U et Th dans une Ca-pv, qui se retrouverait au sein d une couche de matière primitive et radiogénique, récemment proposée dans des modèles géochimiques et sismologiques, à partir de 1600 km de profondeur, et jusqu à la base du manteau inférieurThe internal activity of the Earth is evidenced through earthquakes, volcanic eruptions, continental drift etc ... These events are energetically related to the heat flux at the Earth surface (44 TW). About half of the energy required for this activity is generated by the radioactive decay of uranium, thorium and potassium, with roughly 80 % accounting for uranium and thorium. The location of these heat sources in the mantle is essential for a better understanding of the geodynamics and thermal behaviour of the Earth. In this study, we show that most of the U and Th in the Earth s mantle are mainly concentrated in the Al-bearing CaSiO3 perovskite, which is the third phase in abundance within the lower mantle. We performed experiments at high pressure and high temperature in the (U,Th)-Ca-Al-Si-O system with both multi-anvil apparatus to 26 GPa and diamond anvil cell up to 54 GPa. The occurrence of a tetragonally distorted perovskite structure for the (U,Th)-bearing Al-CaSiO3 phase (space group: P4/mmm) is evidenced by analyzing HP-HT samples with electronic probe and x-ray diffraction methods. X-ray absorption spectroscopy confirmed that the incorporation of U and Th is made through the coupled substitution of CaSi by (U,Th)Al2 in the CaSiO3 perovskite. We performed ab initio calculations by density functional simulations within the generalized gradient approximation (GGA) and projector-augmented wave (PAW) method, to calculate the most favourable scenario of incorporation of U in the Ca-pv. In addition, results obtained in simple systems are confirmed by preliminary HP-HT experiments performed with U and Th in the pyrolitic system. This study propose that U and Th are concentrated in a Ca-pv that can be part of a primitive radiogenic deep layer recently proposed in geochemical and seismological models, from 1600 km depth to the lowermost part of the lower mantlePARIS-EST Marne-la-Vallee-BU (774682101) / SudocSudocFranceF

Etude de la durabilité chimique des verres alcali-résistants de type Cemfil synthétisés à partir des Refiom en vue de la valoriser comme des renforts dans les matrices cimentaires

L'optimisation de la composition des vitrifiats de REFIOM en les rendant alcali-résistants en vue de leur conférer une bonne durabilité chimique en milieu alcalin pour être ensuite utilisés dans les matrices cimentaires a été étudiée. La méthodologie suivie consiste à étudier le comportement à la lixiviation en mode statique de verres modèles alcali-résistants de type CEMFIL et de vitrifiats de REFIOM auxquels on a rajouté SiO2, Na2O et ZrO2 pour leur conférer un caractère alcali-résistant. Les tests de lixiviation menées à 90C et à différents temps (de 6 heures à 28 jours) ainsi que les autres techniques d'analyse chimique (ICP-AES, MEB-EDS, SIMS, ERDA, RBS, PIXE) sur ces verres ont montré que ce sont les vitifiats de REFIOM dont la composition a été optimisée qui présentent la meilleure durabilité chimique quelque soit le pHThe main goal of this research work is to optimize the composition of vitrified REFIOM into alkali-resistant glasses in order to enhance their durability and in alkaline media. The expected industrial application deals with the use of these glasses associated with concrete in composite materials. The experimental approach is based on static leaching tests of model alkali-resistant glasses and vitrified REFIOM in witch we have added SiO2, Na2O et ZrO2 in order they become alkali-resistant vitrified REFIOM. The leachates have been analysed by ICP-AES and the solid surfaces characterized by scanning electron microscopy, electron microprobe analysis, secondary ion mass spectrometry depth profiling, and synchrotron radiation spectroscopies. All those analysis showed that alkali-resistant REFIOM are the best durability in every mediaPARIS-EST-Université (770839901) / SudocSudocFranceF

Morphologie et cristallogenèse de microcristaux supergènes de calcite en aiguilles

The morphological study by scanning electron microscopy (S.E.M.) and crystallographical characterization by transmission electron microscopy (T.E.M.) of needle-shaped calcite microcrystals allowed to put in evidence a jagged needle habit that could correspond to a rapid and differentiated crystal growth, followed by dissolution phenomena.L'étude morphologique au microscope électronique à balayage (M.E.B.), et la caractérisation cristallographique au microscope électronique en transmission (M.E.T.) de microcristaux de calcite en aiguilles ont permis de mettre en évidence un faciès dentelé d'aiguilles qui pourrait correspondre à une croissance cristalline rapide et différenciée, suivie de phénomènes de dissolution.Verges-Belmin Véronique, Madon Michel, Bruand Ary, Bocquier Gérard. Morphologie et cristallogenèse de microcristaux supergènes de calcite en aiguilles. In: Bulletin de Minéralogie, volume 105, 4, 1982. pp. 351-356

Corbino magnetoresistance in ferromagnetic layers: Two representative examples Ni 81 Fe 19 and Co 83 Gd 17

International audienceThe magnetoresistance of Ni 81 Fe 19 and Co 83 Gd 17 ferromagnetic thin films is measured in Corbino disk geometry, and compared to the magnetoresistance of the same films measured in the Hall-bar geometry. The symmetry of the magnetoresistance profiles is drastically modified by changing the geometry of the sample, i.e., by changing the boundary conditions. These properties are explained in a simple model, showing that the Corbino magnetoresistance is defined by the potentiostatic boundary conditions while the Hall-bar magnetoresistance is defined by galvanostatic boundary conditions. The Hall effect was first measured in 1879 by Hall [1] by applying a magnetic field to a conducting slab contacted to an electric generator at the extremities. Later on, Corbino [2] found a similar effect by applying a magnetic field on a disk geometry with two concentric electrodes. Quickly the question arose on whether the effect measured by Corbino (the so-called Corbino effect) in a disk and by Hall in a bar have the same origin. In 1914, Adams and Chapman measured the Corbino effect in many different metals [3] by using an oscillating current flowing from the center of the disk to its outer. Adams concluded in 1915 that "the Corbino effect is, essentially, the same as the Hall effect" [4]. However, the question remains about the exact meaning of the adverb "essentially." In the 1950's, the Hall effect in the Corbino geometry was studied for its practical applications. The magnetoresistance of InSb slabs was shown to depend strongly on the shape of the samples [5]. The reason is that near the current injection edge, the Hall electric field is shorted and a transverse electric current appears which causes an increase of the resistance as in the Corbino geometry [6-9]. Accordingly, one can see the Corbino geometry as the extreme scenario where the Hall electric field is zero everywhere and a Hall current is flowing, or, in other terms, one can view the Corbino disk as a Hall bar in which the electrostatic charge accumulation is reduced to zero everywhere. The system cannot generate a voltage between the edges so that a Hall current is flowing and the Joule heating is higher than in the Hall bar for an equivalent volume [10-12]. The mechanism responsible for both the Hall effect and the Corbino effect is indeed the same, but the Corbino disk is a device that is more constrained than the Hall bar, due to the change of the boundary conditions. At the turn of the last century, the emergence of spintronics has shown the possibility of exploiting spin-polarized currents * [email protected] and spin-dependent potentials, and has paved the way to the realization of new electronic devices. Recently, various developments about the spin-Hall effects (anomalous Hall effect, spin-Hall effect, spin-pumping effect, spin-Seebeck effects, etc. [13,14]) tend to show that the usual Hall-bar conditions with spin relaxation could be turned into "Corbino-like boundary conditions," in the sense that the electric charge accumulation drops to zero at the edges and a pure spin current can be generated instead of a Hall voltage [11]. In this context, the goal of this Rapid Communication is to study NiFe and GdCo ferromagnetic Corbino disks and Hall bars, in order to understand the behavior of the magnetoresistance [13,15-17] when the boundary conditions are switched (by changing the geometry) from spin current to spin-dependent voltage. The alloys Ni 81 Fe 19 and Co 83 Gd 17 are chosen for their maximum contribution to the anisotropic magnetoresistance and the anomalous Hall magnetoresistance (that defines the anomalous Hall angle), respectively. First, we will present our measures of Corbino magne-toresistance performed on NiFe and CoGd rings. The results are then analyzed in the framework of the generalized Ohm's law by defining the Corbino magnetotransport coefficients C as a function of the usual Hall-bar coefficients [see Eq. (12) below]. The consistency of the proposed explanation is checked independently, by measuring the magnetotransport coefficients of the Hall bar. The samples studied are 20-nm-thick layers of Ni 81 Fe 19 and Co 83 Gd 17 sputtered on glass substrates. The magnetic layers are sandwiched between 5-nm-thick Ta buffers and 3-nm-thick Pt caps. The magnetic properties of the thin layers have been previously studied [18] (see Supplemental Material [19]). The sample magnetization is uniform for quasistatic states, although nonuniform states could take place at low magnetic fields (this regime is, however, not considered in the present study). The NiFe is textured with small uniaxial anisotropy lying in the sample plane. The coercivity field in the in-plane geometry is of the order of 1 mT. The out-2469-9950/2018/98(22)/220405(5) 220405-