Export, import, production and use of wire in the Czech Republic

The article deals with the statistics of drawn and rod wires in various areas. The first one is focused on the statistics of export and import of drawn and rod wires within the frame of the Czech Republic during the period of 1999 – 2012. The second area of the statistical factual research will deal with the production of drawn and rod wire. The last research area compares the ratio of use and the total production of wires in the Czech Republic. The research revealed interesting information such as the increasing trend of import of rod and drawn wire, or the ratio of production of rod and drawn wire

The effect of obliquity on temperature in subduction zones: insights from 3-D numerical modeling

The geotherm in subduction zones is thought to vary as a function of the subduction rate and the age of the subducting lithosphere. Along a single subduction zone the rate of subduction may strongly vary due to changes in the angle between the trench and the plate convergence vector, i.e., the subduction obliquity, due to trench curvature. We currently observe such curvature in, e.g., the Marianas, Chile and Aleutian trenches. Recently, strong along-strike variations in subduction obliquity were proposed to have caused a major temperature contrast between Cretaceous geological records of western and central Turkey. We test here whether first-order temperature variation in a subduction zone may be caused by variation in the trench geometry using simple thermo-kinematic finite-element 3-D numerical models. We prescribe the trench geometry by means of a simple mathematical function and compute the mantle flow in the mantle wedge by solving the equation of mass and momentum conservation. We then solve the energy conservation equation until steady state is reached. We analyze the results (i) in terms of mantle wedge flow with emphasis on the trench-parallel component and (ii) in terms of temperature along the plate interface by means of maps and the depth–temperature path at the interface. In our experiments, the effect of the trench curvature on the geotherm is substantial. A small obliquity yields a small but not negligible trench-parallel mantle flow, leading to differences of 30 °C along-strike of the model. Advected heat causes such temperature variations (linked to the magnitude of the trench-parallel component of velocity). With increasing obliquity, the trench-parallel component of the velocity consequently increases and the temperature variation reaches 200 °C along-strike. Finally, we discuss the implication of our simulations for the ubiquitous oblique systems that are observed on Earth and the limitations of our modeling approach. Lateral variations in plate sinking rate associated with curvature will further enhance this temperature contrast. We conclude that the synchronous metamorphic temperature contrast between central and western Turkey may well have resulted from reconstructed major variations in subduction obliquity

Accretion, underplating and exhumation along a subduction interface: From subduction initiation to continental subduction (Tavsanli zone, W. Turkey)

© 2015 Elsevier B.V.. We herein reappraise the pressure-temperature (PT) evolution of the high-pressure and low-temperature (HP-LT) Tavsanli zone (western Turkey) in order to (i) better characterize rock units exhumed along a cooling subduction interface, from birth to steady state and (ii) constrain exhumation and detachment dynamics, as well as mechanical coupling between plates. Based on PT estimates and field observations three oceanic complexes are recognized between the HP-LT continental margin and the obducted ophiolite, with PT estimates ranging from incipient metamorphism to blueschist-facies conditions. PT conditions for the continental unit are reappraised to 24 kbar and ~ 500 °C on the basis of pseudosection modelling and Raman spectroscopy on carbonaceous material. A tentative reconstruction of the subduction zone evolution is proposed using available radiometric and palaeogeographic data and recent thermomechanical modelling. Both PT conditions and field observations point out to the slicing of km-sized units at different preferred depths along the subduction interface, thus providing constraints on the dynamics of accretion and underplating. In particular, the comparison of PT estimates for the Tavsanli zone and for other broadly similar fossil subduction settings (i.e., Oman, Corsica, New Caledonia, Franciscan, Schistes Lustrés) suggests that units are detached preferentially from the slab at specific depths of 30-40 km (i.e., downdip of the seismogenic zone) and ~ 80 km. We propose that these depths are controlled by major changes in mechanical coupling along the plate interface, whereas exhumation through time would rather be controlled by large-scale geodynamic boundary conditions

The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

Highlights • Subduction plate interface constitution, thickness, geometry and viscosity • Rocks recovered are reliable probes of subduction processes and thermal regimes • Long-term mechanical coupling controls rock recovery from subduction zones • Subduction cooling induces a long-term trend in rock detachment from the slab • Rock recovery is a proxy for long- and short-term subduction dynamics and coupling Abstract Short- and long-term processes at or close to the subduction plate interface (e.g.,mineral transformations, fluid release, seismicity and more generally deformation) might be more closely related than previously thought. Increasing evidence from the fossil rock record suggests that some episodes of their long geological evolution match or are close to timescales of the seismic cycle. This contribution uses rocks recovered (episodically) from subduction zones, together with insights from thermomechanical modelling, to provide a new dynamic vision of the nature, structure and properties of the plate interface and to bridge the gap between the mechanical behavior of active subduction zones (e.g.,coupling inferred from geophysical monitoring) and fossil ones (e.g.,coupling required to detach and recover subducted slab fragments). Based on critical observations and an exhaustive compilation of worldwide subducted oceanic units (for which the presence near the plate interface, rock types, pressure, temperature, T/P gradients, thickness and timing of detachment can be assessed), the present study demonstrates how long-term mechanical coupling exerts a key control on detachment from the slab and potential rock recovery. Critical assessment of rock T/P characteristics indicates that these fragments can indeed be used as natural probes and provide reliable information on subduction interface dynamics down to ~2.8 GPa. Rock clusters are identified at depths of 30, 55–60 and 80 km, with some differences between rock types. Data also reveal a first-order evolution with subduction cooling (in the first ~5 Myr), which is interpreted as reflecting a systematic trend from strong to weak mechanical coupling, after which subduction is lubricated and mostly inhibits rock recovery. This contribution places bounds on the plate interface constitution, regular thickness (<300 m; i.e. where/when there is no detachment), changing geometry and effective viscosity. The concept of ‘coupled thickness' is used here to capture subduction interface dynamics, notably during episodes of strong mechanical coupling, and to link long- and short-term deformation. Mechanical coupling depends on mantle wedge rheology, viscosity contrasts and initial structures (e.g.,heterogeneous lithosphere, existence of décollement horizons, extent of hydration, asperities) but also on boundary conditions (convergence rates, kinematics), and therefore differs for warm and cold subduction settings. Although most present-day subduction zone segments (both along strike and downdip) are likely below the detachment threshold, we propose that the most favorable location for detachment corresponds to the spatial transition between coupled and decoupled areas. Effective strain localization involves dissolution-precipitation and dislocation creep but also possibly brittle fractures and earthquakes, even at intermediate depths

Assessing Chemical and Mineralogical Properties of the Alpine Slab Based on Field Analogs and Ambient Noise Tomography

International audienceRecent geophysical campaigns in the Alps produce images with seismic property variations along the slab of sufficiently fine resolution to be interpreted as rock transformations. Since the reacting European lower crust is presumed responsible for the variations of velocities at the top of the Alpine slab, we sampled local analogs of the lower crustal lithologies in the field and modeled the evolution of equilibrium seismic properties during burial, along possible pressure‐temperature paths for the crustal portion of the slab. The results are then compared to the range of the S ‐wave velocities obtained from the S ‐wave velocity tomography model along the CIFALPS transect. The velocity increase from 25 to 45 km within the slab, in the tomographic model is best reproduced by the transformation of specific lithologies in the high‐pressure granulite facies along a collisional gradient (30°C/km). Although the crust is certainly not completely homogeneous, the best candidates for the rocks that make up the top of the Alpine dip crustal panel are a kinzigite from Monte San Petrone, a gneiss from the Insubric line, and blueschist mylonite from Canavese. While they may not represent the entirety of the crust, they are sufficient to explain the tomographic velocity of the Alpine slab. A lateral lithological contrast inherited from the Variscan orogeny is not required. Eclogitization, suggested as the first‐order transformation in convergence zones, could be a second‐order transformation in collisional wedges. These results also imply a partially re‐equilibrated thermal gradient, consistent with the Alpine thermal state data at depth

How continuous and precise is the record of P-T paths? Insights from combined thermobarometry and thermodynamic modelling into subduction dynamics (Schistes Lustrés, W. Alps).

Pressure–temperature (P–T) paths as complete as possible and with a precision on the km-scale or less are needed to further improve the knowledge of deformation, re-equilibration processes and element/fluid transfer, in particular along subduction zones. This contribution attempts to (i) critically evaluate the precision and continuity with which metamorphic P–T histories are retrieved today and (ii) discuss implications for regional-scale accretionary processes in subduction zones, through application to the Schistes Lustrés complex (Haute Maurienne, W. Alps). P–T estimates are compared and combined using several independent approaches: (i) from minerals assumed to be in textural equilibrium; (ii) from electron microprobe compositional maps; and (iii) from pseudosection modelling predictions. Multi-equilibrium calculations were performed with tweequ and thermocalc, and pseudosections were built with Perple_X and Theriak/Domino. These P–T estimates were also compared with maximum temperatures (Tmax) deduced from the Raman spectroscopy of carbonaceous matter. The different methods used here yield the peak of pressure for the lower structural unit of the Schistes Lustrés at 480 °C and 23 kbar and document the retrograde path for both the Median and Lower Units. The results show that P–T conditions are recorded almost continuously and can be determined with a precision of ±1 kbar and ±30 °C at best. This study underlines the complementarity of the various thermobarometric methods and demonstrates that precision could be increased by improving solid solution models for chlorite. Observed tectonic patterns, major lithological boundaries, pressure–temperature and Tmax data suggest that underplating processes and early structural development played a key role in the Schistes Lustrés accretionary complex