Geochemistry and thermodynamic modelling of low-grade metasedimentary rocks from the Sakar-Strandja region, SE Bulgaria

Carbonate-silicate metasedimentary rocks of Triassic protolith age from the Sakar-Strandja region were affected by low-grade metamorphism in the frame of the Maritsa shear zone, which separates two first-order units of the Balkan orogenic system - Rhodopes and Srednogorie zones. The metamorphism was contemporaneous with strike-slip deformation and ductile shearing. We focus attention on whole-rock and mineral chemistry for better understanding of protoliths origin and metamorphic evolution. The major minerals assemblage comprises calcite, dolomite quartz and white mica in variable proportions, minor chlorite, feldspars and rarely biotite. The accessory phases are ilmenite, rutile, monazite and zircon. Most of the samples show well-defined foliation. The siliciclastic component corresponds to shale, wacke or arkose origin and suggests a quartzose sedimentary provenance. The majority of trace elements tend to incorporate in silicate minerals, while Sr shows pronounced preference for calcite. Chondrite normalized REE patterns correspond to continental crust. Immobile elements (La, Th, Sc, Zr, Ti) used for discrimination of tectonic regimes suggest continental island arc setting for the siliciclastic component origin. The P-T pseudosections (Perple_X 6.7.4, Connolly, 1990) combined with observed mineral assemblages and mineral chemistry isopleths of white mica, chlorite and plagioclase correspond to metamorphism in the range 200-400°C and 0.2-0.4 GPa. The results are supported by chlorite solid solution geothermometer. The thermodynamic modelling corroborates petrographic observations and confirms metamorphism at greenschist facies. Geochemical data suggest protoliths origin due to shallow marine terrigenous-carbonate sedimentation with a provenance of typical upper continental crustal composition at continental island arc tectonic setting

Modeling extreme wave heights from laboratory experiments with the nonlinear Schrödinger equation

Spatial variation of nonlinear wave groups with different initial envelope shapes is theoretically studied first, confirming that the simplest nonlinear theoretical model is capable of describing the evolution of propagating wave packets in deep water. Moreover, three groups of laboratory experiments run in the wave basin of CEHIPAR (Canal de Experiencias Hidrodinámicas de El Pardo, known also as El Pardo Model Basin) was founded in 1928 by the Spanish Navy. are systematically compared with the numerical simulations of the nonlinear Schrödinger equation. Although a little overestimation is detected, especially in the set of experiments characterized by higher initial wave steepness, the numerical simulation still displays a high degree of agreement with the laboratory experiments. Therefore, the nonlinear Schrödinger equation catches the essential characteristics of the extreme waves and provides an important physical insight into their generation. The modulation instability, resulting from the quasi-resonant four-wave interaction in a unidirectional sea state, can be indicated by the coefficient of kurtosis, which shows an appreciable correlation with the extreme wave height and hence is used in the modified Edgeworth–Rayleigh distribution. Finally, some statistical properties on the maximum wave heights in different sea states have been related with the initial Benjamin–Feir index

Rogue waters

In this essay we give an overview on the problem of rogue or freak wave formation in the ocean. The matter of the phenomenon is a sporadic occurrence of unexpectedly high waves on the sea surface. These waves cause serious danger for sailing and sea use. A number of huge wave accidents resulted in damages, ship losses and people injuries and deaths are known. Now marine researchers do believe that these waves belong to a specific kind of sea waves, not taken into account by conventional models for sea wind waves. This paper addresses to the nature of the rogue wave problem from the general viewpoint based on the wave process ideas. We start introducing some primitive elements of sea wave physics with the purpose to pave the way for the further discussion. We discuss linear physical mechanisms which are responsible for high wave formation, at first. Then, we proceed with description of different sea conditions, starting from the open deep sea, and approaching the sea cost. Nonlinear effects which are able to cause rogue waves are emphasised. In conclusion we briefly discuss the generality of the physical mechanisms suggested for the rogue wave explanation; they are valid for rogue wave phenomena in other media such as solid matters, superconductors, plasmas and nonlinear opticsComment: will be published in Contemporary Physic

Markers for Inflammation and Oxidative Stress in Patients with Coronary Artery Disease and Microvascular Disease – Is there a Difference?

Introduction: The clinical significance of inflammation (and markers such as resistin, hsCRP) and oxidative stress (e.g. 8-isoprostanes) for microvascular disease (MVD) and coronary artery disease (CAD) is still elusive

Time–frequency analysis of the sea state with the Andrea freak wave

The nonlinear and nonstationary properties of a special field wave record are analysed with the Wigner spectrum with the Choi–Williams kernel. The wave time series, which was recorded at the Ekofisk complex in the central North Sea at 00:40 UTC (universal time coordinated) on 9 November 2007, contains an abnormally high wave known as the "Andrea" wave. The ability of the Wigner spectrum to reveal the wave energy distribution in frequency and time is demonstrated. The results are compared with previous investigations for different sea states and also the state with Draupner's abnormal "New Year" wave

Two partial melting events as recorded by the U-Th-Pb chronometer in monazite: LA-ICPMS in situ dating in metapelites from the Bulgarian Central Rhodopes

International audienc

Late Eocene synmetamorphic thrusting and syn-orogenic extension across the metamorphic pile of the Bulgarian Central Rhodope

International audienc

Persistent synmetamorphic thrusting in the Rhodope until ca. 33 Ma: evidence from the Nestos Shear Zone and implications for Aegean geodynamics

International audienc