Die Osthälfte des schwäbischen Lineaments

Ohne Zusammenfassung     

Zur Geschichte der Umwandlungsgesteine

Ohne Zusammenfassung     

Silver and silver-bearing minerals at the Um Samiuki volcanogenic massive sulphide deposit, Eastern Desert, Egypt

The Um Samiuki Zn–Cu–Pb–Ag mineralisation, south Eastern Desert, Egypt is hosted by felsic volcanic rocks which form part of the 712-Ma-old, east-west-trending Shadli Volcanic Belt. Two major occurrences of massive sulphides are present at the top of rhyolitic breccia in the Western and Eastern mine areas. In each occurrence, a bornite-bearing zone is overlain by a pyrite-chalcopyrite-bearing zone and underlain by a disseminated, Cu-depleted zone. In the massive sulphide ore, sphalerite, chalcopyrite, pyrite, galena, bornite and tetrahedrite–tennantite are major minerals, whereas arsenopyrite, pyrrhotite, molybdenite and magnetite are accessory phases. Covellite and digenite are common secondary minerals. Bornite, tetrahedrite–tennantite and covellite contain high amounts of silver (averages of 1.97, 1.39 and 1.82 wt% respectively). Based on mineralogical balance calculations, bornite and covellite accommodate 80% of silver in the Um Samiuki deposit. Ag was incorporated in the crystal structure of the early-crystallised copper sulphides and sulphosalts and silver minerals. The temperature, sequential precipitation of the fluids and the structure of the crystallising phases control the distribution of silver. Post-depositional deformation and metamorphic processes caused liberation, remobilisation and redeposition of silver within the massive sulphides.Editorial handling: D. Lentz     

La séparation des signaux utiles gravimétriques du fond des perturbations

Summary The paper is dealing with the separation problem of weak intensity anomalies from the perturbation background. By means of the Shannon's form and based on the values estabilished for a measured gravitational field, g, the mean quantity of information sent forth at the source — perturbating body — is calculated in order to intercept the g set. This quantity takes a maximum value above the perturbating body, while for the remainder a deadening of the perturbations is obtained.     

Identification of hydrodynamic coefficients for manoeuvring simulation model of a fishing vessel

The results of numerical and experimental investigations on the manoeuvring performance of a fishing vessel, typical for Mediterranean Sea, are here presented. PMM experiments were used for evaluating hydrodynamic derivatives and implementing the theoretical model. The simulation model was validated, both with zig-zag and spiral experimental model tests results in still water and compared with Tribon Initial Design module results.     

Recent Efforts Toward the Establishment of the Lonjsko Polje Geomagnetic Observatory

More than ten years ago, the Geophysical Institute initiated the installation of a geomagnetic observatory in Croatia. Over the past decade, extensive surveys and studies have been conducted in order to determine the proper location for the observatory. Finally, in 2012, the observatory was established in Lonjsko Polje. This paper presents the first data recorded in the period 2012.5-2015.0. Also presented are the technical aspects and data processing techniques of this remotely operated observatory. Analysis of data quality and comparison with data from the surrounding INTERMAGNET observatories is discussed in detail. Although remote observatories cannot provide the ideal environment for magnetometers, the obtained results accentuate the potential of the new observatory to provide high-quality data. The establishment of this observatory paves the way for scientific and professional development of geomagnetism in Croatia.     

Spherical Elementary Current Systems Method Applied to Geomagnetic Field Modeling for the Adriatic

The aim of this work was to derive an accurate regional model of geomagnetic components on the Adriatic. Data of north, east and vertical geomagnetic components at repeat stations and ground survey sites enclosing the Adriatic Sea were used to obtain a geomagnetic model at 2010.5 epoch. The core field was estimated by use of the global Enhanced Magnetic Model, while the crustal field by a mathematical technique for expanding vector systems on a sphere into basis functions, known as spherical elementary current systems method. The results of this method were presented and compared to the crustal field estimations by the Enhanced Magnetic Model. The maps of isolines of the regional model are also presented.     

Estimation of effect of unequal secular variation on geomagnetic data reduction

The geomagnetic field components are periodically measured at repeat stations. The main objective of the repeat stations is to provide data for tracing the secular variation of the geomagnetic field components. Secular variation at the repeat station is generally different from that at geomagnetic observatory used in the data reduction. The effect of the secular variation differences on geomagnetic data reduction was estimated for the regions of Europe, North America (below 60°N) and Australia, respectively, during the period of 2000-2010. These estimations were obtained by using the monthly mean values of north, east and vertical components of geomagnetic field, recorded at geomagnetic observatories. The effects were calculated by using observatories pairs, with distances from 350 km (in Europe) to 3100 km (in North America and Australia). The maximal effects were found to be the smallest in east component in Europe and North America, and vertical component in Australia; the effects increase with time from a central reduction epoch and they are not constant during mentioned eleven years; they were less than 1 nT only in Europe, for distances between the observatories up to 1000 km in all three components and for periods spanning ±1 month from a central epoch. It was found that their year to year variability is mostly due to the non-eliminated external field residuals in the observatories monthly means; their effect is up to 3 nT for ±3 months from a central epoch. Further, the real effects were compared to those modeled by IGRF-12 model. The maximal differences between the real and the modeled values are below 4.5 nT in all three components, for ±3 months from a central epoch.     

Application of periodic autoregressive process to the modeling of the Garonne river flows

Accurate forecasting of river flows is one of the most important applications in hydrology, especially for the management of reservoir systems. To capture the seasonal variations in river flow statistics, this paper develops a robust modeling approach to identify and to estimate periodic autoregressive (PAR) model in the presence of additive outliers. Since the least squares estimators are not robust in the presence of outliers, we suggest a robust estimation based on residual autocovariances. A genetic algorithm with Bayes information criterion is used to identify the optimal PAR model. The method is applied to average monthly and quarter-monthly flow data (1959–2010) for the Garonne river in the southwest of France. Results show that the accuracy of forecasts is improved in the robust model with respect to the unrobust model for the quarter-monthly flows. By reducing the number of parameters to be estimated, the principle of parsimony favors the choice of the robust approach.