Key pluvial parameters in assessing rainfall erosivity in the south-west development region,Romania

Located in the south-western part of Romania, the south-west development region overlaps the main relief forms: the Carpathians mountains, the Getic Subcarpathians, the Getic piedmont, the Romanian plain and the Danube valley. The study aims at providing an overview on the main pluvial parameters and their role in assessing rainfall erosivity in the study area. The authors assessed the occurrence, frequency and magnitude of some of the most significant pluvial parameters and their impact on the climatic aggressiveness in the study area. Thus, the monthly and annual mean and extreme climatic values for different rainfall related parameters (e.g., maximum amounts of precipitation/24 hr, heavy rainfall), as well as relevant indices and indicators for pluvial aggressiveness (Fournier, Fournier Modified, Angot) were calculated. The rainfall erosivity was assessed in order to provide both the spatial distribution of the triggering extreme weather phenomena and the resulted intensity classes for the analysed indices and indicators. The authors used long-term precipitation records (1961–2010) for the selected relevant meteorological stations distributed throughout all analysed relief units.     

LABORATORIES DE MÉCANIQUE DES FLUIDES DOMAINE UNIVERSITAIRE—38—SAINT-MARTIN d'HERES

Abstract

Artificial recharge is a very suitable approach in the overall water resources management of a given area. What are the matter, the purposes and the past of recharge, the factors and the problems to be taken into account, the methods and the economics of this practice? Those are some questions to which the paper tries to give answers. Several examples are quoted as well as two projects in the Middle-East and North Africa.     

Evidence of NW extension of the North Anatolian Fault Zone in the Marmara Sea: a new interpretation of the Marmara Sea (Izmit) earthquake on 17 August 1999

Active faults aligning in NW–SE direction and forming flower structures of strike-slip faults were observed in shallow seismic data from the shelf offshore of Avcılar in the northern Marmara Sea. By following the parallel drainage pattern and scarps, these faults were traced as NW–SE-directed lineaments in the morphology of the northern onshore sector of the Marmara Sea (eastern Thrace Peninsula). Right-lateral displacements in two watersheds of drainage and on the coast of the Marmara Sea and Black Sea are associated with these lineaments. This right-lateral displacement along the course of these faults suggests a new, active strike-slip fault zone located at the NW extension of the northern boundary fault of the ?ınarcık Basin in the Marmara Sea. This new fault zone is interpreted as the NW extension of the northern branch of the North Anatolian Fault Zone (NAFZ), extending from the ?ınarcık Basin of the Marmara Sea to the Black Sea coast of the Thrace Peninsula, and passing through B üy ük ?ekmece and K ü ? ük ?ekmece lagoons. These data suggest that the rupture of the 17 August 1999 earthquake in the NAFZ may have extended through Avcılar. Indeed, Avcılar and İzmit, both located on the Marmara Sea coast along the rupture route, were strongly struck by the earthquake whereas the settlements between Avcılar and İzmit were much less affected. Therefore, this interpretation can explain the extraordinary damage in Avcılar, based on the newly discovered rupture of the NAFZ in the Marmara Sea. However, this suggestion needs to be confirmed by further seismological studies.     

New parameter for the assessment of blasting efficiency

The efficiency of a blast depends very widely on three groups of parameters: rock mass, blast geometrical parameters and energy distribution in space (borehole bottom, column energy) and time (delays between holes and rows). According to the expected results from a blast, there are several definitions for the term efficiency. The criterion for the block size reduction in the muck pile is often considered as important, because generally it has a great influence on the efficiency of all the operations after the blast. In this paper, a new parameter for the assessment of the blast efficiency is proposed, based on the relative comparison of area delimited by the Rosin-Rammler curves of the in situ rock mass and of the muck pile. This parameter is then compared to others previously established, namely the fragmentation index (Aler et al. 1996) and the surface energy ratio (Hamdi et al. 2001).     

Potential low-grade iron ore deposits in metamorphosed banded iron formations, Northern Province, South Africa

Exploitation of low-grade iron ore would be quite unique in a South African context as South Africa is well endowed with high-grade iron ore resources. Low-grade iron ore, defined as containing between 20 and 47% iron, is thought to be the primary iron-bearing lithology from which most high-grade ore deposits formed, through different processes of enrichment. The low-grade iron ores in the Northern Province represent meta-banded iron formations (BIFs), with an average iron content of about 36%. The main iron-bearing mineral is magnetite. The Northern Province ores have to be milled to sizes smaller than 150 μm in order to liberate the iron minerals from the host rock, and beneficiation is accomplished through a series of magnetic separation processes. Irrespective of the in situ quality of the ore, final concentrates of exceptionally good quality with more than 69% iron and very low contaminant levels can be produced. This, combined with mass yields of between 40 and 50% and iron recoveries greater than 80%, are excellent for this type of iron ore deposit. The beneficiation products are suitable for use in iron- and steel-making processes. Received: 4 July 1996 / Accepted: 7 January 1997     

Evidence of NW extension of the North Anatolian Fault Zone in the Marmara Sea: a new interpretation of the Marmara Sea (İzmit) earthquake on 17 August 1999

Active faults aligning in NW–SE direction and forming flower structures of strike-slip faults were observed in shallow seismic data from the shelf offshore of Avc?lar in the northern Marmara Sea. By following the parallel drainage pattern and scarps, these faults were traced as NW–SE-directed lineaments in the morphology of the northern onshore sector of the Marmara Sea (eastern Thrace Peninsula). Right-lateral displacements in two watersheds of drainage and on the coast of the Marmara Sea and Black Sea are associated with these lineaments. This right-lateral displacement along the course of these faults suggests a new, active strike-slip fault zone located at the NW extension of the northern boundary fault of the Ç?narc?k Basin in the Marmara Sea. This new fault zone is interpreted as the NW extension of the northern branch of the North Anatolian Fault Zone (NAFZ), extending from the Ç?narc?k Basin of the Marmara Sea to the Black Sea coast of the Thrace Peninsula, and passing through B üy ük çekmece and K ü ç ük çekmece lagoons. These data suggest that the rupture of the 17 August 1999 earthquake in the NAFZ may have extended through Avc?lar. Indeed, Avc?lar and ?zmit, both located on the Marmara Sea coast along the rupture route, were strongly struck by the earthquake whereas the settlements between Avc?lar and ?zmit were much less affected. Therefore, this interpretation can explain the extraordinary damage in Avc?lar, based on the newly discovered rupture of the NAFZ in the Marmara Sea. However, this suggestion needs to be confirmed by further seismological studies.     

Petrography of low rank coals with reference to liquefaction potential

Ten sub-bituminous coals were analyzed petrographically and chemically as part of a program by the Alberta Research Council to investigate the compositional properties of Alberta coals and relationship to liquefaction potential. In addition, four lignites, two from Saskatchewan and one each from Texas and North Dakota, were studied for comparative purposes. Liquefaction experiments were carried out on three of the Alberta coals and on density fractions of the two U.S. lignites. Petrographically the ten sub-bituminous coals could be divided into two populations; one with high huminite and liptinite contents (>90%) and one with substantially lower contents (70–75%). The two U.S. lignites showed huminite plus liptinite contents of less than 70% while the Saskatchewan coals were somewhat higher. Reflectance measurements on the sub-bituminous coals showed a range of 0.33 to 0.51 with a rough correlation to the ASTM rank designations of these coals. Reflectivities determined on the lignites were generally lower. Float-sink fractionation of the two U.S. lignites and two sub-bituminous coals showed enrichment of huminite and liptinite in the lighter fractions and inertinite and mineral matter in the heavier splits. Examination of the relationship between liquefaction yields and petrographic composition showed a rough positive correlation with huminite-liptinite content. Examination of liquefaction residues suggested total conversion of the liptinite, extensive conversion of huminite and possible partial conversion and reactivity of the semifusinite maceral of the inertinite group.     

Determination par activation neutronique des rapports Cl/Br des inclusions fluides de divers gypses. Correlation avec les donnees de la microcryoscopie et interpretations genetiques

Gypsum contains liquid inclusions which fill mainly primary cavities. Analysis of inclusions may give some information about the mineral formation process. In places, diagenetic solutions have filled secondary cavities along cleavage planes or replaced initial liquid inclusions in primary cavities; the presence of such secondary inclusions must, therefore, be taken into consideration. This study presents our results on the Cl/Br ratio of liquid inclusions in gypsum. The Cl/Br ratio is practically constant in present sea water, and has been measured in many different types of waters. The Br content of halite has also been extensively studied to trace the compositional changes of a salt-depositing brine. In gypsum Br is present only in microscopic fluid inclusions. For this reason we used the neutron-activation method. We adopted the technique in order to prevent any contamination and obtain directly Cl/Br ratio within 10% accuracy. In order to ascertain that liquid inclusions reside mainly in primary cavities of gypsum, we selected our samples only after microscopic observation. Fifty-eight samples from different types of gypsum were analysed. The salinities of the inclusions, obtained through the data on freezing, and the Cl/Br ratio, obtained through activation-analysis, give us clues as to the nature of the fluids depositing the gypsum. Recent gypsum deposits from French salt-pans of Mediterranean and Atlantic coasts were sampled. The latter has apparently been diagenetically altered by meteoric water; the salinity of many inclusions having been changed while the Cl/Br ratio (315 and 350) in both remains close to the value of present sea water (#300). Liquid inclusions of Recent crystals from New Caledonia, deposited in mangrove swamps are enriched in Br (Cl/Br = 150 and 200). The enrichment might be related to the presence of abundant organic materials. Inclusions in crystals from Sebkha el Melah (Tunisia) also show high Br content (Cl/Br = 194). In this case, the brine was highly concentrated and was saturated with NaCl. The Upper Miocene gypsum from Sicily was studied to test the various models for the genesis of this important evaporite formation of the Mediterranean. Freezing data show some decrease of salinities, probably by groundwater diagenesis, but the Br content is high. The Cl/Br ratio is 175, and this value is similar to that of Sebkha el Melah. Samples from three thick Eocene and Oligocene sequences near Paris and in the South of France were studied. Freezing data and Cl/Br ratio of their inclusions indicate that those gypsum deposits have crystallized in marine environments receiving considerable influx of river-waters.     

Application of portable X-ray fluorescence analyses to metabasalt stratigraphy,Plutonic Gold Mine,Western Australia

Stratigraphy, structure and host-rock chemistry are dominant controls on the location of Au in Archaean greenstone-hosted Au deposits, but the stratigraphy in such deposits is seldom obvious due to the monotonous nature of the host rocks or pervasive alteration associated with Au mineralisation. Portable, hand-held, X-ray fluorescence (pXRF) spectrometry provides a method to rapidly collect large amounts of whole-rock geochemical data that can yield new insights into both stratigraphy and Au localisation. Here we present results of pXRF analyses of samples from a representative section through Au-mineralised amphibolite-facies metabasaltic rocks at Plutonic Gold Mine, Western Australia. These data illustrate a geochemical stratigraphy in which individual lava flows can be identified on the basis of element concentrations. The most evolved basalts are at the structural base of the succession, and the least evolved at the top of the sequence, confirming previous geochemical interpretations and textural evidence that the sequence is overturned, and demonstrating for the first time that the presented section does not involve significant structural repetition. In conjunction with Au assay data, the pXRF data reveal that Au commonly occurs along basalt flow boundaries. The elemental concentration data clearly demonstrates for the first time the stratigraphic control on Au mineralisation that is not readily apparent at the macroscopic level. The methods described in this paper are readily applied, and have the potential to enhance the understanding of otherwise unclear stratigraphy and its control on mineralisation in many different types of deposits worldwide.