GLAVNI TIPOVI STIJENA ZA ODLAGALIŠTE RADIOAKTIVNOG OTPADA

Underground geological storage of high- and intermediate/low radioactive waste is aimed to represent a barrier between the surface environment and potentially hazardous radioactive elements. Permeability, behavior against external stresses, chemical reacatibility and absorption are the key geological parameters for the geological storage of radioactive waste. Three principal rock types were discussed and applied to the Dinarides: (1) evaporites in general, (2) shale, and (3) crystalline basement rocks. (1) Within the Dinarides, evaporite formations are located within the central part of a Carbonate platform and are inappropriate for storage. Offshore evaporites are located within diapiric structures of the central and southern part of the Adriatic Sea and are covered by thick Mesozoic to Cenozoic clastic sediment. Under very specific circumstances they can be considered as potential site locations for further investigation for the storage of low/intermediate level radioactive wast e. (2) Thick flysch type formation of shale to phyllite rocks are exposed at the basement units of the Petrova and Trgovska gora regions whereas (3) crystalline magmatic to metamorphic basement is exposed at the Moslavačka Gora and Slavonian Mts. regions. For high-level radioactive waste, basement phyllites and granites may represent the only realistic potential option in the NW Dinarides.Podzemno odlaganje visoko i srednje do nisko radioaktivnog otpada predstavlja barijeru između površinskog okoliša i potencijalno opasnih radioaktivnih elemenata. Neki od ključnih geoloških parametara za odlaganje radioaktivnog otpada su permeabilnost, ponašanje prilikom opterećenja, intenzitet kemijskih reakcija i apsorpcija. U članku diskutiramo tri pogodna tipa stijena za odlagališta: (1) evaporiti, (2) šejl, i (3) stijene kristalinske podloge, čije predstavnike pronalazimo i u Dinaridima. (1) Evaporitne formacije smještene su na kopnu duž centralnog dijela Karbonatne platforme i u podmorju unutar dijapirskih struktura centralnog i južnog dijela Jadranskog mora. Evaporiti na kopnu sastoje se od gipsa i anhidrita i nepogodni su za odlagališta. Evaporiti u podmorju sastoje se od anhidrita i soli i mogli bi biti pogodni su za odlaganje nisko do srednje radioaktivnog otpada. (2) Debele formacije šejla i filita nalaze su u području Petrove i Trgovske gore, dok su (3) magmatsko-metamorfne stijene kristalinske podloge izložene u području Moslavačke gore i Slavonskih planina. Za odlagališta visoko radioaktivnog otpada, kristalinska podloga i filiti predstavljaju jedine moguće lokacije unutar Dinarida

Post-collisional rapid exhumation and erosion during continental sedimentation: the example of the late Variscan Salvan-Dorénaz basin (Western Alps)

The Salvan-Dorénaz intramontane basin formed between ca. 308-293Ma as an asymmetric graben along crustal-scale transtensional fracture zones within the Aiguilles-Rouges crystalline massif (Western Alps) and represents a feature of the post-collisional evolution of the Variscan orogens. It contains 1.5-1.7km of continental clastic deposits which were eroded from granitic, volcanic, and metamorphic rocks. Textural and compositional immaturity of the sandstones, and the numerous lithic fragments with low chemical and physical stability suggest only short-range transport. 40Ar/39Ar analyses of detrital muscovite are interpreted to represent cooling of the crystalline basement below the respective closure temperatures. Ages from detrital muscovite range between ca. 280-330Ma. 40Ar/39Ar white mica plateau ages from granitic boulders range between 301-312Ma and suggest rapid cooling. The very short time interval recorded between the 40Ar/39Ar cooling ages and the stratigraphic age of the host sediment suggests that considerable portions of the upper crust were removed prior to the formation of the basin. Late Variscan granitic boulders document surface exposure and erosion of Late Carboniferous granites during early stages of the infilling of the basin. Therefore, unroofing of basement units, magmatic activity, and formation of the fault bounded Salvan-Dorénaz basin were acting concomitantly, and are highly suggestive of extensional tectonics. When compared with other orogens, this situation seems specific to the Variscan, especially the exclusively young ages of detrital material, however, modern analogous may exis

Low-grade retrogression of a high-temperature metamorphic core complex: Naxos, Cyclades, Greece

Retrogressive deformation and metamorphism are often reported from the main low-angle shear zones and detachments of metamorphic core complexes, but their importance is not sufficiently emphasized for the footwall interior. In order to contribute to a better understanding of exhumation-related retrogression processes within and at the top of metamorphic core complexes, an integrated detailed microstructural, textural, 40Ar/39Ar geochronological, and thermobarometric study on the Naxos metamorphic core complex within the Aegean Sea is presented that provides a new perspective on low-grade retrogression during exhumation through shallow ductile levels. We found variable retrogressive deformation within the Naxos metamorphic core complex, which even pervasively affected significant portions of the migmatite-grade metamorphic core and remnant high-pressure areas of the metamorphic core complex, where retrogression led to pervasive formation of new fabrics within greenschist-facies metamorphic conditions during brittle-ductile transition. Within a continuum of retrogression, 40Ar/39Ar white mica dating allowed us to deduce three retrogressive ages at 16.52 ± 0.39 Ma (within the Naxos metamorphic core complex), 12.6 ± 0.28 Ma (Moutsounas detachment shear zone on the eastern boundary of the metamorphic core complex), and 10.43 ± 0.44 Ma to 8.40 ± 0.76 Ma (last ductile activity along the Naxos-Paros shear zone to the north of the metamorphic core complex). A further stage of retrogression at 12−11 Ma occurred along distinct low-angle normal faults within the middle Miocene Naxos Granite. Retrogressive microstructures, low-temperature calcite fabrics in marbles, and chloritization in metapelites (at temperatures of ∼350−130 °C) in the metamorphic core complex core resulted mainly from late-stage E-W shortening and folding. Late-stage flow of hydrous fluids resulted in resetting of fabrics and enhancement of ductile deformation. The middle−late Miocene retrogression events are also reflected by a similarly aged tectonic collapse basin in the hanging-wall unit above the detachment. The wide temporal range of retrogression within the Naxos metamorphic core complex coincides in age with retrogressive deformation within other metamorphic core complexes of the Aegean Sea. We interpret the long temporal range of retrogression to reflect outward, southwestward retreat of the subduction and sequential activation of major detachment zones

U-Pb dating, Hf-isotope characteristics and trace-REE-patterns of zircons from Medet porphyry copper deposit, Bulgaria: implications for timing, duration and sources of ore-bearing magmatism

Precise U-Pb geochronology, Hf isotope compositions and trace element distributions in zircons are combined in the present study to define the timing and sources of the magmatism forming the Medet porphyry copper deposit, Bulgaria. ID-TIMS U-Pb-zircon dating demonstrates that ore-bearing magmatism extended for less than 1.12Ma. As inferred from the field relationships, it started with the intrusion of a quartz-monzodiorite at 90.59 ± 0.29Ma followed by granodiorite porphyries at 90.47 ± 0.30 and 90.27 ± 0.60Ma and by crosscutting aplite dykes at 90.12 ± 0.36Ma. These units were overprinted by potassic alteration and host economic copper-(Mo-Au) mineralization. The main magmatic-hydrothermal activity ceased after that, and a later quartz-granodiorite porphyry dyke, dated at 89.26 ± 0.32Ma, only contains an uneconomic quartz-pyrite mineralization. Assimilation of Lower Paleozoic rocks with a mantle to mantle-crust signature is characteristic of the fertile magma in the Medet deposit, as defined by positive ɛ-Hf values of the inherited zircons. The positive Ce-anomalies and the higher Eu/Eu* ratios of the zircons in the mineralized Cretaceous rocks of Medet deposit argue for crystallization from a generally more oxidized magma compared to the later quartz-granodiorite porphyry dyke. A change in paleostress conditions occurred during the intrusion of the Medet pluton and its dykes. The initial stage reveals E-W extension associated with N-S compression, whereas the younger granodiorite dyke was emplaced during subsequent N-S extension. The large-scale switch of the extensional stress regime during the mineralization was favourable for ore deposition by channelling the fluids and increasing the effective permeabilit

C-S-H Pore Size Characterization Via a Combined Nuclear Magnetic Resonance (NMR)-Scanning Electron Microscopy (SEM) Surface Relaxivity Calibration.

A new method for the nuclear magnetic resonance (NMR) surface relaxivity calibration in hydrated cement samples is proposed. This method relies on a combined analysis of 28-d hydrated tricalcium silicate samples by scanning electron microscopy (SEM) image analysis and 1H-time-domain (TD)-NMR relaxometry. Pore surface and volume data for interhydrate pores are obtained from high resolution SEM images on surfaces obtained by argon broad ion beam sectioning. These data are combined with T2 relaxation times from 1H-TD-NMR to calculate the systems surface relaxivity according to the fast exchange model of relaxation. This new method is compared to an alternative method that employs sequential drying to calibrate the systems surface relaxivity

Heavy metals in Neogene sedimentary rocks as a potential geogenic hazard for sediment, soil, and surface and groundwater contamination (eastern Posavina and the Lopare Basin, Bosnia and Herzegovina)

The influence of geochemical processes (weathering, erosion and dilution) of the Internal Dinarides to the Posavina Neogene Basin and their implication to the pollution of the Sava River sediments at four sampling sites in the Eastern Posavina (Zupanja, Brcko, Bosanska Raca and Sremska Mitrovica) was studied.(similar to)For this purpose, comparison of contents of heavy metals (Pb, Zn, Cu, Ni, Cr, Cd, As and Hg) of the Eastern Posavina sediments with local background values was performed. Sediments from two boreholes of the Lopare Basin considered as non-polluted and representative for specific geologic and hydrogeologic system were used for the calculation of local background values. The aim was to assess whether the observed heavy metals concentrations at four sampling sites along the Sava River represent background/natural or anthropogenic contamination. This task was performed using the geo-accumulation index and total enrichment factor. According to values of the total enrichment factor (0.25-0.71), the anthropogenic impact on the investigated area was quite low. The heavy metals contents in river sediments, soil and groundwater were mainly controlled by geochemical processes, particularly weathering (chemical proxy of alteration value approximate to 60). The results also offer novel insights into the elevated geogenic levels of Cr and Ni in the Eastern Posavina region

Skyrmion Lattice in a Doped Semiconductor

We report a comprehensive small angle neutron scattering study (SANS) of the magnetic phase diagram of the doped semiconductor Fe_{1-x}Co_{x}Si for x=0.2 and 0.25. For magnetic field parallel to the neutron beam we observe a six-fold intensity pattern under field-cooling, which identifies the A-phase of Fe_{1-x}Co_{x}Si as a skyrmion lattice. The regime of the skyrmion lattice is highly hysteretic and extents over a wide temperature range, consistent with the site disorder of the Fe and Co atoms. Our study identifies Fe_{1-x}Co_{x}Si is a second material after MnSi in which a skyrmion lattice forms and establishes that skyrmion lattices may also occur in strongly doped semiconductors