NE Part Research Articles

Structure of the Sea of Galilee and Kinarot Valley derived from combined geological geophysical analysis

The Sea of Galilee (Lake Kinneret) is located in northern Israel in an area of complex tectonic setting where the Dead Sea Fault (DSF) (Figure 1) crosscuts other fault systems. This transform is more than 1000 km long, and is a plate boundary separating the Sinai and Arabian plates (Garfunkel et al., 1981). This lake is located with a larger Kinneret - Bet Shean basin which is a part of a series of rhomb-shaped grabens (pull apart basins) along the DSF (Freund et al., 1970). The lake is the main source of fresh water in Israel with an average surface of 166 km2 and an average volume of 4·109m3. Maximal depths of the lake (about 50 m) are located in the NE part of the basin (Figure 1C). The present configuration of Lake Kinneret was formed about 24,000 years ago (Hazan et al.,, 2005). Geological studies indicate that rock outcrops in this area and rock samples discovered in wells surrounding the lake range from Jurassic to Quaternary.

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

The migmatitic metapelites of the Lapland granulite belt (LGB) in the NE part of the Fennoscandian Shield represent an arc-related greywacke basin metamorphosed in the granulite facies. Detrital zircons from migmatitic metapelites are derived from 1.94 etrital zircons from migmatitic metapelites are derived from 1.94 zircons from migmatitic metapelites are derived from 1.94 derived from 1.94 − 2.9 Ga old acid source rocks (U-Pb SIMS ages). The clustering of detrital zircon ages between 1.97 and 2.2 Ga is problematic, because abundant felsic crust of this age is absent in the shield. The metasediments are characterized by Sm-Nd model ages of ca. 2.3 Ga. A younger, 1905 − 1880 Ma population of homogeneous zircons was formed during regional metamorphism. The peak high-grade metamorphism took place at ~1900 Ma and the latest chronological record from subsequent decompression and cooling phase is from ca. 1870 Ma. The norite-enderbite series of the LGB represents arc-magmas, which were intruded into the metasediments at ~1920 − 1905 Ma ago according to zircon U-Pb ages and were probably an important heat source for metamorphism. Older, zoned zircon grains in a quartz norite vein, initial e Nd values of 0 to +1 and the continuous spectrum of LILE enrichment in the enderbite-series probably reflect assimilation of metasediments by magmas. Monazite U-Pb ages of migmatitic metasediments in the range 1906 − 1910 ± 3 Ma overlap the late stage of enderbite intrusion and growth of early metamorphic zircons. Garnetwhole rock Sm-Nd ages from leucosomes in the range 1880 − 1886 ± 7 Ma are concurrent with the growth of the youngest metamorphic zircons and probably indicate the crystallization of leucosomes or the influence of a fluid liberated from them. Isotopic and pet rologic data reveal that the evolution of Lapland Granulite belt from the erosion of source rocks to the generation of a sedimentary basin, its burial, metamorphism and exhumation took place within ca. 60 Ma.

Study of quaternary aquifers in Ganga Plain, India: Focus on groundwater salinity, fluoride and fluorosis

In marginal and central alluvial plains (Ganga Plain) of India, the inland salinity is continuously increasing, canal network and arid to semi-arid climatic conditions that led to excessive evapotranspiration concentrates the salt in soil and thereby escalating the groundwater salinity. In Mat Tahsil, Mathura district (Ganga Plain) study on shallow and deep aquifer salinity and fluoride was carried out in August 2001 and 2004. Groundwater salinity in some parts is more then 4000 μΩ −1/cm. This region is severely affected by endemic fluorosis due to consumption of fluoride-contaminated water. Analysis of F −, Na +, K +, Cl − and HCO 3 − was carried out at 30 sites of dugwells and borewells. Result shows that there is a variation and continuous escalation in the groundwater salinity and fluoride concentration in deep and shallow aquifers on the basis of analysis. Classification of salinity levels was carried out in 2001 and 2004. The deep aquifers (borewells) are found more saline as compare to the shallow aquifers (dugwells) while F −, Na +, K +, Cl − and HCO 3 − shows high concentration in shallow aquifers. The fluoride concentration in the groundwater of these villages showed values from 0.1 to 2.5 mg/l, severe enough to cause dental and skeletal fluorosis among the inhabitants, especially children of these villages. One of the major effects of inland salinity in this region is from saline groundwater, which is reaching the land surface and causing soil salinisations and water logging in the NE and SE parts of Mat block.

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part I: Metamorphic geology

The Palaeoproterozoic Lapland granulite belt was juxtaposed between Archaean and Proterozoic terrains in the NE part of the Fennoscandian Shield concurrently with the accretion of Svecofennian arc complexes at ~1.9 Ga. The belt consists mainly of aluminous migmatitic metagreywackes. Abundant noritic to enderbitic magmas were intruded concordantly into the metasediments and were probably an important heat source for metamorphism, which took place during the crystallization of the magmas. This is supported by structural and contact relations of metasediments and igneous rocks, and by the lack progressive metamorphic reaction textures in the igneous rock series. The peak of metamorphism took place above the dehydration melting temperature of the biotite-sillimanite-plagioclase-quartz assemblage at 750−850°C and 5−8.5 kbar which lead to formation of a restitic palaeosome and peraluminous granitic melt in metapelites. Subsequently, the rocks were decompressed and cooled below the wet melting temperature of pelitic rocks (650°C) under the stability fi eld of andalusite coexisting with potassium feldspar (2−3 kbar). Cooling was accompanied by the crystallization of the neosomes, often carrying aluminium-rich phases. Postmetamorphic duplexing of the LGB is clearly seen in the distribution of calculated PT conditions.

Anthropogenic Pb component in hydrothermal ochres from Marsili Seamount (Tyrrhenian Sea)

Recent hydrothermal Fe-oxyhydroxide precipitates (ochres) were sampled during two submersible expeditions to the NE part of the Marsili Seamount summit (SE Tyrrhenian Sea). The Marsili ochres belong to type 1 primary sulfide-poor Fe-oxyhydroxides according to the classification of Hekinian et al. [Hekinian, R., Hoffert, M., Larqué, P., Cheminée, J.L., Stoffers, P., Bideau, D., 1993. Hydrothermal Fe and Si oxyhydroxide deposits from south Pacific intraplate volcanoes and East Pacific Rise axial and off-axial regions. Econ. Geol. 88, 2099–2121]. They are X-ray amorphous, highly metalliferous [Al/(Al + Mn + Fe) ≪ 0.4], low in Si, transition metals (Co, Ni, Cu, Zn, Pb) and rare earth elements (REE) and enriched in B, V and Mo. Their chemical composition and REE distribution patterns indicate precipitation from low-temperature hydrothermal fluid mixed with seawater. Measured Pb isotope compositions in the ochres indicate that the Pb is dominantly anthropogenic in origin. By contrast, the Pb isotope ratios in the nearby higher temperature hydrothermal deposits from the Panarea arc volcano show that the Pb is derived mainly from local volcanic rocks. The fact that the Pb isotopic signature of the Marsili ochres is controlled by recent anthropogenic input suggests that the Fe-oxyhydroxides precipitated from fluids depleted in transition metals. The low 206Pb/ 207Pb ratios in the ochres reflect the contribution of Pb from Australian ores, indicating precipitation of the ochres somewhere between present-day and the beginning of Australian Pb import to Europe. The young age of the ochres and the presence of other hydrothermal deposits along the Marsili crest suggest that the magmatic chamber beneath the seamount may still be alive. This study represents the first observation of anthropogenic influence on submarine hydrothermal deposits.

Spatial variation in phytoplankton dynamics in the Belgian coastal zone of the North Sea studied by microscopy, HPLC-CHEMTAX and underway fluorescence recordings

Spatial variation in the succession of phytoplankton in the Belgian Coastal Zone (BCZ) was investigated by monitoring phytoplankton biomass and community composition using microscopical cell counts, HPLC pigment analyses and in vivo fluorescence recordings. Monthly monitoring of phytoplankton community composition at five stations revealed a succession of three distinct diatom communities. The succession of these three communities was the same at each site, but the succession from the winter-spring to the summer community occurred one month earlier and the succession from the summer to the autumn community one month later at the SW than at the NE stations of the BCZ. Monthly monitoring of chlorophyll a at ten fixed sites and inspection of in vivo fluorescence recordings during various cruises of RV ‘Zeeleeuw’ indicated that the spring bloom started about one month earlier in the SW part of the BCZ than in the NE part. The spatial difference in the onset of the spring bloom was ascribed to the higher water column turbidity at the NE coast compared to the SW coast. Although a Phaeocystis bloom occurred at all monitoring stations, a clear spatial variation in the magnitude of such blooms was observed, with more intense blooms at the NE coast than at the SW coast. A close relation was observed between the intensity of the Phaeocystis bloom and the availability of inorganic nutrients (N and P) before the onset of the bloom. Comparison of microscopical cell counts and CHEMTAX analysis of accessory pigment data indicated that HPLC analysis may be a useful tool for monitoring Phaeocystis in the North Sea. The presence of chlorophyll c 3 containing diatoms, however, probably resulted in the detection of small quantities of Phaeocystis by HPLC-CHEMTAX analysis when microscopical analyses showed that the species was absent.

Carbon isotope excursions and microfacies changes in marine Permian–Triassic boundary sections in Hungary

Several Permian–Triassic boundary sections occur in various structural units within Hungary. These sections represent different facies zones of the western Palaeotethys margin. The Gárdony core in the NE part of the Transdanubian Range typically represents the inner ramp, while the Bálvány section in the Bükk Mountains of northern Hungary represents an outer ramp setting. The two sections have different patterns for their δ 13C values. The Bálvány section shows a continuous change towards more negative δ 13C values starting at the first biotic decline, followed by a sharp, quasi-symmetric negative peak at the second decline. The appearance of the δ 13C peak has no relationship to the lithology and occurs within a shale with low overall carbonate content, indicating that the peak is not related to diagenesis or other secondary influences. Instead, the shift and the peak reflect primary processes related to changes in environmental conditions. The continuous shift in δ 13C values is most probably related to a decrease in bioproductivity, whereas the sharp peak can be attributed to an addition of C strongly depleted in 13C to the ocean–atmosphere system. The most plausible model is a massive release of methane-hydrate. The quasi-symmetric pattern suggests a rapid warming–cooling cycle or physical unroofing of sediments through slope-failure and releasing methane-hydrate. The Gárdony-1 core shows a continuous negative δ 13C shift starting below the P–T boundary. However, the detailed analyses revealed a sharp δ 13C peak in the boundary interval, just below the major biotic decline, although its magnitude doesn't reach that observed in the Bálvány section. Based on careful textural examination and high-resolution stable isotope microanalyses we suggest that the suppression of the δ 13C peak that is common in the oolitic boundary sections is due to combined effects of condensed sedimentation, sediment reworking and erosion, as well as perhaps diagenesis.

Propagating rift during the opening of a small oceanic basin: The Protector Basin (Scotia Arc, Antarctica)

Abstract The opening of oceanic basins constitutes one of the key features of Plate Tectonics because it determines the rifting and displacement of the continental crustal blocks. Although the mechanisms of development of large oceans are well known, the opening and evolution of small and middle size oceanic basins have not been studied in detail. The Protector Basin, located in the southern Scotia Sea, is a good example of a small oceanic basin developed between two thinned continental blocks, the Pirie Bank and the Terror Rise, poorly studied up to now. A new set of multibeam bathymetry, multichannel seismic reflection, and gravity and magnetic anomaly profiles obtained on the SCAN 2001 cruise led us to determine that the Protector Basin probably opened during the period comprised between C5Dn (17.4 Ma) and C5ACn–C5ABr chrons (13.8 Ma), forming a N–S oriented spreading axis. The end of spreading is slightly younger to the north. The start of spreading is clearly diachronous, with the most complete set of chrons up to C5Dn in the southern profile, C5Cn in the middle section and only up to C5ADn in the northern part of the basin. The spreading axis propagated northwards during the basin development, producing the wedge shape of the basin. In addition, at the NE part of the basin, a reverse fault developed in the border of the Pirie Bank after basin opening accentuates the sharp northern end. Moreover, the northwestern part of the Pirie Bank margin is an extremely stretched continental crust with N–S elongated magnetic anomalies related to incipient oceanic southward propagating spreading axes. The Protector Basin shows the oldest evidence of E–W continental stretching and subsequent oceanic spreading during Middle Miocene, related with the eastward development of the Scotia Arc that continues up to Present. The relative rotation of continental blocks during the development of small sized oceanic basins by continental block drifting favoured the opening of wedge shape basins like the Protector Basin and conjugate propagating rifts.

Les séries silicoclastiques miocènes du Nord-Est au Sud-Ouest de la Tunisie : une mise au point

During the Miocene time, the Atlas-pelagian block, which is limited northward by the atlasic-alpin chain of North Africa-Sicily, southward by the Gafsa–Jeffara–Azizia fault and eastward by the Malta escarpment, resulted from the extension-compression regime, mainly controlled by the subduction–collision processes. This regime induced the opening of many Miocene microbasins, which have been infilled by silicoclastic materials showing lateral and vertical facies variations and several hiatus associated to tectonic and stratigraphic unconformities. Excepting the very local transgressive regimes, such as those of Langhian and Messinian periods, most of the Miocene deposits took place on internal platforms, especially at the NE part of the country. The fluviodeltaic and alluvial sediments are, in fact, lateral equivalents which infilled the valley and depression enclosed systems towards the SW. In this context (rapid facies variations in time and space, superposition of tectonic and eustatic unconformities, climatic variations, rare or absent stratigraphic markers…), some controversies remain as regards the correlation and dating of these series. This work consists of a study of the lateral and vertical facies and thickness variations, coupled to the identification of the main unconformities. It is also a study of significance of the main sedimentological mechanisms and an inventory of the different palynological and paleontological content of the sediments. The aim of this work is to propose a new vision on the Miocene deposits in Tunisia along a NE–SW axis. Then, using these data, we have correlated the different lithological formations, discuss their age and, finally, proposed paleogeographical drafts for them.

Contact zone permeability at intrusion boundaries: new results from hydraulic testing and geophysical logging in the Newark Rift Basin, New York, USA

Hydraulic tests and geophysical logging performed in the Palisades sill and the underlying sedimentary rocks in the NE part of the Newark Rift Basin, New York, USA, confirm that the particular transmissive zones are localized within the dolerite-sedimentary rock contact zone and within a narrow interval below this contact zone that is characterized by the occurrence of small layers of chilled dolerite. Transmissivity values determined from fluid injection, aquifer testing, and flowmeter measurements generally fall in the range of 8.1E-08 to 9.95E-06 m2/s and correspond to various scales of investigation. The analysis of acoustic and optical BHTV images reveals two primary fracture sets within the dolerite and the sedimentary rocks—subhorizontal fractures, intersected by subvertical ones. Despite being highly fractured either with subhorizontal, subvertical or both fracture populations, the dolerite above and the sedimentary rocks below the contact zone and the zone with the layers of chilled dolerite are significantly less conductive. The distribution of the particular conductive intervals is not a function of the two dominant fracture populations or their density but rather of the intrusion path of the sill. The intrusion caused thermal fracturing and cracking of both formations, resulting in higher permeability along the contact zone.

Genesis of itabirite-hosted Au–Pd–Pt-bearing hematite-(quartz) veins, Quadrilátero Ferrífero, Minas Gerais, Brazil: constraints from fluid inclusion infrared microthermometry, bulk crush-leach analysis and U–Pb systematics

Fluid inclusions hosted in quartz and specular hematite from auriferous (jacutinga) and barren veins in the Quadrilatero Ferrifero (QF) have been studied using conventional and near infrared microscopy, respectively. The mineralization consists of veins that cross-cut metamorphosed iron formation (itabirite) of the Paleoproterozoic Itabira Group. The sample suite comprises hematite from veins from the low-strain domain in the W and SW of the study area, as well as hematite samples from the eastern high-strain domain in the central and NE parts of the QF. Halogen ratios of fluid inclusions in quartz and hematite from all studied deposits are consistent with a fluid evolved from dissolving and reprecipitating halite that was subsequently diluted. Fluid inclusions hosted in quartz and hematite are characterized by consistent Na/K ratios and considerable SO4 contents, and suggest similar formation conditions and, perhaps, fluid origin from a common source. Na/K and Na/Li fluid mineral geothermometers indicate water–rock interaction at approximately 340±40°C. Hematites from the high-strain domain contain fluid inclusion assemblages of high-temperature aqueous-carbonic and multiphase high-salinity, high-temperature aqueous inclusions probably due to fluid immiscibility in the system H2O–NaCl–CO2. Fluid inclusions hosted in hematite from barren veins in the low-strain domain, as well as in hematite from jacutinga-type mineralization from the central part of the QF, only host multiphase aqueous fluid inclusions all showing narrow ranges of salinity (7.2–11.7 wt.% NaCl equiv.) and homogenization temperatures (148 to 229°C). Lower homogenization temperatures and the absence of CO2-rich inclusions in specular hematite from these occurrences are attributed to carbonate precipitation and/or CO2 escape due to cooling during fluid migration from the high- to the low-strain domain. Pb–Pb and U–Pb systematics of gold, hematite and hematite-hosted fluid inclusions in combination with geochemical evidence indicate distinct sources for Pd, Au, and Pb. The formation of specular hematite veins may be related to retrograde metamorphic fluids being released during the Brazilian orogenic cycle (600–700 Ma). The Pb isotopic characteristics of all samples are readily reconciled in a simple model that involves two different Paleoproterozoic or Archean source lithologies for lead and reflects contrasting depths of fluid percolation during the Brasiliano orogeny.

Ποσοτική ανάλυση - μορφοτεκτονικοί δείκτες για τις περιοχές των ρηγμάτων Στρατωνίου - Βαρβάρας και Γοματίου - μεγάλης Παναγιάς (Ανατολική Χαλκιδική)

The study area is located at the NE part of Chalkidiki peninsula. Geologicaly it belongs at Servomacedonian mass. The faults of Stratoni - Barbara and Gomati- M. Panagia have an important role at the surface morphology of the area. These are typically active faults and they are the most important neotectonic structures at Eastern Chaikidiki. For the study of surface morphology a quantitative morphotectonic analysis has been done with the contribution of Geographical Information Systems GIS. The morphological indicators we have studied are: hypsometric curve and hypsometric integral, drainage basin asymmetry, mountain - front sinuosity, stream length - gradient index, transverse topographic symmetry, radio of valley - floor width to valley height and fault scarp morphology. This morphotectonic analysis has confirmed the field observations. Major role in this research had the use of satellite pictures and 3D models (Digital Elevation Model - D.E.M.).

The Hardangerfjord Shear Zone in SW Norway and the North Sea: a large-scale low-angle shear zone in the Caledonian crust

The Hardangerfjord Shear Zone is a more than 600 km long low-angle extensional structure that affects the South Norway and North Sea Caledonides. The ductile shear zone, which shows total maximum onshore displacement of the order of 10–15 km, is primarily a basement structure with an associated passive, monoclinal fold structure of the overlying Caledonian nappes. Deep seismic data indicate that the shear zone continues down to the lower crust (20–25 km) at a dip of 22–23°, where it appears to flatten and merge with the general lower-crustal deformation fabric. Onshore, the Hardangerfjord Shear Zone consists of a system of hard-linked ductile shear-zone segments. Brittle faults (the Lœrdal–Gjende fault system) occur in the folded Caledonian allochthons in the NE part of the Hardangerfjord Shear Zone, and reappear in the North Sea. These may represent a high-level brittle response to the Devonian development of the Hardangerfjord Shear Zone, but were reactivated during Permo-Triassic and late Jurassic extensional events. A c . 5 km thick package of seismic reflectors along the Hardangerfjord Shear Zone is presumed to represent a mylonite zone, which is too thick to be formed entirely by 10–15 km of Devonian displacement. Hence the Hardangerfjord Shear Zone is likely to be a Proterozoic shear zone, reactivated during Devonian extension.

Understanding the structural setting in the Southern Apennines (Italy): insight from Gravity Gradient Tensor

The Lucania Apennines form the frontal part of the Apennines in Southern Italy. This orogenic belt was formed in response to late Miocene–Early Pleistocene shortening and allochthon emplacement toward the northeast, and was subsequently affected by extensional faulting which migrated to northeast ahead of the thrust system. As a result, contraction structures are found associated to Pliocene–Early Pleistocene thrust-top basins in the NE part of the area, whereas extensional faults shape Middle Pleistocene–Holocene basin on the SW sector. The main structural grain of the belt is NW–SE, but E–W structures are widespread in the area as a result of phases of non-coaxial thrusting and strike-slip faulting. The analysis, one by one, of the components of the Gravity Gradient Tensor (GGT) has proved to yield a fine image of the structural setting of the investigated area. GGT is a second rank tensor containing the second spatial derivatives of the gravity potential and in this paper is used instead than the more traditional gravity data. The Tzz component allows an accurate description of the location and of the shape of basins and other structures, but different components of the GGT provide even more detailed insights for such structures. In particular, we found that the Tzy and Tyy locate well those structures trending closer to the E–W direction for both thrust-top and extensional basins, and their termination against the main NW–SE structures. The combined use of components of GGT provides a finer definition of the anomaly sources particularly if a good knowledge of their strike and depth is independently estimated with other geological and geophysical investigations.

Problems of the “Cordevolian” Limestone and Dolomite” in the Slovenian part of the Southern Alps

Stratigraphic position and age of the so called Cordevolian limestone and dolomite in the Slovenian part of the Southern Alps is a long lasting problem. Its name originates from the (somewhere abandoned) Cordevolian substage (Lower Carnian). Limestone and dolomite both correspond to the Cassian dolomite from the Italian Southern Alps. Platform type of limestone and dolomite, which could be genetic and time equivalent with the Ladinian Schlem (Scilliar) dolomite, is unknown in Slovenia. In the NE part of the Kamnik-Savinja Alps, the Korošica formation (Upper Ladinian) overlies platform limestone and dolomite of the Ojstrica Formation (Ladinian). Diplopora annulata is also present in the Ojstrica formation. Various Ladinian rocks in the Julian Alps and Southern Karavanke are mainly of the Lover Ladinian age, whereas the overlying massive limestone and dolomite (“Cordevolian limestone and dolomite”) are partially of the Ladinian and partially of the Carnian age. There are no Upper Ladinian “Wengen” beds in the carbonate massive, so it is impossible to draw a time line between the Ladinian and the Carnian stages. We can therefore conclude, that litological boundaries do not coincide with the chronostratigraphic ones.

Magmatism in the Bransfield Basin: Rifting of the South Shetland Arc?

Bransfield Basin is an actively extending marginal basin separating the inactive South Shetland arc from the northern Antarctic Peninsula. Rift‐related volcanism is widespread throughout the central Bransfield Basin, but the wider eastern Bransfield Basin was previously unsampled. Lavas recovered from the eastern subbasin form three distinct groups: (1) Bransfield Group has moderate large‐ion lithophile element (LILE) enrichment relative to normal mid‐ocean ridge basalt (NMORB), (2) Gibbs Group has strong LILE enrichment and is restricted to a relic seamount interpreted as part of the South Shetland arc, and (3) fresh alkali basalt was recovered from the NE part of the basin near Spanish Rise. The subduction‐related component in Bransfield and Gibbs Group lavas is a LILE‐rich fluid with radiogenic Sr, Nd, and Pb isotope compositions derived predominantly from subducting sediment. These lavas can be modeled as melts from Pacific MORB source mantle contaminated by up to 5% of the subduction‐related component. They further reveal that Pacific mantle, rather than South Atlantic mantle, has underlain Bransfield Basin since 3 Ma. Magma productivity decreases abruptly east of Bridgeman Rise, and lavas with the least subduction component outcrop at that end. Both the eastward decrease in subduction component and occurrence of young alkali basalts require that subduction‐modified mantle generated during the lifetime of the South Shetland arc has been progressively removed from NE to SW. This is inconsistent with previous models suggesting continued slow subduction at the South Shetland Trench but instead favors models in which the South Scotia Ridge fault has propagated westward since 3 Ma generating transtension across the basin.

The eastern continuation of the Cadomian orogen: U–Pb zircon evidence from Saxo-Thuringian granitoids in south-western Poland and the northern Czech Republic

We report U–Pb single zircon ages from three pre-Variscan granitoids in the NE part of the Bohemian Massif. The Platerowka granodiorite from the Lausitz-Izera Unit, the Polish Sudetes, has been dated at 533±9 Ma. The Bitouchov granite form the SW part of the South Krkonose Unit, the Czech Sudetes, gave an age of 540+11/–10 Ma, and the Wądroze granodiorite in the Fore-Sudetic Block yielded 548±9 Ma. All these latest Vendian/Early Cambrian granitoids represent the post-tectonic expression of a late Proterozoic Cadomian orogenic cycle and demonstrate the eastward extent of the Cadomian basement into the Variscan orogen. Granodiorites of similar age have so far been reported from Brittany and especially from the Saxo-Thuringian Terrane to the NE and SW of the Elbe Fault Zone. We conclude that the Saxo-Thuringian Terrane extends across the Elbe and Sudetic Marginal Fault Zones into the Fore-Sudetic Block.

HS 0837+4717 – a metal-deficient blue compact galaxy with large nitrogen excess

(Abridged) We present the results of high S/N long-slit spectroscopy with the Multiple Mirror and the SAO 6-m telescopes, optical imaging with the Wise 1-m telescope and HI observations with the Nancay Radio Telescope of the very metal-deficient (12+log(O/H)=7.64) luminous (M_B=-18.1) blue compact galaxy (BCG) HS 0837+4717. The blue bump near lambda4650, characteristic of WR stars is detected in the central supergiant HII region, as well as the barely seen red bump at lambda5808. The derived number of WR stars in the region of the current starburst is ~1000. Evidence for fast motions in this region is also seen as broad, low-contrast components in the Ha, Hb and strong [OIII] lines. While the extinction of the narrow emission lines from the supergiant HII region is low, the very large Balmer decrement of the broad components suggests that the part of current starburst is highly obscured by dust. Abundance ratios X/O for X=Ne, Ar, S, Fe and Cl in the supergiant HII region are in good agreement with the mean values of other BCGs. Nitrogen, however, is overabundant by a factor of ~6. This implies an unusually efficient N enrichment in HS 0837+4717, and probably, a non-typical evolution scenario. The Ha-line Position--Velocity diagrams for directions approximately along the major and minor axes reveal disturbed motions of the ionized gas. The SW part of the major axis P--V diagram looks like a rotation curve, with V_rot ~50--70 km/s at r=4.3 kpc. Its NE part displays, however, strong deviations, indicating either counter-rotation, or strong outflow/supershell. The overall BCG morphology is highly disturbed. With a double-nucleus structure, disturbed velocities of ionized gas, and the very high power of the starburst this suggests a possible explanation of the object as a recent merger.

Archean crustal evolution in the northern Yilgarn Craton: U–Pb and Hf-isotope evidence from detrital zircons

The integrated application of U–Pb dating, Hf-isotope analysis and trace-element analysis to detrital zircon populations offers a rapid means of assessing the geochronology and crustal evolution history of different terranes within a composite craton. In situ U–Pb and Hf-isotope analyses of 550 zircons from 21 modern drainages across the northern part of the Yilgarn Craton and the adjacent Capricorn Orogen provide a broad view of crustal evolution in Archean and Proterozoic time.The oldest crustal components (3.7Ga) are identified in the Yeelirrie geophysical domain [A.J. Whitaker, Proceedings of Fourth International Archaean Symposium Ext. Abstracts AGSO-Geoscience Australia Record, vol. 37, 2001, p. 536] that runs N–S down the middle of the craton; these components are represented by ancient zircons and also are reflected in the Hf model ages of younger magmas. Ancient (>3.4Ga) crust contributed to the generation of younger magmas in the Narryer Province, and the proportion of ancient recycled material increases from east to west across the Murchison Province. In contrast, the Hf-isotope data provide no evidence for crust older than 2.9–3.0Ga in the Southern Cross or Eastern Goldfields (including the Marymia Inlier) domains. The Yeelirrie domain and the composite Narryer–Murchison block are interpreted as ancient microcontinents, sandwiched with the juvenile terranes of the Southern Cross and Eastern Goldfields domains.There is little evidence for the existence of a Depleted Mantle reservoir beneath the Yilgarn Craton prior to 3.1–3.2Ga, but this reservoir is a major contributor to crustal generation from 3.1 to 2.6Ga; this suggests that much of the continental crust in the craton was generated after ca. 3.2Ga. 1.8–2.3Ga magmatism, associated with the Capricorn Orogen, involved the recycling of older crust with little obvious contribution from the Depleted Mantle. A significant (and previously unrecognised) 540Ma episode in the NE part of the craton involved metamorphism or remelting of the 2.7–3.0Ga crust of the Eastern Goldfields Province.

Hydrocarbon migration and entrapment in the Baltic Syneclise

Based on the data concerning the type, quantity and thermal maturity of the organic matter, several petroleum source rock complexes have been distinguished in the Paleozoic succession of the Baltic Syneclise. Maturity of organic matter varies from immature in the NE part of the Baltic Syneclise to peak generation in the central part and postmature stage towards the Teisseyre–Tornquist Zone. The isolated local postmature areas are most likely related to the occurrence of sills. The oils of the Baltic region have moderate gravities (26–42°API) that decrease with present reservoir depth, reflecting the thermal maturity. Quantitative modeling of the oil and gas migration and entrapment was performed by the means of the 3D software SEMI. This confirmed that oil generation and migration was most intense during Late Silurian–Early Devonian time. Based on modeling, the major Cambrian traps accumulated oil expelled from different stratigraphic source rock units: the Cambrian, Ordovician and Silurian organic rich shales.