Petrogenesis of continental mafic dykes from the Izera Complex, Karkonosze-Izera Block (West Sudetes, SW Poland)

The Izera Complex (West Sudetes) contains widespread bodies of metagabbro, metadolerite and amphibolite (the Izera metabasites), and less abundant dykes of weakly altered dolerites, emplaced in a continental setting. The primary magmas of the Izera metabasites were probably formed through adiabatic decompression melting of upwelling asthenosphere (mantle plume) that was associated with the early Palaeozoic fragmentation of Gondwana (initial rift). The rocks are mildly alkaline, transitional-to-tholeiitic basalts and have OIB-like trace element patterns. Trace element modelling reveals that the mafic magmas were generated by variable degrees of partial melting (1–7%) of fertile, garnet-bearing asthenospheric source similar in composition to primitive mantle. Together with an increase in degree of partial melting, the compositional affinity of the magmas and the depth of segregation changed progressively from ca. 70–90 km (mildly alkaline magmas of the metadolerites and amphibolites) to ca. 60–75 km (transitional-to-tholeiitic magmas of the metagabbros). The systematics of incompatible versus compatible element distribution, and major and trace element modelling, indicate that some rocks experienced low-pressure (<5 kbar) differentiation resulting in up to 50% fractionation of clinopyroxene, olivine and minor plagioclase and ilmenite. The genetically distinct weakly altered dolerites are basaltic andesite in composition and possibly related to late- or post-orogenic events in the Karkonosze-Izera Block. These rocks are calc-alkaline, with relatively flat MREE–HREE patterns, enrichment in LREE and other highly incompatible elements relative to primitive mantle, and negative Nb–Ta, Ti, P anomalies. The geochemical features and geochemical modelling, indicate that their primary magmas segregated at depths ≤70 km and were produced by ~2% melting of a metasomatized sublithospheric mantle source presumably containing small amounts of hydrated phases. Although the present study is inconclusive as to the origin of the metasomatic component in the source (? slab-derived fluid/melts, OIB-like alkaline melt percolation of subcontinental lithosphere), the genesis of the Izera basaltic andesites is seemingly related to upwelling of asthenosphere and heat flow triggered by a postulated decoupling of the mantle lithosphere and post-collisional extensional collapse and uplift in the Karkonosze-Izera Block.     

Seismic doublets and multiplets at Polish coal and copper mines

The following criteria for selection of doublets at Polish coal mines were accepted: the difference in magnitude (based on seismic moment) of two events not larger than 0.15, the distance between their hypocenters not greater than 150 m, and the time interval between their occurrence not longer than 10 days. Similarly, the criteria for seismic events at copper mines are: the difference in magnitude not exceeding 0.15, the distance not greater than 200 m, and the time interval not longer than 20 days. Seismic events from the Wujek and Ziemowit coal mines that occurred between 1993 and 1995, and seismic events from the Polkowice copper mine that occurred between 1994 and 1996 and from the Rudna copper mine that occurred between 1994 and 2004 were considered. Their source parameters and focal mechanisms were known in most cases from previous studies. Altogether 108 seismic pairs from coal mines and 118 pairs from copper mines were found, forming doublets, triplets and quadruplets, within the magnitude range from 0.7 to 3.5. The distance and time intervals between two events forming pairs are not dependent on magnitude of these events. The focal mechanism of seismic events forming pairs is similar in over 60 percent of pairs at coal mines and in about one third of pairs at copper mines. Spatial distributions of doublets in particular sections of coal and copper mines display dominant linear trends, characteristic for a given area, which are often in conformity with the direction of nodal planes determined by fault plane solution of one or both the events forming a doublet. In such cases, the rupture plane can be discriminated among the nodal planes.     

The Tepla(?)/Saxothuringian suture in the Karkonosze–Izera massif, western Sudetes, central European Variscides

The southern and eastern Karkonosze-Izera massif (northern Bohemian Massif) exposes blueschist facies rocks and MORB-type magmatic complexes. During Late Devonian to Early Carboniferous times, these were overthrust within a nappe pile toward the NW onto the pre-Variscan Saxothuringian basement composed of the Izera-Kowary metagranitoids and their envelope. The lowermost nappe (or parautochthonous?) unit of the pile is the low-grade metamorphosed Jewt3d complex, comprising a Devonian to Early Carboniferous sedimentary succession of the Saxothuringian passive margin. This is tectonically overlain by the South Karkonosze complex, which represents Ordovician-Silurian volcano-sedimentary infill of the Saxothuringian basin, affected by Late Devonian HP metamorphism. The uppermost nappe is the Early Palaeozoic epidote-amphibolite grade Leszczyniec MORB-like complex, cropping out on the eastern margin of the Karkonosze-Izera massif. It probably represents a fragment of obducted Saxothuringian basin floor. The nappe pile was stacked beneath the overriding upper plate margin, now concealed below the Intra-Sudetic basin and hypothesized to represent a fragment of the Tepla-Barrandian terrane. The nappe stacking, triggered by buoyancy-controlled upward extrusion of the subducted continental slab, was the main mechanism for the exhumation of HP rocks. The final stages of the NW-ward nappe stacking were accompanied and followed by SE-directed Early Carboniferous extensional collapse. The lower plate of the suture zone was uplifted at that time and intruded by the ~330-Ma-old, nearly undeformed Karkonosze granite pluton. As a result of the collapse, the Tepla-Barrandian(?) upper plate was downthrown on shear zones and brittle faults and buried under several km-thick synorogenic Late Tournaisian(?) through Namurian and post-orogenic Late Carboniferous-Early Permian succession of the Intra-Sudetic basin. The south and east Karkonosze suture most probably is a fragment of the Tepla/Saxothuringian (Münchberg-Tepla) suture belt known from the western Bohemian Massif.     

The role of neotectonics and glaciation on terrace formation along the Nysa K odzka River in the Sudeten Mountains (southwestern Poland)

The Nysa K odzka river drainage basin in the Sudeten Mts., SW Poland, preserves a complex late Cainozoic succession that includes eight fluvial series or terraces and deposits from two glacial episodes as well as local volcanic rocks, slope deposits and loess. Fluvial sedimentation took place during the Late Pliocene and from the early Middle Pleistocene (Cromerian), with a long erosion phase (gap) during the Early Pleistocene. Fluvial series are dated to the Late Pliocene, Cromerian, Holsteinian, late Saalian/Eemian, Weichselian, and the Holocene. Glacial deposits represent the early Elsterian and early Saalian stages. Almost all these stratigraphic units have been observed in all geomorphic zones of the river: the mountainous K odzko Basin, the Bardo Mts. (Bardo gorge) and in the mountain foreland. The main phase of tectonic uplift and strong erosion was during the Early Pleistocene. Minor uplift is documented also during the post-early Saalian and probably the post-Elsterian. The post-early Saalian and post-Elstrian uplift phases are probably due to glacio-isostatic rebound. The Quaternary terrace sequence was formed due to base-level changes, epigenetic erosion after glaciations and neotectonic movements. The Cromerian fluvial deposits/terraces do not indicate tectonic influence at all. All other Quaternary terraces indicate clear divergence, and the post-early Saalian terraces also show fault scarps. The fluvial pattern remained stable, once formed during the Pliocene, with only minor changes along the uplifted block along the Bardo gorge, inferring an antecedent origin for the Bardo gorge. Only during the post-glacial times, have epigenetic incisions slightly modified the valley.     

Method for correction of the prestack migration amplitude of converted waves

The paper presents a method for correction of amplitude of prestack migration using the reflectivity function. The solution of wave equations for heterogeneous media expressed in the form of Neumann series for converted waves was used to find the reflectivity function. The performance of the proposed method was verified using synthetic models of wavefields. The synthetic models of wavefields were also used to compare amplitude correction levels required by the presented method and the standard amplitude correction methods, i.e., the methods using the spherical divergence and extention factor.     

Provenance implications of Th–U–Pb electron microprobe ages from detrital monazite in the Carboniferous Upper Silesia Coal Basin, Poland

This paper reports the results of CHIME (chemical Th–U–Pb isochron method) dating of detrital monazites from Carboniferous sandstones in the Upper Silesia Coal Basin (USCB). A total of 4739 spots on 863 monazite grains were analyzed from samples of sandstone derived from six stratigraphic units in the sedimentary sequence. Age distributions were identified in detrital monazites from the USCB sequence and correlated with specific dated domains in potential source areas. Most monazites in all samples yielded ca. 300–320 Ma (Variscan) ages; however, eo-Variscan, Caledonian and Cadomian ages were also obtained. The predominant ages are comparable to reported ages of certain tectonostratigraphic domains in the polyorogenic Bohemian Massif (BM), which suggests that various crystalline lithologies in the BM were the dominant sources of USCB sediments.     

Analysis of particulate matter concentrations in mazovia region, central poland, based on 2007–2010 data

Measurement results of PM10 (particulate matter with diameters below 10 μm) concentrations performed at four stations in central Poland (2007–2010) were analyzed in terms of levels and distributions of concentrations, the number of exceedances of the limit values and the causes of these exceedances. PM10 levels were similar at suburban and rural stations, except of one station located in the vicinity of a busy street. The median of PM10 concentration ranged from 26 μg/m³ at suburban station to 44 μg/m³ at Warsaw Kerb station. Seasonal variability analysis of PM10 concentration revealed an additional maximum beyond the usual autumn-winter one. This maximum occurred in April at all stations, and corresponded to seasonal wildfires activity and dust activation in Eastern Europe. Cluster analysis of back-trajectories revealed that PM10 concentrations depend on the direction of advection of the incoming air; the highest values are registered for air of regional and southern origins, while the lowest are for the airmasses coming from the north and northwest direction.     

Lignin degradation products as palaeoenvironmental proxies in the sediments of small lakes

The quantity and quality of lignin phenols (Σ8, Λ, S/V, C/V and (Ad/Al)_v) in the sediments of three small Lobelia lakes with neither inlets nor outlets were investigated and compared with palynological data and lithology of the profiles. The method of alkaline CuO oxidation was used. Substantial differences with respect to sedimentary lignin concentration and provenance recorded along the profiles and among the sites are in good agreement with pollen data describing the dominant type of vegetation and with indices of soil erosion in the lakes’ catchments. This relation shows that the compositions of lignin degradation products in these lakes are closely related to the local environmental conditions. In all the lakes gymnosperm wood is the main source of lignin products; however, each lake is characterized by different S/V index values. Especially good correlations were obtained between pine pollen proportions in sediments and the S/V index. The correlation between the C/V and (Ad/Al)_v indices indicates a higher degradation of organic matter when non-woody tissue is more abundant. This pilot study illustrates the usefulness and potential for a wider application of lignin oxidation products in palaeoecological reconstructions. This kind of data would be of special importance when investigating local presence/absence of woody plants and the role of angiosperms/gymnosperms in local vegetation. Estimates of lignin biodegradation levels, as well as the data on diagenetic processes, may afford supplementary information on possible disturbances in sedimentation.     

Peralkaline felsic magmatism at the Nemrut volcano,Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV

Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO₂ close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas.