Lamprophyric magmatism in the Sudetes, in the eastern part of the European Variscides, occurred during a period of post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were emplaced as dyke swarms and as scattered veins that cut the crystalline basement and, locally, the overlying molasse deposits. The dyke swarms are adjacent to major regional dislocations, represent distinctive magmatic centres that are related to separate magmatic systems and each are characterized by specific parental melts that have undergone individualised shallow-level differentiation processes. The two largest dyke swarms are associated with the Karkonosze and Klodzko-Zloty Stok granitoid massifs: these show the widest geochemical and petrographic variation, due to more advanced differentiation in long-lived magmatic systems. In contrast, a small dyke swarm emplaced in the SW part of the Orlica-Śnieznik Dome, unrelated to granites, is strongly dominated by minettes only. Geochemical characteristics of the mafic rocks studied herein vary from (ultra)potassic in the minettes to calc-alkaline in the micromonzodiorites and from primitive (Mg# = 80-60 in many lamprophyres) to evolved (Mg# down to 30 in some micromonzodiorites). Some richterite minettes show Nb-enriched trace element patterns, but negative Nb anomalies are more typical. Richterite minettes posesess eNd 300 and 87 Sr/ 86 Sr 300 values that range from +1.9 to -8.3, and from 0.7037 to 0.715, respectively. The other rocks in this study show negatively correlated Nd and Sr isotopic ratios, between these extremes. The geochemical data suggest three types of mantle source for the lamprophyres and associated mafic rocks: (1) An asthenospheric, depleted and later re-enriched source; (2) A lithospheric source contaminated by subducted crustal rocks; (3) A lithospheric source metasomatized by subduction-related fluids. The richterite minette magmas originated from low degrees of partial melting, under high H 2 O/CO 2 conditions, of garnet-phlogopite-peridotites. The Nb-enriched and Nb-depleted minettes are derived from sources (1) and (2), respectively. Kersantite magmas originated from source (3). The factors of source mixing, variable depths and degrees of melting, and aggregation of melts all influenced the compositions of other primitive minette and vogesite magmas. The other rocks studied (spessartites, monzonites, micromonzodiorites) are variably differentiated. Zoning and other disequilibrium textures in phlogopite, biotite, amphibole and clinopyroxene phenocrysts, together with the presence of xenocrysts, xenoliths and enclaves (cognate, restitic, migmatitic) constrain several processes that were involved in the shallow-level evolution of magmas: mixing, fractional crystallization, assimilation of crustal rocks. However, post-magmatic replacement of the igneous phases by albite, chlorite, epidotes, actinolite, blue amphiboles, titanite, carbonates, prehnite, pumpellyite and grossularite-andradite partly obscures the magmatic assemblages and textures. There are four more general results of this study. First, there is evidence for a strong heterogeneity of the upper mantle and of the presence of subduction-modified mantle beneath the Sudetes during the Late Palaeozoic. Second, the lamprophyre magmas originated and evolved in spatially and petrologically distinct, vertically extensive magmatic systems that spanned the asthenospheric and lithospheric mantle and the lower/middle crust. Third, a broad spectrum of source-related and shallow-level magmatic processes gave rise to the emplacement of primitive, mantle-derived magmas and of variably evolved magmas. Fourth, close links existed between late Variscan tectonics, the location of lamprophyric magmatism, and the shallow-level emplacement processes of mafic dykes.
The Carbonifeorus-Permian volcanic rocks of the Intra-Sudetic Basin represent products of late- to post-collisional volcanism associated with extension within the eastern part of the Variscan belt of Europe. The volcanic succession is subdivided into the older, calc-alkaline suite (the early and late Carboniferous) and the younger, mildly alkaline suite (the late Carboniferous and early Permian). The rhyodacites with subordinate basaltic andesites and andesites of the older suite show convergent plate margin affinities. The rhyolitic tuffs, rhyolites with less widespread trachyandesites and basaltic trachyandesites of the younger suite are largely characterised by within-plate affinities, with some gradations towards convergent plate margin affinities. This geochemical variation compares well with that found in some Tertiary-Recent extensional settings adjacent to former active continental margins (e.g. the Basin and Range province of the SW USA). The parental magmas for each suite of the Intra-Sudetic Basin possibly originated from similar, garnet free mantle sources at relatively shallow depths (within the subcontinental mantle?), but at variable degrees of partial melting (lower for the mildly alkaline rocks). The convergent plate margin-like geochemical signatures of the volcanic rocks may either have been inherited from their mantle sources, or be related to the assimilation of crustal rocks by the ascending and fractionating primary magmas. The intermediate-acidic rocks within each suite mainly originated due to fractional crystallisation of variable mineral assemblages equivalent to the observed phenocrysts (mainly plagioclase and pyroxenes, with hornblende and biotite in the calc-alkaline suite, and K-feldspar in the mildly alkaline suite). The trace element patterns of the volcanic rocks were also strongly influenced by fractionation of accessory minerals, such as spinels, ilmenite, zircon, apatite and others. The petrographic evidence (e.g. quartz phenocrysts with reaction rims, complexly zoned or sieve-textured feldspar phenocrysts) suggests that assimilation and/or magma mixing processes might also have taken place during the evolution of the magmas.
Abstract Precise U–Pb zircon dating using the chemical abrasion – isotope dilution – thermal ionization mass spectrometry (CA-ID-TIMS) method constrains the age of the Central Sudetic Ophiolite (CSO) in the Variscan Belt of Europe. A felsic gabbro from the Ślęża Massif contains zircon xenocrysts dated at 404.8 ± 0.3 Ma and younger crystals dated at 402.6 ± 0.2 Ma that determine the final crystallization age of the gabbro. An identical age of 402.7 ± 0.3 Ma was determined for plagiogranite from the Nowa Ruda–Słupiec Massif, and plagiogranite from the Braszowice–Brzeźnica Massif yields a similar, but less reliable, age of > 401.2 Ma. The different massifs in the CSO are therefore considered as tectonically dismembered fragments of a single oceanic domain formed at c. 402.6–402.7 Ma (Early Devonian – Emsian). The magmatic activity recorded in the CSO was contemporaneous with the high-temperature/high-pressure metamorphism of granulites and peridotites in the Góry Sowie Massif, separating dismembered parts of the CSO. This suggests geodynamic coupling between the continental subduction recorded in the Góry Sowie and the oceanic spreading recorded in the CSO. Regional geological data indicate that the CSO was obducted before c. 383 Ma, less than 20 Ma after its formation at an oceanic spreading centre. The CSO is shown to be one of the oldest and first obducted among the Devonian ophiolites of the Variscan Belt. The CSO probably originated in an evolved back-arc basin in which the influence of subduction-related fluids and melts increased with time, from negligible during the formation of predominant mid-ocean-ridge-type magmatic rocks to strong at later stages, when rodingites, epidosites and other minor lithologies formed.
Abstract The Intra-Sudetic Basin is a Late Palaeozoic intramontane trough, situated in the eastern part of the European Permo-Carboniferous Basin and Range Province. Within the basin, tectonics, sedimentation and volcanic/subvolcanic activity were intimately related. Tectonics controlled the location of the depositional and volcanic centres. Many volcanic centres with subvolcanic intrusions of rhyodacitic, rhyolitic and trachyandesitic composition were located close to the intra-basinal depositional troughs, where thick accumulations of sedimentary rocks partly obstructed the movement of magma to the surface. Differences in the structure and geometry of intrusions at separate subvolcanic complexes reflect the influence of different discontinuities, faults, margins of collapse structures, boundaries of contrasting lithologies in the country rocks and the volcanic structures.
Dolnopaleozoiczne skaly wulkanoklastyczne we wschodniej cześci jednostki Bolkowa (Gory Kaczawskie): ich geneza i mechanizm depozycji
Lower Paleozoic metamorphosed greenschist facies volcaniclastic rocks with well preserved primary structures occur in the eastern part of the Bolkow unit, within the Kaczawa complex, West Sudetes. They are interpreted mostly as deposits of turbulent gravity flows ranging from high concentration flows to dilute turbidity currents, with subordinate ash-flow tuffs. These rocks are considered to have been deposited in a relatively deep marine environment, close to active volcanic centres.
Mafic, monogenetic volcanism is increasingly recognized as a common manifestation of post-collisional volcanism in late Variscan, Permo-Carboniferous intramontane basins of Central Europe. Although identification of individual eruptive centres is not easy in these ancient successions, the Permian Rožmitál andesites in the Intra-Sudetic Basin (NE Bohemian Massif) provide an exceptionally detailed record of explosive, effusive and high-level intrusive activity. Based on field study and petrographic and geochemical data on pyroclastic and coherent rocks, the Rožmitál succession is interpreted as the proximal part of a tuff ring several hundred metres in diameter. Initial accumulation of pyroclastic fall and surge deposits occurred during phreatomagmatic eruptions, with transitions towards Strombolian eruptions. Gullies filled with reworked tephra document periods of erosion and redeposition. Andesitic blocky lavas capped the volcaniclastic succession. Invasion of lavas into unconsolidated sediments and emplacement of shallow-level intrusions in near-vent sections resulted in the formation of jigsaw- and randomly-textured peperites. Most geochemical differences between coherent andesites and pyroclastic rocks can be linked to incorporation of quartz-rich sediments during the explosive eruptive processes and to later cementation of the volcaniclastic deposits by dolomite. The Rožmitál tuff ring could have been one of several phreatomagmatic centres in a monogenetic volcanic field located on an alluvial plain.
The Intrasudetic Basin represents one of the larger late- to post-Variscan intramontane troughs of Central Europe. It is situated at the northern margin of the Bohemian Massif. The Basin represents a fault-bounded synclinorial structure and was formed in the late Visean as a depression framed by tectonically active margins. During the Permian, the basin was filled with dominantly fine-grained alluvial to lacustrine deposits, accompanied by volcanic rocks. Volcanic activity evolved with time and comprised emplacement of subvolcanic intrusions, effusion of lava flows as well as deposition of widespread ignimbrites (Awdankiewicz, 1999). These volcano-sedimentary units are known as the Słupiec Formation in the Polish part and the Broumov Formation in the Czech part of the Intrasudetic Basin, respectively. So far, based on generally imprecise biostratigraphic evidence and regional correlations, the Słupiec Formation sedimentary rocks together with the intercalated volcanic rocks were (usually) assigned to the Sakmarian. However, preliminary results of U-Pb SHRIMP zircon dating of the Góry Suche Rhyolitic Tuffs and the Łomnica Rhyolites – a widespread ignimbrite sheet and associated rhyolitic laccoliths intercalated in the Słupiec/Broumov Formation - suggest that these volcanic rocks can be older than supposed by 5-10 My. Such age estimate would assign these ignimbrites and rhyolites to the Asselian, not Sakmarian.In this contribution the biostratigraphic evidence on the position of the Słupiec/Broumov Formation is re-assessed. The fluvio-lacustrine sedimentary members of these formations accumulated probably in semi-arid palaeoclimatic conditions with seasonally-controlled watertable.Numerous footprints of reptiles and amphibians, aquatic vertebrates: chondrichthyans, actinopterygians and amphibians, also palaeobotanical remains were preserved (e. g.  Jerzykiewicz, 1987; Zajíc, 2000; Stamberg & Zajíc, 2008; Voigt et al., 2012; Opluštil et al., 2016). Unfortunately, they appear only fairly suitable for detailed biostratigraphy as their successions may be environmentally-controlled, and most of them indicate a latest Carboniferous to early Permian age. At this level of knowledge, they are not suitable for detailed biostratigraphy, and thus comprehensive and comparative studies of the Late Carboniferous and Early Permian Central European volcanic-sedimentary basins are necessary to better constrain the stratigraphic position of the Słupiec/Broumov Formation of the Intrasudetic Basin.This research is funded by the Polish National Science Centre (Grant 017/26/M/ST10/00646).Awdankiewicz, M. (1999): Geologia Sudetica, 32 (1): 13-47; Jerzykiewicz, J. (1987): Palynology 11: 117-131; Opluštil, S., Schmitz, M., Kachlík, V. & Štamberg, S. (2016): Bulletin of Geosciences, 91: 399–432; Štamberg, S. & Zajíc, J. (2008): Carboniferous and Permian faunas and their occurrence in the limnic basins of the Czech Republic. Museum of Eastern Bohemia; Voigt, S., Niedźwiedzki, G., Raczyński, P., Mastalerz, K. & Ptaszyński, P. (2012): Palaeoclimatology, Palaeoecology, 313-314: 173-180; Zajíc, J. (2000): Courier-Forschungsinstitut Senckenberg, 223: 563-575. 
Abstract The Góry Suche Rhyolitic Tuffs in the Intra-Sudetic Basin, in the eastern part of the Variscan Belt of Europe, represent a voluminous (ca. 100 km 3 ), possibly caldera-related, ignimbrite-dominated complex and the Łomnica Rhyolites are associated, post-ignimbrite sills. Zircon separates from nine samples were dated using the U–Pb SHRIMP method. Well-defined concordia ages were determined in four ignimbrite samples (300.5 ± 2.0, 300.5 ± 1.4, 298.0 ± 1.6 and 297.2 ± 0.9 Ma) and in two rhyolite samples (298.4 ± 1.5 and 292.6 ± 1.9 Ma). Clustering of the ignimbrite sample ages between 300.5 ± 2.0 and 297.2 ± 0.9 Ma and geological evidence indicate the eruption and deposition of the tuffs close to the Carboniferous/Permian boundary, in a geologically rapid event at approximately 299 Ma. Zircon assemblages in three tuff specimens are strongly dominated by xenocrysts of various Palaeozoic and Precambrian ages that were incorporated during the eruption through the basin fill. The emplacement of the tuffs was followed (and partly overlapped?) by the emplacement of the Łomnica Rhyolites as sills in two episodes in the early Permian. The Góry Suche Rhyolitic Tuffs may be a few million years older than assumed so far, and this, as well as rather imprecise biostratigraphic constraints from the host sedimentary rocks, suggest a need for revision of the existing lithostratigraphic and evolutionary schemes for the Permo-Carboniferous of the Intra-Sudetic Basin. The studied tuffs and rhyolites together with coeval granitic plutons in vicinity can be linked to the onset of post-Carboniferous lithospheric thinning in Central Europe. Graphical abstract
Abstract Compared to intensive research on km‐sized meteorite impact craters, fewer studies focus on smaller craters. The small craters are often hard or impossible to recognize using “classical” criteria like the presence of shatter cones, shocked quartz, and geochemical indicators. Therefore, a long list of candidate structures awaiting approval/disapproval of their origin has been formed over the last decades. One of them is the Tor structure in central Sweden. To test a hypothesis of an impact origin of this structure, we have performed topographical analysis, geophysical studies, 10 Be exposure dating of boulders, and 14 C dating of Tor‐associated charcoal. None of the methods gave us a reason to claim the Tor structure is of impact origin. Thus, we support a recently suggested idea of Tor being formed by a grounded iceberg within a glacial lake.
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