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Relics of solitary volcanic edifices in NE Bohemia were newly interpreted as remnants of scoria cones and their conduits. Volcanic activity in this area occurred in a form of scattered Strombolian eruptions of basanitic magmas mostly ascending along E-W trending faults. Nearly all studied volcanoes erupted in similar style, Strombolian, mostly not producing larger lava flows. This volcanic activity took place mainly during Miocene (24.6-16.5 Ma). The lavas known on the Kozákov Hill were produced by much younger volcanic activity (6.7-3.5 Ma) and one of the studied locations is supposed to represent their feeder. The older Strombolian cones are relatively weakly affected by weathering processes. The erosional level at individual sites depends on geomorphology. On some of the edifices non-welded, poorly stratified scoriae are well preserved, at other sites a basal facies or upper vent facies were exposed by selective erosion. Interpretation of the exposed facies with the use of radiometric data brought new insight in relief evolution of this area. Erosion of Cretaceous marine deposits was very intensive during Oligocene, whereas during the last 17 M.y. only some 70 m of weak sediments were eroded.

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Late Miocene volcanic activity in the České středohoří Mountains (Ohře/Eger Graben, northern Bohemia)First occurrences of superficial bodies of Late Miocene volcanic activity were found in the western part of the České středohoří Volcanic Complex (CSVC) and extended our knowledge of its volcanostratigraphy. Their K-Ar ages (9.59, 9.61 and 11.36 Ma) correspond to the age of alkaline basaltic rocks of the youngest known Intrusive Suite of this area. Unlike the previously known subvolcanic bodies of this system, the newly observed bodies are represented by superficial products: two scoria cones with remnants of lava flows and one exclusive lava flow produced from a lava cone. The magmas forming all three occurrences are basanitic. Their primitive chemical composition Sr (0.70347-0.70361) and Nd (0.51279-0.51284) isotope ratios are similar to the products of the first and third volcanic formation of the CSVC. The proved existence of superficial products of the youngest volcanic formation, together with clear superposition relations to sedimentary formations and the chemical character of the youngest magmas in the central part of the Ohře (Eger) Graben support the stratigraphic scheme of volcanic activity in the České středohoří Mts. The eruptive style of the youngest formation volcanoes was purely magmatic (Strombolian) with no phreatic influence.

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A well-preserved set of mid-Miocene scoria-and tuff-cones and their feeders crops out in the Jičín Volcanic Field, Czech Republic. The Trosky volcano is a scoria cone that has been eroded to reveal the volcano's feeder system. This edifice offers the opportunity to improve the understanding how magma is transported through a monogenetic pyroclastic cone. Physical volcanology, petrology, anisotropy of magnetic susceptibility (AMS) and paleomagnetic data were combined to study of the erosional remnant of the Trosky volcano. Selective erosion has exposed spectacular remnants of a twin scoria cone intruded by late volcanic spines. These spines host a medieval castle that is a landmark of the Bohemian Paradise area in northeast Czech Republic. Paleomagnetic and AMS samples were collected from 29 sites, including the conduits, lava flows, and dikes intruding the conduits. The AMS data reveal magmatic flow directions that were variable, vertical (upward and downward) as well as subhorizontal (into and away from the volcano). Paleomagnetic data from the conduits and lava flows yield reverse polarity directions that are statistically indistinguishable from the expected mid-Miocene reverse polarity field direction. The dikes, however, show both normal and reverse polarity magnetizations that are statistically distinct from the expected field direction. We documented significant compositional variability of lavas erupted from the Trosky volcano, in contrast to the uniform composition of later plugs and dikes. The variability of lavas (olivine-rich, olivinepoor, clinopyroxene-rich and olivine-clinopyroxene equal types) suggests magma storage in a zoned shallow magma chamber (containing olivine-or clinopyroxene-depleted/enriched zones). The combined results and the presence of both normal and reverse polarity magnetizations from the dikes crosscutting the volcano indicate that this monogenic system was long-lived. Taken together, the simple external structure of monogenetic volcanoes often hides a rather complex magmatic plumbing system that dynamically evolves during their lifespan.

A variety of fossil woods occur on the northern margin of the Doupovské hory Volcanic Complex in the northwestern part of the Czech Republic. The woods were buried by three different processes reflecting three different settings. First, a large area between the towns of Kadaň and Klášterec is covered by an up to 100 m thick sequence of lahar and debris avalanche deposits. These flows and avalanches gathered wood of Liriodendron, Lauraceae, Platanus, Cercidiphyllum, ?Craigia and Styracaceae from both the volcanic complex slopes and adjacent plains. Second, a rich assemblage of fossil woods with thermophilous elements such as Lauraceae and palms was preserved on the northern volcanic complex periphery by a Strombolian eruption of a monogenic cone. Third, a shallow lake formed to the side of the volcanic complex, where Platanus trunks were fossilized in the travertine. The wood of Liriodendron has never been previously recorded in the localities representing volcanic complex foothills, but is common in the local lahar deposits. This distribution leads us to hypothesize that Liriodendron forests dominated higher topographic levels of the Doupovské hory Volcanic Complex, reaching, but probably not exceeding 1000 m a.s.l.

Field observations, petrography, geochemical data and the results of K-Ar dating are presented for alkaline intrusions at the former township of Doupov (Duppau) in the central part of the Doupovské hory Volcanic Complex (DHVC). The Doupov Intrusive Complex (DIC) is a very limited in area (< 2 km 2 ) but is petrographically highly variable. Several phaneritic rock types have been identified, including clinopyroxenite (both the clinopyroxenite-dominated breccia and xenoliths in younger intrusive phases), essexite, sodalite-bearing monzodiorite, sodalite monzosyenite to nepheline-sodalite syenite, and highly mafic to felsic nephelinolites (melteigite-ijolite-urtite). These rocks are accompanied by vent breccias, and a thermal and metasomatic aureole with zones of pervasive phlogopitization. Phaneritic intrusions and their host rocks are cut by thin aphanitic dykes ranging from mafic alkaline lamprophyres to felsic trachytes and phonolites. All the intrusions are characterized by undersaturated alkaline compositions with high abundances of incompatible elements. Geochemical variations and also subtle differences in the isotopic compositions of Sr and Nd suggest that the less undersaturated essexitic rocks and sodalite syenitoids do not form a common evolutionary line with highly undersaturated nephelinolites. Nephelinolites are isotopically close to the "European Asthenospheric Reservoir" or the "Common Mantle Reservoir" compositions and interaction of their parental magmas with the continental crust was negligible. Magmatic evolution of nephelinolites with "dry" mineral assemblages was dominated by fractionation of clinopyroxene accompanied at the early stage by olivine, and later by titanite, magnetite and apatite. Essexite is isotopically more different though still within the field of mafic lavas from DHVC and other volcanic complexes in Central and Western Europe. Either its parental magma originated in heterogeneous mantle with more distinct lithospheric signature or this magma reacted with the continental crust during its ascent and fractionation. Sodalite monzosyenite displays significantly higher 87 Sr/ 86 Sr ratios and its parental magma probably interacted even more intensively with the crustal rocks. The K-Ar ages of phaneritic intrusive rocks from Doupov are c. 30-29 Ma. Intrusions are older than the tephrite-basanite and foidite lavas forming the upper parts of the DHVC. The rock association resembles that accompanying many carbonatite intrusions around the world. However, brecciation and high-temperature metasomatic overprint including the extensive phlogopitization may be related to ijolitic magma. Nevertheless, the presence of carbonatite at some deeper level cannot be excluded.