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  • 1
    Electronic Resource
    Electronic Resource
    Book reviews (1989)
    Springer
    Bulletin of volcanology 51 (1989), S. 311-312 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073519
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Gross Brukkaros (Namibia)—an enigmatic crater-fill reinterpreted as due to Cretaceous caldera evolution (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 386-397 
    Details
    ISSN: 1432-0819
    Keywords: caldera ; crater sediments ; debris-flow alluvial fan delta ; Gross Brukkaros
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract At Gross Brukkaros a central depression has developed within domed Nama Group sediments and has functioned as a local depocenter, with a primary fill deposited during the Cretaceous and a small secondary fill by alluvial fans during the Tertiary and Quaternary. The diameter of the entire structure is about 10 km and that of the central depression is about 3 km. Within this depocenter the sedimentary sequence consists mainly of debris-flow and mudflow deposits, with minor intercalations of fluviatile (braided channel) sediments and fossiliferous lacustrine deposits. The sedimentary system represents a set of coalesced subaerial fans which formed a fringing sedimentary apron along the margin of the depocenter. This sedimentary apron passed distally and centrally into a permanent lake, which was characterized by a fluctuating water level. Facies transitions observed are typical of those described from modern and ancient fan delta systems. Contact relationships show the Gross Brukkaros sediments to be about the same age (Upper Cretaceous) as the surrounding carbonatitic volcanism. An Upper Cretaceous age is also consistent with the plant fossil association recently recognized within the lacustrine beds of Gross Brukkaros. We attribute the genesis of the dome structure to the shallow intrusion of a laccolith-shaped, strongly alkaline to carbonatitic magma body. Subsequent depletion of the reservoir due to volcanic activity around and in(?) Gross Brukkaros led to subsidence resulting in the development of the Gross Brukkaros depocenter. Differences between Gross Brukkaros and the general caldera model consist of a radially oriented dike pattern and the formation of the caldera by downsagging rather than cauldron subsidence, as derived from the absence of ring faults and ring dikes. The first (radial dikes) may be attributed to comparatively strong initial doming; the latter (lack of ring faults) to the small size of the caldera, its incremental subsidence, and finally the sedimentary wall rocks instead of a rigid crystalline crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326464
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  • 3
    Electronic Resource
    Electronic Resource
    Vesiculated tuffs and associated features (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 21 (1974), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Vesiculated tuffs are tuffs that contain vesicles between the ash particles. Formation of the vesicles is the result of trapping of steam, the transporting agent of volcanic base surges, in wet, muddy or sticky ash deposited by the base surges. Vesiculated tuffs are described from various maars and tuff-rings in Europe (Iceland, France, Germany) and USA together with associated surface features such as: gravity flowage ripples, mud flow channels, current ripples, and current ridges. Other features described are: plastering of ash against obstacles and vesiculated accretionary lapilli, the latter containing vesicles in the outer layer.Vesiculated base surge deposits probably contained as much as 20–30% of interstitial water and fell out of the base surge clouds en masse owing to non-free flow and consequent accretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1974.tb02059.x
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of thermal conductivity of natural silicate melts (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1810-1812 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cooling of natural silicate melts and energy transfer to the environment are controlled by the temperature-dependent thermal conductivity. We describe a method that allows a correlation between temperature-dependent strain rate and a bulk temperature during a cooling or heating process under quasisteady state conditions in a Newtonian flow regime. A rotational viscometer measured data for experimental cooling curves of remelted volcanic rock materials. From these data we can calculate the thermal conductivity of an unknown melt after we calibrate the setup with a melt of known thermal conductivity as a by-product of viscosimetry. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311815
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  • 5
    Electronic Resource
    Electronic Resource
    On the growth of maars and diatremes and its relevance to the formation of tuff rings (1986)
    Springer
    Bulletin of volcanology 48 (1986), S. 265-274 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Small and large maars exist associated with small and large diatremes, respectively, their subsurface feeder structures. The problem of size and growth of maar-diatreme volcanoes is discussed from a phreatomagmatic point of view from field data, some geophysical data, and short-lived historic maar eruptions. A hydrostatic pressure barrier of usually about 20–30 bars is assumed to control the maximum depth level of explosive magma/groundwater interactions. Similar to the situation in submarine and subglacial volcanism, initial maar-forming water vapour explosions are therefore assumed to occur at shallow depth and to produce a small maar with a shallow diatreme. Because of limited availability of groundwater and ejection of groundwater in the form of steam, the confining pressure barrier is displaced downward. Consequently, water vapour explosions can take place at consecutively deeper levels with the result that the diatreme penetrates downward and grows in size. Since maars are collapse craters resulting from ejection of wallrocks fragmented by water vapour explosions at the level of the diatreme root zone, downward penetration of a diatreme not only results in increase in size of a diatreme but also in increase in size of the overlying maar. As availability of groundwater in limited amounts controls formation of diatremes and their downward penetration, lack of groundwater enables magma to rise within a diatreme and to form a scoria cone or lava lake within the maar, as is frequently found in volcanic fields such as the Eifel area in Germany. In contrast, availability of large amounts of water in near surface environments such as shallow marine, lake, water-rich coastal plains, or water-rich fluviatile gravel beds prevents formation of maars and deep diatremes but causes formation of tuff rings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081755
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  • 6
    Electronic Resource
    Electronic Resource
    Gross Brukkaros (Namibia) – an enigmatic crater-fill reinterpreted as due to Cretaceous caldera evolution (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 386-397 
    Details
    ISSN: 1432-0819
    Keywords: Key word caldera ; crater sediments ; debris-flow ; alluvial fan delta ; Gross Brukkaros
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract At Gross Brukkaros a central depression has developed within domed Nama Group sediments and has functioned as a local depocenter, with a primary fill deposited during the Cretaceous and a small secondary fill by alluvial fans during the Tertiary and Quaternary. The diameter of the entire structure is about 10 km and that of the central depression is about 3 km. Within this depocenter the sedimentary sequence consists mainly of debris-flow and mudflow deposits, with minor intercalations of fluviatile (braided channel) sediments and fossiliferous lacustrine deposits. The sedimentary system represents a set of coalesced subaerial fans which formed a fringing sedimentary apron along the margin of the depocenter. This sedimentary apron passed distally and centrally into a permanent lake, which was characterized by a fluctuating water level. Facies transitions observed are typical of those described from modern and ancient fan delta systems. Contact relationships show the Gross Brukkaros sediments to be about the same age (Upper Cretaceous) as the surrounding carbonatitic volcanism. An Upper Cretaceous age is also consistent with the plant fossil association recently recognized within the lacustrine beds of Gross Brukkaros. We attribute the genesis of the dome structure to the shallow intrusion of a laccolith-shaped, strongly alkaline to carbonatitic magma body. Subsequent depletion of the reservoir due to volcanic activity around and in(?) Gross Brukkaros led to subsidence resulting in the development of the Gross Brukkaros depocenter. Differences between Gross Brukkaros and the general caldera model consist of a radially oriented dike pattern and the formation of the caldera by downsagging rather than cauldron subsidence, as derived from the absence of ring faults and ring dikes. The first (radial dikes) may be attributed to comparatively strong initial doming; the latter (lack of ring faults) to the small size of the caldera, its incremental subsidence, and finally the sedimentary wall rocks instead of a rigid crystalline crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326464
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  • 7
    Electronic Resource
    Electronic Resource
    Premixing of magma and water in MFCI experiments (1997)
    Springer
    Bulletin of volcanology 58 (1997), S. 491-495 
    Details
    ISSN: 1432-0819
    Keywords: Key words Explosive volcanism ; Experimental volcanology ; Water ; melt interaction ; Premixing conditions ; Volcanic MFCI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Experimental studies have been performed to evaluate pre-explosive water–melt mixes with respect to explosive volcanic molten–fuel–coolant interaction (MFCI), i.e., phreatomagmatic explosion. Remolten ultrabasic volcanic rock was used as a magma simulant. Measurement of the explosion intensity was used to determine optimal premixing conditions. A well-defined optimal range was found for the hydrodynamic mixing energy (differential flow speed of 4.2 m/s), as well as for the water/melt mass ratio (0.03 to 0.04) under experimental conditions. The mass flux of water had a minor influence on the explosion intensity. Additionally, transparent mixing experiments with silicon oil and inked water were carried out. They indicate a direct dependence of the pre-explosive water-melt interface area on the explosion intensity. The experimental results show that the contact conditions of water and melt required for explosive MFCI may easily be established in natural volcanic systems. Thus, explosive MFCI is a probable mechanism of explosive volcanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050157
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  • 8
    Electronic Resource
    Electronic Resource
    Origin and crystallization history of Permian tholeiites from the Saar-Nahe trough, SW Germany (1973)
    Springer
    Contributions to mineralogy and petrology 40 (1973), S. 327-344 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Hirschberg and Rödern diatremes, within the Permian Saar-Nahe trough, SW Germany, are composed chiefly of basaltic tuffs, with associated small intrusions of K-rich tholeiites. Several tholeiite bodies carry 2–20 mm crystals of magnesian clinopyroxene and orthopyroxene, the latter containing up to 5.5% Al2O3 and often extensively resorbed and rimmed by fine-grained olivine and clinopyroxene. Experimental duplication of these pyroxenes has been achieved under conditions of Pload=6–10 kb, T=1280–1080° C and 2–4 wt.-% H2O, confirming that they represent a rare occurence of high pressure phenocrysts in tholeiitic basalts. These conditions of pyroxene crystallization also place constraints on processes of magma generation, indicating that the tholeiites originated by partial melting of unusually hydrous peridotite mantle (0.4–0.8% H2O) beneath a relatively thin continental crust (maximum thickness approximately 30 km). Water present in the mantle at the site of magma generation may have been derived from the dehydration of oceanic lithosphere prior to the formation of the Saar-Nahe trough. This lithosphere probably underwent subduction at the margin of the Palaeozoic European continent during the Hercynian cycle of sedimentation, andesitic volcanism and folding. The termination of this cycle was followed by a period of basin-range type tensional faulting, leading to the formation of the Permian basins of present-day Central Europe, and widespread bimodal basalt/rhyolite volcanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371023
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  • 9
    Electronic Resource
    Electronic Resource
    Synthese und Eigenschaften von Di(tert-butylcyclopentadienyl)-magnesium. (Mit Bemerkungen zum Di(methylcyclopentadienyl) magnesium) (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 591 (1990), S. 195-198 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Properties of Di(tert-butylcyclopentadienyl)magnesium (With a Comment on Di(methylcyclopentadienyl)magnesium)Di(tert-butylcyclopentadienyl)magnesium (I) can be obtained easily and with good yields from diethylmagnesium and tert-butylcyclopentadiene. The synthesis of di(methylcyclopentadienyl)magnesium (II) was reproduced and differences in bibliography were cleared up. (CH3C5H4)2Mg · TMED (III) is formed from II whereas I does'nt form complexes, apparently from steric reasons. I-III were characterized by their 13C-n.m.r. spectra.
    Notes: Di(tert-butylcyclopentadienyl)magnesium (I) wurde aus Diethylmagnesium und tert-Butylcyclopentadien in reiner Form gewonnen. Weiterhin wurden Angaben zur Darstellung von Di(methylcyclopentadienyl)magnesium (II) überprüft und damit Widersprüche in der Literatur geklärt. Von II wurde das Addukt (CH3C5H4)2Mg · TMED (III) gewonnen, während I offensichtlich aus sterischen Gründen nicht zur Komplexbildung befähigt ist. I-III wurden durch ihre 13C-NMR-Spektren charakterisiert.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19905910123
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  • 10
    Electronic Resource
    Electronic Resource
    Synthese, Eigenschaften und Kristallstrukturen von Magnesium-Diazadien-Komplexen (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 691-696 
    Details
    ISSN: 0044-2313
    Keywords: Magnesium complexes ; diazadiene ligands ; radical anions ; endiamides ; X-ray structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Properties and Crystal Structures of Magnesium Diazadiene ComplexesReactions of phenyl-substituted 1,4-diaza-1,3-butadienes (DAD) RN=CPh—CPh=NR (R = C6H5) 1a, C6H4-4-CH3 1b, C6H4-4-OCH3 (1c) with magnesium in dimethoxyethan lead to complexes of the type [Mg(DAD)2(DME)] 2a-c, with DAD ligands in form of radical anions. Furthermore, highly reactiv complexes of the composition [Mg(DAD)(DME)2] 3a-c could be obtained. The crystal structures of 2a, 3a and 3c were determined.
    Notes: Die Reaktion phenylsubstituierter 1,4-Diaza-1,3-butadiene (DAD) RN=CPh—CPh=NR (R = C6H5 1a, C6H4-4-CH3 1b, C6H4-4-OCH3 1c) mit Magnesium in Dimethoxyethan (DME) führt zu Verbindungen des Typs [Mg(DAD)2(DME)] 2a-c, in denen die DAD-Liganden als Radikalanionen gebunden sind. Außerdem enstehen äußerst reaktive Komplexe der Zusammensetzung [Mg(DAD)(DME)2] 3a-c. Die Kristallstrukturen von 2a, 3a und 3c wurden aufgeklärt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200418
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