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  • 1985-1989  (13)
  • 1975-1979  (20)
  • 1965-1969  (13)
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  • 1
    Electronic Resource
    Electronic Resource
    Ein synthetisches Zwischenglied zwischen dioktaedrischen und trioktaedrischen Glimmern (1965)
    Springer
    Naturwissenschaften 52 (1965), S. 182-183 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00623240
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  • 2
    Electronic Resource
    Electronic Resource
    Synthetische Amphibole mit OH-Überschuß im System Na2O−MgO−SiO2−H2O (1969)
    Springer
    Naturwissenschaften 56 (1969), S. 414-415 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00593623
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  • 3
    Electronic Resource
    Electronic Resource
    High-pressure, high-temperature stability of surinamite in the system MgO-BeO-Al2O3-SiO2-H2O (1986)
    Springer
    Contributions to mineralogy and petrology 92 (1986), S. 113-127 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The MgAl surinamite end member, (Mg3Al3)[6]O[AlBeSi3O15], was synthesized in the requisite system with and without water. The new phase is monoclinic, space group P2/n, with a=9.881(1)Å; b=11.311(1) Å; c=9.593(1) Å; β=109.52(2)°. Refractive indices are n x=1.7015(20); n y=1.7035(20); n z=1.7055(20). The infrared spectrum shows characteristic differences against the structurally related and optically extremely similar phase sapphirine. Using the seeding technique, the preliminary stability field for MgAl surinamite was found to lie at high temperatures (≳650 °C) and high pressures (≳4 kbar). At lower temperatures breakdown takes place to hydrous assemblages of chlorite, talc, and chrysoberyl with kyanite or yoderite; at lower pressures chrysoberyl forms parageneses with sapphirine and cordierite. In crystal chemical terms the underlying principle for the stability of surinamite versus that of the low-pressure assemblages is the higher proportion of octahedrally coordinated Al in surinamite (75%). Following the same principle surinamite itself decomposes at still higher pressures to a paragenesis, in which all Al enters octahedral coordination (pyrope+a chrysoberyl-type phase and some unidentified X-ray peaks). The stability field of synthetic MgAl surinamite is in good agreement with P, T-estimates of some 8–12 kbar, 800°–950° C as taken from the literature for the few occurrences of natural, Fe-bearing surinamite in granulite and upper amphibolite facies environments. The incorporation of iron in surinamite must be limited, because this mineral is known to coexist with its more iron-rich breakdown assemblage almandine-rich garnet+chrysoberyl. As the minimum melting curve of granite under hydrous conditions lies outside the surinamite field up to a water pressure of about 20 kbar, the absence of surinamite in normal granitic pegmatites can already be explained by physical constraints. However, there are probably also chemical constraints in the generally high Fe/Mg bulk chemistry of the pegmatite environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373969
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  • 4
    Electronic Resource
    Electronic Resource
    A miscibility gap in trioctahedral Mn-Mg-Fe chlorites: Evidence from the Lienne Valley manganese deposit, Ardennes, Belgium (1986)
    Springer
    Contributions to mineralogy and petrology 94 (1986), S. 333-342 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Low-temperature veinlets crosscutting low-grade manganiferous ironstones of Ordovician age contain four texturally distinct types of chlorites with nearly constant Al/Si-ratios that form two separate populations regarding their Mn/Mg/Fe-ratios: One with low iron contents (〈1.5 w.% FeO) and molar Mg/Mn-ratios just below unity (magnesian pennantites), the other with higher iron (7–11 w.% FeO) and Mg/Mn≳4 (manganoan clinochlores). The two populations, which can be distinguished readily by their characteristic optical elongation and dispersion colors, are intimately intergrown and have formed partly during consecutive stages of a chlorite crystallization sequence, partly by simultaneous growth and possibly even as exsolution products of a pre-existing homogeneous chlorite phase of intermediate composition. These findings indicate a miscibility gap in the chlorite solid solutions beginning along the binary Mg-Mn series and extending into the ternary system. There may be a solvus relationship with the miscibility gap closing at higher temperatures (400° C?). One very intensely colored chlorite type of the pennantite population may contain Fe3+ or Mn3+ or both. Additional minerals in the veinlets are spessartine, kutnahorite, quartz, and an allanite-piemontite phase. Crystallization began near the centers of the present veins with Mn-rich minerals and continued towards their edges and into the extremely thin ends of the developing fractures with the deposition of the more Fe-rich chlorites that are in equilibrium with the ironstone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371442
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  • 5
    Electronic Resource
    Electronic Resource
    New petrologic evidence for Hercynian metamorphism in the Venn-Stavelot Massif, Belgium (1975)
    Springer
    International journal of earth sciences 64 (1975), S. 819-830 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The basal quartzite (grit) of the Gedinne that overlies unconformably the Salmian of Ordovician age was found to contain a pebble of the typical garnetiferous Mn-rich coticules occurring in the Salmian. However, the metamorphic mineral assemblage Mn-rich garnet-chlorite-muscovite present in the pebble was also formed in the pelitic matrix of the quartzite itself and must, therefore, be due to a post-Gedinnian, Hercynian event of metamorphism. The garnets of the pebble and the matrix are of identical composition and free from chemical zoning, but they are richer in Fe than the spessartine of in situ coticules. This seems to indicate that the pebble did not contain any garnet at the time of its deposition thus ruling out any noteworthy degree of pre-Gedinne, i. e. Caledonian metamorphism. The temperature of the Hercynian metamorphism was about 400
    Abstract: Résumé On a trouvé dans le quarzite du Gedinnien un galet de « coticule » manganésifère à grenat, typique du Salmien (Ordovicien) sur lequel le quartzite repose en discordance. La paragenèse (grenat manganésifère-chlorite-muscovite) observée dans le galet est également celle de la matrice pélitique du quartzite, donc apparue lors d'une phase métamorphique postérieure au Gedinnien, c'est-à-dire Varisque (Hercynienne). Les grenats du galet et de la matrice ne sont pas zonés, ont la mÊme composition chimique, mais ils sont plus riches en fer que la spessartine du coticule en place. Il semble donc que, lors de son dépÔt, le galet n'ait pas contenu de grenat, ce qui exclut une phase métamorphique antérieure au Gedinnien, c'est-à-dire calédonienne. La température régnant lors de l'épisode métamorphique varisque était d'environ 400
    Notes: Zusammenfassung Im Basalquarzit des Gedinne, welcher diskordant das Salmien von ordovizischem Alter überlagert, wurde ein Geröll eines typischen granatführenden, Mn-reichen Coticules des Salmien gefunden. Die metamorphe Mineralparagenese Mn-reicher Granat-Chlorit-Muscovit des Gerölls war jedoch in gleicher Weise in der politischen Matrix des Quarzits selbst gebildet worden und mu\ daher auf einen Metamorphosevorgang nach dem Gedinne, also von varistischem (hercynischem) Alter zurückgehen. Die Granate des Gerölls und der Matrix haben die gleiche chemische Zusammensetzung und zeigen keinen Zonarbau, aber sie sind reicher an Fe als die Spessartine aus Coticules auf primärer Lagerstätte. Dies scheint darauf hinzuweisen, da\ das Geröll keinen Granat enthalten hatte zur Zeit seiner Ablagerung, was gegen eine frühere Metamorphose von prä-Gedinne, also kaledonischem Alter, spricht. Die Temperatur der varistischen Metamorphose lag um 400
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01820698
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  • 6
    Electronic Resource
    Electronic Resource
    Die Möglichkeit der Entstehung ultrabasischer Magmen bei Gegenwart geringer Alkalimengen (1968)
    Springer
    International journal of earth sciences 57 (1968), S. 349-362 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Mixtures of forsterite and enstatite show partial melting in the pressure range 1–5 kb at very low temperatures (approximately 550–700° C), if small amounts of K2O are added in the presence of excess H2O. Since alkalies and water are also expected to be minor constituents of the material forming the earth's mantle, they may cause, in this region, the formation of ultrabasic crystal mushes that may intrude into higher levels, i. e. the earth's crust. The presence of alkalies in ultrabasic melts before or during their emplacement may result in alkali metasomatism of the adjoining country rocks, because most of these alkalies are being incorporated at still lower temperatures in a gas phase leaving the intrusion.
    Abstract: Résumé On a trouvé qu'en présence de K2O et d'un excès d'eau des mélanges de forsterite et d'enstatite peuvent être fondues en partie à des températures très basses (550–700° C), sous une pression d'un à 5 kilobars. La présence des alkalis et de l'eau dans l'enveloppe pierreuse externe est probable. Conséquemment on pourrait supposer la formation de magmas d'ultrabasite par ces components dans l'enveloppe pierreuse externe. Ces magmas pourraient pénétrer dans des étages élevés. La présence des alkalis dans les magmas d'ultrabasite, avant et aussi bien au cours de la formation de ces dernières, pourrait se manifester par des métasomatoses d'alkali dans la roche encaissante, puisque à des températures encore plus basses les alkalis sont présents en phase volatile; cette phase peut quitter l'intrusion.
    Notes: Zusammenfassung Mischungen von Forsterit und Enstatit werden bei Zugabe von wenigen Prozent K2O in Anwesenheit eines Wasserüberschusses unter Drucken von 1 bis 5 Kilobar bereits bei sehr niedrigen Temperaturen (etwa 550–700° C) teilweise aufgeschmolzen. Da auch in den Gesteinen des Erdmantels die Gegenwart von Alkalien und Wasser zu erwarten ist, können diese Komponenten zur Bildung von Ultrabasit-Schmelzbreien im Oberen Erdmantel führen, welche in höhere Stockwerke, d. h. in die Erdkruste, intrudieren können. Die Anwesenheit von Alkalien in Ultrabasitschmelzen vor und während deren Platznahme kann sich durch Alkalimetasomatosen im Nebengestein äußern, da die Alkalien bei noch niedrigeren Temperaturen vorwiegend in eine leichtflüchtige Gasphase eingehen, welche die Intrusion verläßt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01821250
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  • 7
    Electronic Resource
    Electronic Resource
    Calcium-free pumpellyite, a new synthetic hydrous Mg–Al-silicate formed at high pressures (1986)
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 510-511 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During a recent high-pressure investigation of the system MgO-Al2O3-SiO2-H2O (MASH) aimed at synthesizing a Ti-free ellenbergerite3, reflections were encountered in the powder X-ray diffraction pattern that did not fit any of the known crystalline phases of the MASH system, nor could they be ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/321510a0
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  • 8
    Electronic Resource
    Electronic Resource
    Symplectitic cordierite-orthopyroxene-garnet assemblages as products of contact metamorphism of pre-existing basement granulites in the Vredefort Structure, South Africa, and their relations to pseudotachylite (1978)
    Springer
    Contributions to mineralogy and petrology 68 (1978), S. 53-62 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Former idioblastic garnet crystals of an Archaean granulite with Mg/(Mg+Fe+Mn)-ratios (= M) near 0.40 were converted to symplectitic pseudomorphs consisting mainly of cordierite (M=0.61), orthopyroxene (M=0.40), and a relic garnet with a new composition (M=0.18), during a static metamorphism which is related in time to the Vredefort event. On the basis of experimental data for the continuous reaction garnet+quartz=orthopyroxene+cordierite the conditions of metamorphism were near 5 kb, 700 °C. Orthopyroxenes crystallized initially as minute, myrmekitic grains with metastable excess Al contents up to 13 mol% Al2O3 and, through grain growth and Al exsolution, transformed into dense aggregates of coarser crystals with equilibrated compositions near 3 mol% Al2O3. In the absence of free silica hercynitic spinel appears as an additional phase that coexists with cordierite, orthopyroxene, and garnet of more magnesian compositions than in the case of silica saturation. Pseudotachylite veins crosscutting the hornfelsed granulite consist of pyroxene of variable Al contents, two feldspars, opaques, and quartz, and are finely recrystallized. There is textural and mineral chemical evidence from both the Al-contents of the pyroxenes and the Mg/Fe distribution among the phases adjacent to the pseudotachylite that these veins were emplaced late during the static metamorphism, which was probably caused by a local, deep-seated magma diapir. On this basis, the meteorite impact hypothesis for the origin of the Vredefort Structure is considered less likely than a mechanism of internal origin which can be made responsible for the close link in time and space between static metamorphism and the high strain rate deformation that produced the pseudotachylite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375446
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  • 9
    Electronic Resource
    Electronic Resource
    Natural boron-free kornerupine and its breakdown products in a sapphirine rock of the Limpopo Belt, Southern Africa (1976)
    Springer
    Contributions to mineralogy and petrology 54 (1976), S. 109-126 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Large crystals of boron-free kornerupine occurring in MgAl-rich inclusions within meta-anorthosites are partially replaced by symplectitic pseudomorphs consisting essentially of the assemblage sapphirine-cordieritegedrite. The highly magnesian, hydrous kornerupines (F= 0.10–0.14) have compositions close to the oxide ratio (Mg, Fe) O· Al2O3· SiO2. Sapphirines (F=0.09) show decreasing Al-contents with continued grain growth and equilibration. Gedrite (F=0.15) contains sodium in amounts near the limit of solid solution, although the kornerupine starting material is free of this element and it is very rare in the enclosing rock. Cordierite (F=0.05) is also free from sodium. For conditions of P H2O = P tot the appearance of boron-free kornerupine requires relatively high temperatures (〉 700 °C) and a minimum pressure near 4 kb within this zone of the Limpopo Belt. The subsequent replacement reaction occurred nearly isochemically except for Na and probably H2O, which were introduced into the symplectite. Textural features suggest that the breakdown reaction of kornerupine is actually governed by the magnitude of sodium activity: Relatively low values would favor the appearance of boron-free kornerupine, whereas higher values lead to the more common assemblage sapphirine-cordierite-gedrite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372118
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  • 10
    Electronic Resource
    Electronic Resource
    Three-stage metamorphic history of a whiteschist from Sar e Sang, Afghanistan, as part of a former evaporite deposit (1976)
    Springer
    Contributions to mineralogy and petrology 59 (1976), S. 111-130 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Small volumes (in the cm3 range) of a talc-kyanite schist exhibit mosaic equilibria characterized by mineral assemblages conventionally attributed to vastly different pressure temperature conditions of metamorphism. On the basis of petrographic and microprobe studies these assemblages are attributed to three consecutive stages of metamorphism of a chemically exceptional rock composition falling largely into the model system MgO-Al2O3-SiO2-H2O. Stage 1 typified by Mg chlorite-quartz-talc and some paragonite was followed during stage 2 by talc-kyanite, Mg gedrite-quartz, and the growth of large dravites. In stage 3 pure Mg cordierite formed with or without corundum and/or talc, and kyanite was partly converted into sillimanite. Pressures and temperature during this final stage of metamorphism were probably near 5–6 kb, 640 ° C. The preservation of this succession of mineral assemblages related to each other through isochemical reactions suggests that the main factors governing the metamorphic history of this whitheschist were compositional changes of the coexisting fluids with time, whereas pressure temperature variations may be subordinate. In the Sar e Sang area such chemical variations of the metamorphic fluids are probably caused by progressive metamorphism and mobilization of a former evaporite deposit. Microprobe analyses of the phases gedrite and talc indicate variable degrees of sodium incorporation into these phases according to the substitution NaAl→Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371302
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