ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (22)
  • 1975-1979  (20)
  • 1965-1969  (13)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and properties of Mn-bearing yoderite and of Mn-bearing kornerupine as by-product (1993)
    Springer
    Mineralogy and petrology 48 (1993), S. 115-128 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Die Synthese von Yoderiten mit chemischen Zusammensetzungen nahe denjenigen der natürlichen, blau gefärbten Varietät gelang in Ausbeuten bis zu 95% aus Gelen bei hohen Versuchsdrücken (15, 16 kbar) und Temperaturen von 650 bzw. 800°C. Die Sauerstoffugazität wurde durch den Puffer Mn2O3/MnO2 kontrolliert. Aus Mikrosondenanalysen und Wasserbestimmungen wurden folgende chemische Formeln von Yoderit bestimmt: Mg1.90(Al6.01Fe3+ 0.28Mn3+ 0.11)Σ=6.40Si3.80O18.21(OH)1.79 and Mg1.86(Al5.77Fe3+ 0.36Mn3+ 0.04)Σ=6.17Si4O18.20(OH)1.80. Die Stabilisierung der Yoderitstruktur allein durch Mangan wurde durch die Synthese manganhaltigen, aber eisenfreien Yoderits, Mg1.85(Al6.26Mn3+ 0.10)Σ=6.36Si3.91O18.15(OH)1.85 belegt. Sämtliche synthetisierten Yoderite besitzen die typische dunkelblaue Farbe, wie sie vom natürlichen Mineral bekannt ist, und zeigen einen Pleochroismus von dunkelblau ‖ b zu farblos ⊥ b. Dies unterstützt die ursprüngliche auf spektroskopischen Untersuchungen basierende Vermutung, daß Mangan für die blaue Farbe von Yoderit verantwortlich ist. Im Vergleich zu Eisen wird Mn3+ in geringerem Ausmaß in die Yoderit-struktur eingebaut, wobei die hier erreichte maximale Menge von 0.11 Mn3+ p.F.E. unter derjenigen der natürlichen Yoderite von Mautia Hill, Tansania, liegt (dort 0.15 Mn3+ p.F.E.). In einigen Versuchsprodukten koexistierte mit Yoderit auch Fe-Mn haltiger Kornerupin, der einen ausgeprägten Pleochroismus von dunkelgrün ‖ b zu hellrot ‖ c besitzt. Kornerupin enthält im Vergleich zu Yoderit mehr Mangan. Chemische Analysen dieser Phase belegen den Einbau von zweiwertigem Mangan, obwohl wahrscheinlich Spuren von Mn3+ die Farbe von Kornerupin verursachen. Mit Yoderit koexistierender Braunit besitzt Mg und Al, die für Mn2+ bzw. Mn3+ substituiert wurden. Trotz hoher Sauerstoffugazität enthält Granat, der aus einem Fe-freien Gel erhalten wurde, ausschließlich zweiwertiges Mangan und stellt einen Mischkristall zwischen Pyrop und Spessartin dar (Py79Spess21).
    Notes: Summary Yoderite with compositions close to those of the natural purple variety were synthesized from gels at high water pressures (15–16 kbar) and temperatures (650, 800°C) at the oxygen fugacities of the Mn2O3/MnO2-buffer with yields up to 95%. Chemical formulae based on microprobe data and water analyses are Mg1.90(Al6.01Fe3+ 0.28Mn3+ 0.11)Σ=6.40Si3.8O18.21(OH)1.79 and Mg1.86(Al5.77Fe3+ 0.36Mn3+ 0.04)Σ=6.17Si4O18.20(OH)1.80. Manganiferous, but iron-free yoderite with the formula Mg1.85(Al6.26Mn3+ 0.10)Σ=6.36Si3.91O18.15(OH)1.85 was also obtained and proves that Mn3+ alone may stabilize the yoderite structure, although this does not necessarily imply thermodynamic-stability. All these synthetic yoderites exhibit the typical purple color known from the natural mineral with pleochroism of dark blue ‖ b to colorless ⊥ b, which confirms the earlier spectroscopic conclusion that Mn is responsible for the purple color of yoderite. Compared to ferric iron, Mn3+ is incorporated into yoderite in much smaller amounts, although the maximum attained here (0.11 p.f.u.) is still below the 0.15 found in new analyses of natural yoderite from Tanzania. In some runs yoderite coexisted with kornerupine containing Mn and Fe as well and showing spectacular pleochroism from dark green ‖ b to light red ‖ c. Relative to yoderite Mn is fractionated into kornerupine. The analytical data suggest that most of the manganese is incorporated as Mn2+, although some Mn3+ may be the reason for the color. Coexisting braunite contains high amounts of Mg and Al substituting for Mn2+ and Mn3+, respectively. Garnet obtained from the Fe-free gel contains only Mn2+ and has the end member composition Pyrope79Spessartine21 despite high oxygen fugacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01163091
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Potassic cordierites: characteristic minerals for high-temperature, very low-pressure environments (1990)
    Springer
    Contributions to mineralogy and petrology 105 (1990), S. 162-172 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The mineral chemistry of cordierites from three different sanidinite facies localities-1) volcanic xenoliths from the Eifel, Germany; 1) buchites of the Blaue Kuppe, Germany; 3) paralavas from the Bokaro coalfield, India-is characterized by unusually high potassium contents up to 1.71 wt%, equivalent to 0.22 K atoms per formula unit (p.f.u.) based on 18 oxygens. Significantly, these cordierites are either hexagonal highcordierites (indialites) with Δ=0 or exhibit intermediate Δ-values 0〈Δ〈0.20 relative to well Al,Si-ordered orthorhombic low-cordierite. Based on microprobe analyses, the predominant substitutional mechanism for alkali incorporation is Alk[Channel]+Al[4] for □+Si[4], thus leading to Al/Si-ratios deviating considerably from the value 4:5 in ideal cordierite M2[Al4Si5O18]. The most highly substituted cordierite from Blaue Kuppe is about (K0.22Na0.07)[Ch](Mg1.33Fe 0.66 2+ )[6][Al4.16Si4.79O18]. Bokaro cordierites are further characterized by obvious (Al+Si)-deficiencies against the ideal value of 9.0 p.f.u., a tendency of which is apparent in most Blaue Kuppe analyses as well. As the tetrahedral deficiencies are often equivalent to excess cations in the octahedra, we assume that ferric iron fills up the remaining tetrahedral sites, again linked with the introduction of potassium according to K+Fe3+ for □+Si. In comparison with the available experimental data, these natural potassic cordierites are considered stable high-temperature phases regarding their compositions, but not their structural states. Although the substitution KAl for Si in Mg-cordierite is known to lower the maximum Δ-value to be attained, the hexagonal nature of the cordierites must be due to very rapid crystallization and subsequent quenching. The higher Δ-values of the Blaue Kuppe cordierites might be caused by their topotactic origin from preexisting biotite. The complicated twin and domain patterns of the hexagonal Eifel and Bokaro cordierites as observed in thin section could perhaps be attributed to structural modulations as postulated recently for hexagonal cordierite shortly after its growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678983
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Zn-rich högbomite formed from gahnite in the metabauxites of the Menderes Massif, SW Turkey (1993)
    Springer
    Contributions to mineralogy and petrology 113 (1993), S. 314-324 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Gahnite, ZnAl2O4, present as an accessory mineral in regionally metamorphosed low-grade diasporites, has reacted in adjacent higher-grade, corundum-bearing metabauxite equivalents (emeries) to form Zn-rich högbomite, (Zn,Fe2+,Mg,Ni)t-2x (Ti,Sn)xAl2O4, of the 4H polytype. Commonly, the initial högbomite crystals grew epitactically along the octahedral faces of gahnite, which was subsequently dissolved, so that högbomite now forms spectacularly intergrown sets of eight crystals in perfect crystallographic orientation to each other. This indicates a metamorphic reaction, probably involving a fluid, transporting mainly the elements Zn and Al. Reactant Ti minerals in the diasporites were rutile and titanian hematite (10–15 mol% FeTiO3). In the emeries högbomite coexists with still more Ti-rich hematites containing between 26 and 37 mol% FeTiO3. The overall reaction relations involving partial reduction may be subdivided into the intial univariant reaction, gahnite+diaspore+Ti-hematite+rutile=högbomite+H2O+O2. This was followed, in the absence of gahnite, by compositional readjustments of högbomite and Ti-hematite and the appearance of magnetite. Core to rim zoning profiles indicate that, with continued growth, the högbomite crystals became poorer in Zn and Ti, but richer in Fe2+, while the Ti-contents of coexisting hematite increased. Högbomite formation at the expense of gahnite started at temperatures as low as about 400° C for an estimated pressure of 5–6 kbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286924
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...