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
  • 1980-1984  (33)
  • 1965-1969  (13)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Osumilith in der Eifel und die Verwendung dieses Minerals als petrogenetischer Indikator (1983)
    Springer
    Mineralogy and petrology 31 (1983), S. 215-234 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Summary Osumilites from 5 quaternary volcanoes of the Eifel, West Germany, were investigated. They occur within contact-metamorphosed xenoliths, mostly in vesicles as deposits from the gas phase, in one case as porphyroblasts within the rock formed at depth. 6 out of 7 osumilites analyzed show M=Mg/(Mg+Fetot+Mn)-values between 0.66 and 0.86, the porphyroblastic osumilite being the richest in Mg. One osumilite, which has optically negative character and unusually small cell edges, shows M=0.17 and is the most iron-rich osumilite known thus far; in addition, it has the lowest alkali content ever reported. Alkali deficiencies of osumilites seem to be predominantly due to the substitution □+Fe3+→(K,Na)++Fe2+. A histogram of all M-values of osumilites taken from the literature shows practically a complete series of Mg−Fe solid solution in which the deep-seated osumilites formed at high pressure are invariably very Mg-rich magnesio-osumilites, while all ferro-osumilites are of near-surface origin under low pressures. This indicates that the PT-stability range of magnesio-osumilite is considerably larger than that of ferro-osumilite, similarly as for the structurally related series of Mg−Fe-cordierites. Alkali deficiencies in osumilites are not always linked to high total iron contents; they are also observed in Mg-enriched osumilites though never in those formed at high pressures. Probably the alkali-deficiencies are indicators of relatively high oxygen fugacities as they are typical for the Eifel volcanic environment and evidenced by accompanying minerals like hematite, pseudobrookite, and acmitic pyroxenes.
    Notes: Zusammenfassung Osumilithe aus 5 quartären Vulkanen der Eifel wurden untersucht. Sie kommen in kontaktmetamorph veränderten Nebengesteinseinschlüssen (Xenolithen) vor, und zwar meist in Drusenräumen als Abscheidung aus der Gasphase, in einem Fall auch als porphyroblastischer, intratellurisch gebildeter Gefügebestandteil des festen Gesteins. 6 von 7 analysierten Osumilithen zeigen M=Mg/(Mg+Fetot+Mn)-Werte zwischen 0,66 und 0,86, wobei der intratellurische Osumilith der Mg-reichste ist. Ein optisch negativer Osumilith mit kleineren Gitterkonstanten und dem M-Wert von 0,17 ist das bisher Fe-reichste Glied der Reihe, das auch außerdem den niedrigsten bisher bekannten Alkaligehalt aufweist. Alkali-Defizite in Osumilithen scheinen vorwiegend auf die Substitution □+Fe3+→(K,Na)++Fe2+ zurückzugehen. Ein Histogramm aller M-Werte von Osumilithen aus der Literatur zeigt praktisch eine durchgehende Mg−Fe-Mischreihe, in der intratellurische Osumilithe, besonders die bei hohem Druck gebildeten, immer sehr Mg-reiche Magnesio-Osumilithe sind, während alle Ferro-Osumilithe oberflächennahe Bildungen unter niedrigem Druck darstellen. Hieraus ist zu folgern, daß das PT-Stabilitätsfeld von Magnesio-Osumilith beträchtlich größer ist als dasjenige von Ferro-Osumilith, ähnlich wie dei der strukturell ähnlichen Reihe der Mg−Fe-Cordierite. Alkali-Defizite im Osumilith sind keinesfalls immer mit hohem Fetot-Gehalt verknüpft; sie kommen auch in Mg-reicheren Gliedern der Osumilithreihe vor, allerdings nie in intratellurisch, unter hohem Druck gebildetem Material. Wahrscheinlich sind die Alkali-Defizite Indikatoren für relativ hohe Sauerstoff-Fugazitäten, wie sie für das vulkanische Milieu der Eifel typisch und durch Begleitminerale wie Hämatit, Pseudobrookit und akmitische Pyroxene auch erwiesen sind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081370
    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
    CO2-rich fluid inclusions along planar elements of quartz in basement rocks of the Vredefort Dome, South Africa (1981)
    Springer
    Contributions to mineralogy and petrology 77 (1981), S. 93-100 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Along a NW-SE profile through the basement core, starting below the sedimentary unconformity and ending in the center of the nearly circular structure, the constituent quartz grains and their fluid inclusions exhibit the following characteristics: In the NW, fluid inclusions composed of CO2 and occasionally up to 50 Vol.% H2O occur along shock-induced planar elements following predominently {0 0 0 1} of coarse, largely unrecrystallized quartz grains. The planar elements are partly still open microcracks, partly they are healed, the fluid inclusions decorating the former sites of the cracks. Along these planar elements recrystallization into fine grained new quartz fabrics starts, this process increasing decidedly towards the southeast; nevertheless fluid inclusions are still retained. — Near and within the center of the dome the formerly coarse quartz grains are completely recrystallized to medium grained annealing fabrics, in which — surprizingly — the fluid inclusions have often retained their original positions relative to the old grains, so that their planar alignment now traverses the new grain boundaries. Here the enclosed fluid is pure CO2 as far as can be determined. On the basis of the homogenization temperatures of the fluid inclusions measured, and of independent petrologic geothermometry of the basement rocks near the center, the fluids trapped after the shock event had exhibited partial pressures of CO2 as high as 3 kbars at temperatures around 850° C. The derivation of these CO2-rich, post-shock fluids is either through release of older fluid inclusions from the lower crustal granulites affected by the catastrophic shattering event, or it is from a direct mantle source that might be genetically connected with the Vredefort event itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636513
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    High-magnesium staurolite in a sapphirine-garnet rock from the Limpopo Belt, Southern Africa (1984)
    Springer
    Contributions to mineralogy and petrology 86 (1984), S. 200-207 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Unusually Mg-rich staurolite with F=Fe/(Fe+ Mg) = 0.51 occurs in a peraluminous silica-deficient sapphirine-garnet-gedrite-spinel-corundum-phlogopite rock as relic inclusions within pyrope-almandine garnet (F=0.43–0.48), from which it is generally separated by sapphirine (F=0.19). Gedrite has F=0.24–0.27, phlogopite 0.19, and spinel 0.43. The gradual disappearance of staurolite is due to a shift of the 3-phase AFM assemblage staurolite-garnetsapphirine to more Fe-rich compositions according to probably prograde reactions between staurolite and garnet to form sapphirine together with either quartz or gedrite. Thus still more Mg-rich staurolite seems to have existed in the rock at earlier stages of metamorphism characterized by lower temperatures and perhaps higher pressures. The local equilibria now frozen in indicate minimum pressures of 7–8 kbar and temperatures in excess of about 800° C. Staurolite is free from Zn, very low in Si, and richer in Ti than any other staurolite found thus far. Most notable is the unique Mg/Fe fraction between staurolite and garnet with staurolite being the more Fe-rich phase (KD=1.32).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381847
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Fuchsite-aluminium silicate rocks in archaean greenstone belts: Are they metamorphosed alunite deposits? (1982)
    Springer
    International journal of earth sciences 71 (1982), S. 347-360 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract For the origin of fuchsite- and alusite-corundum rocks occurring as lenses within ultramafic schists at O'Briens, Zimbabwe, a model is presented, according to which an ultramafic komatiite flow is altered locally, during postvolcanic near-surface processes, anto chromiferous alunite, that in turn broke down, during subsequent low-grade metamorphism, into fuchsite, or andalusite, or ruby, or assemblages thereof, depending on the availability of silica and on solution chemistry. Pseudomorphs of corundum and andalusite after preexisting euhedral alunite, or after other minerals with alunite structure, support this model. Fuchsite-kyanite- and alusite-quartz schists from the Yilgarn Block of Western Australia forming conformable layers in metasediments may also have originated from alunitequartz rocks, but no textural evidence could be provided. However, in neighboring kyanite- and alusite quartzites the typical cross sections of leached out alunite-group minerals as well as the mineral natrojarosite were discovered within the metamorphic quartz fabric, which appears to indicate that alunite-type minerals coexisted during metamorphism with quartz and kyanite. Alunite-bearing sedimentary educts are not necessarily of postvolcanic origin but may also form under specila climatic conditions.
    Abstract: Résumé Un modèle est présenté qui explique la genèse de roches à fuchsite- and alousite-corindon apparaissant en lentilles dans des schistes ultramafiques à O'Briens, Zimbabwe: une coulée de komatiite ultramafique aurait été altérée localement en alunite chromifère, en relation avec des phénomènes postvolcaniques superficiels. L'alunite se serait, à son tour, décomposée en fuchsite, andalousite ou rubis ou en assemblage de ces phases, selon la teneur en silice de la roch et la composition des solutions mises en jeu. La présence de corindon et d'andalousite qui pseudomorphosent des alunites automorphes ou d'autres minéraux de structure équivalente fournit un argument supplémentaire en faveur de ce modèle de genèse. Les schistes à fuchsite-disthène- and alousite-quartz du bloc de Yilgarn en Australie Occidentale, qui forment des lits concordants dans des métasédiments, pourraient eux aussi s'être développés à partir de roches à quartz et alunite; malheureusement, l'examen de la texture de ces schistes ne fournit aucune indicaiton dans ce sens. Cependant, on a trouvé dans des quartzites à andalousite et disthène avoisinants des quartzites à andalousite et disthène avoisinants des empreintes de sections basaless typiques de minéraux du groupe de l'alunite (ces minéraux étant dissous) et de la natrojarosite, inclus dans la matrice quartzitique métamorphique; celi semble indiques que, pendant l'épisode métamorphique, des minéraux du type de l'alunite coexistaient avec le quartz et le disthène. Les matériaux sédimentaires originels à alunite ne sont pas obligatoirement des produits d'altération post-volcanique; ils paurraient aussi avoir été formés dans ces conditions climatiques particulières.
    Notes: Zusammenfassung Ein Entstehungsmodell wird vorgeführt für Fuchsit-Andalusit-Korund-Felse, welche in Zimbabwe als Linsen in ultramafischen Schiefern vorkommen. Danach wurde ein ultramafischer Komatiitstrom lokal im Zuge postvulkanischer, oberflächennaher Prozesse in chromführenden Alunit umgewandelt, welcher seinerseits während der anschließenden niedriggradigen Metamorphose abgebaut wurde zu Fuchsit oder Andalusit oder Korund oder Paragenesen aus diesen je nach dem Vorhandenseit von SiO2 und der Zusammensetzung der koexistierenden Lösung. Pseudomorphosen von Korund und Andalusit nach den vorher vorhanden gewesenen idiomorphen Kristallen von Alunit oder anderen Mineralen mit Alunitstruktur stützen dieses Modell. Fuchsit-Disthen-Andalusit-Quarz-Schiefer vom Yilgarn Block in West-Australien, welche konkordante Lagen in Metasedimenten bilden, können ebenfalls aus Alunit-Quarz-Gesteinen entstanden sein, aber es konnten keine Gefügebeweise dafür erbracht werden. Dagegen wurden in benachbarten Disthen-Andalusit-Quarziten sowohl die typischen Querschnitte von herausgelösten Mineralien der Alunitgruppe wie auch das Mineral Natrojarosit innerhalb des metamorphen Quarzgefüges entdeckt. Dies scheint daaruf hinzudeuten, daß Minerale der Alunitgruppe während der Metamorphose mit Quarz und Disthen koexisitierten. Alunit-führende sedimentäre Ausgangsmaterialien müssen nicht notwendigerweise postvulkanischer Entstehung sein, sondern bilden sich auch unter speziellen Klimabedingungen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01825046
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    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
  • 8
    Electronic Resource
    Electronic Resource
    Surinamite: A beryllium-bearing mineral (1981)
    Springer
    Contributions to mineralogy and petrology 76 (1981), S. 472-473 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Ion microprobe and wet chemical analyses of surinamite from the type locality have shown the presence of about 4–5 wt.% BeO in addition to the oxides previously reported by de Roever et al. (1976). Attempts at synthesizing surinamite have failed in the BeO-free system, but were successful when running a composition containing 4.5wt.% BeO at 20 kb and 800° C. Therefore, beryllium appears to be an essential element for the crystal chemistry of surinamite. A model formula for surinamite might be (Mg2.25Fe 0.75 2+ )(Al3.75Fe 0.25 3+ )[BeSi3O16].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371489
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Sudoite, di/trioctahedral chlorite: A stable low-temperature phase in the system MgO-Al2O3-SiO2-H2O (1984)
    Springer
    Contributions to mineralogy and petrology 86 (1984), S. 409-417 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sudoite, ideally (Mg2Al3)[AlSi3O10](OH)8, was synthesized in small quantities from a number of starting materials using seeds of the natural mineral. Because its powder X-ray diffraction pattern is very similar to that of normal, trioctahedral chlorite, a technique based on relative intensities of 001-peaks of the chlorite-type phases was used, in addition to the standard X-ray method, to determine growth or breakdown of sudoite. Seeded runs indicate that sudoite is more stable than at least five alternative mineral assemblages in the system MgO-Al2O3-SiO-H2O below about 370°–390° C at water pressures up to at least 7 kbar. At higher temperatures sudoite decomposes into assemblages of normal chlorite with an Al2SiO5-phase and either quartz or pyrophyllite. However, the exact locations of the univariant breakdown curves could not be determined due to very low reaction rates. Schreinemakers analyses indicate that the assemblage sudoite+quartz represents the low-temperature equivalent of the common pair chlorite+pyrophyllite, and that sudoite+quartz is limited to water pressures below about 7 kbar because of its reaction to form the high-pressure phase Mg-carpholite; however, in the absence of quartz, the stability fields of sudoite and of Mg-carpholite overlap at pressures above 7 kbar. These stability data are in general agreement with two well-documented sudoite occurrences in quartz veins cutting highly oxidized, low-pressure manganiferous metapelites, and with one occurrence in a silica-deficient high-pressure metamorphic metabauxite. Sudoites may be more common in low-grade metamorphic rocks than known thus far, but they may not be stable under surface conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01187144
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Metastability of an osumilite end member in the system K2O-MgO-Al2O3-SiO2-H2O and its possible bearing on the rarity of natural osumilites (1967)
    Springer
    Contributions to mineralogy and petrology 14 (1967), S. 343-358 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Ein synthetisches Endglied der Osumilitgruppe mit der Formel KMg2Al3[Si10Al2-O30]·xH2O wurde durch kurzzeitige Hydrothermalversuche bei 650–700° C, 1 kb $$P_{{\text{H}}_{\text{2}} {\text{O}}}$$ aus einem Glas der entsprechenden Zusammensetzung mit voller Ausbeute dargestellt. Seine optischen und röntgenographischen Eigenschaften sind denen natürlicher Osumilite nahe verwandt. Bei niedrigeren und höheren Temperaturen und Wasserdrucken entstanden zusätzlich noch andere Phasen, und zwar um so mehr, je länger die Versuchszeiten gewählt wurden. In sehr langen Versuchen von 3 Monaten und darüber wird der synthetische Osumilit wieder abgebaut, selbst unter den PT-Bedingungen seiner Bildung. Dies bedeutet, daß die Phase unter solchen Bedingungen ein metastabiles Kristallisationsprodukt ist. Die stabilen Abbauprodukte sind, in der Reihenfolge zunehmender Temperatur: Muscovit+amesitischer Chlorit+Quarz; eastonitischer Phlogopit+Cordierit+ Muscovit+ Quarz und Cordierit+Kalifeldspat+Quarz. Ein natürlicher Osumilit von Sakkabira, Japan, wurde unter ähnlichen Bedingungen ebenfalls abgebaut. Diese Versuchsergebnisse sprechen dafür, daß das seltene Mineral Osumilit vielleicht eine metastabile Phase ist, die sich bevorzugt in Bereichen der Sanidinitfacies bildet wegen der dort im allgemeinen raschen, nicht zum Gleichgewicht führenden Kristallisation. Natürliche, myrmekitartige Verwachsungen von Cordierit, Kalifeldspat und Quarz aus metamorphen Gesteinen können möglicherweise durch den Abbau von früher in diesen Gesteinen vorhandenen Osumilitphasen gedeutet werden.
    Notes: Abstract A synthetic end member of the osumilite group with a composition KMg2Al3[Si10Al2-O30]·xH2O was obtained as a single phase through short-time hydrothermal treatment of a glass of the appropriate composition at 1 kb $$P_{{\text{H}}_{\text{2}} {\text{O}}}$$ and 650–700° C. Its optical and x-ray properties are close to those of natural osumilites. At temperatures outside the range 650 to 700°C, and at higher pressures osumilite could not be synthesized as a single phase, even in short runs. With experiment durations of 3 months and more the synthesized osumilite breaks down under the PT conditions of its formation, indicating that it is metastable under these conditions. The stable breakdown products, in the order of increasing temperatures, are: muscovite+amesitic chlorite+quartz; eastonitic phlogopite+cordierite+muscovite+quartz; and cordierite+K-feldspar+quartz. Natural osumilite of Sakkabira, Japan, treated under similar conditions also broke down. These results suggest that the rare mineral osumilite may represent a metastable phase due to rapid and non-equilibrium crystallization common in sanidinite-facies environments. Natural myrmekite-like intergrowths of cordierite with quartz and K-feldspar occurring in metamorphic rocks may be the result of the breakdown of pre-existing osumilite phases in these rocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373812
    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...