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  • 1
    Monograph available for loan
    Monograph available for loan
    London [u.a.] : Chapman & Hall
    Associated volumes
    Call number: 4/M 93.0923
    In: Topics in the earth sciences
    Type of Medium: Monograph available for loan
    Pages: xi, 283 S.
    ISBN: 0412291703
    Series Statement: Topics in the earth sciences 7
    Classification: A.3.5.
    Language: English
    Location: Reading room
    Branch Library: GFZ Library
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  • 2
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Peuyuk kimberlite is divisable into three petrographically distinct phases (A, B, and C) on the basis of oxide mineralogy and the presence or absence of an immiscible carbonate liquid. Phase A contains spinels (titan-magnesian-aluminous chromite) and perovskite with no reaction rims or complex mantles, and no evidence of an immiscible carbonate liquid. Phase B contains complexly zoned and mantled oxides with no evidence of an immiscible carbonate liquid. The spinels are zoned from titan-magnesian-aluminous chromite to members of the magnesian ulvospinel-ulvospinel-magnetite series. The zoned spinels are mantled by a serpentine-carbonate mixture followed by a mixture of Ti free magnetite and minor rutile. Perovskites are mantled by nickeliferous pyrite (0–11 % Ni) and rutile. Phase C is characterized by the presence of an immiscible carbonate liquid. Spinels are either discrete crystals of magnesian ulvospinel-ulvospinel-magnetite or as discrete rims of this composition upon cores of titan-magnesian-aluminous chromite. Rutile rims are poorly developed upon perovskites. Sulphides associated with the silicate groundmass are Cu-pentlandite, heazle-woodite and chalcopyrite. Nickeliferous pyrite is associated with the carbonate fraction. Common to all phases of the intrusion is a red titanium poor aluminous-magnesian chromite which is interpreted to have formed prior to the fluidized intrusion of the kimberlite. All other spinels being considered to have crystallized after fluidization. The spinel composition trends may reflect decreasing oxygen fugacities (10−19 to 10−22 bars) in response to falling temperatures (800–600° C) along the quartz-fayalite-magnetite buffer. In the immediate post-fluidization history of the diatreme all phases crystallized titan-magnesian-aluminous chromite but the trends of Ti and Fe enrichment observed in phases B and C was prevented in phase A possibly by rapid cooling. Slower cooling coupled with reaction of earlier formed phases with residual H2O and CO2 rich fluids resulted in the phase B assemblage. Extensive reaction of this type was prevented in phase C by the separation of an immiscible carbonate liquid.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Accessory andalusite has been found in some late-stage granitic differentiates of the South Mountain batholith. The andalusite is petrographically distinct from the andalusite of the thermal aureole, and it occurs in regions of the batholith which show little evidence of contamination by the country rocks. Analyses of biotites from andalusite-bearing and andalusite-free phases suggest that those coexisting with andalusite actually grew in equilibrium with the andalusite. It is concluded that magmatic andalusite must be confined mainly to water-saturated, peraluminous, epizonal granites, and some possible P-T paths for the crystallization of magmatic andalusite are considered.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The late tholeiitic lavas of southwestern Ubekendt Ejland (63-54 Ma) are intruded by lamprophyre dykes (∼33 Ma). The compositional and temporal differences would seem to preclude any genetic relationship between the two igneous episodes. Competing models of renewed partial melting versus extended batch fractionation are considered to explain the origin of the lamprophyres. Mathematically modelled lamprophyres produced by batch fractionation are very close to observed lamprophyre compositions and this, combined with other temporal and spatial evidence, suggests that renewed partial melting of the mantle is not the best way to explain such bimodal suites.
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  • 5
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Current methods of geothermometry and geobarometry applicable to garnet lherzolite are reviewed with reference to recent experimental studies of the equilibration of natural garnet lherzolite and it is concluded that the Wells and Mori-Green formulations of the two pyroxene solvus provide the most reasonable temperature estimates. Pressures are best estimated by using these temperatures with Wood's formulation of the orthopyroxene-garnet geobarometer without chromium corrections. Pipe 200 garnet lherzolites are considered to have equilibrated at 907°–950° C at 30.0–34.5 kb. It is shown that the transport times of xenoliths from the mantle are sufficiently long (0.5–24 h) to allow thermal equilibration with kimberlite but are too short to allow chemical re-equilibration to occur. Xenolith suites therefore retain information regarding the pressure/temperature history of the upper mantle despite being heated to the temperature of the kimberlite magma during transport. The Pipe 200 xenolith suite indicates that the upper mantle beneath Lesotho has been perturbed to temperatures slightly above those defined by steady state geotherms. The Pipe 200 suite is derived from a narrow depth range (90–110 km) and derivation of chromite and garnet lherzolites from similar depths implies that the mantle is heterogeneous over short vertical distances. No simple stratigraphy, in which chromite lherzolites overlie garnet lherzolites is evident. Comparison with other suites of Lesotho garnet lherzolites shows that it is not possible to construct an upper mantle stratigraphy except in the most general terms because of the prevailing lateral and vertical heterogeneity and apparent limited depth range represented by the xenolith suites.
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  • 6
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Granulite-facies xenoliths from an Upper Devonian lamprophyre dyke near Tangier, Nova Scotia, provide new information about the lower crust in the Meguma Zone. Two mineralogically and chemically distinet groups of xenoliths occur. Both groups contain quartz+feldspar+biotite+Fe−Ti oxides+sulfides. In addition, group A contains garnet+graphite±[aluminosilicates+spinel±sapphirine (hight Al2O3 subgroups A1 and A2)] or [clinopyroxene+sphene+apatite (high CaO sub-group A3)]. Group B has highly variable proportions of orthopyroxene (B1), clinopyroxene (B2), and amphibole (B3). Trace-element contents of the highly aluminous xenoliths compare closely with average to upper crustal model compositions and are similar in many aspects to other “undepleted” granulite-facies rocks. LowP-T sedimentary assemblages of quartz-chlorite-clay minerals-calcite-albite or paragonite can account for the compositions of group A xenoliths. Within group B, a high-MgO (MgO〉13 wt%) subgroup with high transition-metal contents, and low-MgO (MgO〈9 wt%) sub-groups with higher LIL (large-ion-lithophile) element contents exist. Although the rare-earth and high-field-strength elements indicate a tholeiitic or low-K calc-alkaline chemistry, the LIL elements are as high as those from high-K calc-alkaline volcanic are rocks. Isotopically, group A ranges from εNdt=-2.56 to-0.80 and87Sr/86Sr t =0.7046 to 0.7182 fort=370 Ma. For group B these values are +1.45 to +5.33 and 0.7028 to 0.7048, respectively. Model ages (TCHUR) are correspondingly low and are tightly constrained (544±52 Ma). These “young” ages contrast with the middle Proterozoic Nd model ages of the overlying Meguma Zone low-grade flysch. This time-inverted stratigraphy appears to be the product of a tectonic break between a younger autochthonous Tangier lower crust (≡Avalon), and an older allochthonous Meguma Group upper crust.
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  • 7
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract New analyses show that Tertiary tholeiitic basalts from the Baffin Bay area have generally primitive characteristics. Comparison of the bulk chemical compositions of the basalts with material of known phase relations suggests that these basalts have properties intermediate between investigated natural and synthetic compositions. A discrete group of these basalts coincides in projection with the composition of the liquid produced by the partial melting of garnet periodotite at 30 kb. The compositions in this group are believed to be parental to the other rocks in the province principally through a mechanism of olivine fractionation. Eclogite fractionation is invoked to account for the chemical differences between the two suites of basalts in Baffin Bay.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 205 (1965), S. 349-350 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE occurrence of Upper Cretaceous and early Tertiary lava flows and sedimentary beds on the Atlantic coasts of Scotland, East and West Greenland, and of similar, but younger, rocks on intervening islands led to the expectation that such rocks might be found in North America1. Small patches of ...
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  • 9
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/(CaO + Na2O) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250°C under N2 atmosphere at heating rates ranging from 10 to 50°C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different (p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P2O5 and between Q and the Young's modulus (p 〈 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 10
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    Unknown
    PANGAEA
    In:  Supplement to: Clarke, D B (1989): Petrology and geochemistry of basalts from ODP Leg 105, Hole 647A, Labrador Sea and the Davis Strait area. In: Srivastava, SP; Arthur, M; Clement, B; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 105, 863-884, https://doi.org/10.2973/odp.proc.sr.105.175.1989
    Publication Date: 2019-06-17
    Description: Basalt samples recovered from the lowermost 37 m of Leg 105 Hole 647A in the Labrador Sea are fine- to medium grained, have microphenocrysts of clinopyroxene, and show little evidence of alteration. Chemically, these rocks are low potassium (0.01-0.09 wt% K20), olivine- to quartz-normative tholeiites that are also depleted in other incompatible elements. In terms of many of the incompatible trace elements, the Labrador Sea samples are similar both to iV-type midocean ridge basalts (MORBs) and to the terrestrial Paleocene volcanic rocks in the Davis Strait region of Baffin Island and West Greenland. However, significant differences are found in their strontium and neodymium isotope systematics. Hole 647A samples are more depleted in epsilon-Nd (+9.3) and are anomalously rich in 87Sr/86Sr (0.7040) relative to the Davis Strait basalts (epsilon-Nd +2.54 to + 8.97; mean 87Sr/86Sr, 0.7034). We conclude that the Hole 647A and Davis Strait basalts may have been derived from a similar depleted mantle source composition. In addition, the Davis Strait magmas were generated from mantle of more than one composition. We also suggest that there is no geochemical evidence from the Hole 647A samples to support or to refute the existence of foundered continental crust in the Labrador Sea.
    Type: Dataset
    Format: text/tab-separated-values, 390 data points
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