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  • 1
    Electronic Resource
    Electronic Resource
    Oxygen isotope ratios in magnetite core-and-mantle structures (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 2 (1984), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In a polymetamorphic, felsic, biotite-bearing gneiss, biotite has reacted to form magnetite and microcline. The resulting structure is a magnetite core surrounded by a mantle of feldspar and quartz normally not exceeding 20mm in diameter. Measurements of oxygen isotope ratios disclose disequilibrium between mantle microcline and mantle quartz and also between mantle and matrix minerals of the same species. A clustering of temperature estimates from the oxygen isotope distribution between magnetite and quartz and between magnetite and microcline in the interval 550 to 600°C suggests an approach to oxygen isotope equilibrium. No signs of a re-equilibriation of the reacting biotite can be found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1984.tb00594.x
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  • 2
    Electronic Resource
    Electronic Resource
    Mantle buffering of the early oceans (1982)
    Springer
    Naturwissenschaften 69 (1982), S. 173-180 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract Archean calcites and dolomites, if compared to their Phanerozoic counterparts, are enriched in Sr2+, Ba2+, Mn2+, Fe2+, depleted in 18O, (Na+), and contain mantle-like 87Sr/86Sr and, in associated S phases, mantle-like 34S/32S. This may be a consequence of massive seawater pumping through, and equilibration with, the coeval basaltic oceanic crust. The exponential decline of oceanic geothermal gradient in the course of terrestrial evolution led to a waning of this “mantle” flux and to the enhancement of the continental river discharge as the controlling factor of seawater composition; the major transition occurring probably during the late Archean — early Proterozoic time interval. Such evolution is consistent with the observed tectonic, sedimentological, geochemical and metallogenic secular patterns and may also provide an alternative, or complementary, inorganic explanation for the development of the post-Archean oxygenic atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364890
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  • 3
    Electronic Resource
    Electronic Resource
    Extreme 18 O depletion in calcite and chert clasts from the Elephant Moraine on the East Antarctic ice sheet (1988)
    [s.l.] : Nature Publishing Group
    Nature 332 (1988), S. 352-354 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The specimen shown in Fig. 2 (sample 582 in Table 1) was collected during the 1983-84 field season. It consists of black acicular calcite crystals aligned approximately at right angles to undulating layers. It resembles certain kinds of algal stromatolites that may be difficult to distinguish from ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/332352a0
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  • 4
    Electronic Resource
    Electronic Resource
    Immiscible separation of metalliferous Fe/ Ti-oxide melts from fractionating alkali basalt: P-T-f O2 conditions and two-liquid elemental partitioning (1998)
    Springer
    Contributions to mineralogy and petrology 133 (1998), S. 12-29 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Globules of iron-dominated (59–69 wt% FeOtot) and titanium-dominated (43.5 wt% TiO2) oxide melts have been detected in igneous xenoliths from Pliocene-to-Pleistocene alkali basalts of the Western Carpathians. Fluid inclusion and mineral composition data indicate immiscible separation of the high-iron-oxide melt (HIM) at magmatic temperatures. The HIM separation occurred during clinopyroxene (augite) accumulation in an alkali trachybasalt and continued during crystallization of amphibole (kaersutite) and K-feldspar (anorthoclase), the latter coexisting with trachyte and alkalic rhyolite residual melts. Some HIM was also expelled from sub-alkalic rhyolite (70–77% SiO2), coexisting with An27–45 plagioclase and quartz in granitic (tonalite-trondhjemite) xenoliths. Oxygen fugacities during HIM separation range from −1.4 to +0.6 log units around the QFM buffer. A close genetic relationship between HIM-hosted xenoliths and mantle-derived basaltic magma is documented by mineral 18O values ranging from 4.9 to 5.9‰ V-SMOW. δD values of gabbroic kaersutite between −61 and −86‰ V-SMOW are in agreement with a presumed primary magmatic water source. Most trace elements, except Li, Rb and Cs, have preferentially partitioned into the HIM. The HIM/Si-melt partition coefficients for transition elements (Sc, V, Cr, Co, Ni) and base metals (Zn, Cu, Mo) are between 2–160, resulting in extreme enrichment in the HIM. La and Ce also concentrate in the silicic melt, whereas Tb-Tm in the HIM. Hence, the immiscible separation causes REE fractionation and produces residual silicic melt enriched in LREE and depleted in HREE. The weak fractionation among Tb-Tm and Yb, Lu can be attributed to recurrent extraction of the HIM from the magmatic system, while flat HREE chondrite-normalized patterns are interpreted to indicate no or little loss of the HIM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050433
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon isotope fractionation between calcite, graphite and CO2: an experimental study (1992)
    Springer
    Contributions to mineralogy and petrology 112 (1992), S. 35-45 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The partitioning of stable carbon isotopes between calcite, graphite and CO2 was experimentally determined at temperatures from 500 to 1200 °C and 1 to 15 kbar pressure. Attainment of carbon isotope equilibrium in CO2-calcite runs was proven by achieving the same fractionation from isotopically opposite directions. The resultant CO2-calcite fractionation curve for carbon differs from Bottinga's calculation by 1.2‰ and confirms recent experiments of Chacko et al. and Mattey et al. In CO2-graphite experiments equilibrium fractions were extrapolated by applying the partial-exchange technique of Northrop and Clayton and by optimizing the contribution of surface reaction in graphite. CO2-graphite fractionations at temperatures up to 800 °C are in fair agreement with Bottinga's calculation, but yield a surprisingly high fractionation of ≈5‰ at upper mantle temperatures. The combination of CO2-calcite (carbon) and CO2-graphite fractionation results in a new experimentally determined calcite-grapite fractionation curve, expressed by the equation: $$\begin{gathered} 10^3 {\text{ ln }}\alpha _{{\text{cc - gr}}} = 7.99 \times 10^6 /T^2 - 9.58 \times 10^3 / + 5.76 \hfill \\ {\text{ (873 - 1473 Kelvin)}} \hfill \\ \end{gathered} $$ Applying the experimentally determined fractionation curve on graphite-bearing metacarbonates yields metamorphic temperatures distinctly higher than those obtained by Valley and O'Neil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310954
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  • 6
    Electronic Resource
    Electronic Resource
    Petrogenesis of the Kirkpatrick Basalt, Solo Nunatak, northern Victoria Land, Antarctica, based on isotopic compositions of strontium, oxygen and sulfur (1984)
    Springer
    Contributions to mineralogy and petrology 87 (1984), S. 101-108 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Chemical and isotopic compositions of Jurassic tholeiites of the Kirkpatrick Basalt Group from Solo Nunatak, northern Victoria Land, indicate that these rocks are contaminated with crustal material. The basalts are fine grained and contain phenocrysts of augite, pigeonite, hypersthene and plagioclase. The flows on Solo Nunatak are chemically more similar to average tholeiite than flows from Mt. Falla and Storm Peak in the Central Transantarctic Mountains (TAM) which appear to be more highly differentiated. Initial 87Sr/86Sr ratios of the flows on Solo Nunatak are high (〉0.710) and are similar to those reported for the Kirkpatrick Basalt in the Central TAM. Whole-rock δ18O values are also high, ranging from +6.0 to +9.3‰ and correlate positively with initial 87Sr/86Sr ratios, similar to the Kirkpatrick Basalt in the Central TAM. The correlation between initial 87Sr/86Sr ratios and δ18O values is explained as the result of simultaneous fractional crystallization and assimilation of a crustal contaminant. Sulfur isotope compositions vary between limits of δ34S= -4.01 to +3.41‰ Variations in (δ34S probably resulted from outgassing of SO2 under varying oxygen fugacities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376216
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  • 7
    Electronic Resource
    Electronic Resource
    Anomalous isotopic compositions of Sr, Ar and O in the Mesozoic diabase dikes of Liberia, West Africa (1989)
    Springer
    Contributions to mineralogy and petrology 101 (1989), S. 12-18 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Mesozoic diabase dikes of Liberia are tholeiites whose 87Sr/86Sr and 87Rb/86Sr ratios scatter widely on the Rb-Sr isochron diagram. The problem is attributed to differences in the initial 87Sr/86Sr ratios of these rocks which range from 0.70311 to 0.70792, assuming a uniform age of 186 Ma for the dikes and using λ(87Rb)=1.42 × 10−11y−1. The range of values is similar to that observed in the Mesozoic basalt flows and dikes of other Gondwana continents. New whole-rock K-Ar dates confirm previous conclusions that the diabase dikes in the Liberian and Pan-African age provinces of Liberia absorbed extraneous 40Ar after intrusion. Only the dikes in the Paynesville Sandstone have K-Ar dates that range from 117 Ma to 201 Ma and may not contain extraneous 40Ar. However, dikes from all three age provinces of Liberia have elevated initial 87Sr/86Sr ratios. These results indicate that contamination with radiogenic 87Sr occurred primarily before intrusion of the magma whereas the addition of extraneous 40Ar occurred after emplacement and reflects the age and mineral composition of the country rock. The δ 18O values of the Liberian diabase range from +5.6/% to +9.10/% and correlate positively with initial 87Sr/86Sr ratios. The data can be modeled by fractional crystallization and simultaneous assimilation of crustal rocks by the magma. However, samples containing amphibole and biotite replacing pyroxene deviate from the Sr-O isotope trajectories of the model and appear to have been depleted in 18O and enriched in 87Sr by interactions with groundwater at high temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387197
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  • 8
    Electronic Resource
    Electronic Resource
    Oxygen isotope heterogeneity of the mantle deduced from global 18O systematics of basalts from different geotectonic settings (1995)
    Springer
    Contributions to mineralogy and petrology 120 (1995), S. 95-114 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Based upon a compilation and analysis of O-isotope data for Neogene volcanic rocks worldwide, the δ18O variation for 743 basalts (historic lavas, submarine glasses, and lavas with 〈0.75 wt% H2O) is +2.9 to +11.4‰. Mid-ocean-ridge basalt (MORB) has a uniform O-isotope composition with δ180=+5.7±0.2‰. Basalts erupted in different tectonic settings have mean 18O/16O ratios that are both lower and higher than MORB, with continental basalts enriched in 18O by ca. 1‰ over oceanic basalts. The δ18O range for the subset of 88 basalts with Mg# [100·Mg(Mg+Fe2+)] 75–68, considered to be unmodified primary mantle partial melts, is +3.6 to +8.7‰. These features are a clear indication that: (1) the Earth's upper mantle is heterogeneous with respect to its O-isotope composition; (2) that both low-18O and high-18O reservoirs have contributed to basalt petrogenesis. Large-ion lithophile element-enriched basalts associated with subduction at convergent plate margins are slightly enriched in 18O, a characteristic that is considered to be an intrinsic feature of the subduction process. Intraplate oceanic and continental basalts have highly variable 18O/16O ratios, with individual localities displaying δ18O ranges in excess of 1.5 to 2‰. Systematic co-variations between O-, Sr-, Nd-, and Pb-isotope ratios reflect the same principal intramantle end-member isotopic components (DMM, HIMU, EM-I, EM-II) deduced from radiogenic isotope considerations and, therefore, imply that a common process is responsible for the origin of upper mantle stable and radiogenic isotope heterogeneity, namely the recycling of lithospheric material into the mantle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311010
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  • 9
    Electronic Resource
    Electronic Resource
    Fluid history of UHP metamorphism in Dabie Shan, China: a fluid inclusion and oxygen isotope study on the coesite-bearing eclogite from Bixiling (2000)
    Springer
    Contributions to mineralogy and petrology 139 (2000), S. 1-16 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The coesite-bearing eclogites and associated ultramafic rocks of Bixiling form the largest metamorphic complex in the Dabie–Sulu ultrahigh-pressure (UHP) metamorphic belt. They mainly consist of “fresh” eclogite, kyanite-rich eclogite, retrograded eclogite and garnet peridotite. Fluid inclusion and oxygen isotope studies have been carried out on the different types of eclogite and peridotite in order to identify the role of fluids during the metamorphic evolution culminating in UHP metamorphism. Five types of fluid inclusions were distinguished based on textural criteria and fluid compositions: (1) primary Ca-rich brines in quartz blebs in kyanite; (2) primary NaCl-dominated high-salinity inclusions in omphacite and kyanite; (3) primary NaCl-dominated medium- to high-salinity inclusions in matrix quartz; (4) carbonic inclusions in omphacite and matrix quartz; (5) secondary low-salinity aqueous (or pure water) inclusions in matrix quartz. The Ca-rich fluid inclusions in quartz blebs in kyanite represent the earliest recognizable fluids (prograde metamorphism) as they largely escaped late re-equilibration. Fluid inclusions in omphacite and kyanite may have been trapped during peak metamorphic conditions, whereas low-salinity aqueous inclusions in matrix quartz were trapped during the latest stage of uplift. UV-laser oxygen isotope measurements show that garnet and clinopyroxene from the “fresh” eclogite, kyanite-rich eclogite and garnet peridotite have narrow δ18O values ranging from 3.0 to 3.9‰. In contrast, garnet and omphacite in retrograded eclogite have δ18O values of −1.8 to −1.2 and of −1.1 to −0.6‰, respectively. The difference in oxygen isotope composition is interpreted to result from partial oxygen isotope exchange between the UHP complex and retrograde fluids during late exhumation. Fluids derived from the surrounding gneiss were probably responsible for the low-salinity solutions found in secondary fluid inclusions and the lowering of the δ18O values of the retrograded eclogite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050570
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  • 10
    Electronic Resource
    Electronic Resource
    Kohlenstoff- und Sauerstoff-Isotopenuntersuchungen an Karbonatkonkretionen und umgebendem Gestein (1970)
    Springer
    Contributions to mineralogy and petrology 27 (1970), S. 66-79 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The composition of the carbon and oxygen isotopes has been determined in about 40 carbonate concretions and surrounding clays and shales of different geological ages. Two different areas and stratigraphic levels in Northwestern Germany have been sampled: 1. concretions in shales of Lower Cretaceous age fromt he area between Hildesheim and Hannover; 2. concretions in shales of Devonian age from the Harz mountains (and the foreland). While the concretions of Group 1 generally are enriched in the light isotope 12C (δ13C values from −3.3 to −43.2‰ relative to PDB), compared to the surrounding shales (0.9 to −5.3‰), no significant differences could be observed between concretions and shales of Group 2 (concretions: 2.0 to −7.0; shales: −0.3 to −6.2). The average 18O/16O ratios of the Devonian samples are lower than those from the Cretaceous, because the probability of an exchange with “light” meteoric water in diagenetic reactions increases with geologic age. Formed under special conditions of the microenvironment, such as the presence of organic material and local alkalinity during the early stages of diagenesis, the carbon isotopic composition of concretions will probably have preserved some characteristic properties of this mioroenvironment. It is assumed that concretions with the “heavy” carbon contain carbon from CO2 which was in isotope equilibrium with CH4, both of them liberated during the decay of organic material. The “light” carbon from concretions of Group 1 is explained as fixed CO2, originating from microbiological or inorganic oxidation of organic substances, which was not in isotope equilibrium with methane (if this was present at all). After precipitation of the concretionary carbonates, no significant carbon isotope exchange seems to have occurred, otherwise the pattern of a heterogeneous carbon isotope composition found in several concretions could not be explained. Strontium concentrations (see Appendix) range from those of primary calcite precipitated in sea water to diagenetic carbonates formed from solutions with a high Ca/Sr ratio. They indicate that during the formation of concretions in abundant cases the system was closed to ocean water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539542
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