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  • 1
    Electronic Resource
    Electronic Resource
    Unusual Hf contents in metamorphic zircon from coesite-bearing eclogites of the Dabie Mountains, east-central China: implications for the dating of ultrahigh-pressure metamorphism (2004)
    Oxford, UK : Blackwell Science Inc
    Journal of metamorphic geology 22 (2004), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Metamorphic zircon from coesite-bearing eclogites in the Dabie Mountains encloses high-P phases, and may have formed at the peak of ultrahigh-pressure (UHP) metamorphism. Morphologically, the metamorphic zircon typically occurs as small, multi-faceted, near-spherical grains with homogeneous internal structure and weak backscattered electron (BSE) luminescence. Geochemically, it is characterized by extremely high and relatively constant contents of hafnium (Hf) and very low contents of Y, U and Th, reflecting the contraction of the zircon lattice under the UHP conditions. High contents of Hf may be characteristic of zircon formed during UHP metamorphism, which has important consequences for interpretation of geochronological results. We propose that the metamorphic zircon extremely enriched in Hf may be used to date the peak of UHP metamorphism that produced the coesite-bearing eclogites in the Dabie Mountains, and potentially in other UHP terranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.2004.00538.x
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  • 2
    Electronic Resource
    Electronic Resource
    Timing of Late Neoproterozoic glaciation on Baltica constrained by detrital zircon geochronology in the Hedmark Group, south-east Norway (2005)
    Oxford, UK : Blackwell Science Ltd
    Terra nova 17 (2005), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The Moelv Tillite is the Late Neoproterozoic Varanger glacial deposit recorded in the Hedmark Group, SE Norway. Paired U–Pb and Lu–Hf data collected on detrital zircons in the Rendalen Formation underlying the Moelv Tillite have identified an uncommon 677 ± 15 to 620 ± 14 Ma population, that constrain the deposition of the Moelv Tillite to be younger than 620 ± 14 Ma. The youngest detrital zircons may be derived from granite magmatism related to the 616 ± 3 Ma Egersund dolerite magmatism, situated in the western part of the Sveconorwegian orogen. The Moelv Tillite, which is not overlain by a cap carbonate, possibly correlates with the c. 580 Ma Squantum-Gaskiers glacial deposits of Avalonia. Available palaeomagnetic data for the Late Neoproterozoic suggest that Baltica was located at intermediate to high latitude between 620 and 555 Ma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.2005.00609.x
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of equilibration conditions for garnet granulite and garnet websterite nodules in African kimberlite pipes (1981)
    Springer
    Mineralogy and petrology 28 (1981), S. 229-244 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Druck-Temperatur-Berechnungen auf Grund verschiedener Kombinationen von kalibrierten mineralogischen Thermometern und Barometern sowie alternativer Modelle der Fe2+/(Fe2++Fe3+)-Verhältnisse in den Mineralen einer Gruppe von 14 Einschlüssen werden verglichen. BevorzugteP/T-Werte ergaben sich durch simultane Lösung der Gl. (12) für Granat-Orthopyroxen-Gleichgewichte vonWood (1974) und der Gleichung vonEllis undGreen (1979), die dieP-T-X-Abhängigkeit des Fe2+−Mg2+-Verteilungskoeffizienten für koexistierende Granat und Clinopyroxen definiert. Um realistische Ergebnisse zu erhalten, ist es jedoch zuerst notwendig, die Fe3+-Gehalte der Minerale zu berechnen, vorzugsweise auf der Grundlage des Ladungsausgleichs. Die bevorzugten Durchschnittswerte von 654°±36°C und 10.8–3.1 kb sind in guter Übereinstimmung mit einer Herkunft aus der unteren Kruste.
    Notes: Summary Pressure/temperature estimates based on different combinations of calibrated mineralogical thermometers and barometers and alternative assumptions concerning the Fe2+/(Fe2++Fe3+) ratios in the mineral phases are compared for a suite of fourteen nodules. PreferredP/T values have been obtained by simultaneous solution of eq. (12) ofWood (1974) for garnet-orthopyroxene equilibria and theEllis andGreen (1979) equation defining theP,T,X dependence of the Fe2+−Mg2+ partition coefficient for coexisting garnet and clinopyroxene. However, to obtain realistic results it is first necessary to calculate the Fe3+ contents in the minerals—conveniently done on a charge balance basis. The favoured meanP/T estimates of 654±36°C and 10.8±3.1 kbs are compatible with a lower crustal origin for this nodule suite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01084630
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  • 4
    Electronic Resource
    Electronic Resource
    Residence of trace elements in metasomatized spinel lherzolite xenoliths: a proton-microprobe study (1991)
    Springer
    Contributions to mineralogy and petrology 109 (1991), S. 98-113 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Minerals occurring in dry and modally metasomatized spinel lherzolites from western Victoria have been analysed by proton microprobe for Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Ba, Pb, Br, rare-earth elements (REE), Th and U. Mass-balance calculations demonstrate that these trace elements are contained in specific acceptor minerals and do not occur in significant concentrations at clean grain boundaries. The level of particular trace elements in the rock depends on the presence of specific phases: for example high levels of REE, Sr (and U, Th, Br) require apatite, while Ba, Nb and Ta are strongly concentrated in amphibole±mica. Mantle metasomatism in these spinel lherzolites is inferred to result from an open-system process involving infiltration of fluids released by crystallizing silicate melts. This process produces metasomatic zones with different modal mineralogy and hence greatly different trace-element signatures. The data demonstrate that large-ion-lithophile (LIL) and high-field strength (HFS) elements in metasomatized spinel lherzolites are strongly concentrated in non-refractory phases, which will break down easily in heated volumes such as the walls of magma conduits. The heterogeneity observed in trace-element patterns of intraplate alkali basaltic rocks may not reflect source heterogeneity, but may result largely from contamination by metasomatized mantle wall rock. The KDs for most trace elements show little temperature dependence except for KDSr between orthopyroxene and clinopyroxene where KD decreases with increasing temperature. The generally uniform KDs can be used to test for disequilibrium in such assemblages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687203
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  • 5
    Electronic Resource
    Electronic Resource
    Combined U-Pb dating and Sm-Nd studies on lower crustal and mantle xenoliths from the Delegate basaltic pipes, southeastern Australia (1998)
    Springer
    Contributions to mineralogy and petrology 130 (1998), S. 154-161 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Mafic rocks dominate the lower crustal and upper mantle xenolith suites within the Jurassic Delegate basaltic diatremes in the Paleozoic Lachlan Fold Belt, SE Australia. Two upper mantle mafic xenoliths from the Delegate pipes, a garnet pyroxenite and a garnet granulite (equilibrated at 1060 and 1140 °C, and 40–50 km), yield garnet-clinopyroxene Sm-Nd ages of 160 ± 4 Ma and 153 ± 10 Ma, respectively. Both ages are indistinguishable from the time of eruption of the diatremes, and are interpreted as showing continuous isotopic equilibrium within the mantle of Sm and Nd between garnet + clinopyroxene at temperatures ≥ 1050 °C. A lower crustal, 2-pyroxene granulite xenolith (equilibrated at 810–850 °C and ca. 25 km) yields a clinopyroxene + plagioclase + whole rock Sm-Nd isochron ages of 283 ± 26 Ma. This age probably reflects partial resetting of the isotopic systems of much older granulite during slow cooling, or after a heating event in the lower crust associated with the Jurassic magmatic activity represented by the basaltic host rock. Metamorphic zircons from the 2-pyroxene granulite xenolith were dated by the U-Pb method at 398±2 and 391 ± 2 Ma. These ages are considered to date granulite facies metamorphic events in the lower crust of the region. The age gap between the granulite facies metamorphism and granitoid plutonism in the region (420–410 Ma) indicates that the dated granulite is unlikely to represent residue after partial melting and magma extraction that generated the regional granitoids. It is suggested that these ages may record a relatively slow cooling following the cessation of mafic magmatic intrusion that formed the xenolith protoliths and that was probably the heat source responsible for granite production. At about 25 km, this thermal relaxation accounts for the change from an olivine + plagioclase + 2-pyroxene gabbroic assemblage into the granulite facies 2-pyroxene + plagioclase + spinel field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050356
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  • 6
    Electronic Resource
    Electronic Resource
    Parageneses of garnet in granulite-facies rocks, Lofoten-Vesteraalen, Norway (1969)
    Springer
    Contributions to mineralogy and petrology 23 (1969), S. 89-116 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Garnet occurs widely as a secondary mineral in the granulite-facies rocks of the Lofoten-Vesteraalen islands of North Norway. The garnet-forming reactions may be inferred from the resulting textures and are interpreted as being retrograde reactions. Microprobe analyses show that garnets with high proportions of CaO and MgO occur in coronas around olivine grains in anorthosites, whereas the most iron-rich garnets formed by reaction between plagioclase and the very iron-rich pyroxenes of some monzonitic (mangeritic) rocks. Garnets ranging in composition between these extremes formed by reactions involving biotite, plagioclase and magnetite. Textural features indicate that these reactions have been induced by oxidation of the biotite; the liberated water has converted the pyroxenes to amphibole. The net effect of the reactions is to transform the granulite-facies assemblages to amphibolite-facies assemblages. The secondary garnet is nearly ubiquitous in the granulites of the outer Lofoten islands, which may show no other signs of retrogression. On Langöy in Vesteraalen garnet occurs only within a zone of strongly retrograded gneisses. Differences in bulk composition do not satisfactorily explain the distribution of secondary garnet. This distribution, and the observed oxidation textures, imply widespread penetration of the Lofoten granulites by a transient oxidizing fluid. On Langöy these fluids apparently affected only the narrow retrograded zone. The model suggests that the 1700 to 1800 m.y. Rb/Sr date obtained by Heier and Compston (1969) for the Lofoten granulites represents the time of oxidation, whereas the 2800 m.y. date for the Langöy granulites represents the original granulite-facies metamorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375172
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  • 7
    Electronic Resource
    Electronic Resource
    Lherzolite nodules from the Fen alkaline complex, Norway (1973)
    Springer
    Contributions to mineralogy and petrology 38 (1973), S. 135-146 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The alkaline ultrabasic rooks (damkjernite) of the Fen alkaline complex contain abundant rounded inclusions of spinel lherzolite, closely similar in composition and mineralogy to the nodules found in many undersaturated basaltic rocks. Clinopyroxene compositions indicate crystallization at P=10–13 KB, T=1200–1250° C. A model involving partial melting in a rising diapir of mantle peridotite allows interpretation of the nodules either as mantle fragments or as cognate cumulates, and suggests that crustal thinning in the Oslo area possibly began as early as 500–600 m.y. ago. The presence of the nodules indicates that the damkjernite did not pause for intracrustal differentiation during its rapid ascent to the surface. The crustal contamination suggested by recent Sr-isotope studies may have occurred during differentiation at the base of the continental crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373877
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  • 8
    Electronic Resource
    Electronic Resource
    Metamorphic feldspathization of metavolcanics and granitoids, Avnik area, Turkey (1983)
    Springer
    Contributions to mineralogy and petrology 83 (1983), S. 309-319 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In the Avnik area of the Bingöl massif the Lower Unit consists of basic to felsic metavolcanics (ca. 450 Ma), intruded by granitoids (ca. 350 Ma). These are unconformably overlain by an Upper Unit of micaschists and Permian marbles; both units have been deformed and metamorphosed in Alpine time. The metavolcanics and granitoids are extensively feldspathized and silicified. The granitoids, and basic-intermediate volcanics, are albitized, while felsic volcanics are K-feldspathized. Metasomatism has severely modified K/Rb and Rb/Sr ratios, but not REE patterns, and is inferred to have occurred at relatively low T. Nametasomatism of the Upper Unit micaschists has produced albite porphyroblasts. Metasomatism postdates formation of the Upper Unit sediments, and is probably related to reaction with sea water that infiltrated the basement of volcanics and granitoids during deposition of these sediments. Rb-Sr whole-rock dating of extensively feldspathized intermediate-felsic metavolcanics gives an age of ca. 90 Ma, which suggests that the most extensive reaction coincided with expulsion of the trapped sea water during the early stages of the Alpine orogeny. The distribution of albitization vs. K-felds-pathization suggests that the type of metasomatism was controlled on a local scale by permeability and grain size, rather than by T variations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371199
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  • 9
    Electronic Resource
    Electronic Resource
    Caledonian Sm–Nd ages and a crustal origin for Norwegian eclogites (1980)
    [s.l.] : Nature Publishing Group
    Nature 285 (1980), S. 319-321 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Eclogites of the Caledonian orogeny in western Norway are usually divided1 into two types: mafic and ultramafic layers or lenses within garnet-free ultramafic bodies ('internal' or 'Type A' eclogites); and mafic boudins, layers and larger bodies enclosed directly within Precambrian gneisses ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/285319a0
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  • 10
    Electronic Resource
    Electronic Resource
    Trace elements in sulfide inclusions from Yakutian diamonds (1996)
    Springer
    Contributions to mineralogy and petrology 124 (1996), S. 111-125 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Sulfide inclusions in diamonds may provide the only pristine samples of mantle sulfides, and they carry important information on the distribution and abundances of chalcophile elements in the deep lithosphere. Trace-element abundances were measured by proton microprobe in 〉50 sulfide inclusions (SDI) from Yakutian diamonds; about half of these were measured in situ in polished plates of diamonds, providing information on the spatial distribution of compositional variations. Many of the diamonds were identified as peridotitic or eclogitic from the nature of coexisting silicate or oxide inclusions. Known peridotitic diamonds contain SDIs with Ni contents of 22–36%, consistent with equilibration between olivine, monosulfide solid solution (MSS) and sulfide melt, whereas SDIs in eclogitic diamonds contain 0–12% Ni. A group of diamonds without silicate or oxide inclusions has SDIs with 11–18% Ni, and may be derived from pyroxenitic parageneses. Eclogitic SDIs have lower Ni, Cu and Te than peridotitic SDIs; the ranges of the two parageneses overlap for Se, As and Mo. The Mo and Se contents range up to 700 and 300 ppm, respectively; the highest levels are found in peridotitic diamonds. Among the in-situ SDIs, significant Zn and Pb levels are found in those connected by cracks to diamond surfaces, and these elements reflect interaction with kimberlitic melt. Significant levels of Ru (30–1300 ppm) and Rh (10–170 ppm) are found in many peridotitic SDIs; SDIs in one diamond with wustite and olivine inclusions and complex internal structures have high levels of other platinum-group elements (PGEs) as well, and high chondrite-normalized Ir/Pd. Comparison with experimental data on element partitioning between crystals of monosulfide solid solution (MSS) and sulfide melts suggests that most of the inclusions in both parageneses were trapped as MSS, while some high-Cu SDIs with high Pd±Rh may represent fractionated sulfide melts. Spatial variations of SDI composition within single diamonds are consistent with growth histories shown by cathodoluminescence images, in which several stages of growth and resorption have occurred within magmatic environments that evolved during diamond formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050179
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