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  • 1
    Electronic Resource
    Electronic Resource
    Detrital zircon ages from the Loch Maree Group, Lewisian Complex, NW Scotland: confirmation of a Palaeoproterozoic Laurentia—Fennoscandia connection (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 9 (1997), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Ion-microprobe U-Pb zircon ages of detrital zircons from a metasediment of the Loch Maree Group, Lewisian Complex, NW Scotland show striking similarities to those in coeval Palaeoproterozoic belts of Laurentia and Fennoscandia, and confirm previous suggestions of a connection between them. Late-Archaean zircons (3.06–2.48 Gyr old) represent derivation from Lewisian quartzofeldspathic gneisses, andlor a contemporaneous terrane. Palaeoproterozoic zircons (2.2–2.0 Gyrold) place a maximum age constraint upon deposition. An appropriate quartzofeldspathic source for these latter zircons is not presently known, either in the Lewisian or the wider Laurentia-Fennoscandia region, although its requirement would be consistent with a development of the Loch Maree Group, together with juvenile magmatic arc rocks, at an active margin which was probably removed by lateral tectonics. Comparisons are made with contemporaneous supracrustal sequences throughout the Laurentia–Fennoscandia region, which exhibit marked similarities in source region age characteristics, lithologies, and inferred depositional environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.1997.tb00025.x
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  • 2
    Electronic Resource
    Electronic Resource
    Crust formation in the Lewisian (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 366-366 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Burton et al1 have presented U-Pb and Sm-Nd mineral regression ages on rocks from the Lewisian complex at Gruinard Bay, which apparently require that "the history of crustal development in the Lewisian complex will have to be radically rethought"2. They1 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375366a0
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  • 3
    Electronic Resource
    Electronic Resource
    Nestmate recognition in the leaf-cutting antAtta laevigata (1995)
    Springer
    Insectes sociaux 42 (1995), S. 157-166 
    Details
    ISSN: 1420-9098
    Keywords: Ants ; nestmate recognition ; kin recognition ; pheromones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We tested matureAtta laevigata colonies in the field to see if the ants used queen substances, environmental odours (in this case odours produced by the nest's fungi), an odour produced by each individual, or a gestalt odour (resulting from odours distributed between nestmates) as a discrimination signal for nestmate recognition. We found that nestmate recognition inA. laevigata appears to be largely based on an odour produced by each nestmate which appears to be concentrated in the head, although other odours may also be used. We found no evidence of genetic relatedness influencing the discrimination ability, nor did ants respond differently to neighbors in comparison to non-neighbors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242452
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  • 4
    Electronic Resource
    Electronic Resource
    Sr-Nd-Pb isotope data for ultramafic xenoliths from Hierro, Canary Islands: Melt infiltration processes in the upper mantle (1995)
    Springer
    Contributions to mineralogy and petrology 119 (1995), S. 239-246 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We present here Sr, Nd, and Pb-isotopic data from harzburgite (group I) and dunite–pyroxenite (group II) suite mantle xenoliths from the island of Hierro, one of the youngest and westernmost of the Canary Islands. A progressive leaching technique has been developed and applied to the whole-rock powder samples in order to identify and remove as far as possible any recent additions (host basalt and/or seawater). Isotopic analyses of the leached residues show significant systematic differences between these two suites. Dunite–pyroxenite suite xenoliths (olivine pyroxenites, dunites and wehrlites) exhibit a relatively small range of isotopic compositions (87Sr/86Sr from 0.70292 to 0.70315; 143Nd/144Nd from 0.51295 to 0.51302; 206Pb/204Pb from 19.18 to 19.40) compared to the harzburgite suite (87Sr/86Sr from 0.70295 to 0.70320; 143Nd/144Nd from 0.51285 to 0.51296; 206Pb/204Pb from 18.85 to 19.41). In all isotope correlation diagrams the leached dunite–pyroxenite suite xenoliths plot between the Hierro basalt field and a hypothetical depleted mantle suggesting that these xenoliths may have been strongly infiltrated by Hierro-type basalt. Progressive leaching of this suite of samples showed removal of a component with more enriched Sr (higher 87Sr/86Sr relative to depleted mantle) and Nd (lower 143Nd/144Nd) isotopic compositions that is probably host basalt glass. The leached harzburgite suite xenoliths extend to more enriched Sr and Nd isotopic compositions than Hierro-type basalt but always have more depleted Pb. This relationship can best be explained if this suite has been subject to infiltration by earlier magmas of the Canary Island suite (in particular, those from Gran Canaria show appropriate compositional ranges), although additional infiltration by Hierro basalt cannot be ruled out. The leaching experiments for this suite mostly show removal of a radiogenic Sr component only (? seawater) which supports the interpretation of early infiltration and subsequent recrystallisation and equilibration prior to the Hierro event. Isotopic data presented in this study show that complex interaction with percolating basaltic melts of varying composition was occurring in the upper mantle beneath Hierro prior to and during the volcanic event and was probably related to the generation of earlier Canary Island magmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307284
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  • 5
    Electronic Resource
    Electronic Resource
    Sr-Nd-Pb isotope data for ultramafic xenoliths from Hierro, Canary Islands: Melt infiltration processes in the upper mantle (1995)
    Springer
    Contributions to mineralogy and petrology 119 (1995), S. 239-246 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract We present here Sr, Nd, and Pb-isotopic data from harzburgite (group I) and dunite-pyroxenite (group II) suite mantle xenoliths from the island of Hierro, one of the youngest and westernmost of the Canary Islands. A progressive leaching technique has been developed and applied to the whole-rock powder samples in order to identify and remove as far as possible any recent additions (host basalt and/or sea-water). Isotopic analyses of the leached residues show significant systematic differences between these two suites. Dunite-pyroxenite suite xenoliths (olivine pyroxenites, dunites and wehrlites) exhibit a relatively small range of isotopic compositions (87Sr/86Sr from 0.70292 to 0.70315; 143Nd/144Nd from 0.51295 to 0.51302; 206Pb/204Pb from 19.18 to 19.40) compared to the harzburgite suite (87Sr/86Sr from 0.70295 to 0.70320; 143Nd/144Nd from 0.51285 to 0.51296; 206Pb/204Pb from 18.85 to 19.41). In all isotope correlation diagrams the leached dunite-pyroxenite suite xenoliths plot between the Hierro basalt field and a hypothetical depleted mantle suggesting that these xenoliths may have been strongly infiltrated by Hierro-type basalt. Progressive leaching of this suite of samples showed removal of a component with more enriched Sr (higher 87Sr/86Sr relative to depleted mantle) and Nd (lower 143Nd/144Nd) isotopic compositions that is probably host basalt glass. The leached harzburgite suite xenoliths extend to more enriched Sr and Nd isotopic compositions than Hierro-type basalt but always have more depleted Pb. This relationship can best be explained if this suite has been subject to infiltration by earlier magmas of the Canary Island suite (in particular, those from Gran Canaria show appropriate compositional ranges), although additional infiltration by Hierro basalt cannot be ruled out. The leaching experiments for this suite mostly show removal of a radiogenic Sr component only (? seawater) which supports the interpretation of early infiltration and subsequent recrystallisation and equilibration prior to the Hierro event. Isotopic data presented in this study show that complex interaction with percolating basaltic melts of varying composition was occurring in the upper mantle beneath Hierro prior to and during the volcanic event and was probably related to the generation of earlier Canary Island magmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307284
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  • 6
    Electronic Resource
    Electronic Resource
    Detrital zircon ages from southern Norway – implications for the Proterozoic evolution of the southwestern Baltic Shield (1997)
    Springer
    Contributions to mineralogy and petrology 130 (1997), S. 47-58 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract An ion-microprobe (SIMS) U-Pb zircon dating study on four samples of Precambrian metasediments from the high-grade Bamble Sector, southern Norway, gives the first information on the timing of discrete crust-forming events in the SW part of the Baltic Shield. Recent Nd and Pb studies have indicated that the sources of the clastic metasediments in this area have crustal histories extending back to 1.7 to 2.1 Ga, although there is no record of rocks older than 1.6 Ga in southern Norway. The analysed metasediments are from a sequence of intercalated, centimetre to 10-metre wide units of quartzites, semi-metapelites, metapelites and mafic granulites. The zircons can be grouped in two morphological populations: (1) long prismatic; (2) rounded, often flattened. The BSE images reveal that both populations consist of oscillatory zoned, rounded and corroded cores (detrital grains of magmatic origin), surrounded by homogeneous rims (metamorphic overgrowths). The detrital zircons have 207Pb/206Pb ages between 1367 and 1939 Ma, with frequency maxima in the range 1.85 to 1.70 Ga and 1.60 to 1.50 Ga. There is no correlation between crystal habit and age of the zircon. One resorbed, inner zircon core in a detrital grain is strongly discordant and gives a composite inner core-magmatic outer core 207Pb/206Pb age of 2383 Ma. Two discrete, unzoned zircons have 207Pb/206Pb ages of 1122 and 1133 Ma, representing zircon growth during the Sveconorwegian high-grade metamorphism. Also the μm wide overgrowths, embayments in the detrital cores and apparent “inner cores” which represent secondary metamorphic zircon growth in deep embayments in detrital grains, are of Sveconorwegian age. The composite-detrital-metamorphic zircon analyses give generally discordant 206Pb/238U versus 207Pb/235U ratios and maximum 207Pb/206Pb ages of 1438 Ma. These data demonstrate the existence of a protocrust of 1.7 to 2.0 Ga in the southwestern part of the Baltic Shield, implying a break in the overall westward younging trend of the Precambrian crust, inferred from the southeastern part of the Baltic Shield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050348
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  • 7
    Electronic Resource
    Electronic Resource
    Hercynian, Pan-African, Proterozoic and Archean ion-microprobe zircon ages for a Betic-Rif core complex, Alpine belt, W Mediterranean – consequences for its P-T-t path (1999)
    Springer
    Contributions to mineralogy and petrology 134 (1999), S. 134-149 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Ion-microprobe analysis of zircons from an andalusite-bearing orthogneiss within the major Alpujárride nappe complex in the central part of the Betic Cordilleras has yielded a Hercynian age of 285 ± 5 (2σ) Ma for euhedral rims, interpreted as the magmatic age of the andalusite-bearing biotite granite parent rock for the gneisses. Zircon age zoning systematics suggest a Paleozoic sedimentation age for the parent material for the anatectic source rock. Zircon cores represent several groups of ages: (1) Archean, c. 2.7 Ga; (2) Early Proterozoic, 2.2–2.0 Ga; (3) Middle Proterozoic, 1.1–0.9 Ga; (4) Pan-African, 0.8–0.5 Ga; including a well-defined event at 612 ± 13 (2σ) Ma. Paragenetic and textural relations indicate that gneissification took place during a high-P (12–13 kbar) low-T (450–500 °C) collisional event during which the primary Alpine nappe pile was produced. The second and final Alpine tectono-metamorphic event led to reorganization of the primary nappe pile by extensional tetonics with coeval very fast rock uplift and cooling (from c. 8? to c. 1 kbar and c. 600 to 100 °C within the period 19.5–18.5 Ma). The fast uplift/cooling stage was triggered by slab break-off which is thought to have induced diapiric underplating by high-T asthenospheric material. This may have heated the collisional wedge, causing thermal weakening which might have advanced the late stage fast uplift/cooling. The Alpine events did not leave a zircon crystallization record. The inherited, Archean–Pan-African zircon age pattern corresponds to that established for the Hercynian basement in central and southern Europe which is considered as reworked Gondwana crust. Deeper levels of core complexes within the Betic-Rif belt thus belong to the pre-Triassic basement of the Tethyan realm (Betic-Ligurian lithosphere) and represent reworked material ultimately derived from Archean and Proterozoic rock complexes from the Gondwana crustal domain. This study implies that thermobarometry of rock complexes which went through several phases of tectono-metamorphic reworking may render ambiguous results if based upon field observations and petrography alone. Zircon ion-microprobe dating may provide additional constraints required to arrive at a feasible tectono-metamorphic history, that is P-T-t trajectory, for such rock complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050474
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  • 8
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    Shisha Pangma Leucogranite, South Tibetan Himalaya: Field Relations, Geochemistry, Age, Origin, and Emplacement (1997)
    University of Chicago Press
    Details
    Publication Date: 1997-05-01
    Print ISSN: 0022-1376
    Electronic ISSN: 1537-5269
    Topics: Geosciences
    Published by University of Chicago Press
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  • 9
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    Sm-Nd Isotopic Data and Earth's Evolution (1996)
    American Association for the Advancement of Science
    Details
    Publication Date: 1996-09-27
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science
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  • 10
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    Thermal evolution, rate of exhumation, and tectonic significance of metamorphic rocks from the floor of the Alboran extensional basin, western Mediterranean (1998)
    American Geophysical Union
    Details
    Publication Date: 1998-10-01
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by American Geophysical Union
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