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  • 1
    Electronic Resource
    Electronic Resource
    Celestite formation, bacterial sulphate reduction and carbonate cementation of Eocene reefs and basinal sediments (Igualada, NE Spain) (2002)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 49 (2002), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Petrographic and geochemical studies of an Upper Eocene reef and associated basinal sediments from the mixed carbonate–siliciclastic fill of the south-eastern Pyrenean foreland basin near Igualada (NE Spain) provide new insights into the evolution of subsurface hydrology during the restriction of a marine basin. The reef deposits are located on delta-lobe sandstones and prodelta marls, which are overlain by hypersaline carbonates and Upper Eocene evaporites. Authigenic celestite (SrSO4) is an important component in the observed diagenetic sequences. Celestite is a significant palaeohydrological indicator because its low solubility constrains transportation of Sr2+ and SO42− in the same diagenetic fluid. Stable isotopic analyses of carbonates in the reef indicate that meteoric recharge was responsible for aragonite stabilization and calcite cementation. Sulphur and oxygen isotope geochemistry of the celestite demonstrates that it formed from residual sulphate after bacterial sulphate reduction, but also requires that there was a prior episode of sulphate recycling. Meteoric water reaching the reef and basinal areas was most probably charged with SO42− from the dissolution of younger Upper Eocene marine evaporites. This sulphate, combined with organic matter present in the sediments, fuelled bacterial sulphate reduction in the meteoric palaeoaquifer. Strontium for celestite precipitation was partly derived in situ from dissolution of aragonite corals in the reef and basinal counterparts. However, 87Sr/86Sr data also suggest that Sr2+ was partly derived from dissolution of overlying evaporites. Mixing of these two fluids promoted celestite formation. The carbonate stable isotopic data suggest that the local meteoric water was enriched in 18O compared with that responsible for stabilization of other reefs along the basin margin. Furthermore, meteoric recharge at Igualada post-dated evaporite deposition in the basin, whereas other parts of the same reef complex were stabilized before evaporite formation. This discrepancy resulted from the spatial distribution of continental siliciclastic units that acted as groundwater conduits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2002.00437.x
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  • 2
    Electronic Resource
    Electronic Resource
    Revised Sm–Nd systematics of Kambalda greenstones, Western Australia (1984)
    [s.l.] : Nature Publishing Group
    Nature 307 (1984), S. 697-701 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sm–Nd isotope systematics in mafic–ultramafic lavas from the Norseman–Wiluna greenstone belt, Western Australia, have been reinvestigated. A previous age based on mixing lavas and granites is not confirmed: instead, a Sm–Nd age of 3,262 ± 44 Myr is indicated for the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/307697a0
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrothermal alteration associated with gold mineralization in the southern Apuseni Mountains, Romania: preliminary Sr isotopic data (1998)
    Springer
    Mineralium deposita 33 (1998), S. 520-523 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Precious-metal mineralization in the southern Apuseni Mountains of western Romania is hosted by mid-Miocene (∼14 Ma) andesitic stocks and lava flows. The mineralized veins are surrounded by aureoles of hydrothermal alteration, consisting of quartz, sericite, K-feldspar, pyrite and calcite. The alteration process caused a total homogenization of initial 87Sr/86Sr in the rocks. Ages determined for the hydrothermal alteration are 13.7–15.7 Ma, indicating that hydrothermal alteration immediately followed igneous activity. Furthermore, a large influx of radiogenic Sr took place during alteration, this Sr probably being derived from the hydrothermal leaching of continental meta-sedimentary rocks in the basement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001260050167
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  • 4
    Electronic Resource
    Electronic Resource
    1982 eruption of Mount Cameroon, West Africa (1983)
    [s.l.] : Nature Publishing Group
    Nature 306 (1983), S. 327-332 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] MOUNT Cameroon is a large (4,095 m) basanite composite volcano situated on the west African coast (Fig. 1) and is the only active member of the volcanic Cameroon line1,2. The earliest well-authenticated eruption occurred in April 1909 on the northern flank3,4 although earlier eruptions are reported ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/306327a0
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  • 5
    Electronic Resource
    Electronic Resource
    Contamination of Indian Ocean asthenosphere by the Kerguelen–Heard mantle plume (1989)
    [s.l.] : Nature Publishing Group
    Nature 338 (1989), S. 574-576 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 2 illustrates the tectonic evolution of the southern Indian Ocean, and the development of tectono-magmatic features that may be attributable to the Kerguelen-Heard plume. The diagrams suggest that the plume has been involved in the development of several major features of the Indian Ocean ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/338574a0
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  • 6
    Electronic Resource
    Electronic Resource
    Geochemical evidence for plume—mantle interactions beneath Kerguelen and Heard Islands, Indian Ocean (1988)
    [s.l.] : Nature Publishing Group
    Nature 336 (1988), S. 371-374 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Kerguelen and Heard Islands are built on the northern half of the older Kerguelen Plateau, above a geoid high which is indicative of upwelling mantle material8. Although there have been proposals that the plateau represents a continental remnant of the breakup of Gondwana9, recent drilling by the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/336371a0
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  • 7
    Electronic Resource
    Electronic Resource
    Separating mantle from slab signatures in arc lavas using B/Be and radiogenic isotope systematics (1993)
    [s.l.] : Nature Publishing Group
    Nature 362 (1993), S. 530-533 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The volcanoes studied here span 1,500 km of arc length and two very different tectonic settings. In Java, oceanic lithosphere of the Indian plate is subducting beneath Eurasia at a rate7 of 6 cm yrl (Fig. 1). Flores is situated in an arc-continent collision zone and the Australian continental ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/362530a0
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  • 8
    Electronic Resource
    Electronic Resource
    A Ce/Nd isotope study of crustal contamination processes affecting Palaeocene magmas in Skye, Northwest Scotland (1987)
    Springer
    Contributions to mineralogy and petrology 96 (1987), S. 455-464 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Twelve138Ce/136Ce isotope determinations, 31 Nd isotope analyses, and 31 REE profiles are presented for Tertiary basic to intermediate igneous rocks from the Isle of Skye, NW Scotland. The aim of this work is to precisely identify the contamination mechanisms of basic magmas emplaced through old crust, and to test the effectiveness of Ce isotope analysis as a petrogenetic tool. Combined Ce/Nd isotope analysis enables the modelling of the light REE profiles of the mantle-derived precursors to contaminated lavas, using different crustal end-members, in order to compare these with the magmatic lineage of uncontaminated Skye lavas. The geochemical data support a contamination mechanism involving a granitic melt, produced either by large degree melting of Scourian granulitefacies acid sheets, or (possibly) by melting of intermediate gneiss out of isotopic equilibrium. Basaltic lavas showing strong isotopic contamination effects yield calculated degrees of crustal contamination by large degree granitic melts of ca. 8 or 9% based on Ce and Nd isotopic data respectively. However, for lavas with liquidus temperatures of over 1250° C, the temperature dependence of the degree of contamination is weak. The combination of this evidence with new and published Pb isotope data suggests that the bulk of crustal contamination of the Skye lavas occurred in sill complexes at distinct levels in the crust, rather than during the actual ascent of magma through the crust in dykes. It is suggested on the basis of published fluid dynamic and field evidence that the assimilation of large degree melts of acid gneiss by turbulently flowing magma is more likely than assimilation of small degree disequilibrium melts from more refractory intermediate gneisses. It is concluded that Ce isotope analysis is a viable and useful adjunct to Nd isotope data in petrogenetic studies of continental igneous rocks emplaced through old basement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01166690
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  • 9
    Electronic Resource
    Electronic Resource
    Petrology and geochemistry of spinel peridotite xenoliths from the western Pannonian Basin (Hungary): evidence for an association between enrichment and texture in the upper mantle (1992)
    Springer
    Contributions to mineralogy and petrology 109 (1992), S. 340-354 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Twenty spinel peridotite xenoliths from Pliocene alkali basaltic tuffs and lavas of the western Pannonian Basin (Hungary) have been analysed for bulk rock major and trace elements, electron probe mineral compositions, and REE and Sr, Nd isotopes on separated and leached clinopyroxenes. The xenoliths are texturally diverse, including protogranular, porphyroclastic, equigranular and poikilitic textures which can generally be correlated with geochemical features. Protogranular xenoliths are relatively undepleted in Ca, Al, Ti and Na, whereas poikilitic xenoliths are more refractory. LREE-depleted patterns. and MORB-like εNd and εSr values are associated with protogranular peridotites. In contrast, xenoliths with complex textures are generally LREE-enriched. Much of the isotopic variation in the suite (εSr=−20.4 to +10.4, +Nd=+1.8 to +13.7) can be related to interaction between protogranular mantle and melts resembling the host alkali basalts, but a third (high εSr) component may be due to Miocene subduction beneath the region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283323
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  • 10
    Electronic Resource
    Electronic Resource
    Relationship between deformation, equilibration temperatures, REE and radiogenic isotopes in mantle xenoliths (Ray Pic, Massif Central, France): an example of plume-lithosphere interaction? (1997)
    Springer
    Contributions to mineralogy and petrology 127 (1997), S. 187-203 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Anhydrous spinel peridotite xenoliths from the Ray Pic Quaternary alkali basalt volcano (French Massif Central) show a wide range of mineralogical and geochemical compositions, reflecting significant heterogeneities in the shallow sub-continental lithospheric mantle. Variations in modal mineralogy, mineral chem istry, REE patterns and radiogenic isotope data suggest that depletion by partial melting and enrichment by cryptic metasomatism were the major mantle processes which caused the heterogeneity. The lithospheric mantle beneath Ray Pic contains two contrasting types of peridotite: (i) lherzolites with LREE-depleted compositions, high 143Nd/144Nd, low 87Sr/86Sr and unradiogenic Pb isotope ratios; (ii) lherzolites, harzburgites and a wehrlite with LREE-enriched patterns, low 143Nd/144Nd, high 87Sr/86Sr and radiogenic Pb isotope ratios. The former closely resemble depleted MORB-source mantle. The latter are related to enrichment by recent infiltration of small degree partial melts or fluids from the asthenospheric mantle, possibly related to the “low velocity component” observed by Hoernle et al. (1995) in European Neogene alkaline magmas. Thus, the Ray Pic peridotite xenoliths represent interaction between asthenospheric mantle-derived melts/fluids and depleted lithospheric mantle. This is probably linked to the upwelling mantle plume imaged beneath the Massif Central (Granet et al. 1995). A relationship between textural deformation, equilibration temperature and geochemistry of the xenoliths suggests that the hotter (〉 900 °C) undeformed regions are LREE-enriched and tend to have more enriched isotope ratios, whereas the cooler (〈 900 °C) regions have undergone more deformation and are more depleted both in LREE and in isotope compositions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050275
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