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| Mougel, Berengere; Moreira, Manuel; Agranier, Arnaud. |
| We investigate in details helium isotope data reported in Mougel et al. (2014) for 14 basaltic samples collected on the East Pacific Rise by submersible (15 degrees 4N) where the ridge interacts with the Mathematician seamounts. Samples locations are separated by only few hundred meters across a 15km along-axis profile. The data reveal a strong geochemical variability that has never been observed at such high spatial resolution for helium isotope compositions. Moreover, they reveal an unusually high He-4/He-3 mantle component also characterized by unradiogenic lead, atypical in oceanic basalts. He-Pb systematics suggests a mixture between a nonradiogenic lead and radiogenic helium pyroxenitic component, recycled from the deep continental lithosphere and... |
| Tipo: Text |
Palavras-chave: Helium; Isotopes; Mantle geochemistry; MORB; Hot spot; EPR. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00639/75140/75500.pdf |
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| Knijf, G. de; Anselin, A.; Goffart, P.. |
| Trends in dragonfly occurrence in Belgium (Odonata) The group ‘Gomphus’ collected 65 000 records of 69 species of Odonata, more or less equally scattered over Belgium. The best-investigated areas are the northern part and some river valleys in the south. Most hot spots can be found in the northeastern part, with a maximum of 48 species for 25 km². Remarkable is the fact that 50% of the species occurs in less than 7% of the 5 km grid cells (UTM). We determined trends in occurrence by comparing three periods: before 1950, 1950-1989 and 1990-2000. Four species show a clear decline over the three periods, eight species give evidence of a historical decline but survive on a limited number of sites and eight species also display a historical decline but have... |
| Tipo: Article in monograph or in proceedings |
Palavras-chave: Odonata; Dragonflies; Belgium; Atlas; Hot spot; Abundance class shift; Habitat; 42.75. |
| Ano: 2003 |
URL: http://www.repository.naturalis.nl/record/219852 |
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