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Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the family Salmonidae, lake trout (Salvelinus namaycush) are considered the least tolerant of salt water. There are, however, sporadic reports of lake trout in coastal, brackish habitats in the Canadian Arctic. Otolith microchemistry analyses conducted on lake trout and Arctic char (Salvelinus alpinus) from four Arctic lakes in the West Kitikmeot region of Nunavut, Canada, revealed that 37 of 135 (27%) lake trout made annual marine migrations. Anadromous lake trout were in significantly better condition (K = 1.17) and had significantly higher C:N ratios (3.71) than resident lake trout (K = 1.05 and C:N = 3.34). Anadromous lake trout also had significantly higher δ15N (mean = 16.4‰), δ13C (mean = –22.3‰), and δ34S (mean = 13.43‰) isotope ratios than resident lake trout (means = 12.84‰, –26.21‰, and 1.93‰ for δ15N, δ13C, and δ34S, respectively); results were similar for Arctic char and agree with results from previous studies. Mean age of first migration for lake trout was 13 years, which was significantly older than that for Arctic char (5 years). This could be a reflection of size-dependent salinity tolerance in lake trout, but further research is required. These are the first detailed scientific data documenting anadromy in lake trout. Dans la famille des Salmonidae, ce sont les touladis (Salvelinus namaycush) qui sont considérés les moins tolérants à l’eau salée. On signale néanmoins de temps à autre la présence de touladis dans les habitats côtiers et saumâtres de l’Arctique canadien. Des analyses microchimiques des otolithes faites sur des touladis et des ombles chevaliers (Salvelinus alpinus) de quatre lacs arctiques dans la région du Kitikmeot occidental au Nunavut, Canada, montrent que 37 de 135 (27 %) touladis avaient fait des migrations annuelles en mer. Les touladis anadromes sont en significativement meilleure condition (K = 1,17) et possèdent un rapport C:N (3,71) relativement plus élevé que les touladis résidants (K = 1,05 et C:N = 3,34). Les touladis anadromes ont aussi des rapports d’isotopes δ15N (moyenne = 16,4 ‰), δ13C (moyenne = –22,3 ‰) et δ34S (moyenne = 13,43 ‰) plus élevés que ceux des touladis résidants (moyennes de 12,84 ‰, –26,21 ‰ et 1,93 ‰ pour respectivement δ15N, δ13C et δ34S); les résultats sont semblables chez les ombles chevaliers et concordent avec ceux des études antérieures. L’âge moyen de la première migration chez le touladi est de 13 ans, ce qui est significativement plus tard que chez l’omble chevalier (5 ans). Cela pourrait refléter une tolérance à la salinité reliée à la taille chez le touladi, mais il faut des recherches supplémentaires sur le sujet. Nos résultats représentent les premières données scientifiques détaillées sur l’anadromie chez le touladi. [ABSTRACT FROM AUTHOR]

A review of the ages determined for mantle material (xenoliths and xenocrysts entrained in kimberlite) derived from the Slave Province continental lithospheric mantle (CLM) indicates that a portion of the central Slave lithosphere may be ancient (3.5–3.3 Ga) harzburgite, but the majority of this lithosphere is much younger (2.9–2.0 Ga). Relying on the most robust chronometers, the majority of Slave lithosphere peridotite formed in the Neoarchean (peak at 2.75 Ga), whereas the majority of eclogite formed in the Paleoproterozoic (2.2–2.0 Ga). The northern Slave lithosphere contains evidence of peridotite xenolith ages that young with depth. The Paleoproterozoic eclogites may have multiple origins including remnants of subducted oceanic crust and mafic–ultramafic magmas that crystallized at great depth (100–200 km). Re–Os studies of sulfide inclusions in diamond indicate that some diamonds currently mined are ancient (~3.5 Ga), but many Slave diamonds could be considerably younger. Most eclogitic diamonds recovered from the Slave craton are interpreted to be related to the formation of Paleoproterozoic eclogite. There is abundant evidence for Mesoproterozoic modification of the Slave lithosphere (e.g., heating by magma emplacement at great depth and metasomatism) and possible new addition to the lithosphere at that time. The Canadian Slave and African Kaapvaal lithospheres have similar peaks in cratonic peridotite formation ages at about 2.8 Ga, indicating that a large portion of the CLM in these two cratons formed and stabilized in the Neoarchean. One difference is that the Slave peridotites are much less enriched in SiO2, possibly reflecting the more metasomatized nature of the Kaapvaal CLM. The dominance of Paleoproterozoic formation ages for Slave mantle eclogites contrasts with the dominance of Neoarchean formation ages for Kaapvaal mantle eclogites. Une révision des âges déterminés sur des matériaux du manteau provenant du manteau lithosphérique continental de la Province des Esclaves (des xénolites et des xénocristaux entraînés dans de la kimberlite) indique qu’une portion de la lithosphère centrale des Esclaves pourrait être une ancienne harzburgite (3,5–3,3 Ga) mais que la plus grande partie de cette lithosphère est beaucoup plus jeune (2,9–2,0 Ga). En se basant sur les chronomètres les plus robustes, la plus grande partie de la peridotite de la lithosphère des Esclaves s’est formée au Néoarchéen (crête à 2,75 Ga) alors que la plus grande partie de l’éclogite s’est formée au Paléoprotérozoïque (2,2–2,0 Ga). La lithosphère nord des Esclaves contient des évidences d’âges de péridotite xénolite qui rajeunissent en profondeur. Les éclogites datant du Paléoprotérozoïque peuvent avoir de multiples origines, incluant des lambeaux de croûte subductée et des magmas mafiques–ultramafiques qui se sont cristallisés à de grandes profondeurs (100–200 km). Des études Re–Os des inclusions de sulfures dans les diamants indiquent que quelques diamants actuellement exploités sont anciens (~3,5 Ga) mais que plusieurs des diamants provenant de la Province des Esclaves pourraient être beaucoup plus jeunes. La plupart des diamants de paragenèse éclogitique provenant du craton des Esclaves sont interprétés comme étant reliés à la formation de l’éclogite paléoprotérozoïque. Il existe beaucoup de preuves de modifications, au Mésoprotérozoïque, de la lithosphère des Esclaves (p. ex. un réchauffement par la mise en place de magma à grande profondeur et du métasomatisme) et l’ajout possible de nouvelle lithosphère à ce moment. Les lithosphères des Esclaves et de Kaapvaal ont des crêtes similaires dans la formation de la péridotite cratonique vers environ 2,8 Ga, indiquant qu’une grande portion du manteau lithosphérique cratonique dans ces deux cratons s’est formée et s’est stabilizée à ce moment. Une différence est que les péridotites des Esclaves sont beaucoup moins enrichies en SiO2, reflétant possiblement la nature plus métasomatisée du manteau lithosphérique cratonique Kaapvaal. La dominance des âges de formation paléoprotérozoïques pour les éclogites du manteau des Esclaves contraste avec la dominance des âges de formation néoarchéens pour les éclogites du manteau du Kaapvaal. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic. [ABSTRACT FROM AUTHOR]