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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.)

Northwestern Baffin Island, Nunavut, Canada, preserves the stratigraphic record in the northern margin of the Foxe Basin. The Ordovician succession exposed on an unnamed peninsula west of Steensby Inlet, northwestern Baffin Island includes the Lower and Middle Ordovician Ship Point Formation and Upper Ordovician Frobisher Bay and Amadjuak formations. Nearly 7000 conodont specimens recovered from six sections on this peninsula allow the establishment of seven conodont zones throughout this succession: Rossodus manitouensis Taxon-range Zone, Acodus deltatus–Oneotodus costatus Assemblage Zone, Oepikodus communis Interval Zone, and Cooperignathus aranda–Jumudontus gananda Assemblage Zone in units 2 and 3 of the Ship Point Formation, correlative to the upper Tremadocian and Floian, Lower Ordovician; Phragmodus polonicus Taxon-range Zone confined to unit 4 of the Ship Point Formation, correlative to the middle Darriwilian, Middle Ordovician; and Appalachignathus delicatuluss–Belodina confluens and Belodina confluens–Periodon grandis Assemblage zones limited to the Frobisher Bay and Amadjuak formations, respectively, correlative to the lower Katian, Upper Ordovician. The establishment of these conodont zones proves that (1) the Ship Point Formation in the Foxe Basin is not a continuous stratigraphic unit but has a stratigraphic interval missing that is assignable to the Dapingian and lower Darriwilian, Middle Ordovician; (2) the base of the Ship Point Formation is diachronous in the Foxe Basin, which is correlated to the upper Tremadocian on northwestern Baffin Island but to the upper Floian on Melville Peninsula; and (3) the strata younger than lower Amadjuak Formation have been eroded in this area. [ABSTRACT FROM AUTHOR]

Neoproterozoic to early Paleozoic strata exposed along the northeastern margin of North America (Franklinian Basin) record a prolonged history of rifting and passive margin development. An episode of Ediacaran–Cambrian extension is potentially recorded in volcanic and sedimentary rocks of the Yelverton Formation, exposed on northern Ellesmere Island, Nunavut, Canada. Here, we present new whole-rock trace element and isotope geochemistry and hornblende 40Ar/39Ar geochronology from intrusive and extrusive rocks of the Yelverton Formation, along with isotope geochemistry from carbonate rocks underlying the volcanics and detrital zircon U–Pb and Lu–Hf isotopic data from the Yelverton Formation and overlying Grant Land Formation. The carbonate strata yielded an average 87Sr/86Sr value of 0.7076 (n = 6), constraining the overlying volcanics to the late Ediacaran–early Cambrian (ca. 570–530 Ma). Flows and dikes/sills show three distinct compositions: (1) a depleted, low La/YbPM and Th/Nb group, (2) an enriched, higher La/YbPM and low Th/Nb group, and (3) a low to moderate La/YbPM and high Th/Nb group. One of the high Th/Nb intrusions produced saddle-shaped 40Ar/39Ar hornblende spectra with ca. 482 ± 7 Ma age minima and Silurian–Devonian inverse isochron ages, highlighting a hitherto unknown suite of younger intrusions and volcanic rocks. The trace element geochemistry and 143Nd/144Nd(t) ratios of enriched and depleted volcanic rocks of the indisputable Yelverton Formation are consistent with decompression melting during rifting along a continental margin. We suggest that late Ediacaran–early Cambrian rifting recorded in the Yelverton Formation resulted in the separation of peri-Laurentian terranes, such as the North Slope subterrane and eventual development of the passive margin of northern Laurentia. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Reviews 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 structural geology of the northeastern Paleoproterozoic Amer belt, central Nunavut, has been evaluated in light of new field mapping combined with legacy data and independently acquired subsurface geophysics data. Proterozoic sequences Ps1–Ps4 of the Amer supergroup unconformably overlie Archean basement. Of these sequences, Ps1–Ps3 have been intensely deformed (D1) in association with the Snowbird Orogeny (2.05–1.865 Ga). Ps4 was deposited unconformably on the first three sequences and exhibits none of the D1 effects. Deformation within Ps4 is slight compared to the underlying sequences and is restricted to D2 folding that occurred in the 1.84–1.81 Ga Hudsonian Orogeny. Deformation of sequences Ps1–Ps3 forms the core of this study. D1 comprises imbricate thrusting, intersequence detachment, and three generations of isoclinal folding and transposition. The stratigraphic order is maintained in many areas by decoupling of sequence packages along incompetent units so as not to "mix" lithologies; there is a fundamental mechanical stratigraphy. Within sequences, transposition can be otherwise intense. The resultant architecture is a shallowly southwest-dipping sequence of tectonically rotated and transposed layering (primary and tectonic) similar in many ways in orientation regardless of whether preserved with original bedding features or completely transposed. D1 folding is characterized by recumbent folds, noncylindrical folds that are sometimes rooted in detachments, verging to the northeast. D2 folding is controlled by the pre-existing large-scale D1 fabric, resulting in the overturned synforms that parallel the belt. Post-D2 fault modification of northern side of the belt along northwest-trending faults is interpreted to relate to extension and exhumation. [ABSTRACT FROM AUTHOR]

The Amer Belt, hosting eleven informal formations of the Amer supergroup, is proposed as type area for four regional Paleoproterozoic sequences (Ps1–Ps4) in central Rae Craton, western Churchill Province. The ca. 1.9–1.865 Ga Snowbird orogeny (DP1) affected only Ps1–Ps3, whereas the ca. 1.87–1.81 Ga Hudsonian orogeny (DP2) affected all four. Sequence Ps1 Ayagaq Lake formation (<2.3 Ga quartzite) initiates as schistose basal polymict orthoconglomerate unconformably overlying paleoweathered Neoarchean rocks. It transitions upward to lower Ps2 Resort Lake formation: gossanous, recessive, graphitic, pyritic-metalliferous phyllite (Re–Os age: 2126 ± 24 Ma). Ps2 conductors beneath the <1.74 Ga Thelon formation have been drilled for unconformity-related uranium. Gradationally overlying siliceous dolomitic marble (Aluminium River formation) completes Ps2. The gradationally overlying lower Ps3 is either foliated calcareous tholeiitic basalt (Five Mile Lake formation) or grey phyllite (Three Lakes formation). These lateral equivalents host strong linear aeromagnetic markers. The Oora Lake formation foliated feldspathic calcareous sandstone gradationally overlies only the Three Lakes formation and underlies the upper Ps3 Showing Lake formation (interbedded phyllite and foliated calcareous arkose) whose two arkose members host laterally continuous disseminated uraninite + magnetite forming linear aeromagnetic markers. Pristine sequence Ps4 molasse, deposited and weakly deformed during DP2, comprises four formations of rhythmically interbedded, deep maroon to pink and green, feldspathic-lithic arenite, conglomerate, and mudstone that unconformably overlie and include clasts of DP1-deformed Ps1–Ps3 + Neoarchean basement. Ps4 detrital zircon (3.05–1.90 Ga) suggests local + distal provenance from south Rae and Slave Cratons, and Taltson–Thelon magmatic zone. [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.)

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.)

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.)

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.)

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.)

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.)

The Boothia mainland region of the north-central Rae domain is underlain by remnants of a Neoarchean volcano sedimentary sequence dismembered by two regionally extensive Neoarchean high-potassium granitoid suites with rare occurrences of a structurally interleaved, Paleoproterozoic sedimentary cover sequence. The granitoids and their gneissic equivalents are dominated by variably deformed and metamorphosed I-type, metaluminous, polyphase, commonly porphyritic to augen, biotite ±hornblende monzogranite, and subordinate granodiorite, with rare tonalite. New geochronological results, the first for this area, demonstrate that the widespread Neoarchean granitoid plutonism is dominantly 2.61-2.59 Ga, with a less prominent 2.66 Ga plutonic event. The age of zircon recrystallization suggests that ca. 2.60 Ga Archean metamorphism and fabric development (S1) affected the 2.66 Ga plutons prior to or contemporaneously with intrusion of the voluminous ca. 2.6 Ga suite. εNd(t) for the ca. 2.61-2.59 Ga suite range from 1.4 to -1.9, overlapping with the ca. 2.66 Ga suite that range from 1.4 to 1.5. The Nd isotopic data, coupled with the presence of inherited ca. 2.65, 2.70, and 2.85-2.90 Ga zircon, suggests recycling of older, Neoarchean to Mesoarchean crust in the formation of these suites. Metaplutonic rocks preserve Paleoproterozoic deformation (F4 and F5) and amphibolite-facies metamorphism, sporadically recorded in zircon rims that formed at 1.81 Ga. This event strongly reoriented the Neoarchean fabrics in metaplutonic rocks, generally without the development of a new coaxial Paleoproterozoic fabric, and we attribute this strain and metamorphism to the Hudsonian orogeny. La région terrestre Boothia du domaine Rae centre-nord repose sur des vestiges d'une séquence volcano-sédimentaire datant du Néoarchéen; cette séquence est démembrée par deux suites granitoïdes d'échelle régionale, à teneur élevée en potassium et possédant de rares occurrences d'une séquence structurellement intercalée d'une couverture sédimentaire datant du Paléoprotérozoïque. Les granitoïdes et leurs équivalents gneissiques sont dominés par un monzogranite à déformation variable, métamorphisé, de type I, métalumineux, polyphasé, souvent porphyrique à oeillé et à biotite hornblende avec une granodiorite subordonnée et une rare tonalite. De nouveaux résultats géochronologiques, les premiers pour ce secteur, démontrent que le plutonisme granitoïde néoarchéen étendu date surtout de 2,61 à 2,59 Ga, avec un événement plutonique moins important vers 2,66 Ga. L'âge de la recristallisation du zircon suggère que, vers 2,60 Ga, le métamorphisme archéen et le développement de la fabrique (S1) aient affecté les plutons âgés de 2,66 Ga avant ou en même temps que l'intrusion de la volumineuse suite vers 2,6 Ga. Les valeurs εNd(t) pour la suite datant de ~ 2,61 à 2,59 Ga varient de 1,4 à -1,9, chevauchant la suite datant ~2,66 Ga, dont les valeurs εNd(t) varient de 1,4 à 1,5. Les données d'isotopes Nd, jumelées à la présence de zircons hérités dont les âges sont ~2,65, 2,70 et 2,85-2,90 Ga, suggèrent un recyclage de l'ancienne croûte néoarchéenne à mésoarchéenne pour la formation de ces suites. Des roches métaplutoniques ont préservé la déformation paléoprotérozoïque (F4 et F5) ainsi que le métamorphisme au faciès des amphibolites, retrouvé sporadiquement dans les bordures des zircons qui se sont formées à 1,81 Ga. Cet événement a grandement réorienté les fabriques néoarchéennes dans les roches métaplutoniques, généralement sans le développement d'une nouvelle fabrique coaxiale paléoprotérozoïque; nous attribuons cette déformation et ce métamorphisme à l'orogenèse hudsonienne. [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.)

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]

Detrital zircons from the Lower Cretaceous Isachsen Formation of the Sverdrup Basin, Canadian Arctic Archipelago, have been dated by the U–Pb method and analyzed for Hf isotopes by laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS). Five samples from four locations on Ellesmere and Axel Heiberg islands display similar ranges of U–Pb ages, with significant zircon populations at 2.8–2.6, 1.9–1.8, 1.7–1.6, and 1.2–1.0 Ga. Major hiatuses occur between 2.4 and 2.0 Ga and from 0.96 to 0.5 Ga. Low initial εHf values indicating recycled crust components are significant in Palaeoproterozoic (1.9–1.8 Ga) and Neoarchaean (2.8–2.6 Ga) zircon populations. Other U–Pb age populations in the studied samples are dominated by zircon with positive εHf values, indicating a significant contribution from mantle-derived protoliths. The εHf values seen within a given U–Pb age population are generally consistent, with only minor scatter among the different samples. U–Pb and Hf data closely resemble previously published data from Lower Cretaceous rocks in northern Greenland, suggesting they have the same origin. The data are also largely consistent with the East Greenland Caledonides and the Precambrian basement of Greenland and northern Canada as predominant sources of zircon for the studied sandstones. However, based on the level of similarity between data from the Wandel Sea Basin and Sverdrup Basin sediments and on previous Nd isotope work in the Sverdrup Basin, it is likely that the sediments represent redeposited lower and middle Palaeozoic sediments. Des zircons détritiques de la Formation d’Isachsen (Crétacé inférieur) du bassin de Sverdrup, dans l’archipel Arctique, ont été datés par U–Pb et analysés pour les isotopes Hf par ablation au laser et spectrométrie de masse à plasma induit par haute fréquence (LAM–ICP–MS). Cinq échantillons de quatre sites sur les îles d’Ellesmere et d’Axel Heiberg montrent des plages similaires d’âges U–Pb avec des populations significatives de zircons à 2,8 à 2,6, 1,9 à 1,8, 1,7 à 1,6, et 1,2 à 1,0 Ga. Les principales lacunes se situent entre 2,4 à 2,0 et 0,96 à 0,5 Ga. Les faibles valeurs initiales εHf, indiquant la présence de composantes de la croûte recyclée, sont importantes dans les populations de zircons du Paléoprotérozoïque (1,9–1,8 Ga) et du Néoarchéen (2,8–2,6 Ga). D’autres populations dont les âges ont été déterminés par U–Pb dans les échantillons étudiés sont dominées par des zircons à valeurs εHf positives, indiquant une contribution importante de protolites provenant du manteau. Les valeurs εHf perçues à l’intérieur d’une plage donnée de population déterminée par U–Pb sont généralement constantes, avec seulement une dispersion mineure entre les différents échantillons. Les données U–Pb et Hf sont très similaires aux données publiées antérieurement concernant des roches du Crétacé inférieur dans le nord du Groenland, suggérant une origine commune. Les données concordent aussi grandement avec les Calédonides de l’est du Groenland et le socle précambrien du Groenland et du nord du Canada en tant que sources prédominantes de zircons pour les grès étudiés. Toutefois, en se basant sur le niveau de similitude entre les données des sédiments de la mer de Wandel et du bassin de Sverdrup et sur des travaux antérieurs sur les isotopes Nd dans le bassin de Sverdrup, il est probable que les sédiments représentent des sédiments déposés de nouveau au Paléozoïque inférieur et moyen. [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.)

This study presents Last Interglacial and Holocene vegetation and climate changes at Fog Lake (67°11′N, 63°15′W) on eastern Baffin Island, Arctic Canada. The vegetation cover is reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June–July–August–September) were reconstructed from pollen assemblages using the modern analogue technique. The vegetation of the Last Interglacial period evolved from a prostrate dwarf-shrub tundra to a low- and high-shrub tundra vegetation. The succession of four Arctic biomes was distinguished from the Last Interglacial sediments, whereas only one Arctic biome was recorded in the Holocene sediments. From ca. 8300 cal. years BP to present, hemiprostrate dwarf-shrub tundra occupied the soils around Fog Lake. During the Last Interglacial, growing season sunshine was higher than during the Holocene and July air temperature was 4 to 5 °C warmer than present. A principal component analysis helped in assessing relationship between floristic gradients and climate. The major vegetation changes through the Last Interglacial and Holocene were driven by July air temperature variations, whereas the minor, or subtle, vegetation changes seem rather correlated to September sunshine. This study demonstrates that growing season sunshine conditions can be reconstructed from Arctic pollen assemblages, thus providing information on feedbacks associated with cloud cover and summer temperatures, and therefore growing season length. Cette étude présente les changements climatiques et de végétation survenus au cours du dernier interglaciaire et de l’Holocène au lac Fog (67°11′N, 63°15′O), sur la côte est de la Terre de Baffin, dans l’Arctique canadien. La couverture végétale est décrite sous forme de biomes, c.-à-d. de structures de végétation. La température de l’air en juillet et l’ensoleillement lors de la saison de croissance (juin, juillet, août, septembre) ont été reconstitués à partir d’assemblages polliniques selon la méthode des analogues modernes. La végétation de la dernière période interglaciaire a évolué d’une toundra arbustive naine, prostrée à une toundra arbustive basse et haute. Une succession de quatre biomes est visible dans les sédiments du dernier interglaciaire, alors qu’un seul biome est observé dans les sédiments de l’Holocène. Une toundra arbustive hémiprostrée colonize les sols des environs du lac Fog depuis environ 8300 années. Au cours du dernier interglaciaire, l’ensoleillement durant de la saison de croissance était plus élevé que lors de l’Holocène et la température de juillet était de 4 à 5 °C plus chaude qu’actuellement. Une analyse en composantes principales a permis d’évaluer la relation entre les gradients floristiques et le climat. Les changements majeurs de végétation lors du dernier interglaciaire et de l’Holocène découlent principalement des variations de la température de juillet, alors que les changements de végétation plus subtils sont plutôt liés à l’ensoleillement en septembre. Cette étude démontre que les conditions d’ensoleillement lors de la saison de croissance peuvent être déduites à partir des assemblages polliniques des sédiments de l’Arctique, fournissant ainsi de l’information pertinente sur les rétroactions associées au couvert nuageux et aux températures estivales et donc sur la durée de la saison de croissance. [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.)

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.)