| Title | Athapuscow aulacogen revisited: Geochronology and geochemistry of the 2046 Ma Union Island Group mafic magmatism, East Arm of Great Slave Lake, Northwest Territories, Canada |
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| Author | Sheen, A I; Heaman, L M; Kjarsgaard, B ; Ootes, L; Pearson, D G; Creaser, R A |
| Source | Precambrian Research vol. 321, 2019 p. 85-102, https://doi.org/10.1016/j.precamres.2018.11.012 |
| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20200274 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Northwest Territories |
| NTS | 75E/09; 75E/10; 75E/11; 75E/12; 75E/13; 75E/14; 75E/15; 75E/16; 75F/11; 75F/12; 75F/13; 75F/14; 85H/09; 85H/10; 85H/15; 85H/16; 85I/01; 85I/02; 85I/07; 85I/08 |
| Area | Great Slave Lake |
| Lat/Long WENS | -113.0000 -109.0000 62.5000 61.5000 |
| Subjects | geochemistry; geochronology; igneous and metamorphic petrology; sedimentology; Science and Technology; mafic rocks; magmatism; igneous rocks; lead uranium ratios; uranium lead dating; baddeleyite;
volcanism; samarium; neodymium samarium dates; continental drift; Proterozoic |
| Illustrations | location maps; stratigraphic columns; photographs; tables; Concordia diagrams; plots; histograms |
| Released | 2018 11 23 |
| Abstract | The Slave craton underwent widespread extension during the Paleoproterozoic. The East Arm basin of Great Slave Lake formed during this period and preserves a protracted record of sedimentation and
volcanism in the southeastern Slave craton. Within the East Arm basin package, the Union Island Group represents voluminous mafic volcanism with subordinate sedimentary strata. We report the first high precision U-Pb zircon and bad-deleyite dates for
the Union Island Group; 2045.8 +/- 1.0 Ma for a volcaniclastic unit from the lower basalt formation and 2042.7 +/- 3.0 Ma for a diabase intrusion within volcaniclastic horizons in the lower basalt formation. We fundamentally revise the lower basin
stratigraphy and demonstrate that the Union Island Group is the oldest identified supracrustal package in the East Arm basin, similar to 120 Myr older than previously thought. This revised stratigraphy is supported by detrital zircon provenance age
distribution in two Union Island Group sedimentary samples, which is dominated by 2.76-2.56 Ga ages, reflecting prominent input from the local Archean Slave basement. The Union Island Group contains two geochemically distinct mafic volcanic packages.
The lower basalt package is predominantly alkaline, characterized by an OIB-like chemical signature with high and variable incompatible element contents (108-438 ppm Zr, 13-62 ppm Nb). In contrast, the upper basalt package is tholeiitic, contains
much lower and uniform incompatible element contents (83-101 ppm Zr, 2-4 ppm Nb), and has an E-MORB-like chemical signature. Both packages display overlapping, depleted time-integrated epsilon Nd(i) values (+1.1 to +3.2). Petrological modeling
suggests the lower package originated as OIB-like melts from the asthenosphere that interacted with a depleted reservoir; the upper package was produced by larger degree of partial melting of a similar mantle source, in addition to possible
lithospheric input. The petrogenesis established in this study is consistent with a passive continental rift origin for the Union Island Group magmatism and is further supported by geochemical similarities with Proterozoic and Phanerozoic rift
successions. We therefore propose that the 2046 Ma Union Island Group represents an incipient rift basin sequence formed during Paleoproterozoic extension that marked the initial breakup of the southern margin of the Slave craton from a pre-Laurentia
supercontinent. |
| GEOSCAN ID | 326686 |
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