Journal article
U-Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska
Canadian journal of earth sciences, Vol.28(8), pp.1285-1300
Geological Association of Canada symposium on Precambrian basement of the Canadian Cordillera; isotopic insights--Le sous-sol precambrien de la Cordillere canadienne; techniques isotopiques
08/1991
DOI: 10.1139/e91-114
Abstract
Metamorphic rocks within and west of the N Coast Mts in SE Alaska consist of an upper Proterozoic(?) to Upper Palaeozoic continental margin assemblage that is interpreted as belonging to the Yukon- Tanana terrains. U-Pb geochronological analyses of single detrital zircon grains from four samples of quartzite suggest that the zircons were shed from source regions containing rocks of 495, 750, 1050-1400, 1750-2000, approx 2300, 2500-2700 and 3000 m.y. Multigrain fractions from two samples yield upper intercepts between 2000 and 2300 m.y., but the scarcity of single grains of similar age suggests that these fractions comprise a mixture of < 2000 and > 2300 m.y. grains. Zircons in these rocks generally overlap in age with 1) detrital zircons in metasedimentary rocks of the Yukon-Tanana terrain in E Alaska and Yukon; 2) detrital zircons in strata of the Cordilleran miogeocline, and 3) plutonic and gneissic rocks that intrude or are overlain by miogeoclinal strata. In addition, the pre-1700 m.y. grains overlap in age with dated crystalline rocks of the W Canadian Shield. These similarities raise the possibility that metaclastic rocks in the N Coast Mts accumulated in proximity to western North America. The younger zircon populations were probably shed from mid-Proterozoic to early Palaeozoic igneous rocks that now occur locally (but may have been widespread) along the Cordilleran margin. Recognition of a continental margin assemblage of possible North American affinity in the Coast Mts raises the possibility that some arc- type and oceanic terrrains inboard of the Coast Mts may be large klippen that have been thrust over the North American margin.
Details
- Title: Subtitle
- U-Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska
- Creators
- George E Gehrels - University of ArizonaWilliam C McClelland - University of ArizonaScott D Samson - University of ArizonaP. Jonathan Patchett - University of Arizona
- Resource Type
- Journal article
- Publication Details
- Canadian journal of earth sciences, Vol.28(8), pp.1285-1300
- Conference
- Geological Association of Canada symposium on Precambrian basement of the Canadian Cordillera; isotopic insights--Le sous-sol precambrien de la Cordillere canadienne; techniques isotopiques
- Publisher
- National Research Council of Canada
- DOI
- 10.1139/e91-114
- ISSN
- 0008-4077
- eISSN
- 1480-3313
- Alternative title
- Precambrian basement of the Canadian Cordillera; isotopic insights--Le sous-sol precambrien de la Cordillere canadienne; techniques isotopiques
- Language
- English; French
- Date published
- 08/1991
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229180402771
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