GEOSCAN, résultats de la recherche


TitrePaleogeography and provenance of Paleozoic rocks, northwest Laurentia: a story of Phanerozoic zircon recycling in northwest Canada
AuteurLane, L S; Gehrels, G E
Source6th International Conference on Arctic Margins (ICAM VI), conference abstracts and presentations; University of Alaska, Geophysical Institute Report UAG-R-335, 2012 p. 1-26; 1 CD-ROM
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110347
Réunion6th International Conference on Arctic Margins (ICAM VI); Fairbanks AK; US; mai 31 - juin 3, 2011
MediaCD-ROM; numérique
ProvinceYukon; Territoires du Nord-Ouest
SNRC95; 96; 97; 105; 106; 107; 115; 116; 117
Lat/Long OENS-144.0000 -120.0000 72.0000 64.0000
Sujetspaléogéographie; zircon; datations au zircon; roches sédimentaires; roches ignées; roches volcaniques; origine; géochronologie; stratigraphie; Paléozoïque
Illustrationslocation maps; graphs; plots; photographs
Programmebassins sédimentaires du Yukon, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Detrital zircon age distributions are a valuable tool for constraining the provenance of sedimentary successions; but they are non-unique indicators that, in general, require additional information. This non-uniqueness arises from the prevalence of multiple episodes of zircon recycling; and also from our incomplete knowledge of potential sources. Accordingly, additional information is required to reveal insights about provenance and paleogeography.
In northwestern Canada, Precambrian sedimentary successions are dominant source areas for Neoproterozoic and early Paleozoic clastic rocks; whereas cratonic sources provide a relatively minor component. Therefore understanding the zircon fingerprint of potential sedimentary sources is critical. Also, the reality that multiple sources supply a sedimentary basin results in DZ distributions that can be complicated to interpret. Further, in our study area, several key successions in widely scattered inliers are poorly dated, making it unclear as to whether they are potential sources or destinations for detrital zircons. Improving the age control for these pre-Ordovician strata is an area of ongoing work.
For the Paleozoic paleogeography of northwestern Canada, the major issue is to locate the supposed suture between allochthonous Arctic Alaska terrane and autochthonous North America (Lane, 2007). Key to resolving this issue is whether the Neoproterozoic and Cambrian Neruokpuk Formation is autochthonous to the region, or alternatively has been transported with Arctic Alaska from elsewhere. The Neruokpuk is an intensely imbricated succession of turbiditic sandstone, siltstone and slate that depositionally underlies an early Paleozoic basinal succession of graptolitic shale, chert, alkalic volcanic rocks and minor limesone. This succession is correlative in detail to the Neoproterozoic and early Paleozoic Hyland Group and Road River successions of the Selwyn Basin within the northern Canadian Cordillera (Lane, 1991; Cecile, 2000). The Neruokpuk sandstones are commonly lithic and include detrital plagioclase, muscovite and biotite indicative of a high grade metamorphic source area. Its detrital zircon distribution is typical of derivation from a northern Laurentian cratonic source: dominated by a distinctive 1800-2000 Ma population that commonly contains a double peak. However, the primary known sources for Neoproterozoic and Cambrian strata in this region are the Wernecke Supergroup of Paleoproterozoic age (or somewhat younger); and the Mackenzie Mountains and Shaler supergroups of Mesoproterozoic age. Within the region, most clastic rocks of Neoproterozoic and early Paleozoic age have detrital zircon signatures that can be correlated with either of these source units; but contain few, or perhaps no, zircons derived directly from a cratonic source.
In contrast, middle and late Paleozoic clastic rocks across the region show distinctive zircon populations that include important populations similar to that of the Neruokpuk. Those in northwesternmost Yukon, including Devonian, Carboniferous and Permian, have populations that appear to be dominantly recycled from that unit and are distinct from populations derived from Paleo- and Mesoproterozoic sedimentary sources. Farther south and east, Late Devonian and Carboniferous clastic rocks contain distinctive Neruokpuk-like 1800-2000 Ma peaks. Further, the Permian and Triassic units display more complex distributions marked by populations that are found in Mesoproterozoic and Neruokpuk successions. A reasonable inference is that these zircon populations are indirectly derived via local recycling of Cambrian through Carboniferous strata.