DETRITAL ZIRCON GEOCHRONOLOGY OF DEVONIAN AND CARBONIFEROUS SEDIMENTARY ROCKS OF THE PEARYA TERRANE: IMPLICATIONS FOR TESTING TERRANE RECONSTRUCTIONS

The Pearya Terrane of northernmost Ellesmere Island is currently recognized as the only exotic terrane in the Canadian Arctic Islands. It is characterized by Neoproterozoic metaigneous rocks and a sequence of variably metamorphosed sedimentary units of Neoproterozoic to Paleozoic age. Previous work suggests that this terrane originated in the Caledonian realm and was translated along a sinistral strike-slip boundary into position against the northern Laurentian margin as a series of fault bounded slices. Docking is inferred to have been completed in the early Silurian. The Pearya terrane is in a position to test Devonian to Carboniferous paleogeographic models of the northern Laurentian margin, including ties between the northern Caledonides and the North American Cordillera.

Ordovician and Silurian sedimentary units of the Pearya terrane are characterized by unimodal 430-450 Ma peaks and a dominant earliest Neoproterozoic peak accompanied by lesser Mesoproterozoic populations characteristic of the Pearya basement and reworked Neoproterozoic sediments. Devonian to Carboniferous post-accretion clastic sediments define a broader age range suggestive of additional sources beyond the Pearya terrane. The composite age spectrum reveals peaks between 600 to 710 Ma, suggestive of a source influenced by the Timanide orogen, a peak at c. 965 Ma likely derived from the documented North Atlantic-Arctic areas recording early Neoproterozoic magmatic activity (e.g. the Pearya terrane, Svalbard, Finnmark and East Greenland), and a pattern of ages between c 1.0 to 2.0 Ga characteristic of Grenville-Sveconorwegian provinces of Laurentia and Baltica. Archean grains are rare, defining small peaks at c. 2.75 and c. 2.85-2.87 Ga, with single older grains present in the Carboniferous samples. Samples from the Upper Devonian Okse Bay formation yield a young peak between 375 to 430 Ma, reflecting an Arctic Caledonide source, with the Devonian grains possibly originating from the Arctic Alaska-Chukotka microplate. Carboniferous strata show continued mixing of multiple sources with broad spectra ranging from 360 to 3200 Ma.