Petrography and U-Pb zircon geochronology of Caledonian age orthogneisses dredged from the Chukchi Borderland, Arctic Ocean

• Main Authors: Brumley, Kelley, Miller, Elizabeth L, Mayer, Larry A., Wooden, J L, Dumitru, T A
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2011
• Subjects: Arctic Ocean; Chukchi Borderland; geochronology; Petrography; Computer Sciences; Oceanography and Atmospheric Sciences and Meteorology; Arctic; Svalbard; Ellesmere Island; Canada; Greenland; barents region; Chukchi; Alaska
• Online Access: https://scholars.unh.edu/ccom/650; http://abstractsearch.agu.org/meetings/2011/FM/T51K-07.html

The Caledonian orogenic belt developed in the Ordovician to Devonian affecting northern Europe, Greenland and Arctic Canada. Caledonian deformational trends continue into the Arctic region disappearing at the rifted margin of the Arctic Ocean. Syn-orogenic magmatism in the Barents region date deformation of Grenvillian basement during the Caledonian event to be between about 450-410 Ma (Johansson et al., 2005; Gee et al., 2006; Gee and Tebenkov, 2004). Over 500 kilos of metamorphic rock was dredged from outcrops in the central Chukchi Borderland in 2009 (HLY0905) that included amphibolites and orthogneisses metamorphosed to amphibolite facies continuing to deform under greenschist conditions. Zircons were separated from two orthogneiss samples from this dredge, and single grain zircon U-Pb ages were determined by SHRIMP analysis be 428 Ma ± 3.4 for both samples (N=60). One sample had several zircon grains with distinct igneous cores that ranged in age from about 850-1000 Ma. Grenville age plutons (1000-910 Ma) that were later involved in Caledonian deformation and intruded by 450-410 Ma aged plutons are found on western and eastern Svalbard (Johansson et al., 2005), eastern Greenland, and the Pearya Terrane of northern Ellesmere Island (Trettin,1986, 1992). The Franklinian basement of Arctic Alaska and Canada do not share these Grenvillian ages (Trentin et al, 1987). This suggests that the inherited zircon cores in the Chukchi Borderland orthogneisses were derived, at least in part, from an older Grenvillian basement like that of Pearya, Svalbard and parts of Greenland and later intruded by Caledonian aged granites.