Whole-rock Rb/Sr and zircon U/Pb ages of metamorphic rocks from northern Ellesmere Island, Canadian Arctic Archipelago. II. The Cape Columbia Complex

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Sinha, A. K., Frisch, Thomas
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1976
• Subjects: Arctic Archipelago; Canadian Arctic Archipelago; Cape Columbia; Ellesmere Island; North Atlantic
• Online Access: http://dx.doi.org/10.1139/e76-080; http://www.nrcresearchpress.com/doi/pdf/10.1139/e76-080

Although not clearly separable on field and petrographic criteria, the gneisses of the Cape Columbia Complex, one of the two major crystalline terrains in the Northern Ellesmere Fold Belt, fall into two Rb/Sr age groups: nine samples define an isochron corresponding to an age of 1083 ± 18 m.y., Sr 0 = 0.7057, while six samples show more scatter at 512 ± 90 m.y.,Sr 0 = 0.7189. Zircons from two gneisses have 207 Pb/ 206 Pb, i.e. minimum, ages of 926 and 980 m.y. These data are interpreted as indicating that the rocks were recrystallized in the amphibolite facies about 1000 m.y. ago; little significance is attached to the younger Rb/Sr age. However, the possibility that the rocks are orthogneisses emplaced about 1000 m.y. ago and subsequently metamorphosed ~500–600 m.y. ago, cannot be excluded. In any event, the Cape Columbia Complex becomes the latest addition to the growing list of occurrences of 900–1200 m.y.-old ('Grenville-Sveco-Norwegian') rocks in the North Atlantic craton and environs.