Age and Evolution of Deep Continental Roots beneath Northern Canada

Jingao Liu1, Amy J Riches1, Laura Brin1, Graham Pearson1, Bruce Kienlen2, Bruce A. Kjarsgaard3, Thomas Stachel1 and John P. Armstrong4, (1)University of Alberta, Earth & Atmospheric Sciences, Edmonton, AB, Canada, (2)Canterra Minerals Corp, Vancouver, BC, Canada, (3)Geological Survey of Canada, Ottawa, ON, Canada, (4)Lucara Diamond Corp, Vancouver, BC, Canada

Contact First Author: Jingao Liu; jingao@cugb.edu.cn

Previously Published Material: Part of the data were recently presented in a poster at AGU, 2014. No journal publication yet.

Abstract ID#: 33501

 

English Abstract:
The age, composition and extent of Archean lithosphere is well documented beneath the Slave Craton. Little is known, however, about the deep continental roots beneath the rest of Canada’s vast north, despite the discovery of many new diamond-bearing kimberlites. Here we present age and composition information for kimberlite-borne peridotite xenoliths from the central Rae Craton (two localities: Repulse Bay and Pelly Bay) and central Victoria Island (CVI - a possible northern extension of the Slave Craton), and the Parry Peninsula (a possible new micro-craton- the Mackenzie craton), to investigate the nature and evolution of the deep lithosphere in these regions.

The peridotites from the central Rae Craton, CVI and Parry Peninsula are generally characterized by high forsterite contents (Fo 92-93) and low whole-rock Al2O3 contents (< 2 wt.%, many < 1wt.%), similar to typical cratonic peridotites worldwide. However, these peridotites show a large span in Re-depletion model ages (TRD). For the central Rae Craton, both localities preserve evidence of Archean parentage, with more of the Repulse Bay samples yielding Archean TRD ages (>2.5 Ga) than for Pelly Bay. They also show significant Paleoproterozoic (1.6 to 2.2 Ga) ages that indicate reworking or newly formed lithospheric mantle in this period, contrasting with the little disturbed central Slave lithosphere by other studies. This event was most likely associated with either the Thelon-Taltson orogen in the west or the Trans-Hudson orogen in the southeast.

Despite having highly depleted mineral and bulk compositions, we find no definitive evidence of Archean lithosphere beneath the Mackenzie craton (Parry Peninsula peridotites). Similarly, the CVI peridotites yield no Archean TRD ages but are dominated by Paleoproterozoic ages (1.5 to 2.3 Ga). For both CVI and the Mackenzie craton, the local deep lithosphere is more likely an extension of the Wopmay orogen (ca. 1.9 Ga) rather than the northern or western extension of the Slave Craton.

Deep, refractory, diamond-bearing lithosphere can form in post-Archean times, perhaps in subduction zone settings.

Back to: Canadian Cratons Through Time: 4.0 Ga of Chemical Evolution and Tectonism