The Complex History of the Slave Craton Lithospheric Mantle Root in the Context of Regional Tectonics

English Abstract:

The Slave craton is one of the smallest recognised cratons worldwide. It is surrounded by Paleoproterozoic orogenic belts, Wopmay/Great Bear on the west and the Taltson-Thelon on the east and south. Several Proterozoic diabase dike swarms cut the Slave, the most intensive of which being the ~1.27 Ga Mackenzie LIP. Using peridotite xenoliths derived from kimberlites we present a N-S transect across the craton with the aim of examining the effects of these post-Archean events on the composition, age and depth of the lithospheric root. We present new Re-Os isotope data for peridotite xenoliths from Gahcho Kue (southeast Slave), Diavik (central Slave), and the Artemisia kimberlite (northern Slave), that are integrated with previously available data. Late Archean minimum Re-depletion ages dominate the lithospheric mantle of the central Slave and the small available dataset for the southern Slave. Archean ages are present at Jericho, in the lower part of the North Slave but there is an increasing proportion of Paleoproterozoic and Mesoproterozoic Re depletion ages. In contrast, Archean depletion ages are absent from Artemisia, where the peridotite suite is dominated by Proterozoic depletion ages. Progressing North from the Central Slave there is a decreasing proportion of Archean model ages in the lithosphere, through Jericho to Artemisa. Approximately 70% of the dataset at Artemisia give Re depletion ages within error of the Mackenzie LIP event, with a secondary component (~ 30%) close to the Wopmay/Taltson orogenic events. This age spectrum in the far North of the Slave Craton, combined new data from regions to the N and NW of the Slave craton indicate the likelihood of major new lithosphere generation in both the Paleoproterozoic and Mesoproterozoic and adds to the growing evidence for the generation of stable “cratonic-like” lithospheric mantle in the Proterozoic (e.g., the Siberian craton). This observation, if correct, has major implications for post-Archean diamond sources.