UPPER-MANTLE STRATIGRAPHY OF THE SLAVE CRATON, CANADA - INSIGHTS INTOA NEW KIMBERLITE PROVINCE

Mantle xenoliths carried by kimberlite magma provide the only hard evi dence of the rock types that constitute cratonic roots and the conditi ons under which they formed. Here, we present the first such data for the Slave craton (northern Canada) based on samples of peridotite, ecl ogite, and pyroxenite collected from a Middle Jurassic kimberlite (Jer icho pipe). The petrology and thermobarometric analysis of these mantl e xenoliths provide estimates of the thermal state and stratigraphy of the underlying mantle and constrain the evolution of this ancient cra ton. The upper mantle beneath the north Central Slave is relatively co ld, as is typical of cratonic environments, but it is also associated with relatively high values of surface heat flow (47-50 mW/m(2)) becau se of this craton's highly radiogenic crust. Below 160-190 km the Jeri choP-T array shows a significant high-temperature disturbance caused b y transient magmatic events. The apparent source region for both porph yroclastic peridotite and other texturally unequilibrated magmatic roc ks coincides with this thermal excursion and is taken to mark the base of the petrological lithosphere. The depth of this petrological trans ition is also consistent with important geophysical discontinuities ma pped below the Slave craton.