Ultramafic xenoliths from the Elwin Bay kimberlite: the first Canadian paleogeotherm

• Published in: Canadian Journal of Earth Sciences
• Main Author: Mitchell, Roger H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1977
• Subjects: General Earth and Planetary Sciences; Arctic; Canada; Elwin Bay
• Online Access: http://dx.doi.org/10.1139/e77-110; http://www.nrcresearchpress.com/doi/pdf/10.1139/e77-110

Ultramafic xenoliths from the Elwin Bay kimberlite provide samples of the upper mantle beneath arctic Canada. The compositions of coexisting pyroxenes have been used to estimate the temperatures and pressures of equilibration of the three texturally and mineralogically distinct types of xenolith, i.e. spinel lherzolite (840–935 °C), coarse garnet lherzolite (925–1085 °C at 39.5–49.5 kbar (3.95–4.95 × 10 6 kPa)) and porphyroclastic garnet lherzolite (1090–1180 °C at 47.0–51.5 kbar (4.7–5.2 × 10 6 kPa)). The garnet lherzolite data define an inflected paleogeotherm whose upper limb lies at shallower depths than found for the Thaba Putsoa – Mothae paleogeotherm but which is identical to the Montana paleogeotherm. No evidence is found for iron enrichment of the upper mantle in this region.