Geochemical and petrological interpretation of mantle structure beneath the southwest Slave Province, NWT
Date
2013-09-10
Authors
Carbno, Gary Brent
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The Drybones Bay kimberlite has offered an opportunity to compare geophysical
observations of the mantle lithosphere beneath the southwest Slave craton with
geochemical and petrological interpretations through mantle xenoliths and xenocrysts.
Coarse-textured garnet and spinel-garnet peridotite xenoliths, and garnet and garnetclinopyroxene
xenocrysts were analyzed for a suite of trace elements. The Ni-in-garnet
geothermometer (Canil, 1999) yielded equilibration temperatures between 850-1200 DC,
and corresponding depths of 90-160 km, assuming a 41m Wm-2 paleogeotherm. This
method estimates the thickness of the southwest Slave craton in the Ordovician at
approximately 160 km, within the stability field of diamond. Trace element analysis
revealed a distinct geochemical anomaly at a depth of approximately 120 km, which
marks the transition from wehrlite to metasomatized wehrlite and lherzolite. This
anomalous depth has been observed in geophysical studies, and has been interpreted as a
structural discontinuity.
Description
Keywords
mantle lithosphere, xenoliths, xenocrysts, Northwest Territories