Mafic and ultramafic xenoliths from volcanic rocks of the Western United States

Physics and Chemistry of Deep Continental Crust Recycling

“…Most of these cumulates must be recycled back into the mantle in order to explain the lack of seismic evidence for mafic rocks beneath the continental Moho (Niu and James, 2002) and the low proportions of pyroxenites or cumulate peridotites relative to residual peridotites in many, but not all, continental xenolith suites (cf. Wilshire et al, 1988). The above estimates (>50%) of the amount of mafic cumulates formed and ultimately removed is consistent with similar approaches based on major element mass balance, though the two types of pyroxenites were not considered (Ducea, 2002).…”

Dehydrogenation of kaersutitic amphibole under electron beam excitation recorded by changes in Fe3+/ Fe: An EMP and SIMS study

“…Titanian pargasite and kaersutite megacrysts were collected from lava flows, scoria cones, dikes, and maars from the southwestern United States where the regional geology has been discussed by Wilshire et al (1988). The amphiboles were analyzed for major elements and H contents using EMP and SIMS respectively by King et al (1999); a compilation of the analyses is available in that paper.…”

Temperature of the plume layer beneath the Yellowstone hotspot

“…If stress and crystal size are inversely correlated (e.g., Hall and Parmentier, 2003), and the cold lithosphere has higher stresses than the asthenosphere, then lithospheric grain sizes serve as a minimum bound for those in the asthenosphere. Xenoliths from the base of the lithosphere typically have a 0.5-2 mm grain size (Armienti and Tarquini, 2002;Wilshire et al, 1988), and 2 mm is adopted as a lower asthenospheric grain-size bound. There is no well constrained upper grain-size bound, although for grain sizes >8 mm, an excess plume layer temperature of >200 ºC would be required.…”