An experimental study on a minette and its associated mica-clinopyroxenite xenolith from the Milk River area, southern Alberta, Canada
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Abstract
Buhlmann et al. (2000) studied the minettes and xenoliths from southern Alberta, Canada. They hypothesized that the minettes were derived from a source containing phlogopite + clinopyroxene at pressures ≥ 1.7 GPa. To test this hypothesis, we investigated 1) the liquidus mineralogy of a primitive minette; and 2) the melting reactions of a mica + clinopyroxene assemblage. For the minette, we found a multiple saturation point at 1.77 GPa and 1350°C, where liquid coexists with orthopyroxene and olivine. Neither phlogopite nor clinopyroxene were found to be liquidus phases. We suggest that our minette is not primary, but had re-equilibrated with harzburgitic mantle subsequent to formation. For our mica-clinopyroxenite assemblage, we found the solidus is at temperatures above a cratonic geotherm, implying that this mica-clinopyroxenite is stable in a craton. The composition of the melts from our experiments are similar to madupitic lamproites from Leucite Hills, Wyoming, studied by Carmichael (1967).