| 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 reequilibrated 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). |
