Garnet-Clinopyroxenite from the Red Mountain Pluton, Alaska

Garnet websterites and associated ultramafic inclusions from a nepheline mugearite in the Walcha area, New South Wales, Australia

“…While it is possible that some of the more Fe-rich pyroxenites (M < 80-83) (e.g. Beeson and Jackson, 1970;Kornprobst and Conquere, 1972;Forbes and Swainbank, 1974;Wilkinson, 1974;Schulze and Helmstaedt, 1979) are products of partial fusion of upper-mantle peridotites, it is unlikely that the Walcha garnet websterites were produced in this manner because the composition of residual olivine (rag = 95.5) in equilibrium with a liquid of M = 87.6 is significantly more magnesian than is characteristic of olivines from refractory dunites and harzburgites (i.e. mg generally < 92).…”

Petrology, geochemistry, and origin of the Red Mountain ultramafic body near Seldovia, Alaska

“…The pyroxenes from the garnet-bearing rocks also show lower Si02 and MgO and higher total FeO* in comparison to the pyroxenes from the wehrlites and clinopyroxenites. Both pyroxenes are unusual in their low alkali content, but the pyroxenes from the garnet-bearing rocks are especially unusual when compared to other pyroxenes from garnet-bearing rocks (see Forbes and Swainbank, 1974). The pyroxenes from Red Mountain are not only unusual in their high Tschermaks molecule but they are also extremely low in jadeite content.…”

“…Guild (1942) compiled a detailed geologic map of Red Mountain and included in his report detailed megascopic descriptions of the ultramafic rocks enclosing the chromite ore. Rutledge (1946) published work concerning the chromite deposits at Red Mountain. Since his report, no other studies were completed on Red Mountain itself until the petrologic study by Forbes and Swainbank (1974) on garnet pyroxenite bodies found within the Red Mountain dunite. On a regional scale, several papers have been presented concerning the tectonics of the Kenai Peninsula and southern Alaska.…”

“…Garnet Clinopyroxenite: Diopside grains from specimens 031A and 032 were analyzed by the microprobe and the data are presented in the Appendix in table 6 with wet chemical analyses as determined by Forbes and Swainbank (1974). The pyroxenes show a fairly restricted compositional range and are marked by a high CaO content and an unusually high Cr 0 content.…”

“…Compositional determinations of garnet by the microprobe and from mineral separates by Forbes and Swainbank (1974) are given in the Appendix in table 7. End-member calculations are also presented based on six oxygens from Forbes and Swainbank (1974).…”