T. Arlt et T. Peters, Synthesis of pyroxenoids and pyroxenes in the system MnSiO3-MgSiO3-CaSiO3 with excess quartz, N J MINER M, (9), 2000, pp. 385-401
Synthesis experiments in hydrothermal cold seal bombs were performed at 700
degreesC (0.2 and 0.5 GPa) and 900 degreesC (0.2 GPa) using MnO2-MgO-CaO-S
iO2 mixtures and further runs at higher pressure (1.5 and 2 GPa) were perfo
rmed in a piston cylinder apparatus. Run products were the pyroxenoids rhod
onite, pyroxmangite and bustamite, the clinopyroxenes kanoite and manganoan
diopside and the amphibole manganoan cummingtonite. In the 700 degreesC ru
ns pyroxmangite is often formed as a metastable product. The coexistence of
rhodonite and kanoite results in three-phase fields for rhodonite-kanoite-
pyroxmangite and rhodonite-kanoite-bustamite, Transmission electron microsc
ope (TEM) data showed that the pyroxenoids are always intergrown, even in t
he 900 degreesC runs. This limits the application of a previously suggested
rhodonite-pyroxmangite geothermometer. The formation of a nine-fold chain
silicate was observed with TEM at approx. Mn0.6Mg0.4SiO3 composition.