Synthetic armalcolite and pseudobrookite

Armalcolite and pseudobrookite have been crystallized from synthetic melts of basaltic composition with variable amounts of added TiO2. It was found that the composition of the armalcolite and pseudobrookite are dependent on the TiO2 content of the melt and the conditions (particularly oxygen fugacity, but also temperature and quenching rate) of formation. The maximum A1203 content of pseudobrookite appears to be ~14-15 wt. % A1203, a spinel-like phase being exsolved at higher A1203 concentrations. Generally armalcolite is formed at low pO2 and pseudobrookite athigher oxygen fugacities. KEvworms: armalcolite, pseudobrookite, synthetic melts