Abstract
Corundum xenocrysts from ouachititic dikes related to the ultrapotassic Puesto La Peña Complex, Mendoza, Argentina, contain inclusions of oxides, silicides, and silicates. Oxides identified are hibonite, carmeltazite, and as yet unnamed minerals consisting of ZrTiO3, (Al,Ti,Zr) oxide, and (Mn,REE) oxide. An unnamed Ti2(Mn,Fe)4Si5 phase was also recognized. Silicates include wodegongjieite and grossmanite. All minerals are enriched in rare earth elements. The formation of these mineral inclusions under extreme P-T conditions has been dated at 37.7 Ma and would have occurred in the lithospheric mantle and protected from oxidation by crystallization of corundum through the introduction of mantle-derived magma-transported fluids. The corundum crystals would have been transported by a rising plume in a back-arc extensional setting during the Miocene and incorporated as xenocrysts in an alkaline ouachititic magma, conferring its peraluminous signature.