9419240 Yogodzinski An ion microprobe and isotopic study of Aleutian high Mg# silicates (phenocrysts, xenocrysts, xenoliths, glass inclusions, volcanic rocks) is proposed here. The aim of this study is to understand the regional importance of the various primitive Aleutian melt types, and to infer the predominant mixing, melting, and reaction processes that occur in the Aleutian mantle wedge. The approach is to use the trace element and isotopic characteristics of thigh Mg# minerals as tracers of mantle wedge processes. There has been a recent re-emphasis on primary calc-alkaline andesitic magmas in subduction related magmatic arcs, with high Mg#'s, and high Ni and Cr contents, consistent with equilibration with mantle olivine and spinel. The presence of these lavas in arcs raises once again the question of the bulk composition of crust formed by subduction-related magmatism. This study will address this broad issue by defining more clearly the various primitive melts which are represented in the Aleutian arc, and by providing an improved basis for identifying the predominant processes which occur in the Aleutian mantle wedge.
