This proposal addresses the detailed examination of cumulate- textured and layered igneous rocks from a geologic environment not yet thoroughly evaluated in terms of cumulate processes. This project plans a comprehensive study of hundreds of Mauna Kea xenoliths from many cinder cones. The PIs will apply petrography, electron microprobe, ion microprobe, XRF, INA, and O-isotopes to develop models for crustal/cumulate processes, compositions of liquids that produced the cumulate rocks, relationships among the different rock types, and the attending crystal/crystal and crystal/melt fractionations for a closed igneous environment. The results should contribute to a better understanding of cumulate processes, and constrain future crystallization models for Hawaiian basaltic magmas.