9810961 Sen This project will investigate the melting process beneath a 90 million year old mid-oceanic ridge using trace element and isotopic characteristics of lithospheric xenoliths from Oahu, Hawaii. REE and Nd, Sr isotopic analysis will be obtained on clinopyroxenes from a suite of spinel lherzolite and rare plagioclase lherzolite xenoliths. These data will be used to (1) verify the source compositions of the xenoliths, (2) determine the melt production rates (dF/dP) over a depth at less than 0.5 Gpa, (3) evaluate the role of melt refertilization, and (4) reconstruct the super-solidus melting trajectory (i.e., mantle flow lines) from pyroxene thermobarometry.