Understanding the origin and geochemical characteristics of the mantle lithosphere beneath the continents is central to deciphering the processes responsible for mantle differentiation and continental crust formation. The primary goal of this research is to provide new information and insights on a variety of mantle processes; most importantly the formation and evolution of low density, high Mg/Fe peridotites that may form an isostatically stable mantle lithosphere beneath continental cratons. This goal will be achieved by a combination of laboratory and field studies including (1) trace element and isotopic analysis of minerals in mantle xenoliths from Tertiary dikes in the Weidemann Fjord area in Southeast Greenland and Ubekendt Island in West Greenland, (2) comparative studies of samples of similar peridotites worldwide (Papua New Guinea, Wyoming craton, and the Kapvaal craton), and (3) additional collection of peridotite samples from Greenland. The new data will be used to evaluate two hypotheses previously based on major element compositions of the same samples: (1) xenoliths from Weidemann Fjord and Ubekendt Island, with low modal orthopyroxene, are examples of unmetasomatized cratonic peridotite, formed as the residues of about 40% partial melting, and (2) orthopyroxene-rich cratonic peridotites, such as those in the Kapvaal and North American cratons, were produced by open-system, SiO2 enrichment of highly depleted residues.
