Diamond inclusions are thought to preserve the characteristics of rocks from beneath the Archean cratons. We have found that refractory trace element ratios in these inclusions are similar to those measured in both rocks of the present-day oceanic lithosphere and some Archean greenstone belts. These observations are consistent with a model in which Archean continental lithosphere evolved by tectonic stacking of oceanic crust and its underlying mantle during intraoceanic collisions. We conceive the continental lithosphere to consist of alternating layers of basalt and peridotite derived from subducted and obducted Archean oceanic lithosphere. This process provides a mechanism for the genesis of diamonds in the metamorphic equivalent of these Archean rocks.