title: Comment on "A vestige of Earth's oldest ophiolite".
abstract: The claim by Furnes et al. (Reports, 23 March 2007, p. 1704) that Greenland metavolcanic rocks require Paleoarchean sea-floor spreading is incompatible with their own data. The purported sheeted dikes have the composition of pyroxenitic komatiite and could not have fed the adjacent ferroandesitic pillow lavas. Neither type has ophiolitic analogs, and both are likely ensialic.
authors.affiliation: Department of Geophysics, Colorado School of Mines, Golden, CO 80401, USA. whamilto@mines.edu
authors.forename: Warren B
authors.initials: WB
authors.lastname: Hamilton