EarthRef.org Reference Database (ERR) -- Gast 1968

Gast, P.W. (1968). Upper mantle chemistry and evolution of the Earth's crust. In: The History of the Earth's Crust, a symposium. Phinney, R.A. (Editors), Princeton University Press, Princeton, N.J.. 15-27.

Isotopic and chemical data indicate that the mean composition of theEarth differs from that of carbonaceous chondrites in being characterized both by a depletion of certain volatile elements and an enrichment of refractory elements relative to the meteorites. Chemical differentiation of the Earth has been less extensive than generally postulated, and differences in chemistry between the suboceanic and subcontinental mantle material are significantly less than presently accepted heat flow models suggest.