Lamont Geological Observatory (Columbia University), Palisades, New York, U.S.A.

Approximately 700 analyses have been made on silicate rocks and over 300 on carbonate materials (a detailed analysis of the latter appearing in other papers). An attempt was made at a representative sampling of the crust of the earth.

The difference in behaviour of strontium relative to calcium in granitic rocks as compared to basaltic rocks is striking. For granitic rocks there is an increase of strontium content with an increase in calcium not only for samples from a single batholith but also when extended to a universal sampling. On the other hand, though some differentiated basaltic bodies show a covariance of strontium and calcium, it is always with the strontium content increasing as the calcium content decreases. On a worldwide basis, however, this relationship is destroyed because marked regional variations subdue any differentiation effects that might be present locally.

The crustal abundance of strontium in basaltic rocks may be estimated without difficulty by taking a simple average, but a similar procedure for granitic rocks is ruled out because of the dependence of strontium content on rock-type. The table below summarizes the abundances of strontium in the various phases of the earth's crust.