87Sr/86Sr, alkali and alkaline earth element geochemistry of Chichinautzin Sierra, Mexico.

Abstract

Alkali (K, Rb and Cs) and alkaline earth (Ba and Sr) contents, as well as 87Sr/86Sr ratios, are reported for eight selected basalt and andesite samples and for one older dacite. Trace-element data are compatible with fractional crystallization of hornblende, plagioclase, olivine and pyroxenes - in approx decreasing importance. Initial 87Sr/86Sr ratios range 0.7034-0.7045; in the light of this and other evidence a mantle origin with only a small contribution from altered oceanic or sialic continental crust is favoured for the Chichinautzin magmas.-J.M.H.