Geochemistry of Tertiary igneous rocks from Arandas-Atotonilco area, northeast Jalisco, Mexico.

Abstract

Major-element analyses for ten samples of basalt and andesite, selected one each from ten palaeomagnetic sites in NE Jalisco, Mexico, are presented. K/Ar dates and REE data on four samples and contents of alkali (K, Rb and Cs) and alkaline earth (Ba and Sr) elements and 87Sr/86Sr ratios on eight samples are also reported. Evidence of volcanic activity at approx 11 m.y. is shown. Initial 87Sr/86Sr ratios range from 0.7033 to 0.7039 and are not correlated with major- or trace-elements or element ratios. The 87Sr/86Sr ratios are similar to those observed in other areas of the Mexican volcanic belt and are compatible with a sub-crustal origin for the Jalisco magmas. (Authors' abstract) -A.W.H.