Sr–Nd–Pb isotope and trace-element geochemistry evidence for a young HIMU source and assimilation at Tenerife (Canary Island)

Abstract

Late Miocene–Pliocene volcanism on the Tenerife island consists of three different series (Teno, Roque del Conde and Anaga). These three series have distinct differences in isotopic compositions. Teno, the western massif, has the most radiogenic Nd and Pb isotopes and least radiogenic Sr ratios. Anaga, the easternmost massif, has the least radiogenic Nd and Pb, and most radiogenic Sr found in the island. Roque del Conde in the south has isotopic compositions between that of Teno and Anaga, similar to the younger volcanic series. All of the three late Miocene–Pliocene massifs have trace-element characteristics resembling those found in HIMU basalts, and there are only small variations between the different massifs. Variations in isotopic characteristics are attributed to two distinct mantle sources. One source appears to be a young HIMU source. The other source is an “enriched mantle source” with isotopic ratios broadly similar to an EM I source, but with lower 207Pb/204Pb to given 206Pb/204Pb. Assimilation during fractional crystallisation also seems evident.The younger basalts (Las Cañadas, Dorsal and Historic) exhibit relatively homogeneous Nd and Pb isotopic compositions, but show considerable diversity in incompatible trace-element ratios. Fractional crystallisation in periodically refilled magma chambers and assimilation of syenite may have fractionated incompatible trace-element ratios to some degree, but the variations could also be caused by a different degree of partial melting, with the younger basalt generally derived from smaller degrees of partial melt than the older massifs.