Petrogenetic Significance of Isotope and Trace Element Variations in Volcanic Rocks From the Mid-Atlantic

Publisher Website
Google Scholar
Abstract
High precision 87Sr/86Sr analyses, together with determinations of Rb, Sr, K2O, Na2O and, in a few cases, other elements, are reported for about fifty volcanic rocks (mainly basaltic) from the Atlantic Ocean basin. Results for dredged basalts from the Reykjanes Ridge and Charlie Gibbs Fracture Zone, and an enstatite-forsterite basalt from Kolbeinsey islet, support the general observation that ocean-ridge tholeiites have uniformly low 87Sr/86Sr ratios (0.70294±4) and lithophile element contents compared with the most primitive basalts on ocean islands, including the Neovolcanic zones of Iceland, although progressive decrease in these quantities away from Iceland has not been confirmed. In contrast, the ocean island alkali basalts generally have higher 87Sr/86Sr ratios (0.70334±5 for the Snaefellsnes peninsula of Iceland, 0.70343±4 for Jan Mayen, 0.70509±4 for Tristan da Cunha and 0.70369±3 for Bouvetøya). The chief exception is Ascension Island, where volcanic rocks ranging from alkali-olivine basalt to trachyte give a mean value of 0.70284±4. The constancy of this ratio throughout eruptive sequences on any single island indicates that Sr-isotope characteristics are primary features.

This publication has 0 references indexed in Scilit: