SR-ND ISOTOPIC HETEROGENEITY OF BASALTS OF THE SIERRA LEONE TEST SITE, MID-ATLANTIC RIDGE, 5°-7° S

Abstract

Mid-ocean ridge basalts (MORBs) provide important information on the composition and structure of the upper mantle. Isotope–geochemical data are essential for their studies, though their interpretation is still controversial. Observed regularities in the variation of Sr and Nd isotopic composition of MORBs can be regarded either as a result of mixing of different homogeneous isotope reservoirs (depleted mantle, enriched mantle, oceanic island basalt source, and others) or as an isotope heterogeneity of depleted mantle on the kilometer or meter scale.