Coexistence of Enriched and Depleted Primitive Melts as Inclusions in Olivine from Reykjanes Tholeiites, Iceland

Abstract

Theoretical models of magma genesis (e.g. McKenzie, 1985), data from abyssal peridotites and oceanic cumulates (Johnson et al, 1990; Ross and Elthon, 1993), studies of MORBs and Icelandic tholeiites (Sobolev and Shimizu, 1992a,b, 1993, 1994) have shown that ultradepleted melts (UDM) are common within the sub-oceanic lithosphere. As far as UDM really exist, one would expect the existence of enriched melts (EM) having been the first portions of mantle melting. Indeed, these (EM) have been described as olivine-hosted inclusions in FAMOUS lavas (Shimizu and Hassler, 1993). Here we report the first discovery of melts existing as olivine-trapped melt inclusions from glassy rims of rift-related tholeiitic picrites from Reykjanes Peninsula (Iceland), which have major and trace element characteristics varying from EM to UDM varieties.