Mantle Heterogeneity in the North Atlantic: Evidence from Leg 49 Geochemistry

Abstract

One of the principal aims of Leg 49 was to investigate variation in the primary geochemistry of ocean-floor lavas in space and time in North Atlantic. This paper sets out to analyze the geochemical results from Part 2 of this volume with this end in view. We first discuss the setting of sites, and then deal with the implications of the Leg 49 results for mantle heterogeneity. We conclude that there is good evidence for marked heterogeneity at different scales in the North Atlantic area, and that the Leg 49 results provide important evidence of the local and regional patterns of variation in composition. This conclusion is elaborated in the following section, where we compare the North Atlantic area as a whole with other parts of the world's oceans, as far as this is possible with our current state of knowledge. It appears that the basalt type labeled MORB, though common in other parts of the oceans, may be rare or absent in the North Atlantic. In addition, we suggest a possible relative chronology of events of mobility for different elements within the mantle.