Abstract

New Sr, Nd, and Pb isotope data on North Atlantic high-latitude (about 69°30'N to 76°30'N) intraplate and ridge volcanic rocks, together with published data, are used to evaluate the mantle sources contributing to Iceland and the surrounding ridges. Considerable overlap between Icelandic lavas and depth-filtered North Atlantic mid-oceanic-ridge basalts (MORBs) in all isotope plots confirm that a MORB asthenosphere-plume mixing model can explain the ranges of isotope compositions found on Iceland. Regional isotope patterns north of lat 53°N show two distinct mantle domains. Lavas forming a low-radiogenic-Pb, high-radiogenic-Sr array occur north of central Iceland, whereas volcanic rocks forming a high-radiogenic-Pb, low-radiogenic-Sr array mainly erupt on and south of Iceland. The depleted end members of each array most likely represent MORB source material. The enriched end member of the high-radiogenic-Pb, low-radiogenic-Sr array appears to reside in the Iceland plume. The other enriched end member also occurs in on-axis and mainly intraplate magmas north of about lat 71°N.

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