Tungsten-182 heterogeneity in modern ocean island basalts.

New tungsten isotope data for modern ocean island basalts (OIB) from Hawaii, Samoa, and Iceland reveal variable ¹⁸² W/ ¹⁸⁴ W, ranging from that of the ambient upper mantle to ratios as much as 18 parts per million lower. The tungsten isotopic data negatively correlate with ³ He/ ⁴ He. These data indicate that each OIB system accesses domains within Earth that formed within the first 60 million years of solar system history. Combined isotopic and chemical characteristics projected for these ancient domains indicate that they contain metal and are repositories of noble gases. We suggest that the most likely source candidates are mega-ultralow-velocity zones, which lie beneath Hawaii, Samoa, and Iceland but not beneath hot spots whose OIB yield normal ¹⁸² W and homogeneously low ³ He/ ⁴ He.
(Copyright © 2017, American Association for the Advancement of Science.)