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|Geochemical zoning of volcanic chains associated with Pacific hotspots|
|Huang, S.; Hall, P.S.; Jackson, M.G. (2011). Geochemical zoning of volcanic chains associated with Pacific hotspots. Nature Geoscience 4: 874-878. dx.doi.org/10.1038/ngeo1263|
|In: Nature Geoscience. Nature Publishing Group: USA. ISSN 1752-0894, more|
Recent Hawaiian volcanism is manifest as two geographically and geochemically distinct groups of volcanoes, the Loa trend in the south and the Kea trend in the north. The differences between the Loa and Kea lavas are attributed to spatial variations in the geochemical structure of the underlying Hawaiian mantle plume. In turn, the Hawaiian plume structure is thought to reflect heterogeneities in its mantle source. Here we compile geochemical data from the Hawaiian and two other volcanic ocean island chains -the Samoan and Marquesas- that formed above mantle plumes upwelling beneath the Pacific plate. We find that the volcanoes at both Samoa and the Marquesas show geographic and geochemical trends similar to those observed at Hawaii. Specifically, two subparallel arrays of volcanoes exist at both locations. In each case, the southern trend of volcanoes has higher radiogenic lead isotope ratios, 208Pb*/206Pb*, and lower neodymium isotope ratios, eNd, than those of the corresponding northern trend. We suggest that geochemical zoning may be a common feature of mantle plumes beneath the Pacific plate. Furthermore, we find that the pattern repeats between island chains, with the highest 208Pb*/206Pb* and the lowest eNdfound at Samoa in the south and the lowest 208Pb*/206Pb* and the highest eNd observed at Hawaii in the north. We infer that isotopically enriched material is preferentially distributed in the lower mantle of the Southern Hemisphere, within the Pacific low seismic velocity zone.