Extreme HIMU in an oceanic setting: The geochemistry of Mangaia Island (Polynesia), and temporal evolution of the Cook-Austral hotspot

Abstract

New isotope and trace-element data are presented for volcanic rocks from the island of Mangaia in Polynesia, which forms the most extreme example of the HIMU mantle endmember known at the present time. Observations from these data, coupled with published results, provide strong support for an origin of the HIMU signature related to recycling of oceanic crust. Evidence exists for carbonate metasomatism within the mantle beneath Polynesia; however, it is likely that this is also related to the recycling process, rather than being responsible itself for generating HIMU. The elevated U/Pb ratios observed in the HIMU source appear to be largely a result of Pb loss rather than U uptake. The appare..