MICHAEL O. GARCIA¹, KYE-HUN PARK2, 3, GEOFFREY T. DAVIS 1, 4

摘要: The Line Islands chain is a product of multiple hotspots. The main portion of the chain formed between 42 and 93 Ma. Along some parts of the chain, this phase of volcanism was preceded and succeeded by hotspot volcanism. There is no chemical distinction among the lavas from the different episodes of hotspot volcanism. Ratios of Sr and Pb isotopes and trace elements are similar even for tholeiitic and alkalic lavas. These ratios are similar to those for lavas from Easter and Sala y Gomez islands. The range of Sr and Pb isotopes and the Nb/Zr ratios for Line Islands lavas require three source components. The most likely candidates are a high 206 Pb/204Pb and Nb/Zr, low 87 Sr/Sr source (HIMU); an enriched source (EMI); and a depleted mantle source. Backtracking the positions of the age-dated Line Islands volcanoes to where they probably formed indicates that the main group is unrelated to any known hotspot. The pre-hotspot volcanoes may be related to the Easter and/or the Sala y Gomez hotspots. The post-hotspot volcanoes do not backtrack to any known hotspot but are closest to the Marquesas. The compositions, positions and ages of the backtracked Line Islands volcanoes indicate that the eastern portion of the South Pacific isotopic and thermal anomaly (SOPITA) has persisted for at least 90 my and that the Easter and Sala y Gomez hotspots may have produced geochemically similar lavas for the last 70 my