Mid-Cretaceous Wake seamounts in NW Pacific originate from secondary mantle plumes with Arago hotspot composition

The geochemistry of oceanic intraplate (primarily oceanic island and seamount) lavas can provide essential information on the composition and evolution of their mantle source and geodynamics. Due to very limited rock sampling of the many mid-Cretaceous Wake seamounts in NW Pacific, the mantle source lithology and petrogenesis of their lavas, and the geodynamic mechanism responsible for generating the lavas have not been fully delineated. In order to help resolve these issues, here we present whole-rock major-trace element and Sr-Nd-Pb-Hf isotopic data for twenty-one lava samples collected from Lamont, Dacheng, Xufu, Penglai, Niulang, Zhinyu, and Zhanlu seamounts in the Southern Wake seamount trail (WST). These lava samples are silica-undersaturated alkali basalt and basanites/nephelinite. They have high CaO, FeOT and TiO2 contents and CaO/Al2O3 ratios, consistent with their derivation from partial melting of a carbonated peridotite or reaction between carbonated MORB-eclogite-derived silicate melts and fertile peridotite. High Zr/Hf and negative Zr-Hf-Ti anomalies in the most mafic lavas further suggest a contribution from carbonated components in their mantle source. These lavas show FOZO (focal zone)-HIMU (high mu = U-238/Pb-204) like Sr-Nd-Pb-Hf isotopic compositions (e.g., (Pb-206/Pb-204)(i) = 19.36-20.72), falling within the Arago (also known as Young Rurutu or Atiu) hotspot field. Combined with the sparse previous age and geochemical data, we propose that WST lavas were most likely derived from partial melting of secondary plume clusters emanating from the top of Arago mantle plume trapped at the mantle transition zone. Alternatively, WST lavas could have come from a number of secondary plumelets emanating from the top of the Pacific Large Low Shear Velocity Province (LLSVP). The simultaneously upwelling secondary plumes or plumelets generated chronologically overlapping, compositionally similar and closelyspaced Wake seamounts atop the moving Pacific plate.

Automated summary

The geochemical and isotopic analysis of lavas from the Southern Wake seamount trail suggest a derivation from partial melting of secondary plume clusters emanating from the top of the Arago mantle plume. Another possibility is that the lavas could have originated from secondary plumelets associated with the Pacific Large Low Shear Velocity Province (LLSVP). The lavas show signatures of FOZO-HIMU-like isotopic compositions, falling within the Arago hotspot field.