Geochemistry of Mesozoic Basaltic Lavas from the West Pacific Seamount Province (WPSP): Constraints on Their Origin and Genesis

Wednesday, 17 December 2014
Quanshu Yan and Xuefa Shi, First Institute of Oceanography, State Oceanic Administration, Qingdao, China
There distributed many relatively isolated seamounts in several inferred seamount chains in west Pacific, and the area has been named as west Pacific seamount province (WPSP). Studying on basaltic rocks from the WPSP will be helpful to better understanding the diversity of plume geodymanics and developing the plume theory. Basaltic lavas from eight seamounts in the WPSP have been studied for petrography, major-, trace element and Sr-Nd-Pb isotopic composition. The petrographic characteristics of these rocks show moderately to highly altered. Major element compositions show all of these rocks belong to alkalic series, and some samples lost their alkalis elements during submarine seawater alteration. Primitive mantle normalized spider diagram and chondrite normalized rare earth element distributional pattern show that they were originated from OIB-like source and possibly underwent low degree partial melting. Isotopic characteristics imply that three mantle end-members (DMM, EMI and HIMU) can explain Sr-Nd-Pb compositions of these rocks from the WPSP, i.e., DMM is depleted MORB mantle identical to that being created MORB in EPR, EMI (reprecented by Rarotonga island) is possibly from subducted ancient continental crust, and HIMU (represented by Cook-Austral Islands) is typically originated from recycled oceanic crust. Based on the present study combined with published data, we proposed that the origin of some (maybe all) of seamounts in the WPSP are splash plumes proposed by Davies and Bunge (2006) or smaller plumes branched at the base of lithosphere from the Superwell which has created the Ontong Java plateau. (This work was supported by the National Natural Science Foundation of China under contract Nos. 41322036, and 41276003)