Lyra Basin and Louisville Seamount Chain: Two Suspects for the Ontong Java Plateau Hotspot Trail?
Lyra Basin and Louisville Seamount Chain: Two Suspects for the Ontong Java Plateau Hotspot Trail?
Previously Published Material: This abstract highlights some findings from three submitted papers: two on Lyra Basin have been accepted for publication in the GSA Special Volume on Oceanic LIPs and one is under review for G-cubed. Partial results (about 50% each) from these papers were presented at IAVCEI in Japan (2013) and at Goldschmidt in Florence (2013).
Abstract ID#: 34899
English Abstract:
The Ontong Java Plateau (OJP) is believed to have formed during the initial or plume-head stage development of a huge mantle upwelling, but its hotspot trail has not been unequivocally defined or found. One of the longest-lived hotspot traces in the Pacific, the Louisville Seamount Chain (LSC), has long been suspected of representing the trail of the OJP. The International Ocean Drilling Program Expedition 330 is one of the more recent attempts to uncover this link between OJP and LSC. Re-Os isotope and platinum group element investigation of samples from three of the five drilled sites give a very weak lead to the possibility of a plume head to tail relationship between the OJP and the LSC [1]. Meanwhile, the less known Lyra Basin in the western margin of the OJP has been shown by geophysical studies to be underlain by unusually thick oceanic crust, believed to result from emplacement of massive flows from the plateau. Geophysical survey and dredging was conducted by Japan Agency for Marine-Earth Science and Technology to test the relationship between Lyra Basin and OJP. Geochemical and geochronological investigation of the dredged rocks from the basin instead show that younger alkalic rocks, which are geochemically akin to those of alkalic rocks and alnoites in Malaita, Solomon Islands in the southern margin of the OJP, may have covered older plateau crust in the basin [2]. Although not directly related to the main plateau volcanism at 120 Ma, the geochemical data and modeling suggest that the origin of the Lyra Basin alkalic rocks may be genetically linked to the mantle preserved in the thick lithospheric root imaged beneath the OJP, with magmatic contribution from the Rarotongan hotspot [3]. Combined with the other alkalic volcanism on and around the plateau, the Lyra Basin alkalic rocks could represent part of the late-stage magmatic development of the OJP.
References: [1] Tejada, M.L.G., T. Hanyu, A. Ishikawa et al., G-cubed, submitted; [2] Shimizu, K., T. Sano, M.L.G. Tejada et al., GSA Spec. Vol., in press; [3] Tejada, M.L.G., K. Shimizu, K. Suzuki et al., GSA Spec. Vol., in press.