Late-stage evolution of Shatsky Rise oceanic plateau (northwest Pacific Ocean) - First results of R/V SONNE expedition SO265

The origin of large igneous provinces is a subject of an ongoing debate. Proposed models range from formation by deep mantle plumes to origin by shallow processes. In that respect, the submarine Shatsky Rise (SR), located in the northwest Pacific, is unique, since it appears to share both plume- and plate tectonic-related characteristics. SR is the only large oceanic plateau that formed during a time period with frequent magnetic reversals, allowing us to reconstruct its tectonic setting. Accordingly, the 22 km thick plateau formed along the path of a northeast moving triple junction between the Izanagi, Farallon and Pacific plates (e.g. Nakanishi et al., 1999). The IODP Expedition 324 has considerably improved our knowledge about the timing and origin of the early SR (e.g. Sager et al., 2016). Although new evidence has emerged from the drilled samples favoring the origin through interaction of a mantle plume with a triple junction, the evidence for the involvement of a mantle plume is not unequivocal. Therefore, investigating the late stage evolution of SR and in particular finding an age-progressive hotspot track associated with the plateau might solve this question.

Interestingly, two different bathymetric features emanate from the youngest end of SR and could potentially represent a hotspot track: the more than 500 km long Papanin Ridge and the scattered Ojin Seamount Province. Thus, RV SONNE expedition SO265 aimed to investigate the transition of Shatsky plateau to potential hotspot track volcanism. In addition to multi-beam bathymetric mapping, 50 successful dredge hauls were conducted covering the entire geographic extent of Papanin Ridge and the Ojin Seamount Province (Geldmacher et al., 2018). Here we present first, preliminary geochemical data (major and trace element and Sr, Nd, Pb isotope compositions) from both working areas and combine them with new, high-resolution plate-tectonic reconstructions. While Ojin Seamount lavas show enriched OIB trace element composition, Papanin Ridge lavas possess relatively depleted signatures, similar to the main SR plateau edifices.

Geldmacher J, Werner R, Hauff F, eds. (2018) RV SONNE Cruise Report SO265. http://oceanrep.geomar.de/id/eprint/44846

Nakanishi M, Sager WW, Klaus A (1999) J. Geophys. Res. 104

Sager W, Sano T, Geldmacher J (2016) Earth Sci. Rev. 159