Papanin Ridge and Ojin Rise Seamounts (Northwest Pacific): Dual Hotspot Tracks Formed by the Shatsky Plume

Abstract

Although previous findings support an origin of the Shatsky Rise igneous plateau (Northwest Pacific) through interaction of a mantle plume with a mid‐ocean ridge triple junction, the evidence for the involvement of a mantle plume is equivocal. The identification of an intraplate hotspot track emanating from the plateau could solve this controversy. Here we present major and trace element geochemical data from two different bathymetric features that emanate from the youngest end of Shatsky Rise: Papanin Ridge and the Ojin Rise Seamount province. Combining our results with plate tectonic reconstructions, we conclude that Papanin Ridge represents a hotspot track formed by plume‐ridge interaction. Whereas the southwestern part was formed along the path of the retreating Pacific‐Farallon‐Izanagi triple junction, the northeastern part was built by preferential drainage into its Pacific‐Farallon branch. In contrast, the Ojin Rise Seamounts formed as a true intraplate hotspot track of the Shatsky plume tail. Our wide‐ranging study reveals systematic spatial geochemical variations, consistent with a lithospheric thickness control on magma composition derived from melting a heterogeneous plume source. The recognition of two hotspot tracks and in particular of the Ojin Rise Seamounts as an intraplate hotspot track that is directly linked to Shatsky plateau volcanism both in terms of geochemistry and plate tectonic reconstructions confirms the long‐disputed involvement of a mantle plume for the formation of Shatsky Rise.

Plain Language Summary: The origin of Shatsky Rise, a large igneous plateau in the NW Pacific, has long been debated. It could have either formed by shallow mantle melting due to its confirmed creation along a mid‐ocean ridge or with additional contribution of deeper mantle material that upwelled as so‐called mantle plume beneath the spreading ridge (“plume‐ridge interaction”). The identification of an intraplate hotspot track emanating from Shatsky Rise and related to the plateau could answer this question. Here we present major and trace element geochemical data from lava samples dredged from two different structures that arise from the youngest end of the Shatsky Rise plateau: Papanin Ridge and the Ojin Rise Seamount province. By combining our results with plate tectonic reconstructions, we conclude that Papanin Ridge formed, like the main Shatsky Rise, by continued plume‐ridge interaction. In contrast, the Ojin Rise Seamounts formed as a true intraplate hotspot track by the drift of the Pacific Plate over the stationary Shatsky hotspot (plume tail). The recognition of an intraplate hotspot track that is directly linked to the Shatsky plateau volcanism both in terms of geochemistry and plate tectonic reconstructions also confirms the involvement of a mantle plume for the formation of Shatsky Rise.

Key Points:

The Ojin Rise Seamounts are identified as intraplate hotspot track of the same mantle plume that formed the Shatsky Rise oceanic plateau.

Papanin Ridge formed by plume‐ridge interaction and represents the northeastern continuation of the Shatsky plateau.

Linking an intraplate hotspot track to the Shatsky plateau confirms the involvement of a mantle plume for its formation.