Intraplate Volcanism In The Western Pacific Seamount Province



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The Western Pacific Seamount Province (WPSP) is an area characterized by an abundance of large seamounts which are mostly Cretaceous aged and formed in an intraplate setting. The WPSP is located in an area with some of the oldest oceanic crust on earth, dating to the Jurassic in age. Understanding the volcanism in the WPSP has implications for the mechanisms of intraplate volcanism formation, timeline reconstructions of the Pacific Plate, and mechanisms for volcanism in deep ocean settings. I examine previous investigations into WPSP including ODP drilling investigations and reflection and refraction seismic surveys to understand the sediments, volcanic features, and crustal structure of the WPSP. We then compare these previous studies to interpretations from more recently acquired reflection seismic data to describe the age and stratigraphy of sediments in the WPSP. It has been noted in previous studies the prevalence of igneous intrusions which permeate the subsurface in many areas of WPSP and in this study we examine in detail the structure and geometry, interaction with sediments, and emplacement mechanisms for such features in the seismic data. Our observations show that the geometries of igneous intrusions in deep ocean sediments are very different from what is observed in thick sedimentary basins, due to differences in the mechanical properties of the host rock. Thick sedimentary basins often cause intrusions to take the form of saucer-shaped sills and inclined sills, but this is not seen in the WPSP. We show that laccolith mounds are not uncommon and both laccoliths and sills can create volcanogenic vent complexes which can extend for 100s of meters upwards.



Western Pacific, sills, intraplate volcanism