Petit-spot and seamount rejuvenation overprinting western Pacific plate
Abstract
During the Cretaceous, most seamounts and oceanic plateaus were formed within the western Pacific plate. Koppers et al. (2003) called a region of seamounts older than 70 Ma as the West Pacific Seamount Province (WPSP), indicating that seamount distributions in the WPSP are significant as short-lived hotspot trails. The topographic features and geochronologic characteristics of the WPSP cannot be explained by the simple hotspot model as has been applied successfully to the Hawaii-Emperor Seamount Chain because those were caused by secondary hotspots such as intraplate volcanoes in the present French Polynesian region (Koppers et al., 2003). A 140-Ma seamount on the Mariana trench oceanward slope has been characterized by a long-lived (10-m.y.) volcanic sequence of single seamounts owing to the relatively slower absolute motion of the Early Cretaceous Pacific plate than at present (Hirano et al., 2003).
We newly report some overprinting lavas in the WPSP during the Paleogene (based on Ar-Ar dates of samples from dredging or submersible dives) from Ogasawara Plateau, Uyeda Ridge, and Minamitorishima (Marcus) Island. We have called this discovery "belated seamount rejuvenation". The lavas clearly differ in petrography and isotopic composition from the older lavas in the WPSP and from the French Polynesian hotspots. Here, we discuss whether the belated seamount rejuvenations are due to unknown hotspot or petit-spot volcanism. The petit-spot magmas definitively overprint lithosphere as well, ascending along the concavely flexed outer-rise zone prior to plate subduction (Hirano et al., 2006). Sato et al. (2018) recently discovered that "directly ascending petit-spots" completely discriminated from the majority of previously reported petit-spot lavas (shoshonitic) because they are silica-poor and strongly alkaline. They selectively erupt atop the outer rise where the lithosphere behaves entirely in an extensional regime. Otherwise, some of the WPSP seamounts are overprinted by Paleogene lavas. Conventional petit-spots and directly ascending petit-spots are overprinting lithosphere just prior to subduction.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V11E0142H
- Keywords:
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- 1033 Intra-plate processes;
- GEOCHEMISTRY;
- 7208 Mantle;
- SEISMOLOGY;
- 8137 Hotspots;
- large igneous provinces;
- and flood basalt volcanism;
- TECTONOPHYSICS;
- 8416 Mid-oceanic ridge processes;
- VOLCANOLOGY