Determining Age-Progressive Curves of Pacific Seamount Chains for Absolute Plate Motion and Plume Drift Modeling

Abstract:

Age-progressive seamount trails created by long-lived deep mantle plumes have been used to establish absolute reference frames for plate motion. However, when plume drift is considered, changes in seamount trail direction and age-progression rate cannot be attributed to just plate motion change alone. A better understanding of these absolute motions are needed for studying the mantle dynamic processes that drive both plate tectonics and plume drift. Results may also bring clarity to the question of whether or not plate or plume motion changes were the dominant cause of the Hawaiian-Emperor bend formation, which remains a controversial topic. For this study, improvements to age-progessive curves of Pacific hotspot chains are made independent of past plate motion models. Our approach involves bathymetry processing to robustly predict a smooth and continuous hotspot path by connecting high points in seamount bathymetry, with uncertainties in the path based on seamount trail width and amplitude. Ages found using radiometric dating techniques from seamount samples are projected onto the predicted hotspot path. A best fit model of age as a function of along-track distance is found, giving continuous age progressions for each seamount chain with uncertainties in both age and path. These data provide prime constraints on past inter-hotspot motion and will be used in a new modeling scheme to place bounds on both Pacific plate and mantle plume motion simultaneously. As expected, the Hawaiian-Emperor and Louisville seamount chains show bends at similar ages of around 50 Ma. Based on the uncertainty in the age-progressions, it cannot be confidentially determined if the bends formed at the same time or a few million years apart. A bend occurring around the same time is also observed in the Rurutu chain but a lack of data leading up-to the bend creates too high of an uncertainty to properly conclude it is synchronous to Hawaii and Louisville. These findings show continued evidence for major plate motion change in the Pacific approximately 50 million years ago, creating bends in at least three of the hotspot trails that have been active during this time. Going forward, paleolatitudes, age-progressions and inter-hotspot range constraints will be used to separate plate from plume motions.