Past plate and mantle motion from new ages for the Hawaiian-Emperor\ud Seamount Chain

摘要

Estimates of the relative motion between the Hawaiian and Louisville hotspots have consequences for understanding the role and character of deep Pacific-mantle return flow. The relative motion between these primary hotspots can be inferred by comparing the age records for their seamount trails. Our new 40Ar/39Ar ages for 18 lavas from\ud10 seamounts along the Hawaiian-Emperor Seamount Chain (HESC) show that volcanism started in the sharp\udportion of the Hawaiian-Emperor Bend (HEB) at �47.5 Ma and continued for �5 Myr (O’Connor et al., 2013).\udThe slope of the along-track distance from the currently active Hawaiian hotspot plotted versus age is remarkably\udlinear between �57 and 25 Ma in the central �1900 km of the seamount chain, including the HEB. This model\udpredicts an age for the oldest Emperor Seamounts that matches published ages, implying that a linear age-distance\udrelationship might extend back to at least 82 Ma. In contrast, Hawaiian age progression was much faster since\udat least �15 Ma and possibly as early as �27 Ma. Linear age-distance relations for the Hawaii-Emperor and\udLouisville seamount chains predict �300 km overall hotspot relative motion between 80 and 47.5 Ma, in broad\udagreement with numerical models of plumes in a convecting mantle, and paleomagnetic data. We show that a\udchange in hotspot relative motion may also have occurred between �55 Ma and �50 Ma. We interpret this change\udin hotspot motion as evidence that the HEB reflects a combination of hotspot and plate motion changes driven by\udthe same plate/mantle reorganization.\udO’Connor et al. (2013), Constraints on past plate and mantle motion from new ages for the Hawaiian-Emperor\udSeamount Chain, Geochem. Geophys. Geosyst., 14, 4564–4584, doi:10.1002/ggge.20267