Testing the deep mantle plume paradigm and radical alternatives using the Louisville and Hawaiian-Emperor seamount chains

An intense competition is developing between those attributing hotspots and volcanic provinces to mantle plumes originating from great depths, and proponents of radically different ideas involving tectonic processes at shallow depths. The existence of mantle plumes is very important because they have been widely accepted for the last 30 years as evidence for a fundamentally different mode of convection independent of plate tectonics involving upwelling from the Earths deep mantle. Thus, the question of shallow versus deep origin for hotspots is both very significant and controversial due to the potential for a first-order paradigm shift away from deep mantle plumes. We have recently published high-quality age data for the uniquely well-sampled Foundation Seamount Chain (SE Pacific) indicating that the history and distribution of hotspot volcanism can be controlled by a combination of long-lived (deep plume?) and short-lived local (shallow tectonic?) factors linked to lithosphere movement and structure. Our advance in understanding provides a new and unique way of testing both the standard deep plume hypothesis and shallower tectonic alternatives. However, for many key hotspot chains high quality age data are still lacking, thus precluding a sound evaluation of competing models. This is an especially significant problem in the case of the Hawaiian-Emperor and Louisville chains as most of our current ideas about mantle plumes and their implications for global mantle dynamics and plate tectonics are derived from these two principal, yet poorly sampled, Cretaceous to recent Pacific seamount trails. The core of our proposal is to establish a detailed record of the timing and distribution of hotspot volcanism along the Louisville Seamount Chain and neighboring Osbourn Trough using state-of-the-art 40Ar/39Ar rock and mineral ages for dredge samples recovered in late 2002. The currently proposed research is a logical extension of work at present in the final stages of data acquisition and writing up on the Hawaiian-Emperor and Musicians seamount chains. We intend using these combined data sets to distinguish between long-lived (deep plume?) and short-lived (shallow tectonic?) origin factors controlling the temporal and spatial distribution of volcanism responsible for the Louisville and Hawaiian-Emperor Seamount chains. Finally, we will evaluate arguments important to both sides of the escalating hotspot debate in light of our results and conclusions for the two key Pacific seamount chains underpinning most thinking about the deep mantle plume paradigm. Keywords: hotspots; mantle plumes; convection; plate motion