Abstract
Deep-Earth convection can be understood by studying hotspot volcanoes that form where mantle plumes rise up and intersect the lithosphere, the Earth's rigid outer layer. Hotspots characteristically leave age-progressive trails of volcanoes and seamounts on top of oceanic lithosphere, which in turn allow us to decipher the motion of these plates relative to "fixed" deep-mantle plumes, and their (isotope) geochemistry provides insights into the long-term evolution of mantle source regions. However, it is strongly suggested that the Hawaiian mantle plume moved ~15° south between 80 and 50 million years ago. This raises a fundamental question about other hotspot systems in the Pacific, whether or not their mantle plumes experienced a similar amount and direction of motion. Integrated Ocean Drilling Program (IODP) Expedition 330 to the Louisville Seamounts showed that the Louisville hotspot in the South Pacific behaved in a different manner, as its mantle plume remained more or less fixed around 48°S latitude during that same time period. Our findings demonstrate that the Pacific hotspots move independently and that their trajectories may be controlled by differences in subduction zone geometry. Additionally, shipboard geochemistry data shows that, in contrast to Hawaiian volcanoes, the construction of the Louisville Seamounts doesn’t involve a shield-building phase dominated by tholeiitic lavas, and trace elements confirm the rather homogenous nature of the Louisville mantle source. Both observations set Louisville apart from the Hawaiian-Emperor seamount trail, whereby the latter has been erupting abundant tholeiites (characteristically up to 95% in volume) and which exhibit a large variability in (isotope) geochemistry and their mantle source components. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.15.02.2013" target="_blank">10.2204/iodp.sd.15.02.2013</a>
Highlights
Introduction andObjectives plume material (Morgan, 1971; Wilson, 1963)
Because of its linear morphology, its lack of interfering seamount trails, and its long-lived age-progressive volcanism, the Louisville seamount trail (Fig. 1) is the South Pacific counterpart of the much better studied Hawaiian-Emperor seamount trail (Koppers et al, 2004; Lonsdale, 1988). Both the Hawaiian and Louisville hotspots are considered primary hotspots because of characteristics indicating a deep mantle origin (Courtillot et al, 2003), and since they are located on the same plate, the spatial and age patterns of their volcanoes and seamounts should match the same plate motion parameters (Duncan and Clague, 1985; Koppers et al, 2001; Wessel and Kroenke, 2008; Wessel et al, 2006), assuming that these hotspots remained fixed in the mantle
The observed limited mantle plumes into parallel directions with equal speeds. latitudinal motion for the Louisville hotspot (Koppers et al, Hotspots still would provide a valuable reference frame 2012b) suggests that the Hawaiian and Louisville mantle pluagainst which plate motions can be measured, as this net- mes have been moving independently and that the motion of work of mantle plumes would move consistently over geo- the Louisville hotspot is likely governed by the subduction of logical time
Summary
Introduction andObjectives plume material (Morgan, 1971; Wilson, 1963). the individual volcanoes in these trails grow older in the direction of plate motion. Because of its linear morphology, its lack of interfering seamount trails, and its long-lived age-progressive volcanism, the Louisville seamount trail (Fig. 1) is the South Pacific counterpart of the much better studied Hawaiian-Emperor seamount trail (Koppers et al, 2004; Lonsdale, 1988) Both the Hawaiian and Louisville hotspots are considered primary hotspots because of characteristics indicating a deep mantle origin (Courtillot et al, 2003), and since they are located on the same plate, the spatial and age patterns of their volcanoes and seamounts should match the same plate motion parameters (Duncan and Clague, 1985; Koppers et al, 2001; Wessel and Kroenke, 2008; Wessel et al, 2006), assuming that these hotspots remained fixed in the mantle.
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