Australia: The Land Where Time Began

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Pacific Ocean Volcanism Related to Deformation Linked to the Hawaiian-Emperor Bend

According to O’Connor et al. ocean islands, sea mounts and volcanic ridges are believed to have formed above mantle plumes. However, many volcanic features on the floor of the Pacific Ocean (Koppers, 2011) cannot be explained by this mechanism, some of which might have actually have be caused by cracks in the oceanic crust that are linked to reorganisation of the plate motions (Koppers, 2011; Winterer & Sandwell, 1987; Natland & Winterer, 2005). There is a distinctive bend in the Hawaiian-Emperor volcanic chain that has been linked to changes in the direction of movement of the Pacific Plate (Gordon, Cox & Harter, 1978; Sharp & Clague, 2006), movement of the Hawaiian plume (Tarduno et al., 2003; Steinberger, Southerland  & O’Connell, 2004; Tarduno, 2007), or a combination of both (O’Connor et al., 2013). O'Connor et al say that as there is no independent record that dates precisely tectonic events affecting the Pacific Plate these links are uncertain. In this paper O'Connor et al. analyse the geochemical characteristics of samples of lava that have been collected from the Musicians Ridges, which are lines of volcanic seamounts that formed close to the Hawaiian-Emperor bend. They found that the geochemical signature differs from that of the typical ocean island Basalts, instead resembling mid-ocean ridge basalts. O'Connor et al. suggest the seamounts are not related to mantle plume activity, having formed instead in an extensional setting, which resulted from deformation of the Pacific Plate. Dating by ⁴⁰Ar/³⁹Ar revealed that the Musicians Ridges formed during time windows which are bracketed by the time of formation of the Hawaiian-Emperor bend, 53-52 Ma and 48-47 Ma. The conclusion reached by O'Connor et al. is that the Hawaiian-Emperor bend formed as the result of plate-mantle reorganisation, which was potentially triggered by a series of subduction events at the margins of the Pacific Plate.

Sources & Further reading

1. O'Connor, J. M., K. Hoernle, R. D. Muller, J. P. Morgan, N. P. Butterworth, F. Hauff, D. T. Sandwell, W. Jokat, J. R. Wijbrans and P. Stoffers (2015). "Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian-Emperor bend." Nature Geosci 8(5): 393-397.