The Origin of the Marquesas Fracture Zone Ridge and Its Implications for the Nature of Hot Spots

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The Marquesas Island chain departs by 20–30° from the trends of other late Tertiary hot-spot traces and appears more intermittent in activity than most others in having produced volcanos only in the period 1.4–6.4 Ma. In order to explain the Marquesas data, it has been proposed that hot spots can move relatively rapidly with respect to one another and that most plumes are episodic phenomena. We reevaluate these hypotheses based on geophysical data from the Marquesas fracture zone ridge collected during a recent oceanographic expedition to the Marquesas Islands. Our preferred explanation based on analysis of Seabeam bathymetric, seismic, gravity, and magnetic data across the ridge is that it is a young volcanic construct, 20 km wide and almost 2 km high, formed recently as the Marquesas hot spot encountered the Marquesas fracture zone. Examination of regional bathymetric maps reveals that topographically identical ridges also appear along the Galapagos fracture zone and the Nova-Canton Trough at positions corresponding to the predicted trace of the Marquesas plume based on the trends of the Hawaiian and Society island chains. Using these observations, we conclude that the Marquesas hot spot is not moving rapidly with respect to the other Pacific hot spots, nor is it intermittent in nature. We prefer a model in which the Marquesas plume is simply too weak to penetrate normal oceanic lithosphere unless given an easy conduit to the surface, such as a fracture zone. The surface expression of weak plumes such as the Marquesas is therefore strongly controlled by the thermal and mechanical state of the overlying oceanic lithosphere, an effect which must be taken into account before interpreting hot-spot traces in terms of intrinsic plume properties.

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Earth and Planetary Science Letters, v. 91, issues 3-4, p. 381-393