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Published 2005 | public
Book Section - Chapter

Scoring hotspots: The plume and plate paradigms


The origin of midplate and along-ridge melting anomalies is controversial. Hypotheses involve, at one extreme, concentrated hot mantle upwellings from the deepest mantle and, at the other extreme, shallow processes dominated by stress, plate tectonics, and fertility variations, along with an asthenosphere that is near the melting point. An updated hotspot list is presented and is tested against criteria relevant to both the deep thermal plume and the shallow (plate and asthenosphere) hypotheses. The unique polling approach of Courtillot et al. (2003) is applied to the plume hypothesis and to other hypotheses for melting anomalies. Although some "primary" (i.e., potentially deep-seated) hotspots (Iceland, Hawaii, Easter, Louisville, Afar, Ré-union, and Tristan) score well using the chosen subjective plume criteria, they score poorly using criteria more appropriate to deep or thermal processes, such as magma temperature, heatflow, transition zone thickness, and high-resolution upper and lower mantle seismic tomographic results. In particular, Iceland, Easter, Afar, Tristan, and Yellowstone have not been confirmed by tomography. They are shallow features with well-defined plate tectonic explanations. For most melting anomalies (aka "hotspots") the plume hypothesis scores poorly against competing hypotheses such as stress- and crack-controlled magmatism, mechanisms that are associated with plate tectonics. Based on the results, most "hotspots," including proposed "primary" or plume-candidate hotspots, are unlikely to be caused by thermal plumes from deep thermal boundary layers. Melting anomalies, on- or off-ridge, appear to be a natural result of nonrigid plate tectonics, including recycling, and do not require an extraordinary explanation, such as narrow thermal instabilities that traverse the whole mantle. Thus plate tectonics, plate boundaries, global plate reorganization, normal magmatism, melting anomalies, volcanic chains, and mantle geochemistry can be unified into a single theory.

Additional Information

© 2005 Geological Society of America. Manuscript accepted by the Society January 3, 2005. This paper is Contribution Number 9074, Division of Geological and Planetary Sciences, California Institute of Technology. I appreciate the electronic and acoustic conversations with Gillian Foulger, Anders Meibom, Jim Natland, Dean Presnall, and Jerry Winterer, all of whom have commented extensively and usefully on earlier versions of these ideas. My ideas about mantle melting and mantle heterogeneity have matured under their tutelage. Gillian Foulger stimulated my interest in the end game-suturing and desuturing of continents. Vincent Courtillot, Gillian Foulger, Warren Hamilton, Jim Natland, Dean Presnall, and John Tarduno provided useful reviews of the manuscript.

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