Discussion of "Temporal evolution of the Kerguelen plume: geochemical evidence from approximately 38 to 82 Ma lavas forming the Ninetyeast Ridge" by F.A. Frey and D. Weis

Article Abstract:

F.A. Frey and D. Weis's assumption that the composition of the Kerguelen plume source is nearly homogeneous and is the same as the youngest lavas of the Ninetyeast Ridge is erroneous. Their 'static' plume model does not take into account the effects of radioactive decay. Isotopic compositions alone cannot help to relate the Ninetyeast Ridge to the Kerguelen plume. The importance of shallow-level interaction of the plume with the Kerguelen Plateau lithosphere is emphasized. The 'evolving' plume theory gives a well-rounded explanation of the evolution of the plume.

Frey, F.A., Weis, D.

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Reply to the Class et al. discussion of "Temporal evolution of the Kerguelen plume: geochemical evidence from approximately 38 to 82 Ma lavas forming the Ninetyeast Ridge."(response to Cornelia Class, Steven L. Goldstein, Stephen J.G. Galer, in this issue, p.98)

Article Abstract:

The 'evolving' plume hypothesis of Cordelia Class and colleagues to explain the Kerguelen plume, is as unconvincing as the other theories proposed. Very few lavas have the isotopic characteristics needed to establish the 'evolving' plume theory. A generalized view based on a few positive results is not sufficient to explain such an important event. The contention that old lithosphere is a magma source is also not convincing. Lavas from the Central Kerguelen Plateau and Kerguelen Archipelago were largely derived from the plume.

Class, Cornelia, Goldstein, Steven L., Galer, Stephen J.G.

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Temporal evolution of the Kerguelen plume: geochemical evidence from approximately 38 to 82 Ma lavas forming the Ninetyeast ridge

Article Abstract:

The northward drifting of the Indian Plate over the hotspot of Kerguelen Island, which is a constant magma source, caused the volcanic structure, Ninetyeast ridge. Due to the proximity of the hotspot to the spreading ridge axis, a tholeiitic basalt magma is created by melting, melt isolation at low pressures and different proportions of mixing among isotopically identical components and a high Pb(super 206)/Pb(super 204) component. The temporal evolution of the Kerguelen plume is discussed.

Environmental aspects, Indian Ocean, Archipelagoes, Submarine geology, Marine geology

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