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:: Quote of the week ::
contradicted Einstein he thought it over, and if he
was found wrong he was delighted, because he felt that
he had escaped from an error, and that now he knew better
Otto Robert Frisch, on Einstein
Dear WM, I recently came across the paper by Don Anderson in the Australian Journal of Earth Sciences "The persistent mantle plume myth". It is an informative, entertaining and devastatingly logical demolition of the plume 'hypothesis'. The author provides a cogent summary of what is wrong with the physics of plumes, as well as delving into the philosophical and psychological aspects of the plume story. In the almost indiscriminate invocation of plumes in many LIP and ore-deposit studies, plumes appear to have the same role as the Joker in a pack of cards: something that can be pulled out to trump any other card (hypothesis). Probably one of the most maddening aspects to plumes is the apparent lack of agreed upon criteria that can be used to test the model and its alternatives. For example, magmatism related to a plume should be an intense, very short-lived event. Apparently. Unless of course the magmatic event is prolonged, in which case the magmatism may be related to a cluster of plumes or a superplume! It is this polycephalic aspect to the plume story (in more ways than one) that raises the most questions about its legitimacy as a hypothesis.
Don Anderson's paper is also notable for its reference to various plume models published in some of the most elite journals, such as Science and Nature. Like others I pretty much gave up on those journals some years ago, finding them speculative and unhelpful to progress. Unfortunately, many still seem to regard papers in these journals as gospel, rather than somewhat subjective and unreliable material at the "frontier of science" that has been made widely available.–Steve Sheppard
Dear WM, This recent paper published by Mallik & Dasgupta concludes "mantle potential temperatures of 1330-1350°C appear sufficient to produce high-MgO, primitive basanite-nephelinite if carbonated eclogite melt and peridotite interaction is taken into account.".
This is more evidence that the geochemistry of mafic Mg-rich alkaline rocks can be explained with "normal" temperature, simply assuming a non-pyrolitic mantle source.–Michele Lustrino