Observational constraints on mantle melt transport

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• John MacLennan (University of Cambridge)
• Monday 15 February 2016, 14:30-15:30
• Seminar Room 1, Newton Institute.

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MIMW01 - From foundations to state-of-the-art in magma/mantle dynamics

The review paper of Kelemen et al. (1997) summarised the key observations used to develop a model of rapid melt extraction in porous channels. Many subsequent observations have been acquired with the aim of refining estimates of the timescales of melt extraction from the mantle. Nevertheless, substantial uncertainty remains concerning how these observations can be used to characterise variation in melt transport velocities under basaltic volcanoes at spreading ridges and ocean islands. Uranium series disequilibria indicate that melt transport rates are almost certainly >1 m yr-1 and probably >50 m yr-1. An alternative method for estimating melt transport rates is based upon the observational record of the response of magmatism to loading and unloading of a mantle melting region. Such loading cycles may be generated by with glaciation and sea-level change. It is well-established that the record of volcanic productivity in certain regions of Iceland is strongly influenced by variations in the load from glaciation of the island. The minimal time-lag between deglaciation and a burst in volcanic productivity indicates that melt transport is rapid (>50 m yr-1). More recent analyses of seafloor morphology and temporal variation in hydrothermal activity at submerged mid-ocean ridges have made a tentative link between sea-level fall during glacial growth and increased magmatic activity during glacial terminations. This link can only work if melt extraction rates are
A number of models of melt extraction have been developed in order to understand the emergence of rapid channelized melt flow. One promising research direction is the study of the behaviour of mantle where fusible heterogeneities sit in a more refractory matrix.

This talk is part of the Isaac Newton Institute Seminar Series series.

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