M. Spiegelman

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Geochemical and field evidence suggest that melt transport in some regions of the mantle is localized into mesoscale “channels” that have widths of 0.1–100 m or larger. Nevertheless, the mechanisms for formation of such channels from a grain-scale distribution of melt are poorly understood. The purpose of this paper is to investigate one possible mechanism(More)
Radioactive disequilibrium of 23Su nuclides is commonly observed in young lavas and has often been used to infer the rates of melting and melt migration. However, previous calculations do not actually include melt transport. Here we explore the behaviour of short-lived radionuclides in a new calculation that includes the fluid dynamics of melt segregation.(More)
Dynamic models are presented to investigate the consequences of melting and melt transport for stable trace element geochemistry in open systems. These models show that including explicit melt transport in 2-D adds non-trivial behaviour because melts and residues can travel and mix along very diierent tra-jectories. Calculations are presented for both(More)
Abstract. An outstanding problem in Earth science is understanding the method of transport of magma in the Earth’s mantle. Two proposed methods for this transport are percolation through porous rock and flow up conduits. Under reasonable assumptions and simplifications, both means of transport can be described by a class of degenerate nonlinear dispersive(More)
The volcanoes that lie along the Earth's tectonic boundaries are fed by melt generated in the mantle. How this melt is extracted and focused to the volcanoes, however, remains an unresolved question. Here we present new theoretical results with implications for melt focusing beneath mid-ocean ridges. By modelling laboratory experiments, we test a(More)
Using numerical schemes, this paper demonstrates how viscous resistance to volume changes modifies the simplest shock wave solutions presented in Part 1 . For an initial condition chosen to form a step-function shock, viscous resistance causes the shock to disperse into a rank-ordered wavetrain of solitary waves. Large obstructions in flux produce(More)
1 Flow in deformable porous media I 2 Abstract Many processes in the earth, such as magma migration, can be described by the ow of a low viscosity uid in a viscously deformable, permeable matrix. The purpose of this and a companion paper is to develop a better physical understanding of the equations governing these two-phase ows. This paper presents a(More)
1 Flow in deformable porous media II 2 Abstract Using numerical schemes, this paper demonstrates how viscous resistance to volume changes modiies the simplest shock wave solutions presented in the previous paper. For an initial condition chosen to form a step-function shock, viscous resistance causes the shock to disperse into a rank-ordered wavetrain of(More)
[1] Global observations of mid-ocean ridge (MOR) bathymetry demonstrate an asymmetry in axial depth across ridge offsets that is correlated with the direction of ridge migration. Motivated by these observations, we have developed two-dimensional numerical models of asthenospheric flow and melting beneath a migrating MOR. The modification of the flow pattern(More)