Physics
Scientific paper
Jul 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997pepi..102..185s&link_type=abstract
Physics of the Earth and Planetary Interiors, v. 102, p. 185-200.
Physics
3
Scientific paper
The common concept of thermal convection in a magma chamber cooling from above involves only buoyancy due to thermal expansion of the melt neglecting the effect of a solid-liquid phase transition. Whereas, in a crystallizing magma at equilibrium, the total effect of crystal fractionation and cooling on the melt density is often negative, melt can become denser only due to the presence of crystals. In this case, convection would be essentially two-phase in nature. As an end member of this two-phase case, a 2-D model of convection caused entirely by the flux of a solid phase generated at the upper cooling boundary is considered. A semi-analytical solution based on the Green's function representation of the steady state velocity field at constant crystal flux is proposed. It follows from our analysis that critical conditions exist for the onset of steady sedimentary convection. The critical sedimentary Raleigh number (Ras = ΔρH2/(Sμ), where Δρ = (ρs - ρ1)ɛ, ρs is the density of solid, ρ1 is the density of liquid, ɛ is the concentration of crystals, g is the gravity acceleration, H is the vertical size of liquid layer, S is the sedimentation velocity, and μ is the melt viscosity) is found to be about 100. At supercritical conditions Ras > Racrits, two branches of steady state laminar convection exist. The first corresponds to `plume-type' and the second to `bubble-type' convection. Both are characterized by the presence of crystal-free (CF) liquid regions at given supercritical Ras. For `bubble-type' convection, an infinitesimal decrease of the CF volume leads to deviations from stationary convection and the eventual disappearance of the `bubble'. The relation between the maximum convection velocity for the `plume-type' system and Ra1/(2)s is calculated and proven to be asymptotically linear for a fixed aspect ratio. Numerical finite difference solutions demonstrate the evolution of sedimentary convection to a quasi-stationary state at Ras = 1000 and 5000 with parameter values close to those predicted theoretically. One can expect similar forms of convection in a magmatic chamber in the presence of crystal and bubble distributions with variations on the scale above several meters.
Schmeling Harro
Simakin A.
Trubitsyn Valeriy
No associations
LandOfFree
Convection in melts due to sedimentary crystal flux from above does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Convection in melts due to sedimentary crystal flux from above, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Convection in melts due to sedimentary crystal flux from above will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1416803