EFFECT OF MANTLE DEPLETION BUOYANCY ON PLUME FLOW AND MELTING BENEATHA STATIONARY PLATE

Citation
A. Manglik et Ur. Christensen, EFFECT OF MANTLE DEPLETION BUOYANCY ON PLUME FLOW AND MELTING BENEATHA STATIONARY PLATE, J GEO R-SOL, 102(B3), 1997, pp. 5019-5028
Citations number
37
Categorie Soggetti
Geochemitry & Geophysics
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
ISSN journal
21699313 → ACNP
Volume
102
Issue
B3
Year of publication
1997
Pages
5019 - 5028
Database
ISI
SICI code
2169-9313(1997)102:B3<5019:EOMDBO>2.0.ZU;2-M
Abstract
We analyze a dynamical model of plume-lithosphere interaction in two-d imensional Cartesian geometry that takes into account the buoyancy of the depleted residue produced by melt extraction. The plume enters thr ough the open bottom boundary at 400 km depth and leaves through the r ight side boundary of the model box. The viscosity is strongly pressur e and temperature dependent. We use a large number of Lagrangian trace r particles to monitor progressive melting in the plume head and to tr ack the advection of the depleted residue. The density reduction in th e residue enhances small-scale instabilities sinking from the bottom o f the lithosphere into the depleted layer. Initially, the melt product ion rate is slightly enhanced when depletion buoyancy is taken into ac count. However, in the subsequent evolution, melt production rates are lowered by a factor in the range 0.5 - 0.65, depending on the initial thickness of the lithosphere, compared to cases without density diffe rence of the residue. The buoyancy of the residual mantle opposes its advection away from the top of the plume. A depleted root is formed at the bottom of the lithosphere, which inhibits further thermal erosion of the plate. It forces the plume flow to stagnate at greater depth a nd hence reduces the melt production rate. The effect is particularly strong for a case where the plume rises beneath locally stretched lith osphere. The results are compared to the evolution of volcanism at the Cape Verde hotspot and the Kenya rift.