Transmantle fluid flows and plume genesis

Abstract

A mantle plume formation model based on possible migration of fluid in the plastic mantle as subvertical isolated cavities-fractures is offered. Excessive pressure (EP) proportional to the vertical size of the cavity and the difference in fluid and rock densities appears in such cavities under plasticity conditions. The excess of the EP value over rock hardness results in “fluid fracturing” (by analogy with hydrofracturing) in the “head” and, due to the cavity volume stability, in collapse of the fracture tail providing its movement upwards. Gas emission from the Earth’s core is accompanied by its accumulation at the boundary between the core and the mantle as fluid lenses, which having attained a critical size break through the mantle and migrate to the surface. In fact, a relatively stable fluid flow is created in the mantle heating it up and interacting with it. The flow stops down in the hard lithosphere base and spreads laterally initiating mantle metamorphism and melting accompanied by the formation of magmatic reservoirs massively intruding and flowing out when the critical height is attained.