Abstract
Homogeneous differentiation involving separation of crystals nucleated and grown in the main magma body of a crustal magma chamber and boundary layer fractionation involving compositional convection induced by crystal growth in the cooler marginal zone are thought to be the major differentiation mechanisms (Jaupart and Tait, 1995; Marsh, 1996). These contrasting differentiation mechanisms are linked to mechanisms of heat transfer: thermal convection and heat conduction, respectively, showing strong coupling between material and thermal transfer in a magma chamber. There is, however, no consensus about which mechanism is actually operated and its controlling factors determining the fate of magma chamber. This issue can be addressed by combining theoretical modeling and observation on a geometrically simple sheet-like intrusion, which records temporal change of the physical and chemical conditions of the magma system as sequential changes of composition and microstructure from the chilled margins to the last frozen zone.
