Abstract
Natural Environment Research Council Royal Society of London Carlsberg Foundation Danish Council of Independent Research Danish National Research Foundation
Highlights
When mafic magma stalls in a crustal magma chamber, cooling leads to crystallization and the formation of a mushy layer on the walls, roof and floor
To date it has been difficult to constrain the thickness of the floor mushy layer from observations of fully solidified plutons, with estimates ranging from effectively zero (Morse, 1986) to hundreds of metres (e.g. Tait & Jaupart, 1992). In this contribution we argue that tight constraints can be placed on crystal mush thickness at localized stratigraphic horizons in layered intrusions, those recording a change in the assemblage of liquidus minerals, using detailed microstructural analysis
We report only the P2O5 concentrations in this contribution: the rest of the data will be presented in further publications
Summary
When mafic magma stalls in a crustal magma chamber, cooling leads to crystallization and the formation of a mushy layer on the walls, roof and floor. Various processes have been suggested to account for the removal of evolved interstitial liquid, such as diffusion (Hess, 1960; Wager et al, 1960), compositionally driven convection (Hess, 1972; Tait et al, 1984; Tait & Jaupart, 1992) and compaction (Sparks et al, 1985; Shirley, 1986; Tharp et al, 1998; McKenzie, 2011) The effectiveness of these processes in driving fractionation is dependent on the physical properties (such as rheology and permeability) of the mushy layer and, in particular, on its thickness.
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