MPhil Student. Supervisor: Marian Holness

 

 

While the compositional evolution of silicate liquids during progressive solidification has been the subject of intense study for more than a century, it has only recently been realised that basaltic liquids in a certain compositional range unmix into two immiscible conjugates, one dense, mobile and Fe-rich and the other highly viscous, buoyant and Si-rich. The presence of two very different liquids in a magma chamber must have profound effects on the physical and chemical behaviour of the system, although very little is currently known about the extent to which immiscibility occurs, the extent to which the two liquids can separate, and the effects unmixing have on the fluid dynamics of magma chambers. The answers to these questions will provide us with a robust framework for understanding the fluid dynamical behaviour of magma chambers, with applications on all scales from the formation of large ore deposits to the formation of crust on rocky planetary bodies.

A recent study of the Skaergaard Intrusion of East Greenland by the Cambridge group (Holness et al., 2007) demonstrates the potential of microstructural and geochemical analysis of fully solidified mafic plutons in determining the extent and behaviour of immiscible liquids. My current work involves developing these ideas and applying them to the poorly known Sept Iles Intrusion of Quebec, Canada. The aim is to test their wider applicability and to gain invaluable insight into the Sept Iles Intrusion, which has been suggested as a model for the formation of lunar crust. I am relating the microstructural evidence for reactive dissolution of early-formed mineral grains to the presence of a reactive Fe-rich liquid (by the loss of its buoyant Si-rich conjugate). This microstructural evidence is present in the form of symplectites rooted to olivine and oxide grains throughout the stratigraphy of the Sept Iles intrusion. I am documenting the spatial distribution of these symplectites and using geochemical analysis to constrain the composition and amount of reactive liquid present.

 

Holness, M.B., Tegner, C., Nielsen, T.F.D., Stripp, G., and Morse, S.A. (2007) A textural record of solidification and cooling in the Skaergaard Intrusion, East Greenland. Journal of Petrology, 48, 2359-2377.

 

 


Last updated on 20-Mar-13 13:11