Magmatic Distillation

The fundament means of continental growth is through the lateral accretion of oceanic material (island arcs, sea mounts, oceanic crust/lithospheric mantle) at subduction zones or throught the vertical ascent of mantle derived melts. Both processes result in the addition of material that is very mafic (average basaltic or basaltic andesite compositions) relative to typical continental crust (dacitic to rhyolitic composition). This suggests that in order for these newly added materials to become more typical of continental crust a secondary process of distillation is required. Magmatic distillation refers to the process of (re)melting these accreted materials thereby removing and mobilizing the most silicic/felsic components and leaving the most mafic parts in a residum. Ultimately, the residual components may be recycled back into the mantle resulting in a crustal column that is much more similar to continental crust than the original accreted materials. The processes of magmatic distillation and mafic residuum delamination are the focus of a large collaborative research (Continental Dynamics) project known as BATHOLITHS that is funded by the National Science Foundation. As part of my Post-Doctoral position here at the U. of Arizona I am working on the petrologic and geochemical/geochronological aspects of this project. Specifically, I will be helping to quantify the chemical evolution of the Coast Plutonic Complex of British Columbia, Canada (the focus of the BATHOLITHS project). Pictures of the batholith will soon follow.