The proposed work is aimed at understanding high temperature processes that are inferred to have affected the mineralogical and bulk compositions of cumulate rocks formed as the Skaergaard intrusion solidified. In particular it will focus on the conditions leading toe formation of the phosphate mineral apatite -- i.e. did this mineral form by crystallization of trapped interstitial silicate liquids or was it formed in response to introduction of phosphorus and halogens (u, f) from the surrounding wall rocks. The results of this study should provide critical constraints on how mafic intrusions evolve compositionally.