The Kiglapait intrusion affords many opportunities for evaluating plutonic fractionation processes. Estimates of boundary conditions include emplacement of anhydrous high alumina basaltic magma at 4 kbar and about 1250 °C, initial crystallization near the WM buffer, and fractionation to Mg-free ferrosyenite which crystallized at 960°C, somewhat above the WM buffer. The last ferrosyenites represent fractionation to 0.01 per cent of the initial volume.