Dec 13, 2014· Plagioclase Fractionation in Troctolitic Magma Plagioclase Fractionation in Troctolitic Magma Morse, S. A. 00:00:00 Troctolitic intrusive rocks poor in augite are common in certain Proterozoic anorthosite complexes and related rocks. The Lower Zone of the Kiglapait intrusion, Labrador, consists of 1570 km3 troctolite today and possibly 2900 km3 before erosion.