LI DISTRIBUTION IN AEGIRINE LUJAVRITE, ILIMAUSSAQ ALKALINE INTRUSION,SOUTH GREENLAND - ROLE OF CUMULUS AND POST-CUMULUS PROCESSES

Li was analysed by activation analysis in 363 whole:rock samples and 5 3 minerals from a 200 m drill core through aegirine lujavrite I, Ilima ussaq intrusion. The rocks are interpreted as cumulates and Li is domi nantly located in the intercumulus material which is thought to repres ent the coexisting magma with 540 ppm: whole-rock contents generally r ange from 80-260 ppm Li and reflect variations in the amount of interc umulus material from 25-48 wt.%. The proportion of intercumulus materi al is lowest in the deeper parts of the drill core, in layers with a m oderate density stratification resulting from showers of near-liquidus crystals and in compressed cumulates beneath a large naujaite xenolit h from the roof. Intercumulus arfvedsonite with an average of 2200 ppm Li contains the bulk of Li in most samples, but nearly every sample c ontains Li (0-176 ppm) outside the rock-forming minerals (Li-ORFM) whi ch was unlocated by conventional mineral separation. Li-ORFM formed du ring late-magmatic crystallization (a) from the final residues of inte rcumulus magma which crystallised as accessory Li-mica and alteration products and (b) during in situ zeolitization of arvedsonite which rel eased Li. A later, more intense zeolitization released Li from the roc ks of the drill core. Naujaite xenoliths contain 42-130 ppm Li, except where Li-metasomatised, and are associated with low Li values in adja cent lujavrites. Shearing of consolidated lujavrite allowed mobilizati on of the Li and its reprecipitation along narrow channels (< 10 cm). Li is not concentrated in late hydrothermal coatings.