The relationship between relic pillow structures and zoned calc-silicate skarns, and the significance of talc balls in gneisses south of Frederikshåb

Abstract

Amphibolite bands within the pre-Ketilidian gneisses on the island of Igaussaq and the adjacent mainland contain in places clearly recognizable epidotic relic pillow structures, together with probable meta-keratophyre layers and a meta-agglomerate horizon. Zoned calc-silicate skarn bodies have developed from the pillow structures in areas of more intense folding and granitization. In these areas the amphibolites have become agmatitic, and the pillows have suffered more thorough recrystallization and metamorphic differentiation to give zoned bodies consisting of calcite, garnet, diopside, epidote and hornblende.