Metamorphic Evolution of Calc-silicate Rocks at Akarui Point, Lützow-Holm Complex, East Antarctica

Abstract

We report on the petrology and metamorphic history of boudined bodies of zoned calc-silicate rock, up to 1 m in width, which are enclosed in gneisses, transitional between upper amphibolite to granulite facies, at Akarui Point, Lützow-Holm Complex, East Antarctica. Zircons extracted from a closely related body of Mn-exhalative derived calc-silicates indicate that the metamorphism occurred in two separate events, at 546.6 ± 0.6 and 524.3 ± 0.6 Ma, during the Pan African Orogeny. Based on the meionite content of scapolite from different mineral zones in the calc-silicates, we derive a metamorphic history that involved a peak temperature of a minimum 810 – 820 °C, followed by a fall to 760-800 °C and then to 690-765 °C during uplift and decompression to 5.5 – 7 kbar. GAP geothermo-barometry indicates that the enclosing gneiss partially re-equilibrated during retrogression at 500-580 °C.