New constraints on metamorphism in the Highjump Archipelago, East Antarctica

• Published in: Antarctic Science
• Main Authors: Tucker, Naomi M., Hand, Martin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2016
• Subjects: Antarctic; Bunger Hills; Denman Glacier; East Antarctica; Highjump Archipelago; Antarc*; Antarctic Science; Antarctica
• Online Access: http://dx.doi.org/10.1017/s095410201600033x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S095410201600033X

Abstract The age and conditions of metamorphism in the Highjump Archipelago, East Antarctica, are investigated using samples collected during the 1986 Australian Antarctic expedition to the Bunger Hills–Denman Glacier region. In situ U-Pb dating of monazite from three metasedimentary rocks yields ages between c. 1240–1150 Ma and a weighted mean 207 Pb/ 206 Pb age of 1183±8 Ma, consistent with previous constraints on the timing of metamorphism in this region and Stage 2 of the Albany–Fraser Orogeny in south-western Australia. This age is interpreted to date the development of garnet ± sillimanite ± rutile-bearing assemblages that formed at c. 850–950°C and 6–9 kbar. Peak granulite facies metamorphism was followed by decompression, evidenced largely by the partial replacement of garnet by cordierite. These new pressure–temperature determinations suggest that the Highjump Archipelago attained slightly higher temperature and pressure conditions than previously proposed and that the rocks probably experienced a clockwise pressure–temperature evolution.