Prolonged high-grade metamorphism of supracrustal gneisses from Muhlig-Hofmannfjella, central Dronning Maud Land (East Antarctica)

• Published in: Precambrian Research
• Main Authors: Elvevold, Synnøve, Engvik, Ane, Abu-Alam, Tamer, Myhre, Per Inge, Corfu, Fernando
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: VDP::Mathematics and natural science: 400::Geosciences: 450; VDP::Matematikk og Naturvitenskap: 400::Geofag: 450; Dronning Maud Land; East Antarctica; Mühlig-Hofmannfjella; Antarc*; Antarctica
• Online Access: https://hdl.handle.net/10037/19983; https://doi.org/10.1016/j.precamres.2020.105618

Accepted manuscript version, licensed CC BY-NC-ND 4.0. The bedrock of Mühlig-Hofmannfjella, central Dronning Maud Land in eastern Antarctica, is part of the high-grade Maud Belt and comprises a deep-seated metamorphic-plutonic complex. The P-T-t evolution of anatectic supracrustal gneisses has been recovered through a study of mineral assemblages, textural relationships and U-Pb ID TIMS geochronology on zircon and monazite followed by pseudosection modelling. Peak conditions reached granulite facies conditions (T ≥ 810–820 °C) at moderate crustal depths (P = ca. 8 kbar) and resulted in partial melting. Peak-pressure conditions were followed by isothermal decompression at elevated temperatures. After exhumation to crustal levels of about 4–5 kbar, the area underwent a final near-isobaric cooling, which is documented by a secondary growth of garnet. Zircons indicate a period of growth at 570–566 Ma, whereas monazite ages range from 610 to 525 Ma. A likely heat source for the granulite facies metamorphism is decay of radioactive heat-producing elements in the core of the orogen. The combined geochronology and metamorphic data indicate a prolonged, clockwise P-T path, which reflects collision and formation of a long-lived orogenic plateau.