A metamorphic perspective on the Pan African overprint in the Amery area of Mac. Robertson Land, East Antarctica

• Published in: Antarctic Science
• Main Authors: Scrimgeour, I., Hand, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 1997
• Subjects: Amery; East Antarctica; Mac. Robertson Land; Prince Charles Mountains; Prydz Bay; Antarc*; Antarctic Science; Antarctica; Mac Robertson Land
• Online Access: http://hdl.handle.net/2440/13602; https://doi.org/10.1017/S0954102097000400

The Amery area of Mac. Robertson Land lies between the early Palaeozoic granulite terrain of Prydz Bay and Meso-Neoproterozoic granulites in northern Prince Charles Mountains (nPCM). In contrast to the nPCM which shows an apparently simple near-isobaric history, granulites exposed in the Amery area contain reaction textures suggesting a more complex evolution. Peak-M1 Mesoproterozoic assemblages formed at c. 700 MPa and 800°C and initially underwent a near-isobaric cooling. A subsequent increase in temperature (M2) resulted in the formation of cordierite-spinel assemblages at ~450 MPa and 700°C in metapelite. The timing of M2 is not firmly established, however existing data strongly suggest it is an early Palaeozoic event coeval with tectonism in Prydz Bay to the north-east. Thus the metamorphic evolution of granulites in the Amery area reflects a terrain-scale thermal interference pattern between two unrelated orogenic events. In rocks not recording post-M1 isobaric cooling, the superposition of M2 on M1 assemblages resulted in the formation of M2 cordierite-spinel symplectites at the expense of peak M1 garnet and sillimanite. This texture, commonly interpreted to reflect near-isothermal decompression, has no relevance in terms of a single tectonothermal event in the Amery area. Ian Scrimgeour and Martin Hand