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, Ian, Hand, Martin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1997
• Subjects: Antarc*; Antarctic Science; Antarctica; East Antarctica; Mac Robertson Land; Mac. Robertson Land; Prince Charles Mountains; Prydz Bay
• Online Access: http://dx.doi.org/10.1017/s0954102097000400; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/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-M 1 Mesoproterozoic assemblages formed at c. 700 MPa and 800°C and initially underwent a near-isobaric cooling. A subsequent increase in temperature (M 2 ) resulted in the formation of cordierite-spinel assemblages at ~450 MPa and 700°C in metapelite. The timing of M 2 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-M 1 isobaric cooling, the superposition of M 2 on M 1 assemblages resulted in the formation of M 2 cordierite-spinel symplectites at the expense of peak M 1 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.