Insights into geological evolution of Princess Elizabeth Land, East Antarctica-clues for continental suturing and breakup since Rodinian time

Abstract

Svenner Islands-Brattstrand Bluffs-Larsemann Hills constitutes ~70 km long coastal outcrops of Princess Elizabeth Land (PEL), comprising complexly deformed metapelites and orthogneisses. Pelitic granulites from these outcrops are investigated in this work. Conventional geothermobarometric estimations and Pseudosection modelling consistently indicate that the peak metamorphic grade throughout the area is high to ultra-high temperature (800–950 °C) at low to medium pressure (2–5 kbar). A high pressure (~10 kbar) relict metamorphic event and a substantial decompression component of ~5 kbar, corresponding to >15 km uplift, are inferred through petrographic as well as pseudosection analysis. Two set of ages are estimated (~800 Ma and ~500 Ma), corresponding to Tonian and Pan-African metamorphic events, respectively. Field data, petrographic studies and ages estimated from orthogneisses from the Brattstrand Bluffs and the Grovnes Peninsula suggest that this unit is a product of in-situ melting of the pelitic granulites.Pelitic granulites of PEL possess similarities with those exposed in the Eastern Ghat Mobile Belt of India. We propose that these sectors represent a contiguous terrane with two major orogenic imprints, reflecting Rodinia and Gondwana amalgamations. An attempt is made to mark out paleo-orogenic belt axes, supported by both field as well as recent aero-magnetic signatures in interior PEL. We support that the parent sediments of the pelitic granulites were deposited during Stenian period, which underwent compressional UHT-HP(?) metamorphism at ~800 Ma. Another extensive basin is proposed at ~600 Ma prior to the Pan-African orogenic event. We propose that the Pan-African orogeny marked the collision of Indo-Australo-Africo-Antarctic cratons and stitched the East Gondwana. We also propose a thinned lithosphere along the system of subglacial lakes-canyons confirmed by ICECAP data. Analog modelling is used to demonstrate the influence of pervasive mechanical anisotropy of the basement in defining the orientation of this rift system and its connection to the Lambert Graben.