First Precambrian palaeomagnetic data from the Mawson Craton (East Antarctica) and tectonic implications

Area of Science:

• Paleomagnetism
• Geochronology
• Plate Tectonics

Background:

• The Mawson Craton in East Antarctica preserves a paleomagnetic record crucial for understanding supercontinent reconstructions.
• Precise dating of geological formations is essential for correlating paleopoles and testing tectonic models.

Purpose of the Study:

• To establish a well-dated Mesoproterozoic paleopole for the Mawson Craton.
• To investigate the paleogeographic connections between East Antarctic terranes around 1.134 billion years ago.
• To evaluate the validity of paleogeographic reconstructions like SWEAT for the Mesoproterozoic.

Main Methods:

• Pilot paleomagnetic study of Mesoproterozoic dykes from the Bunger Hills, Mawson Craton.
• In situ SHRIMP U-Pb dating of zircon and baddeleyite for precise age determination (1134 ± 9 Ma).
• Palaeomagnetic analysis to determine paleopoles and assess paleogeographic relationships.

Main Results:

• Three of six sampled dykes yielded meaningful paleomagnetic results, establishing the first well-dated Mesoproterozoic paleopole for the Mawson Craton (40.5°S, 150.1°E).
• The new paleopole shows discordance with coeval poles from Dronning Maud Land and Coats Land, indicating these terranes were not rigidly connected to the Mawson Craton at ca. 1134 Ma.
• Comparison with the North Australian Craton's paleopole supports a ~40° late Neoproterozoic rotation and suggests the SWEAT reconstruction is not viable for ca. 1134 Ma.

Conclusions:

• East Antarctic terranes (Mawson Craton, Dronning Maud Land, Coats Land) were likely not part of a single rigid block at ca. 1134 Ma.
• The paleogeographic configuration of Proto-Australia and Laurentia around 1.134 billion years ago differs significantly from the SWEAT model.
• This study provides critical paleomagnetic and geochronological data for refining Mesoproterozoic paleogeographic reconstructions.