Mid-Neoproterozoic extensional tectonics in the Larsemann Hills, East Antarctica: Implications for Indo-Antarctic correlation in Rodinia
Date
2026
Authors
Chatterjee, S.
Dev, J.A.
Debnath, A.
Ghosh, A.
Dey, S.
Mukherjee, A.
Arora, D.
Tomson, J.K.
Guimarães, F.
Pant, N.C.
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Journal article
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Lithos, 2026; 522-523:108358-1-108358-17
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Sandro Chatterjee, J. Amal Dev, Aishi Debnath, Anuj Ghosh, Soham Dey, Anik Mukherjee, Devsamridhi Arora, J.K. Tomson, Fernanda Guimarães, Naresh Chandra Pant, Saibal Gupta
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Abstract
The supercontinents Rodinia and Gondwana are believed to have assembled through orogenic events at ∼1000 Ma and ∼550 Ma, respectively. The Larsemann Hills, part of the extended Rayner Complex of East Antarctica, is a Neoproterozoic granulite terrane that was a part of both supercontinents. The tectonic evolution of the terrane in the Rodinia to Gondwana interval remains uncertain. This study integrates new field, microstructural, metamorphic and geochronological information to unveil a previously undocumented mid-Neoproterozoic thermo-tectonic event in the Larsemann Hills. Granulite facies metamorphism (M₁), synchronous with the deformation, D₁, is interpreted to have occurred in the Larsemann Hills at ∼1000 Ma, followed by a crustal shortening (D₂) event that continued from ∼990–900 Ma, signifying the incorporation of the Rayner crustal unit into Rodinia. Subsequent mid-Neoproterozoic extensional deformation (D₃), characterized by NW-SE trending S₃ shear zones, reoriented pre-existing structural fabrics. The extensional deformation operated under amphibolite facies metamorphic conditions (M₂) and resulted in a post-peak decompressive P-T trajectory. Usingle bondPb LA-ICPMS dates on zircons separated from metapelites within high D₃ strain zone yield clusters at ∼700 Ma; zircons immediately adjacent to the shear zone yield ages around ∼990–900 Ma. A thermal overprint at ∼550 Ma is evident but weakly manifested in the western Larsemann Hills, with no unambiguously correlatable structural or metamorphic evidence, suggesting distance from the Gondwana orogenic front. The extensional deformation documented here is contemporaneous with extension in the northern Eastern Ghats Province, India that was contiguous with the Rayner Complex in the Neoproterozoic. This suggests that a major terrane-wide extensional event was associated with the disintegration of Rodinia. In the Neoproterozoic, the EGP-Rayner unit was therefore a tectonic entity distinct from cratonic India, with only the former being an integral component of Rodinia.
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