Multiple thrust systems from the Southern Granulite Terrane, India: Insights on Precambrian convergent margin tectonics

The geological and structural complexities of the Southern Granulite Terrane (SGT) of India, a key Gondwana collisional orogenic belt, are increasingly recognized and our understanding is still evolving despite several multidisciplinary efforts. Six important structural cross sections along some critical geological corridors have been reconstructed covering the entire stretch of SGT. Subduction related multiple thrust systems for the evolution of the SGT is proposed, based on the salient features derived from the structural cross sections and the currently available geoscientific data sets. The presence of tectonic windows and klippe structures in Madurai block and unusual occurrence of high strain zones on top of some of the highly elevated quartzite hills support the thrust- nappe tectonic model for the SGT implying possible allochthonous nature of many of the supracrustals and granulitic units involving multiphases of thrusting.

The evolution of the SGT involves converging accretionary processes of island arc magmatic intrusives, thrust stacking, crustal coupling, granitic emplacement and the obduction of ophiolite complexes indicating a complete range of geological processes encountered in modern orogenic belts. These features could thus be representative of multiple thrusting related to south directed sub- duction processes followed by wide scale collision of Gondwana fragments during the end Precambrian. The understanding of subduction, accretion and collisional history along the CSZ within the SGT together with a long lived transpres- sional tectonics imply a plate tectonic model for the Neoproterozoic- Cambrian evolution of southern India. The timing of nappe transport can be attributed to the final stage of Gondwana assembly between 480 and 600 Ma, analogous to East Africa Orogen.


Figure: (Kuppam-Kanyakumari N-S structural cross section for the evolution of the Southern Granulite Terrane. NGB-Northern Granulite Block; CSZ-Cauvery shear zone; TMSZ-Theni-Madurai shear zone; MGB-Madurai Granulite Block; AKSZ- Achankovil shear zone; TGB-Trivandrum Granulite Block; K-Kanyakumari; Ku-Kuppam.)


T.R.K. Chetty, (2021) Journal of Asian Earth Sciences, Volume 208, 104674, ISSN 1367-9120,