THE SOUTHERN PARTS OF ARAVALLI MOUNTAIN BELT AND RODINIA ASSEMBLY - IS THERE A CONNECTION?

The southern part of the Aravalli Mountain Belt, western India, comprises granite and gneiss and lies in the proximity of the Narmada Suture. The granite is referred to as Godhra Granite and has been dated as 955±20 Ma. The gneiss is older than the granite, but its exact age is unknown. Field studies have revealed the gneiss underwent at least three episodes of deformation-D1, D2 and D3. The D3 folds are the most prominent; they have ENE-WSW striking axial planes with NW plunging fold axis. The Godhra Granite has a contact with the gneiss in the south and metasedimentary rocks of the Aravalli Supergroup in the north. Both these granite margins are observed to be mylonitized and are high strain zones. Stretching lineations developed at these margins plunge moderately to the NW. Anisotropy of Magnetic Susceptibility (AMS) studies on the granites and gneisses have revealed that the magnetic foliation in the granite is parallel to the D3 axial plane (S3) foliation in the gneiss. Moreover, the magnetic lineation is parallel to the stretching lineation at granite margin as well as the D3 fold axis lineation of reclined folds. Besides this, the granite also preserves within it several microstructural evidence of having been subjected to high temperature solid-state deformation. Therefore, it is inferred that the Godhra Granite is deformed and its emplacement was syntectonic with the D3 deformation of the gneiss. Since the granite is dated to be 955±20 Ma in age, this constraints the age of the D3 deformation of the gneiss. It is known that the formation of Rodinia took place between 1.35-0.9 Ga and raises the following questions. “Is the emplacement of Godhra Granite in anyway related to the assembly of Rodinia in the Aravalli craton part of the Indian Shield? Or, does the granitoid domain of the southern Aravallis represent an erstwhile plate margin where juvenile curst was generated during the assembly of Rodinia? Since the age of D3 deformation, is constrained by the age of the syn-D3 Godhra Granite, it is quite likely that the deformation of the southern Aravalli granitoids is related to the assembly of Rodinia. Moreover, since these granitoids have proximity to the Narmada Suture that formed by accretion of Aravalli and Dharwar Protocontinents during the Mesoproterozoic, the other question that must be answered is “Was this accretion a result of assembly of Rodinia?