Syn- and post-tectonic granite plutonism in the Sausar Fold Belt, central India: Age constraints and tectonic implications

Sausar Fold Belt (SFB) in central India forms the southern part of the Central Indian Tectonic Zone (CITZ) - a crustal scale Proterozoic mobile belt dissecting the Indian craton, whose tectonothermal history and age is important for understanding the Proterozoic crustal history of the Indian craton. SFB comprises a gneissic basement (TBG: Tirodi Biotite Gneiss) overlain by a supracrustal sequence of quartzite-pelite-carbonate (SSG: Sausar Group). SSG and TBG are deformed and metamorphosed in greenschist to amphibolite facies. Two phases of granite intrusion are observed in the SSG - a syntectonic foliated granite and a post-tectonic massive granite, with clear structural relationship with the host rocks. Monazite chemical dating (U-Th-total Pb) of the foliated and massive granites yield Neoproterozoic (ca. 945-928 Ma) ages that contradict many earlier geochronological interpretations. Foliated granites and the immediately adjacent TBG show monazite grains with ca. 945 Ma mean age, interpreted as the timing of D-2 deformation and amphibolite facies metamorphism of SSG. The post tectonic granites intruded these rocks around 928 Ma, and were largely undeformed. A terminal thermal overprint is found in some monazite grain rims at ca. 785 Ma age. The younger Sausar tectonothermal events have overprinted the adjacent high-grade granulites of Ramakona-Katangi Granulite (RKG) belt, and should not be considered as parts of the same tectonothermal event representing different depth sections only. (C) 2015 Elsevier Ltd. All rights reserved.