Kinematics, strain pattern and geochronology of the Salem-Attur shear zone: Tectonic implications for the multiple sheared Salem-Namakkal blocks of the Southern Granulite terrane, India

Insights into the crustal architecture from the analysis of gravity and magnetic data across Salem-Attur Shear Zone (SASZ), Southern Granulite Terrane (SGT), India: an evidence of accretional tectonics

“…The SGT is a collage of tectonic units/blocks, each of which is characterized by distinct protolith, lithological assemblage and isotopic age. The tectonic units/blocks are dissected by crustal-scale shear/suture zones (Santosh et al, 2009;Collins et al, 2014;Behera et al, 2019). From north to south, the tectonic units/blocks are (i) Northern Granulite Block (NGB), (ii) Palghat Cauvery Shear System (PCSS), (iii) the Madurai Block, and (iv) The Trivandrum Block.…”

“…1) is a discrete tectonic block that evolved through Neoarchean arc magmatism in a convergent margin setting (Samuel et al, 2014). The SASZ, which separates the Shevaroy Block (SB) and Namakkal Block (NkB, Li et al, 2018), is interpreted as strike-slip shear zone (Drury and Holt, 1980;Chetty et al, 2003) with basal decollement and along which PCSS is thrusted over NGB (Biswal et al, 2010, Behera et al, 2019. The NkB is bordered by the SASZ at the north, the Cauvery-Bhavani Shear Zone (CBSZ) at the west and the Palghat Cauvery Shear Zone (PCSZ), at the south (Fig.…”

“…1). The lithological assemblages of the study area formed between 3.2 to 2.6 Ga (Behera et al, 2019). Some studies indicate the SASZ, as the northern frontier of the suture zone named as Palghat Cauvery Shear System (PCSS; Bhaskar Rao et al, 2003;Collins et al, 2007;Clark et al, 2009;Santosh et al, 2009Santosh et al, , 2012.…”

“…The Southern Granulite Terrane (SGT) provides a critical window to understand the tectonic evolution of Precambrian crust as it preserves the geological records of continent reconstruction, subductioncollision and terrane accretion (Sato et al, 2011;Praveen et al, 2014;Samuel et al, 2014;Santosh et al, 2015;Ratheesh-Kumar et al, 2016;Santosh and Li, 2018;Santosh, 2020). The SGT consists, collage of Neoarchean to Neoproterozoic terranes/ tectonic blocks, which are characterized by distinct lithological assemblages, grades of metamorphism and isotopic age (Behera et al, 2019). The Meso to Neoarchean terrane adjacent to Dharwar Craton is termed as Northern Granulite Block (NGB; Clark et al, 2009;Brandt et al, 2014;Collins et al, 2014;Ratheesh-Kumar et al, 2016, Chetty, 2017Kumar et al, 2020a), which is made up of orthogneisses, metasedimentary rocks and charnockities.…”

“…Some studies indicate the SASZ, as the northern frontier of the suture zone named as Palghat Cauvery Shear System (PCSS; Bhaskar Rao et al, 2003;Collins et al, 2007;Clark et al, 2009;Santosh et al, 2009Santosh et al, , 2012. However, Behera et al (2019), opined that the SASZ might not be a suture, but represent intra-terrane shear zone within a single Archean-Paleoproterozoic SGT. The geophysical signatures addressing crustal architecture in this important tectonic line is little known.…”