Multi-stage crustal growth and Neoarchean geodynamics in the Eastern Dharwar Craton, southern India

Abstract

The Dharwar Craton is a composite Archean cratonic collage that preserves important records 25 of crustal evolution on the early Earth. Here we present results from a multidisciplinary study 26 involving field investigations, petrology, zircon SHRIMP U-Pb geochronology with in-situ 27 Hf isotope analyses, and whole-rock geochemistry, including Nd isotope data on migmatitic 28 TTG (tonalite-trondhjemite-granodiorite) gneisses, dark grey banded gneisses, calc-alkaline 29 and anatectic granitoids, together with synplutonic mafic dykes along a wide Northwest -30 Southeast corridor forming a wide time window in the Central and Eastern blocks of the 31 Dharwar Craton. The dark grey banded gneisses are transitional between TTGs and calc-32 alkaline granitoids, and are referred to as 'transitional TTGs', whereas the calc-alkaline 33 granitoids show sanukitoid affinity. Our zircon U-Pb data, together with published results, 34

Migmatite rheology of crustal catazone: An example from theSSEpart of T. Sundupalle granite‐greenstone terrain, Eastern Dharwar Craton, India

“…The simple shear deformation fabrics are result of lithospheric convergence probably during amalgamation of EDC with WDC. Profuse juvenile granitic eruption is also a contemporaneous event (Jayananda et al, 2018, 2019). During the metamorphism, deformation can also play role in producing anatectic melt.…”

“…EDC represent relatively later history of the crustal evolution as >3 Ga rocks are rare in the EDC (; Bidyananda et al, 2011; Dey, 2013; Jayananda et al, 2000). According to Jayananda et al (2019), four major phases of crustal growth over a time span from 3,360 to 2,520 Ma indicate involvement of multiple mechanisms. Initial TTG development from older supracrustals till ~2,960 Ma (Jayananda et al, 2019) is indicative of enough crustal growth for anatexis by that time.…”

“…According to Jayananda et al (2019), four major phases of crustal growth over a time span from 3,360 to 2,520 Ma indicate involvement of multiple mechanisms. Initial TTG development from older supracrustals till ~2,960 Ma (Jayananda et al, 2019) is indicative of enough crustal growth for anatexis by that time. Peninsular gneiss equivalents with TTG composition possibly represents static mode partial melting of older supracrustal amphibolite in the presence of water (Rapp & Watson, 1995) possibly derived from hydrous minerals.…”

“…In fact, mafic greenstone volcanism is derived from partial melting of TTG and felsic volcanism with contemporaneous calc‐alkaline granitic magmatism (Jayananda et al, 2019) is derived from migmatites in a convergent tectonic setting (Goswami & Upadhyay, 2019; Goswami et al, 2017; Goswami, Sivasubramaniam, Bhagat, Kumar, & Sarbajna, 2016). Therefore, in addition to the several evidences of convergent tectonic settings (Chadwick et al, 2000, 2007; Jayananda et al, 2013, 2019; Manikyamba & Kerrich, 2012; Naqvi, 2005, 2008; Pandey et al, 2017; Raju, Eriksson, Catuneanu, & Banerjee, 2014; Ramakrishnan & Vaidyanadhan, 2008; Sesha Sai, Mahapatro, Bhattacharjee, Khanna, & Korakoppa, 2019) for the EDC, the subduction can be supported from such migmatites also. All of the distinguishable stages in this complicated process of episodic partial melting are summarized as flowchart for better visualization of anatectic events (Figure 29b).…”

“…All of the distinguishable stages in this complicated process of episodic partial melting are summarized as flowchart for better visualization of anatectic events (Figure 29b). There are multi‐stage crustal growth and frequently changing geodynamics during Neoarchean (Jayananda et al, 2019).…”