Metamorphic P-T path of the eastern Trivandrum Granulite Block, southern India: implications for regional correlation of lower crustal fragments

Abstract

We report here the metamorphic P -T path for granulite -facies metapelites from the eastern part of the Trivandrum Granulite Block (TGB), southern India, and compare with the paths from the western part of the block as well as from other granulite blocks and shear zones in this region for understanding of exhumation history of the southern granulite terrane. The peak temperature condition of the eastern part (900 -1000 °C) is almost consistent with that from the western part, suggesting regional ultrahigh -temperature (UHT) metamorphism throughout the TGB. However, there is a slight difference in peak pressure conditions between the eastern part (12 kbar) and the western part (10 kbar) estimated from different Zn content within spinel in equilibrium with quartz. Such P ~ 12 kbar high -pressure event is consistent with that obtained from granulite -facies rocks further north in the Palghat -Cauvery Shear Zone system (PCSZ) and Madurai Granulite Block (MGB). The results therefore suggest that the TGB, MGB, and PCSZ underwent similar prograde high -pressure metamorphism followed by peak UHT event along a clockwise P -T trajectory, related to the collisional orogeny during the assembly of the Gondwana Supercontinent.

Sapphirine + quartz assemblage from Ganguvarpatti: diagnostic evidence for ultrahigh-temperature metamorphism in central Madurai Block, southern India

“…The southern granulite terrane (SGT) in India is characterized by the occurrence of Late Neoproterozoic to Early Cambrian (Santosh et al, 2003Collins et al, 2007, and references therein) high -grade metamorphic rocks that underwent T > 900 °C peak metamorphism related to the collisional orogeny during the final stage of assembly of Gondwana supercontinent (Santosh et al, 2009a(Santosh et al, , 2009b and references therein). The peak UHT metamorphism in this terrane is supported by the occurrence of some key mineral assemblages such as orthopyroxene + sillimanite + quartz, spinel + quartz, Al -rich orthopyroxene, and mesoperthite as well as sapphirine + quartz (e.g., Tateishi et al, 2004;Morimoto et al, 2004;Ishii et al, 2006;Tadokoro et al, 2007Tadokoro et al, , 2008Tsunogae et al, 2008a;Shimizu et al, 2009). In spite of the widespread occurrence of UHT metamorphic rocks in southern India, the equilibrium sapphirine + quartz assemblage has been reported only from one locality (Rajapalaiyam in the southern Madurai Block, Tateishi et al, 2004;Santosh, 2006, 2009;Braun et al, 2007).…”

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

“…There are spatial variations in metamorphic grade (Nandakumar and Harley, 2000;Pattison et al, 2003), but typical peak conditions of 0.7-1.3 GPa and 850-1050°C are followed by decompression as part of a clockwise P-T path (Raith et al, 1997;Nandakumar and Harley, 2000;Cenki et al, 2002;Sajeev et al, 2004Sajeev et al, , 2006Tadokoro et al, 2008;Tsunogae and Santosh, 2010;Brandt et al, 2011;Johnson et al, 2015;Taylor et al, 2015). Monazite and zircon ages of 0.63-0.47 Ga imply a long metamorphic history (Braun and Bröker, 2004;Ghosh et al, 2004;Braun and Appel, 2006;Taylor et al, 2014).…”

Laser ablation ICP mass spectrometry for zircon U-Pb geochronology of metamorphosed granite from the Salem Block: Implication for Neoarchean crustal evolution in southern India

“…Further, the rocks in several localities have recorded imprints of UHT thermal event (e.g., Brown and Raith, 1996;Morimoto et al, 2004;Tateishi et al, 2004;Tadokoro et al, 2008;Shimizu et al, 2009;Nishimiya et al, 2010). Therefore, the thermal history of the Salem Block which is different from the other blocks in the SGT needs to be addressed in more detail to understand the composite evolution of the terrane.…”