First report of garnet–corundum rocks from southern India: Implications for prograde high-pressure (eclogite-facies?) metamorphism

Sodicgedrite in ultrahigh-temperature Mg-Al-rich rocks from the Palghat-Cauvery Shear Zone system, southern India

“…Localities of the examined samples are discussed in Tsunogae and Santosh (2003) and Shimpo et al (2006), respectively. Below we summarize the petrography of six representative gedrite bearing rocks from these areas.…”

“…The aim of this short report is to describe new occurrence and chemistry of extremely Na rich gedrite (~ 3.1 wt% Na 2 O) in Mg Al rich rocks from the northernmost flank of the Pan African Madurai Block along the Palghat Cauvery Shear Zone system (PCSS) in southern India. Such high Na gedrite has not been reported in previous studies from this area (cf., Koshimoto et al, 2004;Shimpo et al, 2006;Santosh and Sajeev, 2006) and from other UHT terranes. Shimpo et al (2006) and Tsunogae and Santosh (2006) reported near eclogite facies high pressure (HP) metamorphism at P>12 kbar and following UHT peak event of T = 940 990 ºC from the PCSS, which is probably related to Neoproterozoic continent continent collision orogeny from this terrane.…”

“…Such high Na gedrite has not been reported in previous studies from this area (cf., Koshimoto et al, 2004;Shimpo et al, 2006;Santosh and Sajeev, 2006) and from other UHT terranes. Shimpo et al (2006) and Tsunogae and Santosh (2006) reported near eclogite facies high pressure (HP) metamorphism at P>12 kbar and following UHT peak event of T = 940 990 ºC from the PCSS, which is probably related to Neoproterozoic continent continent collision orogeny from this terrane. Available petrological data from adjacent areas along the PCSS also support such HP and UHT metamorphism (Tsunogae and Santosh, 2003;Koshimoto et al, 2004;Santosh and Sajeev, 2006).…”

Origin of graphite in glimmerite and spinellite in Achankovil Shear Zone, southern India

“…ACSZ has figured prominently as a deep -rooted shear zone of intercontinental scale in many Gondwana reconstruction models (e.g., Windley et al, 1994 and references therein). It is bounded to the north by the massif charnockites and intercalated high to ultrahigh temperature grade metasediments of the Madurai block (MB), and to the south by high temperature granulite facies supracrustals of the Trivandrum block (TB) (Drury et al, 1984;Bart lett et al, 1998;Shimpo et al, 2006). Rocks in ACSZ are dominated by intensely deformed garnetiferous biotite gneiss, quartzofeldspathic gneiss, cordierite -orthopyroxene gneiss, and charnockite (e.g., Santosh, 1987;Nandakumar and Harley, 2000;Cenki et al, 2004;Ishii et al, 2006).…”

Carbonic fluid inclusions in ultrahigh-temperature granulite from Kumiloothu in the northern Madurai Block, southern India

“…This is also regarded as the trace of the collisional suture of the Gondwana supercontinent during its final assembly in the Late Neoproterozoic to Early Cambrian (e.g., Chetty and Bhaskar Rao, 2006;Collins et al, 2007a). Recently, ultrahigh -temperature (UHT; T > 1000 °C at ~ 8 kbar) granulites have been reported from several localities in the northern MGB and PCSZ probably formed by deep subduction and subsequent continent -continent collision along this suture zone Koshimoto et al 2004;Shimpo et al, 2006;Sajeev, 2006: Collins et al, 2007b;Santosh, 2006a, 2007;Tsunogae et al, 2008a). However, only few studies on the role of fluids related to the UHT metamorphism have been carried out in this region.…”