Abstract:
We report the monazite dates of the granulites from Daltonganj (Palamau), Chhotanagpur granite–gneiss complex (CGGC) which covers the significant part of the granulite blocks in central India by using an electron micro probe analyser dating. The monazite grain varies between 70 and 80 μm and shows the distribution of U, Th and Pb in all monazite grains of both samples. Two different dates were obtained from different monazite grains; the first age suggests that the granulite from CGGC preserves the first remnant of the protolith of the Mesoproterozoic era at ~1424 Ma and second one at ~972 Ma which provides evidence of metamorphism of the protolith. The CGGC rocks preserve four regional metamorphic events, namely M1, M2, M3 and M4. But in this work, two different ages from the Daltonganj granulites were obtained which are similar to the M2 (<1500 Ma, i.e., the age of protolith of the granulitic gneiss) and M3 (1200–930 Ma) metamorphic events as reported in the CGGC. The M3 metamorphism attained its average P–T condition at ~7.35 kbar/792°C, and it represents the prograde metamorphic event. The M3 metamorphic event supported the Grenville-orogeny, and it was responsible for the metamorphism of the magmatic protolith of granulitic gneiss from the CGGC at the time of amalgamation of the Rodinia supercontinent. The Rodinia assembly had occurred through the global Grenville-orogenic events between 1100 and 900 Ma, with continental blocks which exist at that time. © 2019, Indian Academy of Sciences.
