The significance of Indian Proterozoic gneiss complexes in Rodinia and Gondwana supercontinent reconstructions

 The Indian Shield was formed by a terminal collision between the northern and the southern Indian continental blocks (NIB and SIB) at the end of Mesoproterozoic and Early Neoproterozoic after initial plate interactions in Early Mesoproterozoic. The Late Mesoproterozoic-Early Neoproterozoic was also the time when Rodinia was assembled, but it is unclear whether India was a part of Rodinia. After Rodinia disintegrated in Mid-Neoproterozoic, the resulting blocks reassembled in Early Paleozoic to form Gondwana. In classical reconstructions, the position of India with respect to Australia-Antarctica is approximately the same in Rodinia and Gondwana. The granulite gneiss complexes of the Central Indian Tectonic Zone (CITZ) comprised of the Sausar Belt in central India and the Chotanagpur Gneissic Complex (CGC) in eastern India, the Shillong-Meghalaya Gneissic Complex (SMGC) in northeastern India, and the Eastern Ghats Belt (EGB) along the Indian east coast preserve key evidence of the above mentioned tectonic events. In this study, we attempt to correlate the metamorphic histories of these gneissic complexes with the tectonic events through P-T pseudosection analysis, U-Pb zircon dating with isotope dilution-thermal emission mass spectrometry (ID-TIMS), and U-Th-Pb monazite chemical dating with the electron microprobe (EPMA).

Peraluminous granite intrusion is recorded at 1697 ± 17 Ma in the north of CGC. Granulite-facies metamorphism related to a collision of the SIB with an island arc occurred at ~1.6 Ga along the southern boundary of Sausar Belt and in northwestern SMGC. Calculated P-T pseudosections in the KFMASH and MnCKFMASH-PYCe systems indicate that the 1609 ± 9 Ma anatectic metapelite granulites of northwestern SMGC were metamorphosed at peak P-T conditions of ~8 kb/850oC and along a counterclockwise P-T path with <3 kb/600oC progade and ~5.5 kb/630oC retrograde conditions. This path is consistent with prograde and post-peak monazite growth, formation of cordierite + K-feldspar + garnet/orthopyroxene bearing assemblages during peak metamorphism, and retrograde growth of xenotime and staurolite. The lithological association, and age and P-T path of metamorphism at northwestern SMGC are similar to those in southern Sausar Belt. Thus, the ~1.6 Ga collision zone extends over >1000 km in an ENE-WSW direction. The collision was followed by emplacement of the Bengal Anorthosite in southeastern CGC at 1550 ± 2 Ma. Subsequent high-grade Grenvillian metamorphism (peak P-T: 7-10.5 kb/788-861oC at northern CGC) recorded by xenotime growth at 975 ± 67 Ma in northwestern CGC granite gneiss, zircon growth at 947 ± 27 Ma in Bengal Anorthosite, and monazite growth at 995-950 Ma in northeastern CGC metapelite granulite indicate an Early Neoproterozoic terminal collision between the SIB and the NIB. This event is coeval with the collision between EGB and Rayner Complex of East Antarctica, and emplacement of the Chilka Lake Anorthosite in northeastern EGB at 983.0 ± 2.5 Ma. All these Early Neoproterozoic (983-947 Ma) events may be temporally correlated with the assembly of Rodinia.

 The eastern margins of CGC, North Singhbhum Mobile Belt (NSMB) and Singhbhum Craton (SC) are overprinted by Mid-Neoproterozoic high-grade metamorphism, ductile deformation and sinistral shearing along the north-south oriented Eastern Indian Tectonic Zone (EITZ). Monazite chemical dates and garnet zoning profiles in anatectic quartzofeldspathic gneiss indicate that metamorphism in northern EITZ occurred at 876-784 Ma along a counterclockwise P-T path (11.3-12.7 kb/800oC peak, 9 kb/730oC retrograde). Similar dates from Chilka Lake of EGB, Elan Bank of Kerguelen Plateau (where 824-675 Ma conglomerate-hosted metapelitic clasts show a retrograde P-T path from 10.2kb/760oC to 6.2kb/560oC), and Oygarden Group and Mt. Vechernyaya of Rayner Complex indicate that the EITZ was an ~1800 km long Neoproterozoic orogenic belt stretching from eastern India through Kerguelen Plateau to East Antarctica. Sinistral shearing in the EITZ at 876-784 Ma indicates a distinct period of southward movement of the Indian block with respect to Australia-Antarctica. Hence, rifting between India and Australia-Antarctica and northwestward movement of India during Rodinia break-up, as proposed in classical models, did not occur before ~780 Ma.

 Early Paleozoic high-grade metamorphism and thrusting at the contact of EGB with the Archean cratons of India, as well as at the southeastern margin of Rayner Complex, occurred during the Pan-African assembly of Gondwana. During this time (Late Cambrian, 494 ± 6 Ma), the central part of SMGC was intensely reworked by granulite-facies metamorphism along a clockwise P-T path with near isobaric prograde heating between 635oC and 730oC at ~5.7-5.5 kb, peak metamorphism at ~5.5 kb/730oC, and cooling between 650oC and 595oC at 3.4-3.2 kb. The retrograde segment of this P-T path is similar to that from Prydz Bay in East Antarctica. Thus, the Prydz Bay Pan-African suture passes through SMGC, and the Early Paleozoic (494 ± 6 Ma) metamorphism in SMGC may be correlated with a collision between India and Australia-Antarctica during the assembly of East Gondwana.

Publications:

  1. Chatterjee, N. (2017) Constraints from monazite and xenotime growth modelling in the MnCKFMASH-PYCe system on the P-T path of a metapelite from Shillong-Meghalaya Plateau: implications for the Indian shield assembly. Journal of Metamorphic Geology, 35, 393-412. doi:10.1111/jmg.12237
  2. Chatterjee, N. and Nicolaysen, K. (2012) An intercontinental correlation of the mid-Neoproterozoic Eastern Indian Tectonic Zone: evidence from the gneissic clasts in Elan Bank conglomerate, Kerguelen Plateau. Contributions to Mineralogy and Petrology, 163, 789-806. doi: 10.1007/s00410-011-0699-z
  3. Chatterjee, N., Bhattacharya, A., Duarah, B.P. and Mazumdar, A.C. (2011) Late Cambrian reworking of Paleo-Mesoproterozoic granulites in Shillong-Meghalaya Gneissic Complex (Northeast India): evidence from PT pseudosection analysis and monazite chronology and implications for East Gondwana assembly. Journal of Geology, 119, 311-330. doi: 10.1086/659259
  4. Chatterjee, N. and Ghose, N.C. (2011) Extensive Early Neoproterozoic high-grade metamorphism in north Chotanagpur Gneissic Complex of the Central Indian Tectonic Zone. Gondwana Research, 20, 362-379. doi:10.1016/j.gr.2010.12.003
  5. Chatterjee, N., Banerjee, M., Bhattacharya, A. and Maji, A.K. (2010) Monazite chronology, metamorphism-anatexis and tectonic relevance of the mid-Neoproterozoic Eastern Indian Tectonic Zone. Precambrian Research, 179, 99-120. doi:10.1016/j.precamres.2010.02.013
  6. Chatterjee, N., Crowley, J.L., Mukherjee, A. and Das, S. (2008) Geochronology of the 983 Ma Chilka Lake Anorthosite, Eastern Ghats Belt, India: implications for pre-Gondwana tectonics. Journal of Geology, 116, 105-118.doi: 10.1086/528901
  7. Chatterjee, N., Crowley, J.L. and Ghose, N.C. (2008) Geochronology of the 1.55 Ga Bengal anorthosite and Grenvillian metamorphism in the Chotanagpur gneissic complex, eastern India. Precambrian Research, 161, 303-316.doi:10.1016/j.precamres.2007.09.005
  8. Chatterjee, N., Mazumdar, A.C., Bhattacharya, A. and Saikia, R.R. (2007) Mesoproterozoic granulites of the Shillong-Meghalaya Plateau: Evidence of westward continuation of the Prydz Bay Pan-African suture into Northeastern India. Precambrian Research, 152/1-2, 1-26. doi:10.1016/j.precamres.2006.08.011