Abstract The Older Metamorphic Group and the Older Metamorphic Tonalite Gneiss are classic examples of Palaeaoarchaean high-grade metamorphic rocks of the Singhbhum Craton of India. The Older Metamorphic Group is a supracrustal assemblage that was probably deposited as a greenstone belt-type succession before c. 3.32 Ga, the low-grade equivalents of which are found in parts of the Iron Ore Group. The Older Metamorphic Tonalite Gneiss represents a suite of granitoids that are tectonically interleaved with the supracrustal gneisses and that formed over an extended period of time, 3.53–3.45 Ga and possibly later, by processes of Archaean crustal growth.

Abstract The Singhbhum Craton in eastern India preserves a depositional record from the Palaeo-Mesoarchaean to the Mesoproterozoic. Herein, we have summarized the Palaeo-Mesoproterozoic supracrustal record of the Singhbhum Craton, discussed tectonosedimentary processes and discriminated Palaeo-Mesoproterozoic global and craton-specific events. The late Palaeo-Mesoproterozoic supracrustal record of the Singhbhum Craton is limited. It includes evidence for high continental freeboard conditions during 2.6–2.1 Ga in the form of terrestrial deposits (alluvial fan–fluvial) of the Dhanjori Formation. This was followed by a major transgression and a transition to the relatively deeper-water shelf to shallow intertidal environments recorded by the Chaibasa Formation. A long hiatus ensued before deposition of the Dhalbhum Formation and conformably overlying Dalma and Chandil formations, suggesting continued high continental freeboard during 2.2–1.6 Ga. In significant contrast to the craton-specific Dhanjori Formation volcanism, the 1.7–1.6 Ga plume-related Dalma volcanism was probably part of a global tectonothermal event.

Abstract Tectonostratigraphic development of the c. 300 km-long Nellore schist belt (NSB) of southern India is described in relation to the post-Neoarchaean growth of the Dharwar cratonic nucleus. Lying along the eastern margin of the Dharwar cratonic nucleus, the NSB comprises several geologically and geochemically distinct tracts of deformed Palaeoproterozoic to Mesoproterozoic volcanosedimentary successions: the Vinjamuru Group, the Kandra ophiolite complex (KOC), the Kanigiri ophiolitic melange (KOM) and the Udaigiri Group, arranged in relative order of younging. The high-grade Eastern Ghats belt occurs further to the east of the NSB with a tectonic contact. Thrust-transported oceanic crust remnants occur in the 1.9 Ga KOC, 1.34 Ga KOM, and the Vinjamuru Group, which show multiple deformation, amphibolite facies metamorphism and granitic intrusions. The available geological, geochemical and geochronological data have been examined to tentatively constrain the relative age of the different tectonostratigraphic units of the NSB, tectonic juxtaposition and implications in relation to global events in the Proterozoic. Subduction-related ocean closures outboard and east of the Dharwar Craton, evidenced by the KOC and KOM, possibly had links with the assembly of Columbia and its final dispersal, respectively.

Abstract The geology, inferred evolution and classification according to widely accepted schemes of 22 basins from the Indian Precambrian record on the Arravali–Bundelkhand, Singhbhum, Bastar and Dharwar cratons are discussed in this volume. Although their classification is biased owing to all depositories having continental lithospheric substrates, most of the basins reflect divergent plate motion and thus lithospheric stretching and cooling. Convergent plate motion and concomitant lithospheric flexure owing to loading are postulated for the Kurnool Basin and the Eastern Dharwar Craton supracrustals. Transcurrent plate motion is interpreted for the Bhima and Kaladgi–Badami basins. The Cuddapah Basin suggests a complex polyhistory influenced by both mantle circulation/dynamic topography and loading-related flexure of the lithosphere. Mantle circulation and dynamic topography may have played a role in the evolution of the Dhalbhum and Dalma–Chandil basins. Examination of possible time trends indicates that pre- c. 2.0 Ga basins were mostly continental rifts, followed by some intracratonic basins and lesser rift-sag and back-arc basins; post- c. 2.0 Ga basins exhibit a much larger range of basin types. While this Memoir offers a broad sample of the application of plate-tectonic principles to the Precambrian basins of the large Indian shield, it also underscores that Phanerozoic-style plate tectonics and basin evolution histories are widely identified within the Precambrian sedimentary rock record. Analogously, the case studies in this book support the essential similarity between the features observed within the Precambrian basins of India and the norms that describe Phanerozoic successions in terms of sequence stratigraphic architecture. The Indian Precambrian basin-fill record shows that all types of sequence, systems tract and sequence stratigraphic surface that are known from the Phanerozoic record also occur within Precambrian successions. Differences between the stratigraphic architecture of Precambrian and Phanerozoic basin-fill successions can be ascribed to variable rates and intensities of the controls on accommodation and sediment supply, the changes inherent in the evolution of the hydrosphere–atmosphere system and related physical processes, and the evolution of the biosphere system and associated biogenic processes.

Abstract A relatively rapid change in the Earth's surface processes has been anticipated across the Archaean–Palaeoproterozoic boundary as a consequence of changes in the crust–mantle system and tectonic regime ( Condie 1989 , 1997 ; Eriksson et al. 2004 ; Reddy & Evans 2009 ). The Palaeoproterozoic era (2500–1600 Ma: Plumb 1991 ) represented perhaps the first supercontinent cycle, from the amalgamation and dispersal of a Neoarchaean supercontinent to the formation of the 1.9–1.8 Ga supercontinent Nuna ( Reddy & Evans 2009 ), and encompasses one or more global tectonic event that coincides with fundamental changes in the integrated system of core, mantle, lithosphere, hydrosphere, atmosphere and biosphere (i.e. an integrated Earth System). An integration of seemingly disparate geoscience disciplines is therefore an essential prerequisite to understand these changes ( Reddy & Evans 2009 ); and that was the aim of the UNESCO-IGCP 509 project (2005–2009) on Palaeoproterozoic Supercontinents and Global Evolution. The fifth and final conference and post-conference field workshop (in the Singhbhum Craton) related to the UNESCO-IGCP 509 project was organized by the Indian Statistical Institute (ISI), Kolkata with financial support from the UNESCO, the ISI, and the Council of Scientific and Industrial Research, Government of India during the period 26 October–3 November 2009. An entire session was devoted to the Palaeoproterozoic geology of India, as the Indian Shield represents a vast repository of the Palaeoproterozoic geological record. While most of the papers presented in this session were essentially on Palaeoproterozoic geology of the Indian Shield

Abstract The Archaean–Proterozoic rock successions in India have the potential to enrich the global database on Precambrian stratigraphic development, and to offer valuable clues to global tectonic reconstructions. Built over four distinct Archaean cratonic nuclei, the major Palaeoproterozoic supracrustal belts/cover sequences include the Dhanjori Group, the Singhbhum Group (including the Dalma volcanics and the Chandil Formation in eastern India), the Cuddapah Supergroup and the adjoining Nellore Schist Belt bordering the eastern Dharwar Craton, the Aravalli Supergroup in the Aravalli–Delhi Fold Belt in NW India, the lower Vindhyan (Semri Group) and the Mahakosal/Sausar/Betul belts close to the Central Indian Tectonic Zone (CITZ), and, possibly, the Dongargarh Supergroup in Bastar. A major erosional unconformity separates the Archaean tonalite–trondjhemite gneiss basement in these cratons from the overlying volcano-sedimentary successions. An overview of Palaeoproterozoic stratigraphic development in these cratonic blocks is presented to bring out the salient features for global comparison and to highlight issues requiring further attention. Multiple metamorphic, magmatic and deformation events are recorded in the fold belts at the join of the cratons or their margins, inviting application of the plate tectonic paradigm. However, a comprehensive tectonic model for the amalgamation of the Indian Archaean nuclei is yet to emerge, and is crucial for our understanding of Palaeoproterozoic supercontinent development.

Abstract Native Fe in the Chaibasa Formation may be the oldest native Fe ever found. The Chaibasa Formation contains pre-1.6 Ga offshore shelf sediments from the Singhbhum Craton in India. The sediments are light green in colour, consistent with a low content of organic matter and a metamorphic grade of greenschist–lower amphibolite facies. The native Fe grains are enclosed in fibrous mica. The native Fe occurs with magnetite crystals, evidence of relatively oxidizing conditions in the Chaibasa Formation during diagenesis. (Mn,Fe)S, a compound characteristic of reducing conditions, is found within the native Fe. The native Fe contains small amounts of native Si. Most grains of native Fe have rough edges. One bulbous grain has smooth edges and an internal wavy structure that is suggestive of a drop of melted iron. The melting temperature of pure Fe is 1535 °C. We also found native Fe with small amounts of carbon in it that appears to have a plate-like, pearlitic structure. Pearlite typically forms at temperatures of 723–500 °C. All of these temperatures are too high to be achieved during greenschist-facies metamorphism. As a result, we infer that the native Fe is primary rather than secondary. Our work and that of others suggests a primary, impact origin for the native Fe.