Correlations between the Eastern Block of the North China Craton and the South Indian Block of the Indian Shield: An Archaean to Palaeoproterozoic link

Abstract

Recent tectonometamorphic data reveal that the North China Craton formed by amalgamation of an Eastern Block (EB) and a Western Block (WB) along the Trans-North China Orogen (TNCO), and the Indian Shield formed by amalgamation of the South Indian Block (SIB) and the North Indian Block (NIB) along the Central Indian Tectonic Zone (CITZ). The EB of the North China Craton and the SIB of the Indian Shield share many similar magmatic and sedimentary features. The early Archaean supracrustal sequences in both the EB and SIB consist of 3.6-3.4 Ga (fuchsite) quartzites, pelitic gneisses, calc-silicates, marbles, banded magnetic quartzites and amphibolites, called the Caozhuang Group in the EB and the Older Metamorphic Group (OMG) in the SIB. The middle Archaean assemblages in both the blocks can be divided into an early (3.4-3.3 Ga) phase, represented by the Chentaigou supracrustal rocks and orthogneisses in the EB and the Holenarsipur supracrustal rocks and the Gorur orthogneisses in the SIB, and a late (3.1-2.9 Ga) phase, represented by the Qianan supracrustal rocks and the Yangyashan orthogneiss in the EB and the Sargur Group and the Peninsular gneiss in SIB. The late Archaean Taishan Group and its equivalents in the EB are stratigraphically similar to the Dharwar Supergroup in the SIB. Moreover, both the EB and SIB are characterised by near-contemporaneity of late Archaean granitoid intrusive and metamorphic events. In addition, dome-and-basin structures are dominant in both the EB and SIB, and anficlockwise P-T paths charaterise the metamorphic evolution of the late Archaean granulites in the two blocks. The Palaeoproterozoic sedimentary-volcanic rocks in both blocks comprise lower clastic-rich, middle volcanic-rich and upper clastic + carbonate sequences. The strong resemblance of the Archaean to Palaeoproterozoic magmatic and sedimentary records suggests that it is possible that the EB and SIB are dispersed remnants of what was once a single continent. A possible fit is proposed for the reconstruction of the EB and SIB, where the northern margin of the EB is placed adjacent to the western margin of the SIB, with the TNCO and WB representing the continuations, respectively, of the CITZ and NIB. This fit suggests that the EB + SIB and the WB + NIB represent two discrete continental blocks that joined along the TNCO + CITZ orogen during a Palaeoproterozoic collisional event. Fragmentation of the EB and SIB may have occurred at the beginning of the Mesoproterozoic and, by 1.4 Ga, the EB and SIB may have separated into two different continental blocks, as evidenced by striking differences in the Mesoproterozoic sedimentary successions and associated bimodal volcanics in the two blocks. © 2002 Elsevier Science B.V. All rights reserved.