Palaeoproterozoic Indian shield in the global continental assembly: Evidence from the palaeomagnetism of mafic dyke swarms

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• 作者：T. Radhakrishna ; N.R. Krishnendu ; G. Balasubramonian
• 关键词：Palaeomagnetism ; Palaeoproterozoic ; Mafic dykes ; Indian shield ; Continental reconstruction
• 刊名：Earth-Science Reviews
• 出版年：November, 2013
• 年：2013
• 卷：126
• 期：Complete
• 页码：370-389
• 全文大小：3416 K

文摘

Palaeomagnetic study of Palaeoproterozoic mafic dykes in the basement along the margins of the Cuddapah basin, the largest Precambrian sedimentary basin in south India, is presented in detail for a general discussion of Palaeoproterozoic igneous activity in India. The results are compared with all earlier published data on mafic dykes in India and are integrated with recently-published high-precision U-Pb baddeleyite ages to provide a comprehensive account of Palaeoproterozoic igneous activity in India. The analysis consolidates palaeomagnetic poles for six age divisions between 2.45 and 1.85 Ga with robust statistical criteria. Our best estimates of overall mean poles from 241 dykes are situated at (1) 位 = 17.7掳N; 桅 = 106.0掳E (A₉₅ = 9.0掳; 7N = 24) at c. 2.45 Ga, (2) 位 = 7.1掳N; 桅 = 57.2掳E (A₉₅ = 4.5掳; N = 69) at c. 2.37 Ga, (3) 位 = 41.6掳S; 桅 = 5.5掳E (A₉₅ = 5.1掳; N = 34) at c. 2.22 Ga, (4) 位 = 4.7掳N; 桅 = 343.0掳E (A₉₅ = 4.4掳; N = 31) at 2.18 Ga, (5) 位 = 49.2掳N; 桅 = 332.9掳E (A₉₅ = 4.8掳; N = 24) at 1.99-1.89 Ga and (6) 位 = 73.7掳N; 桅 = 282.6掳E (A₉₅ = 2.9掳; N = 39) at 1.86 Ga. The data permit us to construct an apparent polar wander path for the Indian shield for an ~ 600 Ma interval of the Palaeoproterozoic eon (2.45-1.85 Ga). Testing and evaluation of continental reconstructions for this interval, which are mostly based on geological correlations, reveal many inconsistencies. Between 2.45 and 2.37 Ga, the Indian shield was situated at higher latitudes similar to the Yilgarn craton of Australia. It was subsequently located near the equator at 2.22, 2.18, 1.99 and 1.86 Ga. Thus, an India-Australia connection is supported during these times, but a proposed Australia-Kaapvaal link in 鈥淶imvaalbara鈥?and a Dharwar (India)-Slave connection in 鈥淪clavia鈥?or a Superior-Zimbabwe-India connection in 鈥淪uperia鈥?are inconsistent with Indian data. In addition, the close palaeomagnetic comparison between the Palaeoproterozoic dykes of Dharwar-Bastar-Bundelkhand cratons in India indicates an age of > 2.45 Ga for orogenic activity along the central Indian tectonic zone; hence, matching this zone with the 2.0-1.8 Ga Trans-North China orogenic belt, or positioning North China adjacent to India or juxtaposition of the Indian shield along the western margin of Laurentia in the Columbia reconstructions is not supported. The Indian data appear to be in accord with the essential features of the refined Protopangaea model and the original Ur configuration. Finally, the results are interpreted in terms of four dyke emplacement events in the age range 2.45-2.18 Ga linked to short-lived (5-10 Ma) LIPs developed over mantle plumes. The dykes of ~ 1.99-1.89 Ga age probably relate to continued long lived igneous activity while the ~ 1.86 Ga dykes are relatively fewer in number and may represent waning stage of a large igneous event related to a major mantle plume.