Portal de Periódicos da CAPES

Central/Eastern Indian Bundelkhand and Bastar cratons in the Palaeoproterozoic supercontinental reconstructions: A palaeomagnetic perspective

2012; Elsevier BV; Volume: 226; Linguagem: Inglês

10.1016/j.precamres.2012.11.013

1872-7433

T. Radhakrishna, Ram Chandra, Akhilesh Kumar Srivastava, G. Balasubramonian,

Geomagnetism and Paleomagnetism Studies

Mafic dykes in the central Indian Bundelkhand and eastern Indian Bastar cratons are potential sources for tracing the location of the Indian shield within Palaeoproterozoic supercontinent reconstructions. A total of 610 oriented core samples were collected from 27 mafic dykes (342 samples) in Bundelkhand craton and 20 dykes (268 samples) in Bastar craton. The characteristic magnetisations identify distinct groups of directions. The derived palaeopoles are integrated with recently reported U–Pb isotopic ages from the Bundelkhand and Bastar cratons and correlated with palaeopoles from the mafic dykes in the Dharwar craton, South India. Characteristic remanence (ChRM) identified in these dykes are classified into (i) steep upward/downward components further sub-grouped as ca. 2.37 Ga steep 1 (λ = 10.2°S; Ф = 75.0°E; A95 = 18.1° in Bundelkhand and λ = 22.3°N; Ф = 71.4°E; A95 = 21.6° in Bastar), component comparable with ca. 2.4–2.45 Ga steep 2 group from one dyke in Bundelkhand (λ = 14°S; Ф = 101°E; A95 = 26.1°) and one dyke in Bastar (λ = 6°N; Ф = 113°E; A95 = 26.5°). A steep component (λ = 60.4°N; Ф = 45.3°E; A95 = 9.7° in Bundelkhand and a comparable component λ = 49°N; Ф = 129°E; A95 = 15.1° from one dyke in Bastar) is not assigned an age at present. (ii) ca. 2.18 Ga shallow easterly and antipodal shallow westerly components (λ = 0.4°S; Ф = 347°E; A95 = 21.6° in Bundelkhand and λ = 18.0°N; Ф = 344.0°E; A95 = 8.1° in Bastar) and (iii) 1.99 Ga shallow northwest and antipodal shallow southeast (λ = 57.5°N; Ф = 309.0°E; A95 = 4.7° in Bundelkhand and λ = 39°N; Ф = 321°E; A95 = 28° in Bastar). A group (iv) of ∼2.2 Ga northeast shallow components (λ = 36.0°S; Ф = 357.0°E; A95 = 9.4°) is found only in the Bundelkhand craton. The distinct groups of palaeomagnetic pole determinations from dykes of the Bundelkhand and Bastar craton exhibit a remarkable match with palaeomagnetic poles determined from Precambrian mafic dykes in the Dharwar craton. The close comparison of mafic dyke magnetisations between the cratons suggests close proximity since 2.45–2.5 Ga. Models suggesting amalgamation of crustal blocks along the Central Indian Tectonic Zone at 1.8 Ga or a 1.0 Ga collision along this zone to form Rodinia are untenable. Testing of proposed NeoArchaean-Palaeoproterozoic supercontinent reconstructions showing a north China–India linkage or India's close proximity to Slave craton to form a supercraton 'Sclavia' are not supported. Instead, the data are compatible placing India in close proximity to the Yilgarn block of Western Australia.