Formation of intracratonic Gondwana basins: Prelude of Gondwana fragmentation?

抄録

The disposition of the Indian Gondwana basins along some linear zones coinciding with the boundaries of the Precambrian protocontinental components of the peninsular shield mosaic primarily indicates a major tectonic control on intracratonic rifting. These rift systems along with the late Paleozoic fault systems developed within the reconstructed Gondwanaland define broad concentric patterns with some radial strike–slip varieties about ‘centers’ tentatively located along the south–eastern margin of Africa. The reconstructed directions of ice movement of the late Paleozoic ice–sheet also define broad radial patterns about ‘centers’ located roughly between Madagascar and India, and western part of Antarctica. The radial pattern of ice movement and development of concentric fault zones can be attributed to some regional domal uplift, due to penetration of plume heads into the upper mantle. These ‘centers’ were located very close to the linear zone along which a rift system developed during Sakmarian (~ 280 Ma) and the Gondwana fragmentation was initiated with the separation of East and West Gondwana at around 170 Ma. The geochemical signatures indicate that this plume was possibly responsible for the earlier phases of emplacement of the potassium–rich lamproites within the Gondwana basin–fill succession and was finally led to the emplacement of Panjal volcanics. Therefore, it appears that the process of Gondwanaland break–up was initiated with the formation of the Gondwana rift system in India and its equivalents in the rest of the supercontinent. Acquisition of systematic geochemical and geochronological data from the intrusive bodies from the Gondwana basins can help in tracing back the complete history.