New U-Pb SHRIMP Zircon Ages of the Dhamda Tuff in the Mesoproterozoic Chhattisgarh Basin, Peninsular India: Stratigraphic Implications and Significance of a 1-Ga Thermal-Magmatic Event

作者：Bickford Marion E; Basu Abhijit^*; Mukherjee Arunangshu; Hietpas Jack; Schieber Juergen; Patranabis Deb Sarbani; Ray Ranjan Kumar; Guhey Rajeeva; Bhattacharya Purbasha; Dhang Pratap Chandra

来源：Journal of Geology, 2011, 119(5): 535-548.

DOI：10.1086/661193

Magmatic zircons from two samples of the Dhamda Tuff in the Tarenga Formation of the Mesoproterozoic Chhattisgarh Supergroup in central India were dated by U-Pb SHRIMP methods, which yielded a concordia upper-intercept age of 993 +/- 8 Ma. The samples are from outcrops located about 10 km apart, approximately along strike and stratigraphically near the top of the Chhattisgarh Succession in the western Hirri Subbasin. These results indicate that the Dhamda Tuff is coeval with the Sukhda Tuffs of the eastern Baradwar Subbasin, which previously yielded ages of 990-1020 Ma. The new ages confirm the prediction of geologists of the Indian Statistical Institute who, when creating a new mapping of part of the Chhattisgarh Basin, suggested that the Sukhda and Dhamda tuffs are correlative. The new data also confirm that deposition in the Chhattisgarh Basin occurred essentially between ca. 1400 and ca. 1000 Ma. The Eastern Ghats Mobile Belt (EGMB), then a part East Antarctica, docked with the southern Indian block at about 1000 Ma; hence, EGMB could not have supplied detritus to Chhattisgarh and other Mesoproterozoic basins in the region. Further, the new age data, combined with earlier dating of the Sukhda Tuffs, indicate that a major event of rhyolitic volcanism occurred in central India at about 1000 Ma, possibly coinciding with the closure or perhaps the uplift or inversion of the Chhattisgarh and other similar basins. Several approximately coeval thermal-magmatic events are recorded in rocks of south-central India. We hypothesize that these events are far-field effects of the collision of EGMB during the final assembly of Rodinia.

• 出版日期2011-9