Early Precambrian crustal evolution in Eastern India: The ages of the Singhbhum granite and included remnants of older gneiss

摘要

Geochronology of samples from the Indian Shield was discussed. New Sm-Nd data was given for the Singhbhum granite, which give model ages (T sub DM of 3.36 to 3.40 Ga, essentially equivalent to ages of included gneissic remnants of the older metamorphic group (OMG) (T sub DM = 3.35 to 3.41 Ga). Lead-lead and Rb-Sr ages of the granite and OMG range between 3.28 to 3.38 Ga. These results are considerably younger than the 3775 or - 89 Ma Sm-Nd isochron of Basu et al., which Taylor and colleagues interpret as an artifact caused by regressing two suites of unrelated rock samples.