Age and Provenance study of Paleoarchean rocks from the Singhbhum Craton (India)

Abstract

This study has performed in situ U-Pb and Lu-Hf isotope analysis on zircons and in situ U-Pb isotope analysis on apatites, by LA-ICP-MS and MC-ICPMS, from three Tonalite-Trondhjemite-Granodiorite (TTG) samples from the Paleoarchean rocks of the Singhbhum Craton, eastern India. One sample, RM1, from the Older Metamorphic Tonalite Gneiss (OMTG) and two samples, RT11 and CH2, from the Singhbhum Granites. Presenting 207Pb/206Pb zircon crystallization ages for the three samples: RT11 - 3384.4 +- 3.9 Ma, CH2 - 3308.4 +- 7.6 Ma and RM1 - 3396 +- 14 Ma. These U-Pb zircon ages are supported by very similar U-Pb apatite ages. Hf-isotopes in zircons indicates a dominantly juvenile provenance, but single zircons aged ~3.6 Ga from RT11 and RM1 indicates reworking of at least one older Archean component. RM1 yielded eight concordant 207Pb/206Pb ages of ~4.0 Ga, which rendered both radiogenic and unradoigenic 176Hf/176Hf values. Four zircons exhibited Epsilon(Hf,t) values of -10.6 to -13.6, indicating an enriched source with a separation age of 4.5 Ga, and may indicate an initially enriched reservoir at the formation of the Earth.