ISOTOPIC ANALYSIS OF DETRITAL ZIRCON FROM QUARTZITE IN THE PALEOPROTEROZOIC MURMAC BAY GROUP ON THE RAE CRATON

The Rae craton occupying middle part of the Laurentia shield is mainly composed of the c. 3.0-2.6 Ga Archean granitic basement. Recently, however, Eoarchean detrital zircon back to 3.9 Ga were reported from two sedimentary rock samples in the 2.3 Ga Murmac Bay Group (MBG) on western margin of the Rae craton ^[1]. In present study, to constrain evolution of the Rae craton, detrital zircons from 11 MBG quartzite sample were analyzed U-Pb age and Hf isotopic value using LA-ICPMS. U-Pb age spectra show three age cluster; i.e. 1) c. 2.3-3.0 Ga, 2) 3.0-3.5 Ga, 3) 3.5-3.9 Ga. The oldest detrital zircon grain shows 3881±12 Ma. The MBG zircons show wide range εHf value from +5 to ―25. The oldest T_DM is represented by a 3.86 Ga zircon grain which shows 4.13 Ga. These results indicate that the MBG contain both juvenile and recycled crust formed between Paleoproterozoic and Late Hadean.

Reference: [1] Ashton et al. (2013) Precam. Res., 232, 70-88.