TY - DATA T1 - On the difficulty of assigning crustal residence, magmatic protolith and metamorphic ages to Lewisian granulites: constraints from combined in situ U–Pb and Lu–Hf isotopes PY - 2016/06/21 AU - M. J. Whitehouse AU - A. I. S. Kemp UR - https://geolsoc.figshare.com/articles/dataset/On_the_difficulty_of_assigning_crustal_residence_magmatic_protolith_and_metamorphic_ages_to_Lewisian_granulites_constraints___from_combined_em_in_situ_em_U_Pb_and_Lu_Hf_isotopes/3454805 DO - 10.6084/m9.figshare.3454805.v1 L4 - https://ndownloader.figshare.com/files/5427008 L4 - https://ndownloader.figshare.com/files/5427011 L4 - https://ndownloader.figshare.com/files/5427014 L4 - https://ndownloader.figshare.com/files/5427017 L4 - https://ndownloader.figshare.com/files/5427020 KW - granulite facies gneisses KW - Lewisian granulites KW - Ga KW - Hf isotopes show KW - Hf isotope compositions KW - pattern KW - crust extraction events KW - model evolution curves KW - magmatic protolith age KW - granulite facies metamorphism KW - CL KW - zircon KW - sample KW - crustal KW - Geology N2 - Zircons from two granulite facies gneisses from the central region of the Lewisian Complex have been investigated by high spatial resolution ion-microprobe U–Pb dating and laser ablation combined Pb–Hf isotope methods. The ion-microprobe data reveal a complex pattern of zircon ages distributed along the concordia curve between the time of granulite facies metamorphism at c. 2.5 Ga and the oldest zircon in each sample (respectively 2.89 Ga and 3.04 Ga). This Pb-loss pattern complicates assignment of an unambiguous magmatic protolith age to the zircon although cathodoluminescence (CL) imaging is used to suggest a preferred age of c. 2.85 Ga for both samples, with older grains being inherited. In situ Hf isotopes show a larger spread in the sample containing older grains which is also consistent with inheritance and further suggests that several crust extraction events are represented in the inherited population. Comparison of Hf isotope compositions with plausible model evolution curves suggests that crustal precursors to the Lewisian granulites were derived from their mantle source at c. 3.05–3.2 Ga. ER -