Hadean protocrust reworking at the origin of the Archean Napier Complex (Antarctica)

• Published in: Geochemical Perspectives Letters
• Main Authors: Guitreau, Martin, Boyet, M., Paquette, Jean-Louis, Gannoun, Abdelmouhcine, Konc, Z., Benbakkar, M., Suchorski, K., Hénot, J.-M.
• Other Authors: Laboratoire Magmas et Volcans (LMV), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0006,CLERVOLC,Clermont-Ferrand centre for research on volcanism(2010), ANR-16-IDEX-0001,CAP 20-25,CAP 20-25(2016)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; East Antarctica; Canada; Greenland; Napier; Mount Sones; Gage Ridge; Gage; Antarc*; Antarctica
• Online Access: https://uca.hal.science/hal-02399658; https://uca.hal.science/hal-02399658/document; https://uca.hal.science/hal-02399658/file/Guitreau%20M%20GPL%202019.pdf; https://doi.org/10.7185/geochemlet.1927

International audience The origin of the first continents is still poorly constrained due to the great scarcity of >3.7 Ga rocks. The Napier Complex (East Antarctica) hosts such rocks but the extreme metamorphic conditions it experienced have compromised most isotopic systematics. Here we have studied Mount Sones and Gage Ridge orthogneisses from the Napier complex using microbeam (LA-MC-ICP-MS) U-Pb and Lu-Hf isotope measurements in zircon, together with 146,147Sm-143,142Nd isotope systematics in the corresponding whole rocks to uncover primary information about their origin. Our U-Pb results reveal that these orthogneisses formed at 3794 ± 40 and 3857 ± 39 Ma, respectively, by reworking of 4456-4356 Ma mafic protocrust, as testified to by 176Lu-176Hf and 147,146Sm-143,142Nd systematics. Other Eoarchean terranes in Greenland, Canada, and China also show involvement of Hadean crust(s) in their formation which suggests that protocrusts were massively reworked to form new continents around the Hadean-Eoarchean boundary. Such a mechanism would account for the absence of early-formed protocrust from the geological record despite recent models proposing rapid crustal growth in the Hadean (~25 % of present day volume or surface).