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  • Petersson, Andreas
    Swedish Museum of Natural History, Department of Geology. University of Western Australia.
    A new 3.59 Ga magmatic suite and a chondritic source to the east Pilbara Craton2019In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, p. 51-70Article in journal (Refereed)
    Abstract [en]

    The Pilbara Craton, Western Australia hosts one of the best-preserved Paleoarchean granite-greenstone terrains on Earth, and is inferred to have developed on an older (> 3.8 Ga), possibly Hadean, continental substrate. Such ancient crust has, however, never been identified in outcrop. Here, we show that metamorphosed gabbroic, leucogabbroic and anorthositic rocks of the South Daltons area, in the western part of the Shaw Granitic Complex, formed at 3.59–3.58 Ga and were intruded by granitic magma at 3.44 Ga. The 3.59–3.58 Ga gabbroic rocks, here named the Mount Webber Gabbro, represent the oldest, unambiguous igneous rock emplacement in the Pilbara Craton and significantly predate the oldest volcanic activity of the 3.53–3.23 Ga Pilbara Supergroup within the East Pilbara Terrane. We interpret the Mount Webber Gabbro samples to represent fragments of a dismembered layered mafic intrusion. Mantle-like zircon δ18O and Hf isotope signatures indicate derivation from a chondritic to near chondritic mantle at ~3.59 Ga, and do not support the existence of a>3.8 Ga basement to the East Pilbara Terrane. These results strengthen the notion of an approximately chondritic>3.5 Ga mantle beneath the Pilbara Craton, and provide further evidence that recent estimates of Archean stabilised continental volumes, based on the assumption of crust extraction from a global, convecting depleted mantle reservoir, may be overestimated.

  • Miyawaki, Ritsuro
    et al.
    National Museum of Nature and Science, Tokyo, Japan.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Hatert, Frédéric
    Université de Liège, Belgium.
    Pasero, Marco
    Università di Pisa, Italy.
    Mills, Stuart J.
    Museum Victoria, Melbourne, Australia.
    IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) Newsletter 472019In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 31, no 1, p. 197-202Article in journal (Other academic)