Manfred Complex
The Manfred Complex is a heavily attenuated and discontinuous series of ultramafic to mafic cumulates contained within a matrix or wall-rocks of mixed Dugel and Meeberrie Gneisses. The rock types are primarily pyroxene gabbro to amphibolite, with rare serpentinised peridotite and dunite, occasionally containing relict igneous or metamorphic olivine.
These boudins of material range from centimetre-scale to ~100m thick and one kilometre long and, based on their position within anticlines and synclines in the Mount Narryer area, are interpreted to have intruded subparallel to bedding and are now strung out by shearing.
The Manfred Complex is interpreted to represent an early Archaean mafic to ultramafic layered intrusion which has been disaggregated. This disaggregation is partly tectonic, but in some areas evidence suggests that this was mostly achieved by the intrusion of the Dugel and Meeberrie gneisses as sills or sheets.
Geochronology on the Manfred Complex places its age at around 3.73 billion via Pb-Pb on zircon. This makes it the oldest recognised intrusive rock on the Earth, containing the oldest known igneous textures and mineral assemblages.
Read more about this topic: Narryer Gneiss Terrane
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