Metasedimentary Rocks
Metasedimentary rocks from within the Narryer Gneiss terrane account for about 10% of the outcrop and are variably deformed but uniformly of at least amphibolite grade metamorpism.
The most abundant rock types are quartzite and banded iron formation, with subordinate metamorphic gneisses, metaconglomerates and pelitic to semi-pelitic quartz-muscovite schists.
The conglomerates are primarily orthoquartzite monomict vein-pebble conglomerates, or polymict pebble conglomerates. In low-strain zones they preserve graded bedding, cross-bedding and heavy mineral-rich horizons.
These rocks provide the bulk of age determinations from the Narryer Gneiss Terrane from detrital zircons, with the bulk of readings bracketing 3.5 to 3.75 billion years old, 3.35 to 3.45 billion years old, and a population of 4.1 to 4.2 billion years, with outliers of up to 4.45 billion years old.
Read more about this topic: Narryer Gneiss Terrane
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