METEORITE IMPACT MELT, Idiwhaa Tonalitic Gneiss, Oldest Rock In the World S587

  

"Oldest Rock In The World". Sliced and Polished on the front.

Late Hadean 4.2 Billions Years Old. Acasta Gneiss complex, North Shore.

Approx: 24 x 7 x 1.5 cm. An impact melt origin for Earth's oldest known evolved rocks. 1, Katarina Miljkovic1, Christopher J. Earth's oldest evolved (felsic) rocks, the 4.02-billion-year-old Idiwhaa gneisses of the Acasta Gneiss Complex, northwest Canada, have compositions that are distinct from the felsic rocks that typify Earth's ancient continental nuclei, implying that they formed through a different process. Using phase equilibria and trace element modelling, we show that the Idiwhaa gneisses were produced by partial melting of iron-rich hydrated basaltic rocks (amphibolites) at very low pressures, equating to the uppermost 3? Km of a Hadean crust that was dominantly mafic in composition. The heat required for partial melting at such shallow levels is most easily explained through meteorite impacts. Hydrodynamic impact modelling shows not only that this scenario is physically plausible, but also that the region of shallow partial melting appropriate to formation of the Idiwhaa gneisses would have been widespread. Given the predicted high flux of meteorites in the late Hadean, impact melting may have been the predominant mechanism that generated Hadean felsic rocks.

All prices are Australian Dollars. Crystal World Australia has a focus on deep time geology with a large range of Stromatolites, Microbiolites, Acasta gneiss, Jack Hills zircons and Banded iron formations. Crystal World is the largest retail and wholesale suppliers of crystals, fossils, meteorites, lapidary, gems, minerals and metaphysical supplies in Australia. Our wholesale warehouse (approx 10000 sq feet) has been operating since 1986; we hold over 50 mining leases to obtain carving rough, fine minerals and fossil specimens.

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