Browsing by Author "Ellis, David J."

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Precambrian Tectonics and the Physiochemical Evolution of the Continental Crust. Part I: The Gabbro-eclogite Transition
    (1992) Ellis, David J.; Maboko, Makenya A. H.
    We report the first occurrence of retrograde eclogite shear zones cutting Proterozoic granulites from Australia. The Musgrave Range granulites were metamorphosed at about 12 kbar pressure and 850–900°C. The granulites then cooled isobarically and developed a variety of lower-temperature mineral reaction coronas typical of garnet granulites. These rocks are cut by a major shear zone, the Davenport Shear, in which lower-temperature, fine-grained eclogite developed. This demonstrates that mafic rocks in the deep crust can cool down into the thermodynamic stability field of eclogite without undergoing transformation to eclogite. We agree with Harte et al. (1981) that rocks lacking a fluid phase in stable tectonic regions are unlikely to maintain local equilibrium at ambient geotherm conditions until depths well within the upper mantle are reached.