|
|||||
|
|
Reaction textures in calc-silicate granulites from the Bolingen Islands, Prydz Bay, East Antarctica: implications for the retrograde P–T path |
|
| Authors: | Y MOTOYOSHI D E THOST B J HENSEN |
| Institution: | National Institute of Polar Research, 9–10, Kaga 1-chome, Itabashi-ku, Tokyo 173, Japan;Department of Applied Geology, University of New South Wales, Kensington, NSW 2033, Australia |
| Abstract: | Calc-silicate granulites from the Bolingen Islands, Prydz Bay, East Antarctica, exhibit a sequence of reaction textures that have been used to elucidate their retrograde P–T path. The highest temperature recorded in the calc-silicates is represented by the wollastonite- and scapolite-bearing assemblages which yield at least 760°C at 6 kbar based on experimental results. The calc-silicates have partially re-equilibrated at lower temperatures (down to 450°C) as evidenced by the successive reactions: (1) wollastonite + scapolite + calcite = garnet + CO The reaction sequence observed indicates that a CO A retrograde P–T path, from the sillimanite stability field ( c. 760°C at 6 kbar) into the andalusite stability field ( c. 450°C at <3 kbar), is suggested by the occurrence of secondary andalusite in an adjacent cordierite–sillimanite gneiss in which sillimanite occurs as inclusions in cordierite. |
| Keywords: | Antarctica Bolingen Islands Prydz Bay calc-silicates retrograde P–T path scapolite wollastonite |