Abstract
We report ultrahigh-temperature (T > 950°C) peak metamorphic conditions for the Southern Marginal Zone of the Archean Limpopo Belt in South Africa. Pelitic granulites of the zone have a typical mineral assemblage of garnet + biotite + orthopyroxene + cordierite + quartz + K-feldspar + plagioclase ± sillimanite, to which the latest geothermobarometers are applicable. The revised P-T conditions were obtained from a ternary feldspar geothermometer using antiperthitic feldspars in leucocratic granulite (920-980°C), Al solubility in orthopyroxene in pelitic granulite (970-1020°C), and a revised garnet-orthopyroxene geothermometer corrected for retrograde Fe-Mg exchange (920-990°C). The estimated peak temperature of metamorphism is about 100°C higher than previously estimated based on conventional Fe-Mg exchange geothermometers (800-870°C), and indicates a high geothermal gradient of ~35°C/km in Archean continental lower crust.
| Original language | English |
|---|---|
| Pages (from-to) | 213-224 |
| Number of pages | 12 |
| Journal | Journal of Mineralogical and Petrological Sciences |
| Volume | 99 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 2004 |
ASJC Scopus subject areas
- Geophysics
- Geology
