THE THERMAL EVOLUTION OF METAPELITIC GRANULITES FROM JUBRIQUE SEQUENCE (BETIC CORDILLERA, S SPAIN)
We recognized two types of quartz included in garnet: 1) large (≈800 μm) irregularly shaped inclusions, yielding an average Ti-in-quartz temperature of 878 ± 65 °C; 2) small (< 50 μm) single-crystal inclusions, at the garnet core, yielding an average temperature of 906 ± 36 °C. Matrix quartz gave temperatures of 692 ± 44 °C (in melanosome) and 665 ± 24 °C (in leucosome). Crystallization temperatures calculated for rutile are 847 ± 50 °C (in garnet) and 810 ± 25 °C (in matrix). Average Ti-in-zircon temperatures for zircon included in garnet are 747 ± 34 °C (rim) and 750 ± 55 °C (core), whereas for matrix zircon the average temperatures are 766 ± 38 °C (rim) and 759 ± 46 °C (core).
Ti-in-quartz and Zr-in-rutile isopleths intersect at ≈850°C and 12 kbar, in agreement with peak conditions published in the literature. However, these rocks likely reached temperatures approaching UHT metamorphism conditions, as suggested by quartz in garnet (≈900 °C). Lower Ti-in-zircon temperatures probably record growth of zircon during cooling from peak temperatures. Lower temperatures calculated for matrix quartz (<700 °C) probably record dynamic recrystallization during deformation. These temperatures are much lower than those previously obtained.