Abstract
We report the finding of sapphirine + quartz equilibrium assemblage in an orthopyroxene-sapphirine granulite from Ganguvarpatti in southern India, providing diagnostic evidence for ultrahigh-temperature (UHT) metamorphism in the central Madurai Block. The sapphirine-quartz-bearing rock is composed of coarse-grained (∼ 3 mm) porphyroblastic orthopyroxene and sapphirine which were probably stable phases during the peak UHT condition within the stability field of sapphirine + quartz. The rock also contains corona textures such as orthopyroxene + sapphirine + cordierite and orthopyroxene + cordierite symplectites formed by post-peak decompression. The porphyroblastic sapphirine contains rare inclusions of quartz. The equilibrium sapphirine + quartz reported here is regarded as a diagnostic indicator of peak metamorphism at T > 1000 °C and confirms the formation and exhumation of ultra-hot orogens during the accretionary history of the Madurai Block related to the Pacific-type orogeny and final collisional assembly of the Gondwana supercontinent in the Late Neoproterozoic-Cambrian.
