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We report equilibrium sapphirine þ quartz assemblage in biotiteeorthopyroxeneegarnet granulites from a new locality in Panasapattu of Paderu region in the Eastern Ghats granulite belt, which provide new evidence for ultrahigh-temperature (UHT) metamorphism at 1030e1050 C and 10 kbar in this region. The development of migmatitic texture, stabilization of the garneteorthopyroxenee plagioclaseeK-feldspar association, prograde biotite inclusions within garnet and sapphirine as well as sapphirine and cordierite inclusions within garnet in these granulites indicate that the observed peak assemblages probably formed during prograde dehydration melting of a BteSilleQtz assemblage, and constrain the prograde stage of the peT path. The core domains of orthopyroxene porphyroblasts have up to w(Al 2 O 3 ) 9.6%, which suggest that the temperatures reached up to 1150 C suggesting extreme crustal metamorphism. These conditions were also confirmed by the garneteorthopyroxene thermobarometery, which yields a peT range of 1012e960 C and 9.4 kbar. The peT phase topologies computed using isochemical sections calculated in the model system Na 2 OeCaOeK 2 OeFeOeMgOeAl 2 O 3 eSiO 2 eH 2 O (NCKFMASH) for metapelites, garnet-free sapphirine granulites and garnet-bearing sapphirine granulites match the melt-bearing assemblages observed in these rocks. Isochemical sections constructed GEOSCIENCE FRONTIERS journal homepage: www.elsevier.com/locate/gsf GEOSCIENCE FRONTIERS 3(1) (2012) 9e31 in the NCKFMASH system for an average sub-aluminous metapelite bulk composition, and contoured for modal proportions of melt and garnet, as well as for the compositional isopleths of garnet, predict phase and reaction relations that are consistent with those observed in the rocks. Garnet and orthopyroxene contain Ti-rich phlogopite inclusions, suggesting formation by prograde melting reactions at the expense of phlogopite during ultrahigh-temperature conditions. These peT results underestimate 'peak' conditions, in part as a result of the modification of garnet compositions in the domains where some melt was retained. The post-peak evolution is constrained by a succession of melt-present reactions that occur at p < 10 kbar, inferred from micro-structural relations among various minerals. After high-temperature decompression from the metamorphic peak, the peT path followed a near isobaric cooling stage to T < 900 C. The UHT rocks investigated in this study occur within a continental collision suture which witnessed prolonged subductioneaccretion history prior to the final collision. We correlate the extreme metamorphism and the stabilization of UHT mineral assemblages to heat and volatile input from an upwelled asthenosphere during subductionecollision tectonics in a Proterozoic convergent plate margin. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.