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The Granulite Terrane of Southern India is a collage of Mesoarchean–Neoproterozoic crustal blocks that underwent high‐grade metamorphism associated with the final assembly of the Gondwana supercontinent during late Neoproterozoic–Cambrian. Here, we investigate the charnockites and associated sapphirine‐bearing semipelitic granulites from the eastern part of the Madurai Block (MB). We present new petrographic, mineral chemistry, and geochronological data to constrain the P–T–t evolution of the block and unravel the timescale and source of heat for the ultrahigh‐temperature metamorphism. Both the rock types contain coarse‐grained porphyroblastic garnet and orthopyroxene, yielding peak P–T conditions of 950 ± 30°C at 10.5 ± 0.8 kbar and 970 ± 40°C at 10 ± 0.5 kbar for semipelite and charnockite, respectively, using conventional thermobarometry. Peak ultrahigh temperatures are further supported by high Al content in the orthopyroxene (8.78 wt% Al2O3) coexisting with garnet (XMg: up to 0.57) and feldspar thermometry of the mesoperthites and antiperthites in the semipelite, yielding 950–980°C at 10 kbar. Subsequent decompression has led to the formation of coronal orthopyroxene3 + plagioclase3 in the charnockite and symplectic orthopyroxene3 + cordierite ± sapphirine ± plagioclase3 in the semipelite, yielding P–T range of 950–850°C and 9.5–6.8 kbar for semipelites and 950–820°C and 8–6.5 kbar for charnockite. Based on the obtained P–T estimates, preserved reaction textures, and phase equilibria modelling in the MnNCKFMASHTO system, a clockwise P–T evolution with isothermal decompression followed by cooling is inferred for both the rock types. Texturally constrained in situ monazite dating and rare earth element (REE) patterns show that the core of matrix monazite having low‐Th, Y, and extreme heavy rare earth element (HREE) depletion, yielding weighted mean ages of 582 ± 12 and 590 ± 22 Ma for semipelite and charnockite, respectively, dates the prograde evolution. The mantle of the matrix monazite in semipelite and comparable rim in charnockite, having relative Th‐enrichment compared to the core, yielding weighted mean ages of 552 ± 9 and 557 ± 13 Ma, respectively, dates extensive dissolution–reprecipitation from the melt at the peak stage. The relatively Th‐ and Y‐rich and moderately HREE‐depleted rim of matrix monazite in the semipelite, yielding weighted age of 516 ± 6 Ma, date initial garnet breakdown during post‐peak melt crystallization. By contrast, compositionally homogenous HREE + Y‐enriched monazite in the symplectite and retrograde monazites yielding weighted mean ages of 487 ± 47 Ma for semipelites and 508 ± 19 Ma for charnockites dates extensive garnet breakdown during final stages of melt crystallization and subsequent cooling. Our findings point to collision initiation at ~590 Ma, with the peak conditions attained at ~550 Ma followed by extensional collapse at ~510–490 Ma, resulting in rapid exhumation of lower crustal rocks to mid‐crustal levels under sustained ultrahigh‐temperature (UHT) conditions, followed by cooling to reach a stable geotherm. Our results suggest a long‐lived hot orogeny in the MB, where the UHT conditions were sustained for at least 40 MYr. The UHT conditions were most likely attained in the core of a long‐lived hot orogen by the combined effect of conductive heating through radioactive decay and mantle heat supply, with the former being the primary driver. [ABSTRACT FROM AUTHOR]

Abstract Five successive deformation phases have been identified from structural analysis of granitoid and gneissic rocks of the study area. The magnetic foliation data of the studied granitoids show two distinct NW and NE trending sets. The NW trending magnetic foliation is found to be essentially parallel to the mesoscale planar structures of regional D1-D2 deformations and is thus correlated with the D1-D2 phases. On the contrary, the NE trending magnetic foliation appears to be kinematically compatible with the NW-SE compression direction deciphered from conjugate ductile shear zone patterns of the D3 event. Combining AMS, field and microstructural data, the granitoid outcrop have been separated into older D1-D2 and younger D3 domains. The published geochronological data from the area when compared with the established D1-D2 and D3 domains, shows a good correlation pointing tentatively the timing of the D1-D2 deformation phase to be ∼2550 Ma while the D3 phase to be ∼2524 Ma. Hence the study highlights the importance of combining AMS data with field and microstructural studies to constraint the timing of regional successive deformation imprints. It also helps to identify the chronologically separated emplacement phases of the granitoid massif in question, which would not have been possible otherwise. Highlights • The deformed Neoarchaean granitoids of the study area in the EDC, south India show evidences of five successive deformation imprints (D1-D5). • The D1-D3 phases represent early ductile episodes which are well documented from the EDC. • The hitherto undetected D4-D5 phases represent essentially brittle shallow crustal events of which the overlying Mesoproterozoic Srisailam Formation manifests the D5 phase only. • The observed magnetic fabrics from granitoids depict NW-SE and NE-SW trends which are correlated with D1-D2 and D3 deformation phases respectively. • AMS data along with field, microstructural and published geochronological data help to constraint the chronology of successive deformation imprints and identify the separate emplacement phases in the granitoid massif. [ABSTRACT FROM AUTHOR]

[Display omitted] • Duration of sedimentation in the Srisailam sub-basin was > 1840 Ma ≤ 1770 Ma. • The Srisailam Formation formed in a passive margin setting. • The dominant source area for the Srisailam Formation was the Dharwar Craton. • The Srisailam Formation contains Palaeo-Mesoarchaean and traces of Haedean zircons. • The Srisailam Formation is correlated with the Pulivendla Formation, Chitravati Group. The Mesoproterozoic Cuddapah Basin consists of four unconformity-bound sequences, i.e., Papaghni Group, Chitravati Group, Srisailam Formation and Kurnool Group. A fair amount of geochronological and geochemical data is available from the basal Papaghni Group and Chitravati Group as well as the overthrusted Nallamalai Group. Due to limited geochronological and geochemical constraints, the Srisailam Formation, however, remains a subject of speculation regarding the time of sediment deposition, sediment source locations, and tectonic setting. In this work, we present new geochronological and geochemical data (zircon U-Pb) from samples of the Srisailam Formation. The new data suggest that the Srisailam Formation correlates temporally with the basal Chitravati Group and is largely disparate from the allochthonous Nallamalai Group. The sediments of the Srisailam Formation contain a minor yet significant number of Palaeo-Mesoarchaean detrital zircon with traces of Haedean zircon. Based on our detrital zircon data, we argue that the sedimentation in the Srisailam sub-basin initiated after ca. 1840 Ma and continued till ≤ ca. 1770 Ma and the sediments were mainly sourced from Neoarchaean to Paleoproterozoic terrains including the Dharwar Craton, and sedimentation was initiated in a rift basin that subsequently evolved to a passive margin setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Charnockite magma intruded the lower crust of the Eastern Ghats Province in two pulses (∼980–940 Ma and ∼ 1020–1000 Ma). • The magma had variable chemistry and shows subduction-collision signatures. • This charnockite later suffered granulite facies metamorphism. • This charnockite is a of the Mawson charnockite of the Rayner Province. • Charnockites of the India-Antarctica sector formed by successive arc-continent collisions. Massif type charnockite was emplaced in the lower crust of the Eastern Ghats Province and is now exposed over a large geographic area. The rock shows clear evidence of magmatic emplacement in lower crustal metasedimentary rocks, which occur as enclaves within the charnockite. Textural data suggest the magma underwent subsolidus cooling and subsequently metamorphosed to granulite facies (up to ∼ 910 °C, 9 kbar). Geochemical data show that the charnockite magma had variable chemistry which was acquired by differentiation and possible crustal contamination. The rock shows both high- and low-SiO 2 types, with weakly peraluminous to metaluminous characters. Trace and REE fractionation trends suggest the magma had calcic to calc-alkaline affinities and was emplaced in a continental arc type collisional setting. Theoretical modelling suggests that such a magma could be generated by melting of a hydrated basaltic slab under CO 2 -rich fluid. U-Pb analysis on oscillatory zoned zircon domains from eight samples yields crystallization ages for the magma. While the majority of the samples show crystallization ages within ca. 980–940 Ma (978 ± 16 Ma, 968 ± 22 Ma, 951 ± 9 Ma, 954 ± 8 Ma, 951 ± 13 Ma and 939 ± 27 Ma), two samples yield crystallization ages of 1002 ± 13 Ma and 1020 ± 16 Ma. This implies two-phase emplacement of the charnockite magma which can be correlated with the tectonometamorphic evolution of the province. While the earlier pulse of charnockite magmatism is broadly synchronous with the first cycle (M 1) of metamorphism, the later pulse followed when the lower crust was still hot. The two pulses of charnockite magmatism are broadly synchronous with those of the Mawson charnockite of the Rayner Province, East Antarctica. It is argued that the charnockite magmatism in the combined Rayner-Eastern Ghats Province was extensive and resulted from arc-continent accretion and collision between the India and East Antarctica during ca. 1030–900 Ma. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Proterozoic Eastern Ghats Province evolved in two metamorphic cycles. • Two cycles represent contrasting tectonic modes in an accretionary orogeny. • Non-linear cooling from high temperature is estimated from geospeedometry. • Two cycles occurred at ca. 1030–990 Ma and ca. 950–900 Ma respectively. • Pulsed tectonic evolution is the hallmark of the entire Rayner-Eastern Ghats orogeny. This study characterizes two metamorphic cycles from two samples of an aluminous granulite of the Eastern Ghats Belt, India using petrological, phase equilibria, geospeedometric, and, petrochronological data. The first metamorphic cycle ensued through dehydration melting of F-biotite along a shallow d P /d T prograde path reaching ultrahigh temperature (>950 °C) at 7–8 kbar pressure. The peak metamorphic assemblage is represented by sapphirine + spinel + Al-orthopyroxene + cordierite + ilmenite + plagioclase + quartz which constitute the coarse granoblastic assemblage. Reaction corona comprising orthopyroxene + sillimanite + garnet ± F-biotite over the peak phases imply near-isobaric cooling from the peak with the termination of the first cycle. The melt produced during the prograde stage has been lost to a large extent to stabilize the peak assemblage. The second metamorphic cycle ensued with the decomposition of cordierite by a skeletal intergrowth of orthopyroxene + sillimanite + quartz and a symplectic intergrowth of garnet + quartz between orthopyroxene and cordierite. A delicate symplectite comprising cordierite + quartz + K-feldspar ± plagioclase also formed at this stage within the leucocratic layers. These intergrowth textures resulted from reworking of the cooled granulite (increasing P - T) through incipient melting of F-biotite subsequent decompression, and melt-solid interaction during the terminal stage of the second metamorphic cycle. Geospeedometric data involving garnet and biotite suggest the nonlinear nature of cooling with an initial fast cooling from the peak condition of the first metamorphic cycle. Monazite petrochronological data yield 1002 ± 3 Ma and 944 ± 6 Ma ages that belong to the peaks of first (ca. 1030–990 Ma) and the second (ca. 950–900 Ma) metamorphic cycles respectively of the central crustal province of the belt. This two-cycle evolution is related to several alternate extension (pull) and compression (push) cycles in an accretionary tectonic setting during ca. 1030–900 Ma. [ABSTRACT FROM AUTHOR]