Episodic metamorphism of the central Gondwana revealed by zirconology of pegmatites and regional granulites from Sri Lanka and its peripheral terranes

Reconstructing ancient continents hinges on deciphering polymetamorphic records. Here, we integrate new U–Pb zircon ages with pressure–temperature–time–deformation (P–T–t–D) constraints to resolve the late Cryogenian–Ordovician evolution of the Highland Complex (HC), Sri Lanka (~660–460 Ma). Our results reveal a reworked crust comprising Palaeoarchean to Neoproterozoic (>700 Ma) sedimentary sequences and magmatic additions at ~2500 Ma, 2000–1650 Ma, 1050–810 Ma, 730–670 Ma, 620–570 Ma, 560–520 Ma, and ~490–460 Ma, with possible ~1800 Ma metamorphism. Four episodic metamorphic phases (MP1–MP4) overprinted these lithologies during Gondwana amalgamation. MP1 (~660–640 Ma) reflects early prograde metamorphism during crustal thickening. MP2 (~630–550 Ma), peaking at 590–570 Ma and followed by near-isobaric cooling (570–550 Ma), records high-temperature metamorphism during major collision. MP3 (~550–510 Ma) marks retrograde metamorphism, deep crustal exhumation (~550–545 Ma), and subsequent extension (545–510 Ma). MP4 (~490–460 Ma) represents a later thermal overprint, likely linked to post-collisional extension. These events correlate with the East African (MP1), Kirwan (MP2), and Kuunga (MP3), while the responsible tectonothermal event for MP4 is not confirmed. Pegmatitic intrusions dated at 560–550 Ma, 550–510 Ma, and 490–460 Ma capture late- to post-orogenic reworking. The temporal and thermal alignment of MP1–MP4 with metamorphic histories in the Trivandrum Block (southern India) and Lützow–Holm Complex (East Antarctica) supports their interpretation as once-contiguous fragments of central Gondwana. This integrated study refines the tectonometamorphic framework of the HC and highlights its significance in reconstructing crustal architecture shaped by the formation of central Gondwana.