Unraveling Sedimentary Provenance and Tectonothermal History of High-Temperature Metapelites, Using Zircon and Monazite Chemistry: A Case Study from the Eastern Ghats Belt, India

The geochemical behavior of detrital zircon and monazite during granulite facies anatexis in metapelites from the Eastern Ghats Belt (EGB), India, is explored using U-Pb geochronology, Hf isotopes, and trace elements. In ametapelite from the Ongole Domain, detrital zircon reequilibrated by coupled dissolution-reprecipitation and diffusion reaction during ultrahigh-temperature metamorphism at 1.63 Ga. The event completely reset the U-Pb systems, but Hf isotopes and trace elements were only partially reequilibrated. Overgrowths on the altered cores date migmatization at 1.61 Ga. Monazite yields metamorphic ages similar to those of zircon. In metapelites from the Eastern Ghats Province (EGP), detrital zircon grains give 2.44-1.40-Ga ages and metamorphic ones 1.2-0.5-Ga ages. Metamorphic components include detrital grains reequilibrated by coupled dissolution-reprecipitation in the presence of anatectic melt and newly crystallized overgrowths and grains. In reequilibrated domains, the U-Pb system was completely reset, but Hf isotope compositions of precursors were often retained. The Hf-176/Hf-177 of most zircon scatters between 2.7- and 1.9-Ga crust evolution lines, indicating late Archaean to Mesoproterozoic juvenile provenance with major crust formation between 2.7 and 1.9 Ga and only minor perturbation of the Lu-Hf system during metamorphism. The 1.2-0.92-, and 0.62-0.50-Ga metamorphic populations are related to Rodinia and Gondwana assembly, respectively. The 1.63-, 1.2-0.92-, and 0.62-0.50-Ga ages allow correlation of the Ongole Domain and EGP with the Rayner Complex, suggesting that East Antarctica was contiguous with Proto-India in the Paleoproterozoic. Rifting in this terrane and sedimentation in the resulting basin deposited the EGP metapelites between 1.42 and 1.2 Ga, culminating in reamalgamation of East Antarctica with Proto-India during Rodinia assembly. The final crustal architecture of the belt was attained during Pan-African orogenesis when the EGB granulites were thrust westward over the cratons.