[S-MP22] Supercontinents and Crustal Evolution

[SMP22-P04] Remnants of the Columbia supercontinent from the Sri Lankan beach placers and its trails to the Indian peninsula

*Athira Pendanath Gopinathan¹, Krishnan Sajeev², Sanjeewa P.K. Malaviarachchi³, George P.M⁴, Mingguo Zhai⁵, Gayathri K. Wijeratne³, Dharmapriya P.L³, Brian F. Windley⁶, Ayisha V.A⁷ (1.Niigata Univ., 2.Indian Institute of Science, 3.Univ. of Peradeniya, 4.Nazarbayev Univ., 5.IGGCAS, 6.Univ. of Leicester, 7.MES Ponnani College)

Beach placer deposits derive from multiple sources and are the erosional products of large areas of continental crust and can act as key to unravelling the evolution of past supercontinents on Earth. Understanding where the majority of sediments came from would provide valuable insights into broader issues such as orogenic recycling, crustal growth, composition of the continental crust and constraining crustal evolution over time. This study demonstrates provenance interpretations based on U-Pb dating of zircon and monazite and trace elements combined with Hf isotope in zircons from beach placers on the southwest coast of Sri Lanka. Zircon data record a wide range of ages from 650 – 450 Ma, 1000 – 650 Ma to 2300 -1600 Ma, and a few grains with >2500 Ma. Based on the data obtained, primary groups of ages fall within 2300 – 1600 Ma and 650 – 450 Ma. The Paleoproterozoic ages range from 2300 – 1600 Ma with a prominent peak at ca. 1800 Ma reflecting the primary sources of contribution to the beach placer deposits. The similarity of Paleoproterozoic zircon age peaks with comparable Hf isotopic signatures of zircons from the beach sands of Sri Lanka and those of India suggests that they could have similar provenances. These ages also show similarities with metasedimentary and magmatic data, which is comparable with the ages of East African Orogens such as southern India, Madagascar, and East Africa. Similar age distributions and Hf isotopic signatures indicate that East Africa and central Madagascar could have been juxtaposed during the Paleoproterozoic to the early Mesoproterozoic period, and southern India and Sri Lanka were perhaps contiguous with Madagascar at the time of deposition during the Paleoproterozoic, and with sediment source including those in the East African cratons. Hence, the Paleoproterozoic age peak implied from the beach sediments from the Southern Sri Lanka corresponds to direct evidence for derivatives of the Columbia Supercontinent.