Magmatic evolution of the Western Myanmar Arc documented by U–Pb and Hf isotopes in detrital zircon

• Sediments in the Chindwin basin dominantly derived from Western Myanmar Arc (WMA)
• Detrital zircons record magmatic stages at ~ 100–80 Ma and ~ 70–40 Ma for WMA.
• Zircons have positive Hf isotopes indicating magma generation from juvenile source.
• WMA is the southeast prolongation of the Gangdese arc in Tibet.
• New data have potential implications to source-to-sink study in eastern Himalayas.

The evolution of the magmatic arc formed along the Asian margin of Neo-Tethys is a key to understand India–Asia convergence. In contrast to the well studied trans-Himalayan magmatic rocks in Tibet, the southeast extension of the arc is still poorly documented in Myanmar, where it is largely buried by sedimentary rocks. This study investigates the magmatic evolution of the western Myanmar arc and the potential along-strike variation of subduction-related magmatism by analyzing U–Pb and Hf isotopes of detrital zircons from the Chindwin Basin in western Myanmar. Our data indicate that the Western Myanmar Arc (WMA) experienced a long-lasting magmatism since the Early Cretaceous, with a main magmatic stage between 110 and 80 Ma and a subordinate magmatic stage at ~ 70–40 Ma. Arc-derived detrital zircons yield positive εHf(t) values and young model ages (0.1–1.2 Ga), indicating magma generation from a juvenile source. Such geochronologic and geochemical signatures compare well with those of the Kohistan-Ladakh-Gangdese arc in Tibet, indicating uniform magmatic-arc activity all along the Asian margin of Neo-Tethys.

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