The Western Ailaoshan Volcanic Belts and their SE Asia connection: a new tectonic model for the Eastern Indochina Block

The Western Ailaoshan (WAL) Volcanic Belts mark the western boundary of the South China–Indochina Suture Zone along the Ailaoshan Fold Belt. Geochronological and geochemical evidence suggests that the WAL Volcanic Belts vary in ages and origins, and includes (1) L. Carboniferous–earliest M.-Permian (ca. 300–270 Ma) incipient backarc basin magmatism; (2) M. Permian (ca. 265 Ma) island arc/mature backarc basin magmatism; (3) early L. Permian (ca. 260–255 Ma) WAL–Indochina arc–continent collision and the associated syn-collisional granitic magmatism, as well as subsequent (4) E. Triassic (ca. 250–245 Ma) post-collisional magmatism. Regional geological comparison indicates that the post-L. Carboniferous WAL tectonic evolution was closely related to the Eastern Indochina Block. We present a new G-Plate geodynamic evolution model for the Ailaoshan Fold Belt and its surrounding South China–Indochina region, based on new and published U–Pb zircon ages, together with whole rock and Pb-isotope geochemical data.