A new model for the Indochina and South China collision during the Late Permian to the Middle Triassic

A comparative analysis of Indochina and South China during the Early Paleozoic indicates the former may be extended to include North Vietnam, part of the Qinzhou tectonic zone and southern Hainan Island. These three regions were traditionally regarded as parts of South China separated from Indochina by the Song Ma suture in Central-North Vietnam. A new suture, called the Dian-Qiong suture, is proposed here, approximately along the southern margin of the present Nanpanjiang basin. This suture is linked to its eastern counterpart in Hainan Island through a NNE-trending dextral transform fault zone along the eastern margin of the Nanpanjiang basin. The conventional Song Ma suture originally constitutes its western extension and was translated to its present location by sinistral displacement along the Red River Fault Zone during the Tertiary. Upper Paleozoic deep-water turbidites and associated mid-oceanic ridge basalts along the suture in the Nanpanjiang basin illustrate a coeval ocean between Indochina and South China. The ocean was consumed by south-directed subduction beneath Indochina during the Late Permian to the Middle Triassic. This suture zone was finally re-shaped by the indentation between the active margin of Indochina and the irregular passive continental margin of South China during the Late Triassic as well as displacement along the Red River fault zone during the Cenozoic.