Abstract

Southwest Vietnam and adjacent areas in late Early Mesozoic belonging to four main tectonic blocks, namely: Sibumasu, Chanthaburi, Tonle Sap - Sai Gon and Indochina. Their boundaries are Klaeng (Chanthaburi) - Bentong Raub, Sa Kaeo - Hòn Chuối and Tây Ninh tectonic sutures, respectively. The Late Paleozoic - Early Mesozoic tectonic evolution of the region undergone five stages: 1) From the Devonian to early Late Carboniferous: the Indochina continental block rifted and drifted apart from Gondwana, opening Paleo-Tethys; 2) From the Late Carboniferous to Early Permian, the Paleo- Tethys oceanic crust subducted beneath Indochina, forming active continental margin; 3) During the Permian to Middle Triassic, not only the Chanthaburi arc but also Tonle Sap - Sài Gòn block separated from Indochina, forming Sisophon - Hà Tiên back-arc and Ro Viêng - Tà Thiết basins between them. In the late Early Permian, the Sibumasu dispersed from Gondwana, opening Meso-Tethys; 4) Subduction of the Paleo-Tethys oceanic crust and closing Sisophon - Hà Tiên and Ro Viêng - Tà Thiết basins from the late Middle to early Late Triassic forming Chanthaburi, Sa Kaeo - Kampot - Hòn Khoai and Attapeu - Chau Thoi volcanic arcs; 5) Amalganation and collision of Sibumasu, Chanthaburi, Tonle Sap - Sài Gòn and Indochina in Late Triassic caused the Phú Quốc foreland intermontane basin in Late Triassic - Middle Jurassic and the S-granite tin belt in south Thailand - west Malaysia. There are some relics of the Sa Kaeo - Hòn Chuối extending southward and Tây Ninh sutures, however, it is necessary to have additional studies on this.