The Meso-Tethys Ocean: The nature, extension and spatial-temporal evolution

The nature, extension, and evolution of the Meso-Tethys still remain unclear to researchers, and this has thereby hindered in-depth study of the Tethys tectonic domain. In this paper, we review the geology of the Tethys tectonic domain and suggest that the Meso-Tethys is a massive tectonic zone divided into three segments. The central segment includes the Bangong-Nujiang Suture Zone on the Tibetan Plateau and the Shyok Suture Zone in the South Pamir Mountains. This segment has been well studied and is the key link that fully records the birth, evolution, and demise of the Meso-Tethys Ocean from the Permian to Cretaceous, as well as the subsequent continental collision and crustal uplift. The western segment includes the Sanandaj-Sirjan Suture Zone and the Izmir-Ankara-Erzincan Suture Zone in the Middle East. Due to limited research on the western segment, our understanding of it is mainly derived from records of the Jurassic forearc extension,development of arc, and subsequent arc-continent collision. The eastern segment includes the Shan Boundary in Southeast Asia. It has received widespread attention in recent years, and it contains complete records of the Jurassic subduction of the Meso-Tethys Ocean. Based on the latest comprehensive data, we propose that the evolution of the Meso-Tethys Ocean can be divided into four stages: (1) the Early Permian rifting and opening stage; (2) the Middle Permian-Triassic seafoor spreading stage; (3) the Late Triassic-Jurassic convergence stage; and (4) the Late Jurassic-Early Cretaceous diachronous closure from east to west in the central segment and transition from the Meso-Tethys evolution to the Neo-Tethys evolution in both the eastern and western segments. The Meso-Tethys Ocean underwent complex evolution for at least ∼160 Myrs. It has an east-west length of over 8000 km and a maximum north-south width of close to 5000 km during the Late Triassic, which basically reached the scale of the current Indian Ocean. It was an important ocean basin that coexisted with the Paleo- and Neo-Tethys oceans, a key intermediate link in the evolution of the Tethys, and one of the major contributors to the continuous disintegration of Gondwana and the accretion of the Eurasian continent. Its complex evolution process and multiple periods of accretion resulted in the formation of complex geological records and the wide scale of the Meso-Tethys (e.g., the Bangong-Nujiang Suture Zone), making this area a rare natural laboratory for in-depth study of orogenesis, which is of great significance for studying tectonic processes on the global scale from seafloor geology to continental accretion and mineralization.