Ophiolites in Mongolia: implications for tectonic evolution of the CAOB

Ophiolites in Mongolia, the central part of the Central Asian Orogenic Belt (CAOB), can be divided, based on their spatial distribution and regional geological features, into six zones: Central Mongolian, Mongol-Okhotsk, Lake, Mongol Altai, Trans-Altai, and South Gobi. These formations document five distinct magmatic periods involving three paleo-oceans: the Mirovian, Paleo-Asian (PAO), and Mongol-Okhotsk (MOO). The oldest remnants (1.02–0.93 Ga) represent the Mirovian Ocean, with subsequent events (800–560 Ma) documenting its crustal generation and subduction. The closure of the Mirovian Ocean (540–520 Ma) likely triggered subduction initiation in the Paleo-Asian Ocean (PAO), evidenced by Cambrian supra-subduction zone (SSZ) ophiolites (529–500 Ma). Carboniferous-Permian (350–255 Ma) ophiolites in southern Mongolia reflect late Paleozoic PAO crustal generation, while those in the northeast record the initial subduction of the Mongol-Okhotsk Ocean. We propose that the Gurvansaikhan-Manlay ophiolite belt connects with the Armantai ophiolite belt in East Junggar, China, and that the Edren-Altan Uul ophiolite belt extends and links westward to the Kalameili ophiolite belt in East Junggar, China. Undoubtedly, ophiolites in Mongolia provide critical insights into the tectonic evolution of the CAOB, including the protracted subduction-accretion processes, the complex transition dynamics and the final closure of the multipleoceanic basins.