Geological transect through the Hangay-Hentey Basin: Implications for the contraction of the Mongol-Okhotsk Ocean, Mongolia

The Hangay Hentey (H-H) Basin may hold key evidence of the tectonic setting and history of the Mongol-Okhotsk (M-O) ocean basin. Due to the tectonic complexity of the region, the history, basin type, closure and location of the M-O ocean are key to unraveling the tectonic history of the Central Asian Orogenic Belt. This study provides lithologic and sedimentological evidence through a series of measured stratigraphic sections distributed across ∼400 kilometers of the H-H Basin. These data are used in conjunction with petrographic analyses and high-precision geochronologic dating of detrital-zircon. Approximately 75% of the zircon grains are Lower Carboniferous age; the source being the Carboniferous calc-alkaline magmatic arc located in northern Mongolia and southern Russia. This age distribution characterizes the sediment package of the H-H Basin as being deposited in an isolated forearc that was subsequently incorporated into a subduction-accretion complex along the northern edge of the Mongolian continental block.