Tectonic mélange in the northern Tarshan area is an intraplate suture of Paleozoic Armantai plate consisting of disorder matrix and exotic blocks.It is composed of ophiolite mélange and muddy and sandy mélange and divided into Suoerbastao formation and Kekearder formation.Comprehensive study shows that oceanic floor crust of the small Armantai ocean basin was formed in Early Devonian-Late Devonian period and is related to extension of Paleo-Siberia plate and paleo-Jungar block.