DISINTEGRATION AND REUNDERSTANDING OF THE “KAIYUAN ROCK GROUP” IN THE EAST SECTION OF THE NORTHERN MARGIN OF NORTH CHINA CRATON

According to recently obtained isochronologic data, the authors have a new understanding of the tectonic metamorphic rock series, formerly known as "Kaiyuan rock group" or "Qinghezhen rock group", in northern Liaoning Province, and redefine it as Qinghe tectonic melange. It consists of the Mesoarchean, Neoarchean and Mesoproterozoic rocks from North China Craton, and also the Neoproterozoic and Permian rocks from Xing'an-Mongolian orogenic belt with various tectonic conditions. The original Shenjiapuzi rock formation is redivided into Neoarchean metamorphic supracrustal rocks and Meso-Neoarchean metamorphic plutonic rocks;while the original Zhaobeishan rock formation into Neoproterozoic Nanping slices and Late Permian Zhaobeishan rock formation. The original Banshigou rock formation (or Lujiapuzi rock formation) is redefined as Mesoproterozoic Shimen rock formation. The original Tongjiatun rock formation and Jianshanzi volcanic rock are combined into the Late Permian Tongjiatun rock formation. Finally, the authors suggest that the Qinghe tectonic melange belt be the boundary between North China Craton and Xing'an-Mongolian orogenic belt, and the final closing time of Paleo-Asian Ocean in the east section of northern margin of North China plate should be the early Middle Triassic (ca. 245 Ma).