LATE PALAEOPROTEROZOIC TO EARLY MESOPROTEROZOIC TECTONIC FRAMEWORK AND MAJOR TECTONO-THERMAL EPISODES OF NORTH CHINA: NEW INTERPRETATION OF “LLIANG OROGENY”
Li Jianghai Qian Xianglin Hou Guiting Liu Shuwen Chen Jing (Department of Geology, Peking University, Beijing100871, China)
The Lüliang orogeny (1.9-1.7?Ga) has long been thought to have been responsible for the cratonization of the North China craton (NCC). In fact, the NCC was dominated in the late Palaeoproterozoic by an extensional_tectonic regime, associated with the development of an aulacogen system, anorogenic magmatism (rapakivi granites, anorthosites, gabbros, granites and pegmatites), with the emplacement of large_scale mafic dyke swarms and with the uplift of the early metamorphic basement or the tectonothermal events of the retrogressive metamorphism. The statistical analysis of the known isotopic age data of the late Palaeoproterozoic to early Mesoproterozoic rocks suggests that several age peaks are revealed by the chronological distributions of the magmatic emplacement and basement tectonothermal events and that the uplift and retrogressive metamorphic events of the craton basement lagged behind the magmatic emplacement, distinctively different from the structural deformation_metamorphism_magmatic emplacement sequences characteristic of orogenic belts. The re_understanding of the late Palaeoproterozoic extensional tectonic framework clarifies the most basic restricting condition for the reconstruction of North China craton within Rodinia in the Mesoproterozoic.