Columbia supercontinent: New insights from the western margin of the Yangtze landmass

Three suites of epimetamorphic rock series dated at 1.6-18 Ga (Statherian of the Palaeoproterozoic) are cropped out in the Lala,Xiaoguanhe-Dongchuan and Dahongshan areas on the western margin of the Yangtze landmass,named the Hekou Group,Tong'an Formation-Tangdan Group-Dongchuan Group,and Dahongshan Group,respectively. The evolution of geologic history of the above-mentioned rock series from 2.0 Ga to 1.4 Ga went through:(1) orogenic movements at ca. 2.2-1.8 Ga; (2) anorogenic splitting event groups at ca. 1.7-1.5 Ga; (3) penetrating of basic dike swarms and stratified intrusions into the Palaeoproterozoic strata at ca. 1.7-1.5 Ga; (4) shelf rifting events in the Yinmin-Luoxue zone at ca. 1.5-1.2 Ga,and (5) collision-orogenic events on the western margin of the upper Yangtze landmass around 1.0 Ga. The emphasis in the present paper focuses on the nature,characteristics and isotopic dating data for the 1.8-1.6 Ga pervasive shelf rifting events on the western margin of the Yangtze landmass,which may well be compared with the nature,characteristics and age determinations for North China,North America,Siberia and Northwest Europe,and thus have provided evidences in favour of the unity of the Yangtze landmass with other continental masses during the Palaeoproterozoic.