Ages and Compositions of the Precambrian High‐grade Basement of the Qilian Terrane and Its Adjacent Areas

Abstract

Abstract Based on geological, chronological, geochemical and Nd isotopic studies of the high‐grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high‐grade basement of the Qilian terrane consists mainly of meta‐argillo‐arenaceous rocks and granites and its bulk part was formed in the period of 0.8–1.0 Ga (the Jinningian period); (2) most of the meta‐argillo‐arenaceous rocks and granitic rocks have strong negative Eu and Ba anomalies (Eu/Eu*= 0.47–0.71 and Ba/Ba*=0.16–0.64), with fDM and ENd (1.0 Ga) ranging from 1.87 to 2.26 Ga and from −8.54 to −4.06 respectively, showing relatively high maturity; and (3) the Jinningian granitic rocks are a typical product of continent‐continent collision, being probably related to the formation of the supercontinent Rodinia. These studies, combined with the study of high‐grade basement rocks near the Qilian terrane, suggest that before the Jinningian period, the Qilian‐Qaidam northern‐margin terrane and Dunhuang‐Alxa terrane were separated from each other, belonging to different plate systems of the North China craton and Yangtze platform respectively. The Qilian orogenic belt was the same as or similar to the Qiling orogenic belt in terms of the geological evolution history at least before the Jinningian period.