ABSTRACT

Sm-Nd isotopic compositions of Late Neoproterozoic (Sinian), Early Cambrian, Early Ordovician, Late Triassic, and Jurassic sedimentary rocks from the northwestern Yangtze Craton, Guangyuan, Sichuan province, China show that the averaged Nd model age is 1.9 Ga. Based on Nd model ages (1.0 Ga to 3.3 Ga) combining geochronological data, three end-members are identified, which are represented by ca. 3.3 Ga, and 1.0 Ga, and 2.0 Ga respectively. The 2.0 Ga is postulated from geographical distribution of Nd model ages and partly geochronological data. Because the highest ε_Nd(t) values only occurred in Cambrian and Ordovician sedimentary rocks, Early Paleozoic was a very important stage of orogen, which led to newly formed crustal end-member elevated and denudated widely. The 1.0 Ga growth episode occurred in the circum-Yangtze Craton principally.