ABSTRACT
The growth pattern of continental crust is a fundamental issue in earth sciences and has been a long-existing hot debate in geological community. Geochemical evolution of sediments and granitoids has been proposed by several authors in late 1980’s, which is quite effective to recognize juvenile addition, crustal forming event and recycling mechanism. The growth pattern and rate variation can also be studied. Based on a systematic sampling of major crust rocks, mainly granitoids, sedimentary cover and metasediments in South China, combined with the published data, geochronology study, survey of TGC, generalized crust residence age and Nd isotope approach have been employed to investigate growth pattern of the continent crust in South China. Analysis of age histogram and spectrum of TGC distribution as well as the Sm-Nd isotope system (each rock formation for a given geological age is calculated to its initial Nd isotope ratio, eNd(T)) provides strong arguments to support the episodic growth model. Nd isotope data of crustal rocks in the region do not show gradual changes with time, but the evolution curve suggests that episodic crustal growth occurred in ca. 2.5 Ga, 1.8–2.0 Ga, 1.4 Ga, 1.0–1.2 Ga in Precambrian, and 0.4 Ga and ca. 0.2 Ga in Phanerozoic. The eNd(T) oscillate widely in between, especially in Phanerozoic. These imply a high frequency of mixing between distinct sources. All the above implications would place severe constraints on the interpretation of tectonic evolution of South China.
