Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
; Tianjin Inst Geol & Mineral Resources, Tianjin 300170, Peoples R China
; Univ Hong Kong, Dept Earth Sci, Hong Kong, Hong Kong, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
Late Mesozoic intermediate-acid granitoids are widespread in eastern China. They are basically distributed in three regions according to the geochemical characteristics: Northeastern China, North China and Southeastern China. Theoretically granitoids can be divided into five types based on their Sr and Yb contents: i.e., high-Sr and low-Yb type (Sr > 400 mu g/g, Yb < 2 mu g/g), low-Sr and low-Yb type (Sr < 400 mu g/g, Yb < 2 mu g/g), low-Sr and high-Yb type ( Sr < 400 mu g/g, Yb > 2 mu g/g), high-Sr and high-Yb type (Sr > 400 mu g/g, Yb > 2 mu g/g), and very low-Sr and very high-Yb type (Sr < 100 mu g/g, Yb = 2 similar to 18 mu g/g). The granitoids in NE China and SE China are mainly composed of low-Sr and high-Yb type with minor high-Sr and low-Yb type and very low-Sr and very high-Yb type, whereas the granitoids in North China consist mainly of high-Sr and low-Yb type with minor low-Sr and high-Yb type and low-Sr and low-Yb type and very low-Sr and very high-Yb type. Based on the geochemical characteristics of these granitoids, it is suggested here that the geochemical diversity of the granitoids in the North China and in the SE China is mainly caused by the composition and depth of the magma source and have a close correlation with the depth of the source. High-Sr and low-Yb type granitoids are derived from a magma source with eclogite composed of garnet + pyroxene + rutile +/- amphibole as a residual phase such that the evolved granitoids are highly depleted in HREE, Nb, Ta and Ti and enriched in Sr and Al without negative Eu anomalies, consistent with the characteristics of adakite. Low-Sr and high-Yb type granitoids are formed in a relatively shallow magma source where amphiolites or gneisses composed of plagioclase + pyroxene +/- amphiolite are the major residual phases. These differences indicate that the crust thickness of the North China and SE China is different in the late Mesozoic (late Jurassic to early Cretaceous) : the crust of the North China was thicker than that of the SE China. North China may have undergone delamination such that the chemical composition of the lower crust of the North China is different from that of the SE China: the average crustal composition of the North China is more felsic-rich than that of the SE China after the delamination of the lower crust of the North China with mafic components.
Qi, Z,Li, CD,Wang, Y,et al. Mesozoic high-Sr and Low-Yb granitoids and low-Sr and high-Yb granitoids in eastern China: comparison and geological implications.[J]. ACTA PETROLOGICA SINICA,2005,21(6):1527-1537.
Qi, Z.,Li, CD.,Wang, Y.,Wang, YL.,Jin, WJ.,...&韩松.(2005).Mesozoic high-Sr and Low-Yb granitoids and low-Sr and high-Yb granitoids in eastern China: comparison and geological implications..ACTA PETROLOGICA SINICA,21(6),1527-1537.
Qi, Z,et al."Mesozoic high-Sr and Low-Yb granitoids and low-Sr and high-Yb granitoids in eastern China: comparison and geological implications.".ACTA PETROLOGICA SINICA 21.6(2005):1527-1537.