Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, 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
Mesozoic intermediate-acid intrusive rocks from Tongling area have the characteristics of adakites in geochemistry, they show SiO2 greater than or equal to 56%, high Al2O3 content (> 15%) Na2O/K2O > 1, HREE depletion, (La/Yb)(N) > 12, slightly negative Eu anomaly (Eu-./Eu = 0.71 (0.96), high Sr concentration (> 750mug/g) and high Sr/Y ratios (> 38). The rocks are divided arbitrarily into three types according to their HREE patterns: (1) flat HREE pattern, with high Yb content (> 1.8mug/g); (2) flat HREE pattern, with Yb < 1.8mug/g and (Ho/Yb)(N) approximate to 1; (3) depleted HREE pattern, with Yb < 1.8mug/g and (Ho/Yb)(N) approximate to 1.2. The high K2O content and the similarity to the composition of the lower crust of Yangtze basement in isotopic composition of the rocks exclude the possibility of direct derivation from slab partial melting, but suggest that the rocks are the products of partial melting of underplating basaltic rocks in the lower crust. The differences among the three types are not resulted from fractional crystallization or continental contamination. Differences in the source composition due to variable percentage of the mantle and the lower crust components are probably the main reasons for the differences of the three types. It is assumed that the adakitic rocks in Tongling and other areas in east China are related to crust accretion and thickening of east China in Mesozoic. The further discussion for the assumption will be helpful to understand the geodynamic process and evolution of east China in Mesozoic.
Wang, YL,Wang, Y,Zhang, Q,et al. The geochemical characteristics of Mesozoic intermediate-acid intrusives of the Tongling area and its metallogenesis-geodynamic implications.[J]. ACTA PETROLOGICA SINICA,2004,20(2):325-338.
Wang, YL.,Wang, Y.,Zhang, Q.,Jia, XQ.,Han, S.,...&韩松.(2004).The geochemical characteristics of Mesozoic intermediate-acid intrusives of the Tongling area and its metallogenesis-geodynamic implications..ACTA PETROLOGICA SINICA,20(2),325-338.
Wang, YL,et al."The geochemical characteristics of Mesozoic intermediate-acid intrusives of the Tongling area and its metallogenesis-geodynamic implications.".ACTA PETROLOGICA SINICA 20.2(2004):325-338.