1. 华北克拉通辽南地块新太古代晚期TTG岩石成因及其构造意义.
- Author
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张洪祥, 刘 锦, 孙 博, 刘正宏, 于泓超, and 董亚超
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NEOARCHAEAN , *GEOCHEMISTRY , *PETROGENESIS , *ZIRCON , *AGE - Abstract
In order to enhance the understanding of Archean continental crust formation and evolution history of Liaonan block in North China Craton, the Neoarchean TTG(tonalite-trondhjemite-granodiorite)gneisses in Shijianfang area of Liaonan block were focused on, and the detailed field investigation, zircon U-Pb dating and Lu-Hf isotope analysis, and whole-rock geochemical analysis were intergrated. The results show that TTG gneiss in Shijianfang area crystallizes at(2 499.7±5.4)Ma. The TTG gneiss samples have high contents of SiO2(66.1%-69.1%)and Al2O3(14.6%-15.6%), are enriched in Na and depleted in K(K2O/Na2O is 0.41-0.51)with weakly positive Eu anomalies(1.06-1.59); the samples are relatively enriched in large ion lithophile elements(Ba, Rb, K, etc.)and high field strength elements(Zr, Hf, etc.), featured by high Sr/Y(44.3-69.5)and(La/Yb)N(11.8-24.0), and depleted zircon Hf isotopic composition with two-stage model ages of 2 903-2 687 Ma. Compared with TTG rocks derived from partial melting of the thickened lower crust, TTG gneisses in Shijianfang area have relatively higher contents of MgO, Cr and Ni. The above geochemical characteristics reveal TTG gneisses in Shijianfang area are typical medium-pressure TTG rocks, which is the product of partial melting of Meso-Neoarchean basaltic crust. The source area is rich in garnet and amphibolite, but short of rutile and plagioclase. Combined with previous studies, TTG gneisses in Shijianfang area are likely formed by the partial melting of subduction slabs, indicating the warm subduction tectonic system of the ancient continental margin. The North China Craton might be controlled by both plate tectonics and mantle plume tectonics during Late Neoarchean. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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