引用本文：杨玉伟,余超,王广伟,苏特,杨新宇,张天元.2020.辽东黑沟地区古元古代碱长花岗岩年代学、地球化学、Hf同位素特征及其对辽吉造山带构造演化的制约[J].地质学报,94(8):2212-2226. YANG Yuwei,YU Chao,WANG Guangwei,SU Te,YANG Xinyu,ZHANG Tianyuan.2020.Chronology, geochemistry and zircon Hf isotopes of the Paleoproterozoic alkali feldspar granite from the Heigou area in the eastern Liaoning Province:constraints on the tectonic evolution of the Liao- Ji orogenic belt[J].Acta Geologica Sinica,94(8):2212-2226.
Chronology, geochemistry and zircon Hf isotopes of the Paleoproterozoic alkali feldspar granite from the Heigou area in the eastern Liaoning Province:constraints on the tectonic evolution of the Liao- Ji orogenic belt
Abstract:The middle Paleoproterozoic (2. 1～2. 2 Ga) magma in the eastern orogenic belt of the north China craton recorded important crustal evolution information in the early stage of the orogenic belt, which is of great significance for understanding the Paleoproterozoic geological evolution in the Liaoning- Jilin orogenic belt. In this paper, we have studied petrology, geochemistry, zircon U- Pb chronology and Hf isotope characteristics of Paleoproterozoic alkali feldspar granite in the Heigou area, eastern Liaoning province. The zircon U- Pb dating result of the granite by LA- ICP- MS was 2186. 5±6. 5 Ma, and the formation age was Paleoproterozoic. The rocks belong to the alkaline and weakly peraluminous A- type granites. The rocks are high in Si and rich in alkali, poor in Ca, Mg and Al, extremely rich in sodium and poor in potassium. They are also rich in the HFSEs (such as Hf, Zr, Nb, Y), deficient in the LILEs (such as Rb, K, Ba), have high (K 2O+Na 2O)/Al 2O 3, FeOT/MgO, Ga/Al ratios, and negative Eu anomaly. The rare earth elements distribution curve shows the right- leaning seagull pattern. The saturation temperature of zircon ranges is between 857 ℃ and 884 ℃, and has a very low Sr and high Yb characteristic, indicating that the rock was formed in the extensional tectonic background of low pressure and high temperature. ε Hf ( t ) values of zircons in the granites range from -0. 96~+4. 58, and two- stage Hf model ages ( t DM 2 ) are 2476～2821 Ma, which are significantly older than the zircon U- Pb ages of the granites. Combined with lithogeochemical characteristics, it indicates that the Paleoproterozoic granites were derived from partial melting of Archean TTG gneisses under an extensional environment at shallow crustal level. Based on the data of petrology, geochemistry and isotopic characteristics, the Liaoning- Jilin region was likely to be in the tectonic environment of continental back- arc basin in the early Paleoproterozoic, and the Heigou alkali feldspar granite is the product of the extensional environment of back- arc basin.