The identification of the Grenvillian granite on the western margin of the Yangtze Block and its geological implications

Abstract：A deformed and metamorphosed monzogranite intrusion was ruled off from the Lengzhuguan Formation at Yakou Town, Miyi County, which is situated on the western margin of the Yangtze Block. The intrusion is high in SiO2 and K2O and shows obvious negative anomalies of Ba, Sr, P, Nb, Ta and Ti in the mantle-normalized trace element spidergram. In addition, the rock has high Rb/Sr (2.66~10.5) and Rb/Zr (0.43~1.12) ratios, and the 87Sr/86Sr and εNd (t，1.0 Ga) values are 1.209549 and -0.89, respectively, suggesting a crust-derived collisional granite. The zircon SHRIMP data give a granite crystallization age of ca 1014±8 Ma. It is proposed that the Huoshangou granite might have resulted form the collision between the Yangtze Block and the Cathysia Block during the Grenvillian event. It can also be deduced that the Jiangnan orogenic belt can probably extend westward to Huili-Panzhihua area on the western margin of the Yangtze Block instead of turning southward from the Guizhou-Yunnan area.