The 208.5 Ma Syenite of the Mogou syenite body in Songxian County, Henan Provi n ce, dated by the single zircon UPb dating method and the 221 Ma ReOs isochron of Carbonati te related to molybdenite mineralization in Huayangchuan, Shaanxi Province indic ate that the alkali magmatic activities of the Indosinian epoch in the Xionge r fault basin were mainly developed on both the east and west sides of the Xiaoqinli ng old ridge located in the south part of the fault basin. The magmatism, princi pally the syenites on the east side of the ridge, was rich in patassium and related to gold mineralization, while on the west side, the carbonatites direct ly produced the MoPb mineral deposits. The alkali magmatism of the Indosinian epoch shows a character of the crust mantle m ixed magma type, occurred at the tectonic setting of intraplate and nonorogenic environment and induced by the subduction of the Qinling mi cromassif towards the North China massif during the collison after rhe Middle Tr iassic.