Discovery and origin of helium-rich gas on the Shixi area,eastern margin of the Ordos Basin

Helium is a kind of rare and strategic resources for national defense industry and global high-technology applicati ons.However,the helium resource in China is short and the dependence on imported helium exceeds 98%.Based on analysis of the 81 gas samples from 25 wells in Shixi area,the helium volume contents range from 0.02~0.23%,with average of 0.089%.3He/4He ratios are 0.02×10-6~0.05×10-6 and R/Ra ((3He/4He)sample/(3He/4He)atmospheric) values are 0.01~0.08,implying that helium in this area is typically of crustal origin.Shixi area is located in the Lishi nose structural belt.The Yanshanian Kimberlite belt (B.P.180~110 Ma) in Liulin Jianjiagou is situated at the east of Shixi area,and the Zijinshan alkaline (B.P.158~130.4 Ma) rock is located in hundred miles north of Kimberlite belt.In mapping the aero-magnetic anomaly,Shixi area is located in the range of positive aeromagnetic anomalies belt.Thus,the helium of Shixi area may associate with the Jianjiagou-Zijinshan complex,the transcrust/crust deep fault have provided passage for helium gas,and the multilayer deposition strata is the excellent trap conditions.Therefore,a helium-rich gas enrichment area maybe formed in the Ordos basin owing to specific geological conditions.This finding is important for the further evaluation and development of the resource.