Leakage of mantle helium from the Liaodong Peninsula, China

The isotopic compositions of helium have been investigated in hot spring gases sampled from the Liaodong Peninsula, China. The 3He/ 4He ratios range from 0.14 Ra (0.14 times the atmospheric 3He/ 4He ratio of 1.40×10 -6) to 0.72 Ra. 3He/ 4He versus 4He/ 20Ne ratios and He contents suggest that a small amount of mantle-derived helium reaches the earth’s surface. Helium isotope ratios of the hot spring gases show a distribution pattern similar to the regional heat flow values, indicating that the positive thermal anomaly occurring in the area is closely associated with the presence of mantle-derived helium. The observations described above provide some significant evidence that the molten magma originating from partial melting of the upper mantle may have intruded into the continental crust along the activity fault. The coupling of the presence of mantle He and heat flow anomalies to seismic activity in studied region seem to imply that there is an internal relationship between mantle degassing and seismic activity