LEAKAGE OF MANTLE HELIUM FROM THE LIAODONG PENINSULA, CHINA

The isotopic compositions of helium have been investigated in hot spri ng gases sampled from the Liaodong Peninsula, China. The He-3/He-4 rat ios range from 0.14 Pa (0.14 times the atmospheric 3He/4He ratio of 1. 40 x 10(-6)) to 0.72 Pa. 3He/4He versus He-4/Ne-20 ratios and He conte nts suggest that a small amount of mantle-derived helium reaches the e arth's surface. Helium isotope ratios of the hot spring gases show a d istribution pattern similar to the regional heat flow values, indicati ng that the positive thermal anomaly occurring in the area is closely associated with the presence of mantle-derived helium. The observation s described above provide some significant evidence that the molten ma gma originating from partial melting of the upper mantle may have intr uded into the continental crust along the activity fault. The coupling of the presence of mantle He and heat flow anomalies to seismic activ ity in studied region seem to imply that there is an internal relation ship between mantle degassing and seismic activity.