Studies on He isotope ratios of gas and rock samples in various parts of the world have shown a close relation between the 3He/4He ratio and geotectonic features of the sampling area. Emission of primordial He is commonly found in gases and fluid in Cenozoic volcanic areas (mid-ocean ridges, hot spots, and subduction zones), whereas that of radiogenic He is predominant in continental areas. Thus, the 3He/4He ratio is considered a useful tool for evaluating a variety of geotectonic environments.

Supplement to: Wakita, Hiroshi; Sano, Yuji; Fujii, Naoyuki; Takeuchi, Akira (1986): 3He/4He ratios of pore gases in deep-sea sediments, Legs 89 and 90. In: Kennett, JP; von der Borch, CC; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 90, 1261-1263