"Helium Spots": Caused by a Diapiric Magma from the Upper Mantle

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Science  28 Apr 1978:
Vol. 200, Issue 4340, pp. 430-432
DOI: 10.1126/science.200.4340.430


"Helium spots," where a significant amount of helium is present in the soil [up to 350 parts per million with a high 3He to 4He ratio of (8.90 ± 0.31) x 10–6], have been found along the fault zone formed by the 1966 Matsushiro swarm earthquakes. The formation of the "helium spots" and the occurrence of the earthquakes are interpreted as the results of a diapiric uprise of a magma approximately 1 kilometer in diameter.