Tritium Released from Mantle Source: Implications for Natural Nuclear Fusion in the Earth’s Interior
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This paper summarizes the observation results of mantle tritium (3H) in two volcanic lakes, Lakes Nemrut (Turkey) and Laacher (Germany). The presence of excess 3H in the lakes can be explained as material released from mantle source because of the correlation of excess 3H with mantle 3He and 4He. We conclude that excess 3H in these two lakes, after the origin of the excess 3H from atmosphere and conventional nuclear reactions are excluded and the correlation of the excess 3H and mantle 3He is considered, might be from a mantle source and produced by nuclear fusion (d–d reaction) in the deep Earth. We have also investigated helium isotopes in the hydrothermal vent fluids at Mid-Ocean Ridge (MOR). The results show nearly constant 3He/4He ratio (3He/4He = 1.12 ± 0.13 × 10−5) and approximately constant 3He/heat ratios ((5–10) × 10−18 mol/J). The correlation of 3He with 4He and heat suggests that it is reasonable to suppose 3He is produced by nuclear fusion (d–d reaction) and 4He from α-decay of U and Th in the deep Earth. Based on that, 3He/4He ratios for 10 hydrothermal vent fluids are calculated. The results agree with the measurement at hydrothermal vent fluids and Mid-Ocean Ridge Basalts (MORB) on the average. We concludes that the narrow distribution of 3He/4He ratio peaked at ∼8 RA in MORB can be explained by the hypothesis that 3He is produced in nuclear fusion.