关键词: 氚, ³He起源, 天然核聚变, 地球内部

Abstract: The origin of ³He has been assumed to be of primordial origin, trapped within the Earth at the time that the Earth formed 4.6 billion years ago. However, the obstacles for hypothesis of primordial origin of ³He have been met in explanation of 3He paradoxes in the Earth, for example, ①extremely high ³He/⁴He ratios in the diamonds and ②narrow distribution of ³He/⁴He in midocean ridge basalts (MORB) and the hydrothermal vent fluids at midocean ridge (MOR). Author have made a new investigation on the vertical profiles of tritium concentration in the crater lakes and found that both ³He and ³H released from Earthmantle were injected at the bottoms of Lakes Nemrut (Turkey) and Laacher (Germany). Both ³H and ³He are the products of nuclear fusion (d-d reaction). Tritium has a halflife of 12.4 years. The primordial tritium formed in the Earth 4.6 billion years ago already decayed to a negligible level in the Earth history. 3H concentration from any known nuclear reactions has been estimated to be less than 0.01 TU (1 TU means ³H/H=10^-18)，below detection limit. Author conclude that the d-d reaction might be induced near (in) the Earth core where are of hydrogenbearing minerals and rich U and Th at high temperature and high pressure.