Helium flux from the solid earth

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Taking into account the ³He/⁴He ratio in pore water of Pacific deep sea sediments and the ratio variation with thickness of sedimentary layers in the continental crust area, we estimated ³He and ⁴He fluxes for each part of the solid earth: ocean floor, the continent, and volcanic areas. Results suggest that the ⁴He flux from the continent accounts for large amount of total outflow, whereas the principal sources of ³He are volcanic areas including mid-ocean ridges, hot spots and subduction zones. Helium-3 flux from the ocean floor contributes little to its mass balance in the atmosphere in spite of the ocean's dominance in the surface of the earth. Based on the total fluxes and inventories of ³He and ⁴He in the atmosphere, their average residence times can be obtained as 3.3 × 10⁶ and 8.4 × 10⁶ years, respectively.