From the "Ferility & Vitality" section of our Dictionary of Semenyms:

fountain of life - used to describe semen as a wellspring of vitality. “A warmth spread over my entire body as the muscles of his arms and legs tightened and loosened and tightened again. Inexorably a tension built within him, until at last he erupted, a fountain inside me, a fountain of life that went on and on forever. I closed my eyes and didn’t move, feeling the fountain go on.” —Tiffany Christian